Merge github.com:grpc/grpc into wc

69 files changed, 3262 insertions, 1443 deletions

diff --git a/src/core/lib/channel/channel_args.c b/src/core/lib/channel/channel_args.c
index 8fdef0bc64..02db798b5c 100644
--- a/src/core/lib/channel/channel_args.c
+++ b/src/core/lib/channel/channel_args.c
@@ -221,6 +221,21 @@ grpc_compression_algorithm grpc_channel_args_get_compression_algorithm(
   return GRPC_COMPRESS_NONE;
 }
 
+grpc_stream_compression_algorithm
+grpc_channel_args_get_stream_compression_algorithm(const grpc_channel_args *a) {
+  size_t i;
+  if (a == NULL) return 0;
+  for (i = 0; i < a->num_args; ++i) {
+    if (a->args[i].type == GRPC_ARG_INTEGER &&
+        !strcmp(GRPC_STREAM_COMPRESSION_CHANNEL_DEFAULT_ALGORITHM,
+                a->args[i].key)) {
+      return (grpc_stream_compression_algorithm)a->args[i].value.integer;
+      break;
+    }
+  }
+  return GRPC_STREAM_COMPRESS_NONE;
+}
+
 grpc_channel_args *grpc_channel_args_set_compression_algorithm(
     grpc_channel_args *a, grpc_compression_algorithm algorithm) {
   GPR_ASSERT(algorithm < GRPC_COMPRESS_ALGORITHMS_COUNT);
@@ -231,6 +246,16 @@ grpc_channel_args *grpc_channel_args_set_compression_algorithm(
   return grpc_channel_args_copy_and_add(a, &tmp, 1);
 }
 
+grpc_channel_args *grpc_channel_args_set_stream_compression_algorithm(
+    grpc_channel_args *a, grpc_stream_compression_algorithm algorithm) {
+  GPR_ASSERT(algorithm < GRPC_STREAM_COMPRESS_ALGORITHMS_COUNT);
+  grpc_arg tmp;
+  tmp.type = GRPC_ARG_INTEGER;
+  tmp.key = GRPC_STREAM_COMPRESSION_CHANNEL_DEFAULT_ALGORITHM;
+  tmp.value.integer = algorithm;
+  return grpc_channel_args_copy_and_add(a, &tmp, 1);
+}
+
 /** Returns 1 if the argument for compression algorithm's enabled states bitset
  * was found in \a a, returning the arg's value in \a states. Otherwise, returns
  * 0. */
@@ -251,6 +276,26 @@ static int find_compression_algorithm_states_bitset(const grpc_channel_args *a,
   return 0; /* GPR_FALSE */
 }
 
+/** Returns 1 if the argument for compression algorithm's enabled states bitset
+ * was found in \a a, returning the arg's value in \a states. Otherwise, returns
+ * 0. */
+static int find_stream_compression_algorithm_states_bitset(
+    const grpc_channel_args *a, int **states_arg) {
+  if (a != NULL) {
+    size_t i;
+    for (i = 0; i < a->num_args; ++i) {
+      if (a->args[i].type == GRPC_ARG_INTEGER &&
+          !strcmp(GRPC_STREAM_COMPRESSION_CHANNEL_ENABLED_ALGORITHMS_BITSET,
+                  a->args[i].key)) {
+        *states_arg = &a->args[i].value.integer;
+        **states_arg |= 0x1; /* forcefully enable support for no compression */
+        return 1;
+      }
+    }
+  }
+  return 0; /* GPR_FALSE */
+}
+
 grpc_channel_args *grpc_channel_args_compression_algorithm_set_state(
     grpc_exec_ctx *exec_ctx, grpc_channel_args **a,
     grpc_compression_algorithm algorithm, int state) {
@@ -292,6 +337,48 @@ grpc_channel_args *grpc_channel_args_compression_algorithm_set_state(
   return result;
 }
 
+grpc_channel_args *grpc_channel_args_stream_compression_algorithm_set_state(
+    grpc_exec_ctx *exec_ctx, grpc_channel_args **a,
+    grpc_stream_compression_algorithm algorithm, int state) {
+  int *states_arg = NULL;
+  grpc_channel_args *result = *a;
+  const int states_arg_found =
+      find_stream_compression_algorithm_states_bitset(*a, &states_arg);
+
+  if (grpc_channel_args_get_stream_compression_algorithm(*a) == algorithm &&
+      state == 0) {
+    char *algo_name = NULL;
+    GPR_ASSERT(grpc_stream_compression_algorithm_name(algorithm, &algo_name) !=
+               0);
+    gpr_log(GPR_ERROR,
+            "Tried to disable default stream compression algorithm '%s'. The "
+            "operation has been ignored.",
+            algo_name);
+  } else if (states_arg_found) {
+    if (state != 0) {
+      GPR_BITSET((unsigned *)states_arg, algorithm);
+    } else if (algorithm != GRPC_STREAM_COMPRESS_NONE) {
+      GPR_BITCLEAR((unsigned *)states_arg, algorithm);
+    }
+  } else {
+    /* create a new arg */
+    grpc_arg tmp;
+    tmp.type = GRPC_ARG_INTEGER;
+    tmp.key = GRPC_STREAM_COMPRESSION_CHANNEL_ENABLED_ALGORITHMS_BITSET;
+    /* all enabled by default */
+    tmp.value.integer = (1u << GRPC_STREAM_COMPRESS_ALGORITHMS_COUNT) - 1;
+    if (state != 0) {
+      GPR_BITSET((unsigned *)&tmp.value.integer, algorithm);
+    } else if (algorithm != GRPC_STREAM_COMPRESS_NONE) {
+      GPR_BITCLEAR((unsigned *)&tmp.value.integer, algorithm);
+    }
+    result = grpc_channel_args_copy_and_add(*a, &tmp, 1);
+    grpc_channel_args_destroy(exec_ctx, *a);
+    *a = result;
+  }
+  return result;
+}
+
 uint32_t grpc_channel_args_compression_algorithm_get_states(
     const grpc_channel_args *a) {
   int *states_arg;
@@ -302,6 +389,17 @@ uint32_t grpc_channel_args_compression_algorithm_get_states(
   }
 }
 
+uint32_t grpc_channel_args_stream_compression_algorithm_get_states(
+    const grpc_channel_args *a) {
+  int *states_arg;
+  if (find_stream_compression_algorithm_states_bitset(a, &states_arg)) {
+    return (uint32_t)*states_arg;
+  } else {
+    return (1u << GRPC_STREAM_COMPRESS_ALGORITHMS_COUNT) -
+           1; /* All algs. enabled */
+  }
+}
+
 grpc_channel_args *grpc_channel_args_set_socket_mutator(
     grpc_channel_args *a, grpc_socket_mutator *mutator) {
   grpc_arg tmp = grpc_socket_mutator_to_arg(mutator);
diff --git a/src/core/lib/channel/channel_args.h b/src/core/lib/channel/channel_args.h
index f649a8d9ec..0599e189c3 100644
--- a/src/core/lib/channel/channel_args.h
+++ b/src/core/lib/channel/channel_args.h
@@ -59,12 +59,24 @@ void grpc_channel_args_destroy(grpc_exec_ctx *exec_ctx, grpc_channel_args *a);
 grpc_compression_algorithm grpc_channel_args_get_compression_algorithm(
     const grpc_channel_args *a);
 
+/** Returns the stream compression algorithm set in \a a. */
+grpc_stream_compression_algorithm
+grpc_channel_args_get_stream_compression_algorithm(const grpc_channel_args *a);
+
 /** Returns a channel arg instance with compression enabled. If \a a is
  * non-NULL, its args are copied. N.B. GRPC_COMPRESS_NONE disables compression
  * for the channel. */
 grpc_channel_args *grpc_channel_args_set_compression_algorithm(
     grpc_channel_args *a, grpc_compression_algorithm algorithm);
 
+/** Returns a channel arg instance with stream compression enabled. If \a a is
+ * non-NULL, its args are copied. N.B. GRPC_STREAM_COMPRESS_NONE disables
+ * stream compression for the channel. If a value other than
+ * GRPC_STREAM_COMPRESS_NONE is set, it takes precedence over message-wise
+ * compression algorithms. */
+grpc_channel_args *grpc_channel_args_set_stream_compression_algorithm(
+    grpc_channel_args *a, grpc_stream_compression_algorithm algorithm);
+
 /** Sets the support for the given compression algorithm. By default, all
  * compression algorithms are enabled. It's an error to disable an algorithm set
  * by grpc_channel_args_set_compression_algorithm.
@@ -76,6 +88,17 @@ grpc_channel_args *grpc_channel_args_compression_algorithm_set_state(
     grpc_exec_ctx *exec_ctx, grpc_channel_args **a,
     grpc_compression_algorithm algorithm, int enabled);
 
+/** Sets the support for the given stream compression algorithm. By default, all
+ * stream compression algorithms are enabled. It's an error to disable an
+ * algorithm set by grpc_channel_args_set_stream_compression_algorithm.
+ *
+ * Returns an instance with the updated algorithm states. The \a a pointer is
+ * modified to point to the returned instance (which may be different from the
+ * input value of \a a). */
+grpc_channel_args *grpc_channel_args_stream_compression_algorithm_set_state(
+    grpc_exec_ctx *exec_ctx, grpc_channel_args **a,
+    grpc_stream_compression_algorithm algorithm, int enabled);
+
 /** Returns the bitset representing the support state (true for enabled, false
  * for disabled) for compression algorithms.
  *
@@ -84,6 +107,14 @@ grpc_channel_args *grpc_channel_args_compression_algorithm_set_state(
 uint32_t grpc_channel_args_compression_algorithm_get_states(
     const grpc_channel_args *a);
 
+/** Returns the bitset representing the support state (true for enabled, false
+ * for disabled) for stream compression algorithms.
+ *
+ * The i-th bit of the returned bitset corresponds to the i-th entry in the
+ * grpc_stream_compression_algorithm enum. */
+uint32_t grpc_channel_args_stream_compression_algorithm_get_states(
+    const grpc_channel_args *a);
+
 int grpc_channel_args_compare(const grpc_channel_args *a,
                               const grpc_channel_args *b);
 
diff --git a/src/core/lib/compression/algorithm_metadata.h b/src/core/lib/compression/algorithm_metadata.h
index 4717af6e2b..08feafc1bb 100644
--- a/src/core/lib/compression/algorithm_metadata.h
+++ b/src/core/lib/compression/algorithm_metadata.h
@@ -26,13 +26,27 @@
 grpc_slice grpc_compression_algorithm_slice(
     grpc_compression_algorithm algorithm);
 
+/** Return stream compression algorithm based metadata value */
+grpc_slice grpc_stream_compression_algorithm_slice(
+    grpc_stream_compression_algorithm algorithm);
+
 /** Return compression algorithm based metadata element (grpc-encoding: xxx) */
 grpc_mdelem grpc_compression_encoding_mdelem(
     grpc_compression_algorithm algorithm);
 
+/** Return stream compression algorithm based metadata element
+ * (content-encoding: xxx) */
+grpc_mdelem grpc_stream_compression_encoding_mdelem(
+    grpc_stream_compression_algorithm algorithm);
+
 /** Find compression algorithm based on passed in mdstr - returns
  * GRPC_COMPRESS_ALGORITHM_COUNT on failure */
 grpc_compression_algorithm grpc_compression_algorithm_from_slice(
     grpc_slice str);
 
+/** Find stream compression algorithm based on passed in mdstr - returns
+ * GRPC_STREAM_COMPRESS_ALGORITHM_COUNT on failure */
+grpc_stream_compression_algorithm grpc_stream_compression_algorithm_from_slice(
+    grpc_slice str);
+
 #endif /* GRPC_CORE_LIB_COMPRESSION_ALGORITHM_METADATA_H */
diff --git a/src/core/lib/compression/compression.c b/src/core/lib/compression/compression.c
index 8deae2798f..ec84c01811 100644
--- a/src/core/lib/compression/compression.c
+++ b/src/core/lib/compression/compression.c
@@ -46,6 +46,19 @@ int grpc_compression_algorithm_parse(grpc_slice name,
   }
 }
 
+int grpc_stream_compression_algorithm_parse(
+    grpc_slice name, grpc_stream_compression_algorithm *algorithm) {
+  if (grpc_slice_eq(name, GRPC_MDSTR_IDENTITY)) {
+    *algorithm = GRPC_STREAM_COMPRESS_NONE;
+    return 1;
+  } else if (grpc_slice_eq(name, GRPC_MDSTR_GZIP)) {
+    *algorithm = GRPC_STREAM_COMPRESS_GZIP;
+    return 1;
+  } else {
+    return 0;
+  }
+}
+
 int grpc_compression_algorithm_name(grpc_compression_algorithm algorithm,
                                     char **name) {
   GRPC_API_TRACE("grpc_compression_algorithm_parse(algorithm=%d, name=%p)", 2,
@@ -66,6 +79,24 @@ int grpc_compression_algorithm_name(grpc_compression_algorithm algorithm,
   return 0;
 }
 
+int grpc_stream_compression_algorithm_name(
+    grpc_stream_compression_algorithm algorithm, char **name) {
+  GRPC_API_TRACE(
+      "grpc_stream_compression_algorithm_parse(algorithm=%d, name=%p)", 2,
+      ((int)algorithm, name));
+  switch (algorithm) {
+    case GRPC_STREAM_COMPRESS_NONE:
+      *name = "identity";
+      return 1;
+    case GRPC_STREAM_COMPRESS_GZIP:
+      *name = "gzip";
+      return 1;
+    case GRPC_STREAM_COMPRESS_ALGORITHMS_COUNT:
+      return 0;
+  }
+  return 0;
+}
+
 grpc_compression_algorithm grpc_compression_algorithm_from_slice(
     grpc_slice str) {
   if (grpc_slice_eq(str, GRPC_MDSTR_IDENTITY)) return GRPC_COMPRESS_NONE;
@@ -74,6 +105,13 @@ grpc_compression_algorithm grpc_compression_algorithm_from_slice(
   return GRPC_COMPRESS_ALGORITHMS_COUNT;
 }
 
+grpc_stream_compression_algorithm grpc_stream_compression_algorithm_from_slice(
+    grpc_slice str) {
+  if (grpc_slice_eq(str, GRPC_MDSTR_IDENTITY)) return GRPC_STREAM_COMPRESS_NONE;
+  if (grpc_slice_eq(str, GRPC_MDSTR_GZIP)) return GRPC_STREAM_COMPRESS_GZIP;
+  return GRPC_STREAM_COMPRESS_ALGORITHMS_COUNT;
+}
+
 grpc_slice grpc_compression_algorithm_slice(
     grpc_compression_algorithm algorithm) {
   switch (algorithm) {
@@ -89,6 +127,19 @@ grpc_slice grpc_compression_algorithm_slice(
   return grpc_empty_slice();
 }
 
+grpc_slice grpc_stream_compression_algorithm_slice(
+    grpc_stream_compression_algorithm algorithm) {
+  switch (algorithm) {
+    case GRPC_STREAM_COMPRESS_NONE:
+      return GRPC_MDSTR_IDENTITY;
+    case GRPC_STREAM_COMPRESS_GZIP:
+      return GRPC_MDSTR_GZIP;
+    case GRPC_STREAM_COMPRESS_ALGORITHMS_COUNT:
+      return grpc_empty_slice();
+  }
+  return grpc_empty_slice();
+}
+
 grpc_mdelem grpc_compression_encoding_mdelem(
     grpc_compression_algorithm algorithm) {
   switch (algorithm) {
@@ -104,10 +155,25 @@ grpc_mdelem grpc_compression_encoding_mdelem(
   return GRPC_MDNULL;
 }
 
+grpc_mdelem grpc_stream_compression_encoding_mdelem(
+    grpc_stream_compression_algorithm algorithm) {
+  switch (algorithm) {
+    case GRPC_STREAM_COMPRESS_NONE:
+      return GRPC_MDELEM_CONTENT_ENCODING_IDENTITY;
+    case GRPC_STREAM_COMPRESS_GZIP:
+      return GRPC_MDELEM_CONTENT_ENCODING_GZIP;
+    default:
+      break;
+  }
+  return GRPC_MDNULL;
+}
+
 void grpc_compression_options_init(grpc_compression_options *opts) {
   memset(opts, 0, sizeof(*opts));
   /* all enabled by default */
   opts->enabled_algorithms_bitset = (1u << GRPC_COMPRESS_ALGORITHMS_COUNT) - 1;
+  opts->enabled_stream_compression_algorithms_bitset =
+      (1u << GRPC_STREAM_COMPRESS_ALGORITHMS_COUNT) - 1;
 }
 
 void grpc_compression_options_enable_algorithm(
@@ -126,6 +192,13 @@ int grpc_compression_options_is_algorithm_enabled(
   return GPR_BITGET(opts->enabled_algorithms_bitset, algorithm);
 }
 
+int grpc_compression_options_is_stream_compression_algorithm_enabled(
+    const grpc_compression_options *opts,
+    grpc_stream_compression_algorithm algorithm) {
+  return GPR_BITGET(opts->enabled_stream_compression_algorithms_bitset,
+                    algorithm);
+}
+
 /* TODO(dgq): Add the ability to specify parameters to the individual
  * compression algorithms */
 grpc_compression_algorithm grpc_compression_algorithm_for_level(
@@ -181,3 +254,30 @@ grpc_compression_algorithm grpc_compression_algorithm_for_level(
       abort();
   };
 }
+
+GRPCAPI grpc_stream_compression_algorithm
+grpc_stream_compression_algorithm_for_level(
+    grpc_stream_compression_level level, uint32_t accepted_stream_encodings) {
+  GRPC_API_TRACE("grpc_stream_compression_algorithm_for_level(level=%d)", 1,
+                 ((int)level));
+  if (level > GRPC_STREAM_COMPRESS_LEVEL_HIGH) {
+    gpr_log(GPR_ERROR, "Unknown compression level %d.", (int)level);
+    abort();
+  }
+
+  switch (level) {
+    case GRPC_STREAM_COMPRESS_LEVEL_NONE:
+      return GRPC_STREAM_COMPRESS_NONE;
+    case GRPC_STREAM_COMPRESS_LEVEL_LOW:
+    case GRPC_STREAM_COMPRESS_LEVEL_MED:
+    case GRPC_STREAM_COMPRESS_LEVEL_HIGH:
+      if (GPR_BITGET(accepted_stream_encodings, GRPC_STREAM_COMPRESS_GZIP) ==
+          1) {
+        return GRPC_STREAM_COMPRESS_GZIP;
+      } else {
+        return GRPC_STREAM_COMPRESS_NONE;
+      }
+    default:
+      abort();
+  }
+}
diff --git a/src/core/lib/iomgr/combiner.c b/src/core/lib/iomgr/combiner.c
index 518024fcfd..0e496829f6 100644
--- a/src/core/lib/iomgr/combiner.c
+++ b/src/core/lib/iomgr/combiner.c
@@ -73,10 +73,8 @@ static const grpc_closure_scheduler_vtable finally_scheduler = {
 static void offload(grpc_exec_ctx *exec_ctx, void *arg, grpc_error *error);
 
 grpc_combiner *grpc_combiner_create(void) {
-  grpc_combiner *lock = gpr_malloc(sizeof(*lock));
+  grpc_combiner *lock = gpr_zalloc(sizeof(*lock));
   gpr_ref_init(&lock->refs, 1);
-  lock->next_combiner_on_this_exec_ctx = NULL;
-  lock->time_to_execute_final_list = false;
   lock->scheduler.vtable = &scheduler;
   lock->finally_scheduler.vtable = &finally_scheduler;
   gpr_atm_no_barrier_store(&lock->state, STATE_UNORPHANED);
diff --git a/src/core/lib/iomgr/ev_epoll1_linux.c b/src/core/lib/iomgr/ev_epoll1_linux.c
index b89b8af15a..b940d48ba9 100644
--- a/src/core/lib/iomgr/ev_epoll1_linux.c
+++ b/src/core/lib/iomgr/ev_epoll1_linux.c
@@ -48,7 +48,60 @@
 #include "src/core/lib/support/string.h"
 
 static grpc_wakeup_fd global_wakeup_fd;
-static int g_epfd;
+
+/*******************************************************************************
+ * Singleton epoll set related fields
+ */
+
+#define MAX_EPOLL_EVENTS 100
+#define MAX_EPOLL_EVENTS_HANDLED_PER_ITERATION 1
+
+/* NOTE ON SYNCHRONIZATION:
+ * - Fields in this struct are only modified by the designated poller. Hence
+ *   there is no need for any locks to protect the struct.
+ * - num_events and cursor fields have to be of atomic type to provide memory
+ *   visibility guarantees only. i.e In case of multiple pollers, the designated
+ *   polling thread keeps changing; the thread that wrote these values may be
+ *   different from the thread reading the values
+ */
+typedef struct epoll_set {
+  int epfd;
+
+  /* The epoll_events after the last call to epoll_wait() */
+  struct epoll_event events[MAX_EPOLL_EVENTS];
+
+  /* The number of epoll_events after the last call to epoll_wait() */
+  gpr_atm num_events;
+
+  /* Index of the first event in epoll_events that has to be processed. This
+   * field is only valid if num_events > 0 */
+  gpr_atm cursor;
+} epoll_set;
+
+/* The global singleton epoll set */
+static epoll_set g_epoll_set;
+
+/* Must be called *only* once */
+static bool epoll_set_init() {
+  g_epoll_set.epfd = epoll_create1(EPOLL_CLOEXEC);
+  if (g_epoll_set.epfd < 0) {
+    gpr_log(GPR_ERROR, "epoll unavailable");
+    return false;
+  }
+
+  gpr_log(GPR_INFO, "grpc epoll fd: %d", g_epoll_set.epfd);
+  gpr_atm_no_barrier_store(&g_epoll_set.num_events, 0);
+  gpr_atm_no_barrier_store(&g_epoll_set.cursor, 0);
+  return true;
+}
+
+/* epoll_set_init() MUST be called before calling this. */
+static void epoll_set_shutdown() {
+  if (g_epoll_set.epfd >= 0) {
+    close(g_epoll_set.epfd);
+    g_epoll_set.epfd = -1;
+  }
+}
 
 /*******************************************************************************
  * Fd Declarations
@@ -122,7 +175,7 @@ struct grpc_pollset {
   bool kicked_without_poller;
 
   /* Set to true if the pollset is observed to have no workers available to
-   * poll */
+     poll */
   bool seen_inactive;
   bool shutting_down;             /* Is the pollset shutting down ? */
   grpc_closure *shutdown_closure; /* Called after after shutdown is complete */
@@ -228,7 +281,7 @@ static grpc_fd *fd_create(int fd, const char *name) {
 
   struct epoll_event ev = {.events = (uint32_t)(EPOLLIN | EPOLLOUT | EPOLLET),
                            .data.ptr = new_fd};
-  if (epoll_ctl(g_epfd, EPOLL_CTL_ADD, fd, &ev) != 0) {
+  if (epoll_ctl(g_epoll_set.epfd, EPOLL_CTL_ADD, fd, &ev) != 0) {
     gpr_log(GPR_ERROR, "epoll_ctl failed: %s", strerror(errno));
   }
 
@@ -237,30 +290,43 @@ static grpc_fd *fd_create(int fd, const char *name) {
 
 static int fd_wrapped_fd(grpc_fd *fd) { return fd->fd; }
 
-/* Might be called multiple times */
-static void fd_shutdown(grpc_exec_ctx *exec_ctx, grpc_fd *fd, grpc_error *why) {
+/* if 'releasing_fd' is true, it means that we are going to detach the internal
+ * fd from grpc_fd structure (i.e which means we should not be calling
+ * shutdown() syscall on that fd) */
+static void fd_shutdown_internal(grpc_exec_ctx *exec_ctx, grpc_fd *fd,
+                                 grpc_error *why, bool releasing_fd) {
   if (grpc_lfev_set_shutdown(exec_ctx, &fd->read_closure,
                              GRPC_ERROR_REF(why))) {
-    shutdown(fd->fd, SHUT_RDWR);
+    if (!releasing_fd) {
+      shutdown(fd->fd, SHUT_RDWR);
+    }
     grpc_lfev_set_shutdown(exec_ctx, &fd->write_closure, GRPC_ERROR_REF(why));
   }
   GRPC_ERROR_UNREF(why);
 }
 
+/* Might be called multiple times */
+static void fd_shutdown(grpc_exec_ctx *exec_ctx, grpc_fd *fd, grpc_error *why) {
+  fd_shutdown_internal(exec_ctx, fd, why, false);
+}
+
 static void fd_orphan(grpc_exec_ctx *exec_ctx, grpc_fd *fd,
                       grpc_closure *on_done, int *release_fd,
-                      const char *reason) {
+                      bool already_closed, const char *reason) {
   grpc_error *error = GRPC_ERROR_NONE;
+  bool is_release_fd = (release_fd != NULL);
 
   if (!grpc_lfev_is_shutdown(&fd->read_closure)) {
-    fd_shutdown(exec_ctx, fd, GRPC_ERROR_CREATE_FROM_COPIED_STRING(reason));
+    fd_shutdown_internal(exec_ctx, fd,
+                         GRPC_ERROR_CREATE_FROM_COPIED_STRING(reason),
+                         is_release_fd);
   }
 
   /* If release_fd is not NULL, we should be relinquishing control of the file
      descriptor fd->fd (but we still own the grpc_fd structure). */
-  if (release_fd != NULL) {
+  if (is_release_fd) {
     *release_fd = fd->fd;
-  } else {
+  } else if (!already_closed) {
     close(fd->fd);
   }
 
@@ -313,7 +379,10 @@ static void fd_become_writable(grpc_exec_ctx *exec_ctx, grpc_fd *fd) {
 
 GPR_TLS_DECL(g_current_thread_pollset);
 GPR_TLS_DECL(g_current_thread_worker);
+
+/* The designated poller */
 static gpr_atm g_active_poller;
+
 static pollset_neighbourhood *g_neighbourhoods;
 static size_t g_num_neighbourhoods;
 
@@ -367,7 +436,8 @@ static grpc_error *pollset_global_init(void) {
   if (err != GRPC_ERROR_NONE) return err;
   struct epoll_event ev = {.events = (uint32_t)(EPOLLIN | EPOLLET),
                            .data.ptr = &global_wakeup_fd};
-  if (epoll_ctl(g_epfd, EPOLL_CTL_ADD, global_wakeup_fd.read_fd, &ev) != 0) {
+  if (epoll_ctl(g_epoll_set.epfd, EPOLL_CTL_ADD, global_wakeup_fd.read_fd,
+                &ev) != 0) {
     return GRPC_OS_ERROR(errno, "epoll_ctl");
   }
   g_num_neighbourhoods = GPR_CLAMP(gpr_cpu_num_cores(), 1, MAX_NEIGHBOURHOODS);
@@ -393,7 +463,14 @@ static void pollset_init(grpc_pollset *pollset, gpr_mu **mu) {
   gpr_mu_init(&pollset->mu);
   *mu = &pollset->mu;
   pollset->neighbourhood = &g_neighbourhoods[choose_neighbourhood()];
+  pollset->reassigning_neighbourhood = false;
+  pollset->root_worker = NULL;
+  pollset->kicked_without_poller = false;
   pollset->seen_inactive = true;
+  pollset->shutting_down = false;
+  pollset->shutdown_closure = NULL;
+  pollset->begin_refs = 0;
+  pollset->next = pollset->prev = NULL;
 }
 
 static void pollset_destroy(grpc_exec_ctx *exec_ctx, grpc_pollset *pollset) {
@@ -425,6 +502,7 @@ static void pollset_destroy(grpc_exec_ctx *exec_ctx, grpc_pollset *pollset) {
 }
 
 static grpc_error *pollset_kick_all(grpc_pollset *pollset) {
+  GPR_TIMER_BEGIN("pollset_kick_all", 0);
   grpc_error *error = GRPC_ERROR_NONE;
   if (pollset->root_worker != NULL) {
     grpc_pollset_worker *worker = pollset->root_worker;
@@ -450,7 +528,7 @@ static grpc_error *pollset_kick_all(grpc_pollset *pollset) {
   }
   // TODO: sreek.  Check if we need to set 'kicked_without_poller' to true here
   // in the else case
-
+  GPR_TIMER_END("pollset_kick_all", 0);
   return error;
 }
 
@@ -458,6 +536,7 @@ static void pollset_maybe_finish_shutdown(grpc_exec_ctx *exec_ctx,
                                           grpc_pollset *pollset) {
   if (pollset->shutdown_closure != NULL && pollset->root_worker == NULL &&
       pollset->begin_refs == 0) {
+    GPR_TIMER_MARK("pollset_finish_shutdown", 0);
     GRPC_CLOSURE_SCHED(exec_ctx, pollset->shutdown_closure, GRPC_ERROR_NONE);
     pollset->shutdown_closure = NULL;
   }
@@ -465,16 +544,16 @@ static void pollset_maybe_finish_shutdown(grpc_exec_ctx *exec_ctx,
 
 static void pollset_shutdown(grpc_exec_ctx *exec_ctx, grpc_pollset *pollset,
                              grpc_closure *closure) {
+  GPR_TIMER_BEGIN("pollset_shutdown", 0);
   GPR_ASSERT(pollset->shutdown_closure == NULL);
   GPR_ASSERT(!pollset->shutting_down);
   pollset->shutdown_closure = closure;
   pollset->shutting_down = true;
   GRPC_LOG_IF_ERROR("pollset_shutdown", pollset_kick_all(pollset));
   pollset_maybe_finish_shutdown(exec_ctx, pollset);
+  GPR_TIMER_END("pollset_shutdown", 0);
 }
 
-#define MAX_EPOLL_EVENTS 100
-
 static int poll_deadline_to_millis_timeout(gpr_timespec deadline,
                                            gpr_timespec now) {
   gpr_timespec timeout;
@@ -493,52 +572,93 @@ static int poll_deadline_to_millis_timeout(gpr_timespec deadline,
   return millis >= 1 ? millis : 1;
 }
 
-static grpc_error *pollset_epoll(grpc_exec_ctx *exec_ctx, grpc_pollset *pollset,
-                                 gpr_timespec now, gpr_timespec deadline) {
-  struct epoll_event events[MAX_EPOLL_EVENTS];
-  static const char *err_desc = "pollset_poll";
-
-  int timeout = poll_deadline_to_millis_timeout(deadline, now);
+/* Process the epoll events found by do_epoll_wait() function.
+   - g_epoll_set.cursor points to the index of the first event to be processed
+   - This function then processes up-to MAX_EPOLL_EVENTS_PER_ITERATION and
+     updates the g_epoll_set.cursor
+
+   NOTE ON SYNCRHONIZATION: Similar to do_epoll_wait(), this function is only
+   called by g_active_poller thread. So there is no need for synchronization
+   when accessing fields in g_epoll_set */
+static grpc_error *process_epoll_events(grpc_exec_ctx *exec_ctx,
+                                        grpc_pollset *pollset) {
+  static const char *err_desc = "process_events";
+  grpc_error *error = GRPC_ERROR_NONE;
 
-  if (timeout != 0) {
-    GRPC_SCHEDULING_START_BLOCKING_REGION;
-  }
-  int r;
-  do {
-    r = epoll_wait(g_epfd, events, MAX_EPOLL_EVENTS, timeout);
-  } while (r < 0 && errno == EINTR);
-  if (timeout != 0) {
-    GRPC_SCHEDULING_END_BLOCKING_REGION;
-  }
+  GPR_TIMER_BEGIN("process_epoll_events", 0);
+  long num_events = gpr_atm_acq_load(&g_epoll_set.num_events);
+  long cursor = gpr_atm_acq_load(&g_epoll_set.cursor);
+  for (int idx = 0;
+       (idx < MAX_EPOLL_EVENTS_HANDLED_PER_ITERATION) && cursor != num_events;
+       idx++) {
+    long c = cursor++;
+    struct epoll_event *ev = &g_epoll_set.events[c];
+    void *data_ptr = ev->data.ptr;
 
-  if (r < 0) return GRPC_OS_ERROR(errno, "epoll_wait");
-
-  grpc_error *error = GRPC_ERROR_NONE;
-  for (int i = 0; i < r; i++) {
-    void *data_ptr = events[i].data.ptr;
     if (data_ptr == &global_wakeup_fd) {
       append_error(&error, grpc_wakeup_fd_consume_wakeup(&global_wakeup_fd),
                    err_desc);
     } else {
       grpc_fd *fd = (grpc_fd *)(data_ptr);
-      bool cancel = (events[i].events & (EPOLLERR | EPOLLHUP)) != 0;
-      bool read_ev = (events[i].events & (EPOLLIN | EPOLLPRI)) != 0;
-      bool write_ev = (events[i].events & EPOLLOUT) != 0;
+      bool cancel = (ev->events & (EPOLLERR | EPOLLHUP)) != 0;
+      bool read_ev = (ev->events & (EPOLLIN | EPOLLPRI)) != 0;
+      bool write_ev = (ev->events & EPOLLOUT) != 0;
+
       if (read_ev || cancel) {
         fd_become_readable(exec_ctx, fd, pollset);
       }
+
       if (write_ev || cancel) {
         fd_become_writable(exec_ctx, fd);
       }
     }
   }
-
+  gpr_atm_rel_store(&g_epoll_set.cursor, cursor);
+  GPR_TIMER_END("process_epoll_events", 0);
   return error;
 }
 
+/* Do epoll_wait and store the events in g_epoll_set.events field. This does not
+   "process" any of the events yet; that is done in process_epoll_events().
+   *See process_epoll_events() function for more details.
+
+   NOTE ON SYNCHRONIZATION: At any point of time, only the g_active_poller
+   (i.e the designated poller thread) will be calling this function. So there is
+   no need for any synchronization when accesing fields in g_epoll_set */
+static grpc_error *do_epoll_wait(grpc_exec_ctx *exec_ctx, grpc_pollset *ps,
+                                 gpr_timespec now, gpr_timespec deadline) {
+  GPR_TIMER_BEGIN("do_epoll_wait", 0);
+
+  int r;
+  int timeout = poll_deadline_to_millis_timeout(deadline, now);
+  if (timeout != 0) {
+    GRPC_SCHEDULING_START_BLOCKING_REGION;
+  }
+  do {
+    r = epoll_wait(g_epoll_set.epfd, g_epoll_set.events, MAX_EPOLL_EVENTS,
+                   timeout);
+  } while (r < 0 && errno == EINTR);
+  if (timeout != 0) {
+    GRPC_SCHEDULING_END_BLOCKING_REGION;
+  }
+
+  if (r < 0) return GRPC_OS_ERROR(errno, "epoll_wait");
+
+  if (GRPC_TRACER_ON(grpc_polling_trace)) {
+    gpr_log(GPR_DEBUG, "ps: %p poll got %d events", ps, r);
+  }
+
+  gpr_atm_rel_store(&g_epoll_set.num_events, r);
+  gpr_atm_rel_store(&g_epoll_set.cursor, 0);
+
+  GPR_TIMER_END("do_epoll_wait", 0);
+  return GRPC_ERROR_NONE;
+}
+
 static bool begin_worker(grpc_pollset *pollset, grpc_pollset_worker *worker,
                          grpc_pollset_worker **worker_hdl, gpr_timespec *now,
                          gpr_timespec deadline) {
+  GPR_TIMER_BEGIN("begin_worker", 0);
   if (worker_hdl != NULL) *worker_hdl = worker;
   worker->initialized_cv = false;
   SET_KICK_STATE(worker, UNKICKED);
@@ -643,14 +763,17 @@ static bool begin_worker(grpc_pollset *pollset, grpc_pollset_worker *worker,
 
   if (pollset->kicked_without_poller) {
     pollset->kicked_without_poller = false;
+    GPR_TIMER_END("begin_worker", 0);
     return false;
   }
 
+  GPR_TIMER_END("begin_worker", 0);
   return worker->kick_state == DESIGNATED_POLLER && !pollset->shutting_down;
 }
 
 static bool check_neighbourhood_for_available_poller(
     pollset_neighbourhood *neighbourhood) {
+  GPR_TIMER_BEGIN("check_neighbourhood_for_available_poller", 0);
   bool found_worker = false;
   do {
     grpc_pollset *inspect = neighbourhood->active_root;
@@ -672,6 +795,7 @@ static bool check_neighbourhood_for_available_poller(
               }
               SET_KICK_STATE(inspect_worker, DESIGNATED_POLLER);
               if (inspect_worker->initialized_cv) {
+                GPR_TIMER_MARK("signal worker", 0);
                 gpr_cv_signal(&inspect_worker->cv);
               }
             } else {
@@ -707,12 +831,14 @@ static bool check_neighbourhood_for_available_poller(
     }
     gpr_mu_unlock(&inspect->mu);
   } while (!found_worker);
+  GPR_TIMER_END("check_neighbourhood_for_available_poller", 0);
   return found_worker;
 }
 
 static void end_worker(grpc_exec_ctx *exec_ctx, grpc_pollset *pollset,
                        grpc_pollset_worker *worker,
                        grpc_pollset_worker **worker_hdl) {
+  GPR_TIMER_BEGIN("end_worker", 0);
   if (GRPC_TRACER_ON(grpc_polling_trace)) {
     gpr_log(GPR_DEBUG, "PS:%p END_WORKER:%p", pollset, worker);
   }
@@ -782,42 +908,71 @@ static void end_worker(grpc_exec_ctx *exec_ctx, grpc_pollset *pollset,
     pollset_maybe_finish_shutdown(exec_ctx, pollset);
   }
   GPR_ASSERT(gpr_atm_no_barrier_load(&g_active_poller) != (gpr_atm)worker);
+  GPR_TIMER_END("end_worker", 0);
 }
 
 /* pollset->po.mu lock must be held by the caller before calling this.
    The function pollset_work() may temporarily release the lock (pollset->po.mu)
    during the course of its execution but it will always re-acquire the lock and
    ensure that it is held by the time the function returns */
-static grpc_error *pollset_work(grpc_exec_ctx *exec_ctx, grpc_pollset *pollset,
+static grpc_error *pollset_work(grpc_exec_ctx *exec_ctx, grpc_pollset *ps,
                                 grpc_pollset_worker **worker_hdl,
                                 gpr_timespec now, gpr_timespec deadline) {
   grpc_pollset_worker worker;
   grpc_error *error = GRPC_ERROR_NONE;
   static const char *err_desc = "pollset_work";
-  if (pollset->kicked_without_poller) {
-    pollset->kicked_without_poller = false;
+  GPR_TIMER_BEGIN("pollset_work", 0);
+  if (ps->kicked_without_poller) {
+    ps->kicked_without_poller = false;
+    GPR_TIMER_END("pollset_work", 0);
     return GRPC_ERROR_NONE;
   }
-  if (begin_worker(pollset, &worker, worker_hdl, &now, deadline)) {
-    gpr_tls_set(&g_current_thread_pollset, (intptr_t)pollset);
+
+  if (begin_worker(ps, &worker, worker_hdl, &now, deadline)) {
+    gpr_tls_set(&g_current_thread_pollset, (intptr_t)ps);
     gpr_tls_set(&g_current_thread_worker, (intptr_t)&worker);
-    GPR_ASSERT(!pollset->shutting_down);
-    GPR_ASSERT(!pollset->seen_inactive);
-    gpr_mu_unlock(&pollset->mu);
-    append_error(&error, pollset_epoll(exec_ctx, pollset, now, deadline),
-                 err_desc);
-    gpr_mu_lock(&pollset->mu);
+    GPR_ASSERT(!ps->shutting_down);
+    GPR_ASSERT(!ps->seen_inactive);
+
+    gpr_mu_unlock(&ps->mu); /* unlock */
+    /* This is the designated polling thread at this point and should ideally do
+       polling. However, if there are unprocessed events left from a previous
+       call to do_epoll_wait(), skip calling epoll_wait() in this iteration and
+       process the pending epoll events.
+
+       The reason for decoupling do_epoll_wait and process_epoll_events is to
+       better distrubute the work (i.e handling epoll events) across multiple
+       threads
+
+       process_epoll_events() returns very quickly: It just queues the work on
+       exec_ctx but does not execute it (the actual exectution or more
+       accurately grpc_exec_ctx_flush() happens in end_worker() AFTER selecting
+       a designated poller). So we are not waiting long periods without a
+       designated poller */
+    if (gpr_atm_acq_load(&g_epoll_set.cursor) ==
+        gpr_atm_acq_load(&g_epoll_set.num_events)) {
+      append_error(&error, do_epoll_wait(exec_ctx, ps, now, deadline),
+                   err_desc);
+    }
+    append_error(&error, process_epoll_events(exec_ctx, ps), err_desc);
+
+    gpr_mu_lock(&ps->mu); /* lock */
+
     gpr_tls_set(&g_current_thread_worker, 0);
   } else {
-    gpr_tls_set(&g_current_thread_pollset, (intptr_t)pollset);
+    gpr_tls_set(&g_current_thread_pollset, (intptr_t)ps);
   }
-  end_worker(exec_ctx, pollset, &worker, worker_hdl);
+  end_worker(exec_ctx, ps, &worker, worker_hdl);
+
   gpr_tls_set(&g_current_thread_pollset, 0);
+  GPR_TIMER_END("pollset_work", 0);
   return error;
 }
 
 static grpc_error *pollset_kick(grpc_pollset *pollset,
                                 grpc_pollset_worker *specific_worker) {
+  GPR_TIMER_BEGIN("pollset_kick", 0);
+  grpc_error *ret_err = GRPC_ERROR_NONE;
   if (GRPC_TRACER_ON(grpc_polling_trace)) {
     gpr_strvec log;
     gpr_strvec_init(&log);
@@ -852,7 +1007,7 @@ static grpc_error *pollset_kick(grpc_pollset *pollset,
         if (GRPC_TRACER_ON(grpc_polling_trace)) {
           gpr_log(GPR_ERROR, " .. kicked_without_poller");
         }
-        return GRPC_ERROR_NONE;
+        goto done;
       }
       grpc_pollset_worker *next_worker = root_worker->next;
       if (root_worker->kick_state == KICKED) {
@@ -860,13 +1015,13 @@ static grpc_error *pollset_kick(grpc_pollset *pollset,
           gpr_log(GPR_ERROR, " .. already kicked %p", root_worker);
         }
         SET_KICK_STATE(root_worker, KICKED);
-        return GRPC_ERROR_NONE;
+        goto done;
       } else if (next_worker->kick_state == KICKED) {
         if (GRPC_TRACER_ON(grpc_polling_trace)) {
           gpr_log(GPR_ERROR, " .. already kicked %p", next_worker);
         }
         SET_KICK_STATE(next_worker, KICKED);
-        return GRPC_ERROR_NONE;
+        goto done;
       } else if (root_worker ==
                      next_worker &&  // only try and wake up a poller if
                                      // there is no next worker
@@ -876,7 +1031,8 @@ static grpc_error *pollset_kick(grpc_pollset *pollset,
           gpr_log(GPR_ERROR, " .. kicked %p", root_worker);
         }
         SET_KICK_STATE(root_worker, KICKED);
-        return grpc_wakeup_fd_wakeup(&global_wakeup_fd);
+        ret_err = grpc_wakeup_fd_wakeup(&global_wakeup_fd);
+        goto done;
       } else if (next_worker->kick_state == UNKICKED) {
         if (GRPC_TRACER_ON(grpc_polling_trace)) {
           gpr_log(GPR_ERROR, " .. kicked %p", next_worker);
@@ -884,7 +1040,7 @@ static grpc_error *pollset_kick(grpc_pollset *pollset,
         GPR_ASSERT(next_worker->initialized_cv);
         SET_KICK_STATE(next_worker, KICKED);
         gpr_cv_signal(&next_worker->cv);
-        return GRPC_ERROR_NONE;
+        goto done;
       } else if (next_worker->kick_state == DESIGNATED_POLLER) {
         if (root_worker->kick_state != DESIGNATED_POLLER) {
           if (GRPC_TRACER_ON(grpc_polling_trace)) {
@@ -897,59 +1053,64 @@ static grpc_error *pollset_kick(grpc_pollset *pollset,
           if (root_worker->initialized_cv) {
             gpr_cv_signal(&root_worker->cv);
           }
-          return GRPC_ERROR_NONE;
+          goto done;
         } else {
           if (GRPC_TRACER_ON(grpc_polling_trace)) {
             gpr_log(GPR_ERROR, " .. non-root poller %p (root=%p)", next_worker,
                     root_worker);
           }
           SET_KICK_STATE(next_worker, KICKED);
-          return grpc_wakeup_fd_wakeup(&global_wakeup_fd);
+          ret_err = grpc_wakeup_fd_wakeup(&global_wakeup_fd);
+          goto done;
         }
       } else {
         GPR_ASSERT(next_worker->kick_state == KICKED);
         SET_KICK_STATE(next_worker, KICKED);
-        return GRPC_ERROR_NONE;
+        goto done;
       }
     } else {
       if (GRPC_TRACER_ON(grpc_polling_trace)) {
         gpr_log(GPR_ERROR, " .. kicked while waking up");
       }
-      return GRPC_ERROR_NONE;
+      goto done;
     }
   } else if (specific_worker->kick_state == KICKED) {
     if (GRPC_TRACER_ON(grpc_polling_trace)) {
       gpr_log(GPR_ERROR, " .. specific worker already kicked");
     }
-    return GRPC_ERROR_NONE;
+    goto done;
   } else if (gpr_tls_get(&g_current_thread_worker) ==
              (intptr_t)specific_worker) {
     if (GRPC_TRACER_ON(grpc_polling_trace)) {
       gpr_log(GPR_ERROR, " .. mark %p kicked", specific_worker);
     }
     SET_KICK_STATE(specific_worker, KICKED);
-    return GRPC_ERROR_NONE;
+    goto done;
   } else if (specific_worker ==
              (grpc_pollset_worker *)gpr_atm_no_barrier_load(&g_active_poller)) {
     if (GRPC_TRACER_ON(grpc_polling_trace)) {
       gpr_log(GPR_ERROR, " .. kick active poller");
     }
     SET_KICK_STATE(specific_worker, KICKED);
-    return grpc_wakeup_fd_wakeup(&global_wakeup_fd);
+    ret_err = grpc_wakeup_fd_wakeup(&global_wakeup_fd);
+    goto done;
   } else if (specific_worker->initialized_cv) {
     if (GRPC_TRACER_ON(grpc_polling_trace)) {
       gpr_log(GPR_ERROR, " .. kick waiting worker");
     }
     SET_KICK_STATE(specific_worker, KICKED);
     gpr_cv_signal(&specific_worker->cv);
-    return GRPC_ERROR_NONE;
+    goto done;
   } else {
     if (GRPC_TRACER_ON(grpc_polling_trace)) {
       gpr_log(GPR_ERROR, " .. kick non-waiting worker");
     }
     SET_KICK_STATE(specific_worker, KICKED);
-    return GRPC_ERROR_NONE;
+    goto done;
   }
+done:
+  GPR_TIMER_END("pollset_kick", 0);
+  return ret_err;
 }
 
 static void pollset_add_fd(grpc_exec_ctx *exec_ctx, grpc_pollset *pollset,
@@ -993,7 +1154,7 @@ static void pollset_set_del_pollset_set(grpc_exec_ctx *exec_ctx,
 static void shutdown_engine(void) {
   fd_global_shutdown();
   pollset_global_shutdown();
-  close(g_epfd);
+  epoll_set_shutdown();
 }
 
 static const grpc_event_engine_vtable vtable = {
@@ -1028,28 +1189,29 @@ static const grpc_event_engine_vtable vtable = {
 };
 
 /* It is possible that GLIBC has epoll but the underlying kernel doesn't.
- * Create a dummy epoll_fd to make sure epoll support is available */
+ * Create epoll_fd (epoll_set_init() takes care of that) to make sure epoll
+ * support is available */
 const grpc_event_engine_vtable *grpc_init_epoll1_linux(bool explicit_request) {
+  if (!explicit_request) {
+    return NULL;
+  }
+
   if (!grpc_has_wakeup_fd()) {
     return NULL;
   }
 
-  g_epfd = epoll_create1(EPOLL_CLOEXEC);
-  if (g_epfd < 0) {
-    gpr_log(GPR_ERROR, "epoll unavailable");
+  if (!epoll_set_init()) {
     return NULL;
   }
 
   fd_global_init();
 
   if (!GRPC_LOG_IF_ERROR("pollset_global_init", pollset_global_init())) {
-    close(g_epfd);
     fd_global_shutdown();
+    epoll_set_shutdown();
     return NULL;
   }
 
-  gpr_log(GPR_ERROR, "grpc epoll fd: %d", g_epfd);
-
   return &vtable;
 }
 
diff --git a/src/core/lib/iomgr/ev_epoll_limited_pollers_linux.c b/src/core/lib/iomgr/ev_epoll_limited_pollers_linux.c
index 5166dc2ac2..f2f3e15704 100644
--- a/src/core/lib/iomgr/ev_epoll_limited_pollers_linux.c
+++ b/src/core/lib/iomgr/ev_epoll_limited_pollers_linux.c
@@ -931,7 +931,7 @@ static int fd_wrapped_fd(grpc_fd *fd) {
 
 static void fd_orphan(grpc_exec_ctx *exec_ctx, grpc_fd *fd,
                       grpc_closure *on_done, int *release_fd,
-                      const char *reason) {
+                      bool already_closed, const char *reason) {
   grpc_error *error = GRPC_ERROR_NONE;
   polling_island *unref_pi = NULL;
 
@@ -952,8 +952,7 @@ static void fd_orphan(grpc_exec_ctx *exec_ctx, grpc_fd *fd,
        before doing this.) */
   if (fd->po.pi != NULL) {
     polling_island *pi_latest = polling_island_lock(fd->po.pi);
-    polling_island_remove_fd_locked(pi_latest, fd, false /* is_fd_closed */,
-                                    &error);
+    polling_island_remove_fd_locked(pi_latest, fd, already_closed, &error);
     gpr_mu_unlock(&pi_latest->mu);
 
     unref_pi = fd->po.pi;
diff --git a/src/core/lib/iomgr/ev_epoll_thread_pool_linux.c b/src/core/lib/iomgr/ev_epoll_thread_pool_linux.c
index 1058f69a83..07c8eadf4f 100644
--- a/src/core/lib/iomgr/ev_epoll_thread_pool_linux.c
+++ b/src/core/lib/iomgr/ev_epoll_thread_pool_linux.c
@@ -493,8 +493,8 @@ static int fd_wrapped_fd(grpc_fd *fd) {
 
 static void fd_orphan(grpc_exec_ctx *exec_ctx, grpc_fd *fd,
                       grpc_closure *on_done, int *release_fd,
-                      const char *reason) {
-  bool is_fd_closed = false;
+                      bool already_closed, const char *reason) {
+  bool is_fd_closed = already_closed;
   grpc_error *error = GRPC_ERROR_NONE;
   epoll_set *unref_eps = NULL;
 
@@ -505,7 +505,7 @@ static void fd_orphan(grpc_exec_ctx *exec_ctx, grpc_fd *fd,
      descriptor fd->fd (but we still own the grpc_fd structure). */
   if (release_fd != NULL) {
     *release_fd = fd->fd;
-  } else {
+  } else if (!is_fd_closed) {
     close(fd->fd);
     is_fd_closed = true;
   }
diff --git a/src/core/lib/iomgr/ev_epollex_linux.c b/src/core/lib/iomgr/ev_epollex_linux.c
index a2fa4ad9a5..1f4adea5d4 100644
--- a/src/core/lib/iomgr/ev_epollex_linux.c
+++ b/src/core/lib/iomgr/ev_epollex_linux.c
@@ -49,7 +49,7 @@
 #include "src/core/lib/support/spinlock.h"
 
 /*******************************************************************************
- * Pollset-set sibling link
+ * Polling object
  */
 
 typedef enum {
@@ -380,8 +380,8 @@ static int fd_wrapped_fd(grpc_fd *fd) {
 
 static void fd_orphan(grpc_exec_ctx *exec_ctx, grpc_fd *fd,
                       grpc_closure *on_done, int *release_fd,
-                      const char *reason) {
-  bool is_fd_closed = false;
+                      bool already_closed, const char *reason) {
+  bool is_fd_closed = already_closed;
   grpc_error *error = GRPC_ERROR_NONE;
 
   gpr_mu_lock(&fd->pollable.po.mu);
@@ -392,7 +392,7 @@ static void fd_orphan(grpc_exec_ctx *exec_ctx, grpc_fd *fd,
      descriptor fd->fd (but we still own the grpc_fd structure). */
   if (release_fd != NULL) {
     *release_fd = fd->fd;
-  } else {
+  } else if (!is_fd_closed) {
     close(fd->fd);
     is_fd_closed = true;
   }
diff --git a/src/core/lib/iomgr/ev_epollsig_linux.c b/src/core/lib/iomgr/ev_epollsig_linux.c
index a84c208e1a..070d75e42a 100644
--- a/src/core/lib/iomgr/ev_epollsig_linux.c
+++ b/src/core/lib/iomgr/ev_epollsig_linux.c
@@ -854,7 +854,7 @@ static int fd_wrapped_fd(grpc_fd *fd) {
 
 static void fd_orphan(grpc_exec_ctx *exec_ctx, grpc_fd *fd,
                       grpc_closure *on_done, int *release_fd,
-                      const char *reason) {
+                      bool already_closed, const char *reason) {
   grpc_error *error = GRPC_ERROR_NONE;
   polling_island *unref_pi = NULL;
 
@@ -875,8 +875,7 @@ static void fd_orphan(grpc_exec_ctx *exec_ctx, grpc_fd *fd,
        before doing this.) */
   if (fd->po.pi != NULL) {
     polling_island *pi_latest = polling_island_lock(fd->po.pi);
-    polling_island_remove_fd_locked(pi_latest, fd, false /* is_fd_closed */,
-                                    &error);
+    polling_island_remove_fd_locked(pi_latest, fd, already_closed, &error);
     gpr_mu_unlock(&pi_latest->mu);
 
     unref_pi = fd->po.pi;
@@ -1731,7 +1730,7 @@ const grpc_event_engine_vtable *grpc_init_epollsig_linux(
   if (!is_grpc_wakeup_signal_initialized) {
     /* TODO(ctiller): when other epoll engines are ready, remove the true || to
      * force this to be explitly chosen if needed */
-    if (explicit_request) {
+    if (true || explicit_request) {
       grpc_use_signal(SIGRTMIN + 6);
     } else {
       return NULL;
diff --git a/src/core/lib/iomgr/ev_poll_posix.c b/src/core/lib/iomgr/ev_poll_posix.c
index 593d53e4eb..266c280c48 100644
--- a/src/core/lib/iomgr/ev_poll_posix.c
+++ b/src/core/lib/iomgr/ev_poll_posix.c
@@ -42,6 +42,7 @@
 #include "src/core/lib/iomgr/wakeup_fd_posix.h"
 #include "src/core/lib/profiling/timers.h"
 #include "src/core/lib/support/block_annotate.h"
+#include "src/core/lib/support/murmur_hash.h"
 
 #define GRPC_POLLSET_KICK_BROADCAST ((grpc_pollset_worker *)1)
 
@@ -239,22 +240,43 @@ struct grpc_pollset_set {
  * condition variable polling definitions
  */
 
+#define POLLCV_THREAD_GRACE_MS 1000
 #define CV_POLL_PERIOD_MS 1000
 #define CV_DEFAULT_TABLE_SIZE 16
 
-typedef enum poll_status_t { INPROGRESS, COMPLETED, CANCELLED } poll_status_t;
-
-typedef struct poll_args {
+typedef struct poll_result {
   gpr_refcount refcount;
-  gpr_cv *cv;
+  cv_node *watchers;
+  int watchcount;
   struct pollfd *fds;
   nfds_t nfds;
-  int timeout;
   int retval;
   int err;
-  gpr_atm status;
+  int completed;
+} poll_result;
+
+typedef struct poll_args {
+  gpr_cv trigger;
+  int trigger_set;
+  struct pollfd *fds;
+  nfds_t nfds;
+  poll_result *result;
+  struct poll_args *next;
+  struct poll_args *prev;
 } poll_args;
 
+// This is a 2-tiered cache, we mantain a hash table
+// of active poll calls, so we can wait on the result
+// of that call.  We also maintain a freelist of inactive
+// poll threads.
+typedef struct poll_hash_table {
+  poll_args *free_pollers;
+  poll_args **active_pollers;
+  unsigned int size;
+  unsigned int count;
+} poll_hash_table;
+
+poll_hash_table poll_cache;
 cv_fd_table g_cvfds;
 
 /*******************************************************************************
@@ -398,11 +420,14 @@ static int fd_wrapped_fd(grpc_fd *fd) {
 
 static void fd_orphan(grpc_exec_ctx *exec_ctx, grpc_fd *fd,
                       grpc_closure *on_done, int *release_fd,
-                      const char *reason) {
+                      bool already_closed, const char *reason) {
   fd->on_done_closure = on_done;
   fd->released = release_fd != NULL;
-  if (fd->released) {
+  if (release_fd != NULL) {
     *release_fd = fd->fd;
+    fd->released = true;
+  } else if (already_closed) {
+    fd->released = true;
   }
   gpr_mu_lock(&fd->mu);
   REF_BY(fd, 1, reason); /* remove active status, but keep referenced */
@@ -1284,43 +1309,205 @@ static void pollset_set_del_fd(grpc_exec_ctx *exec_ctx,
  * Condition Variable polling extensions
  */
 
-static void decref_poll_args(poll_args *args) {
-  if (gpr_unref(&args->refcount)) {
-    gpr_free(args->fds);
-    gpr_cv_destroy(args->cv);
-    gpr_free(args->cv);
-    gpr_free(args);
+static void run_poll(void *args);
+static void cache_poller_locked(poll_args *args);
+
+static void cache_insert_locked(poll_args *args) {
+  uint32_t key = gpr_murmur_hash3(args->fds, args->nfds * sizeof(struct pollfd),
+                                  0xDEADBEEF);
+  key = key % poll_cache.size;
+  if (poll_cache.active_pollers[key]) {
+    poll_cache.active_pollers[key]->prev = args;
   }
+  args->next = poll_cache.active_pollers[key];
+  args->prev = NULL;
+  poll_cache.active_pollers[key] = args;
+  poll_cache.count++;
 }
 
-// Poll in a background thread
-static void run_poll(void *arg) {
-  int timeout, retval;
-  poll_args *pargs = (poll_args *)arg;
-  while (gpr_atm_no_barrier_load(&pargs->status) == INPROGRESS) {
-    if (pargs->timeout < 0) {
-      timeout = CV_POLL_PERIOD_MS;
-    } else {
-      timeout = GPR_MIN(CV_POLL_PERIOD_MS, pargs->timeout);
-      pargs->timeout -= timeout;
+static void init_result(poll_args *pargs) {
+  pargs->result = gpr_malloc(sizeof(poll_result));
+  gpr_ref_init(&pargs->result->refcount, 1);
+  pargs->result->watchers = NULL;
+  pargs->result->watchcount = 0;
+  pargs->result->fds = gpr_malloc(sizeof(struct pollfd) * pargs->nfds);
+  memcpy(pargs->result->fds, pargs->fds, sizeof(struct pollfd) * pargs->nfds);
+  pargs->result->nfds = pargs->nfds;
+  pargs->result->retval = 0;
+  pargs->result->err = 0;
+  pargs->result->completed = 0;
+}
+
+// Creates a poll_args object for a given arguments to poll().
+// This object may return a poll_args in the cache.
+static poll_args *get_poller_locked(struct pollfd *fds, nfds_t count) {
+  uint32_t key =
+      gpr_murmur_hash3(fds, count * sizeof(struct pollfd), 0xDEADBEEF);
+  key = key % poll_cache.size;
+  poll_args *curr = poll_cache.active_pollers[key];
+  while (curr) {
+    if (curr->nfds == count &&
+        memcmp(curr->fds, fds, count * sizeof(struct pollfd)) == 0) {
+      gpr_free(fds);
+      return curr;
     }
-    retval = g_cvfds.poll(pargs->fds, pargs->nfds, timeout);
-    if (retval != 0 || pargs->timeout == 0) {
-      pargs->retval = retval;
-      pargs->err = errno;
-      break;
+    curr = curr->next;
+  }
+
+  if (poll_cache.free_pollers) {
+    poll_args *pargs = poll_cache.free_pollers;
+    poll_cache.free_pollers = pargs->next;
+    if (poll_cache.free_pollers) {
+      poll_cache.free_pollers->prev = NULL;
     }
+    pargs->fds = fds;
+    pargs->nfds = count;
+    pargs->next = NULL;
+    pargs->prev = NULL;
+    init_result(pargs);
+    cache_poller_locked(pargs);
+    return pargs;
+  }
+
+  poll_args *pargs = gpr_malloc(sizeof(struct poll_args));
+  gpr_cv_init(&pargs->trigger);
+  pargs->fds = fds;
+  pargs->nfds = count;
+  pargs->next = NULL;
+  pargs->prev = NULL;
+  pargs->trigger_set = 0;
+  init_result(pargs);
+  cache_poller_locked(pargs);
+  gpr_thd_id t_id;
+  gpr_thd_options opt = gpr_thd_options_default();
+  gpr_ref(&g_cvfds.pollcount);
+  gpr_thd_options_set_detached(&opt);
+  GPR_ASSERT(gpr_thd_new(&t_id, &run_poll, pargs, &opt));
+  return pargs;
+}
+
+static void cache_delete_locked(poll_args *args) {
+  if (!args->prev) {
+    uint32_t key = gpr_murmur_hash3(
+        args->fds, args->nfds * sizeof(struct pollfd), 0xDEADBEEF);
+    key = key % poll_cache.size;
+    GPR_ASSERT(poll_cache.active_pollers[key] == args);
+    poll_cache.active_pollers[key] = args->next;
+  } else {
+    args->prev->next = args->next;
   }
-  gpr_mu_lock(&g_cvfds.mu);
-  if (gpr_atm_no_barrier_load(&pargs->status) == INPROGRESS) {
-    // Signal main thread that the poll completed
-    gpr_atm_no_barrier_store(&pargs->status, COMPLETED);
-    gpr_cv_signal(pargs->cv);
+
+  if (args->next) {
+    args->next->prev = args->prev;
   }
-  decref_poll_args(pargs);
-  g_cvfds.pollcount--;
-  if (g_cvfds.shutdown && g_cvfds.pollcount == 0) {
-    gpr_cv_signal(&g_cvfds.shutdown_complete);
+
+  poll_cache.count--;
+  if (poll_cache.free_pollers) {
+    poll_cache.free_pollers->prev = args;
+  }
+  args->prev = NULL;
+  args->next = poll_cache.free_pollers;
+  gpr_free(args->fds);
+  poll_cache.free_pollers = args;
+}
+
+static void cache_poller_locked(poll_args *args) {
+  if (poll_cache.count + 1 > poll_cache.size / 2) {
+    poll_args **old_active_pollers = poll_cache.active_pollers;
+    poll_cache.size = poll_cache.size * 2;
+    poll_cache.count = 0;
+    poll_cache.active_pollers = gpr_malloc(sizeof(void *) * poll_cache.size);
+    for (unsigned int i = 0; i < poll_cache.size; i++) {
+      poll_cache.active_pollers[i] = NULL;
+    }
+    for (unsigned int i = 0; i < poll_cache.size / 2; i++) {
+      poll_args *curr = old_active_pollers[i];
+      poll_args *next = NULL;
+      while (curr) {
+        next = curr->next;
+        cache_insert_locked(curr);
+        curr = next;
+      }
+    }
+    gpr_free(old_active_pollers);
+  }
+
+  cache_insert_locked(args);
+}
+
+static void cache_destroy_locked(poll_args *args) {
+  if (args->next) {
+    args->next->prev = args->prev;
+  }
+
+  if (args->prev) {
+    args->prev->next = args->next;
+  } else {
+    poll_cache.free_pollers = args->next;
+  }
+
+  gpr_free(args);
+}
+
+static void decref_poll_result(poll_result *res) {
+  if (gpr_unref(&res->refcount)) {
+    GPR_ASSERT(!res->watchers);
+    gpr_free(res->fds);
+    gpr_free(res);
+  }
+}
+
+void remove_cvn(cv_node **head, cv_node *target) {
+  if (target->next) {
+    target->next->prev = target->prev;
+  }
+
+  if (target->prev) {
+    target->prev->next = target->next;
+  } else {
+    *head = target->next;
+  }
+}
+
+gpr_timespec thread_grace;
+
+// Poll in a background thread
+static void run_poll(void *args) {
+  poll_args *pargs = (poll_args *)args;
+  while (1) {
+    poll_result *result = pargs->result;
+    int retval = g_cvfds.poll(result->fds, result->nfds, CV_POLL_PERIOD_MS);
+    gpr_mu_lock(&g_cvfds.mu);
+    if (retval != 0) {
+      result->completed = 1;
+      result->retval = retval;
+      result->err = errno;
+      cv_node *watcher = result->watchers;
+      while (watcher) {
+        gpr_cv_signal(watcher->cv);
+        watcher = watcher->next;
+      }
+    }
+    if (result->watchcount == 0 || result->completed) {
+      cache_delete_locked(pargs);
+      decref_poll_result(result);
+      // Leave this polling thread alive for a grace period to do another poll()
+      // op
+      gpr_timespec deadline = gpr_now(GPR_CLOCK_REALTIME);
+      deadline = gpr_time_add(deadline, thread_grace);
+      pargs->trigger_set = 0;
+      gpr_cv_wait(&pargs->trigger, &g_cvfds.mu, deadline);
+      if (!pargs->trigger_set) {
+        cache_destroy_locked(pargs);
+        break;
+      }
+    }
+    gpr_mu_unlock(&g_cvfds.mu);
+  }
+
+  // We still have the lock here
+  if (gpr_unref(&g_cvfds.pollcount)) {
+    gpr_cv_signal(&g_cvfds.shutdown_cv);
   }
   gpr_mu_unlock(&g_cvfds.mu);
 }
@@ -1329,24 +1516,29 @@ static void run_poll(void *arg) {
 static int cvfd_poll(struct pollfd *fds, nfds_t nfds, int timeout) {
   unsigned int i;
   int res, idx;
-  gpr_cv *pollcv;
-  cv_node *cvn, *prev;
+  cv_node *pollcv;
   int skip_poll = 0;
   nfds_t nsockfds = 0;
-  gpr_thd_id t_id;
-  gpr_thd_options opt;
-  poll_args *pargs = NULL;
+  poll_result *result = NULL;
   gpr_mu_lock(&g_cvfds.mu);
-  pollcv = gpr_malloc(sizeof(gpr_cv));
-  gpr_cv_init(pollcv);
+  pollcv = gpr_malloc(sizeof(cv_node));
+  pollcv->next = NULL;
+  gpr_cv pollcv_cv;
+  gpr_cv_init(&pollcv_cv);
+  pollcv->cv = &pollcv_cv;
+  cv_node *fd_cvs = gpr_malloc(nfds * sizeof(cv_node));
+
   for (i = 0; i < nfds; i++) {
     fds[i].revents = 0;
     if (fds[i].fd < 0 && (fds[i].events & POLLIN)) {
       idx = FD_TO_IDX(fds[i].fd);
-      cvn = gpr_malloc(sizeof(cv_node));
-      cvn->cv = pollcv;
-      cvn->next = g_cvfds.cvfds[idx].cvs;
-      g_cvfds.cvfds[idx].cvs = cvn;
+      fd_cvs[i].cv = &pollcv_cv;
+      fd_cvs[i].prev = NULL;
+      fd_cvs[i].next = g_cvfds.cvfds[idx].cvs;
+      if (g_cvfds.cvfds[idx].cvs) {
+        g_cvfds.cvfds[idx].cvs->prev = &(fd_cvs[i]);
+      }
+      g_cvfds.cvfds[idx].cvs = &(fd_cvs[i]);
       // Don't bother polling if a wakeup fd is ready
       if (g_cvfds.cvfds[idx].is_set) {
         skip_poll = 1;
@@ -1356,81 +1548,68 @@ static int cvfd_poll(struct pollfd *fds, nfds_t nfds, int timeout) {
     }
   }
 
+  gpr_timespec deadline = gpr_now(GPR_CLOCK_REALTIME);
+  if (timeout < 0) {
+    deadline = gpr_inf_future(GPR_CLOCK_REALTIME);
+  } else {
+    deadline =
+        gpr_time_add(deadline, gpr_time_from_millis(timeout, GPR_TIMESPAN));
+  }
+
   res = 0;
   if (!skip_poll && nsockfds > 0) {
-    pargs = gpr_malloc(sizeof(struct poll_args));
-    // Both the main thread and calling thread get a reference
-    gpr_ref_init(&pargs->refcount, 2);
-    pargs->cv = pollcv;
-    pargs->fds = gpr_malloc(sizeof(struct pollfd) * nsockfds);
-    pargs->nfds = nsockfds;
-    pargs->timeout = timeout;
-    pargs->retval = 0;
-    pargs->err = 0;
-    gpr_atm_no_barrier_store(&pargs->status, INPROGRESS);
+    struct pollfd *pollfds = gpr_malloc(sizeof(struct pollfd) * nsockfds);
     idx = 0;
     for (i = 0; i < nfds; i++) {
       if (fds[i].fd >= 0) {
-        pargs->fds[idx].fd = fds[i].fd;
-        pargs->fds[idx].events = fds[i].events;
-        pargs->fds[idx].revents = 0;
+        pollfds[idx].fd = fds[i].fd;
+        pollfds[idx].events = fds[i].events;
+        pollfds[idx].revents = 0;
         idx++;
       }
     }
-    g_cvfds.pollcount++;
-    opt = gpr_thd_options_default();
-    gpr_thd_options_set_detached(&opt);
-    GPR_ASSERT(gpr_thd_new(&t_id, &run_poll, pargs, &opt));
-    // We want the poll() thread to trigger the deadline, so wait forever here
-    gpr_cv_wait(pollcv, &g_cvfds.mu, gpr_inf_future(GPR_CLOCK_MONOTONIC));
-    if (gpr_atm_no_barrier_load(&pargs->status) == COMPLETED) {
-      res = pargs->retval;
-      errno = pargs->err;
-    } else {
-      errno = 0;
-      gpr_atm_no_barrier_store(&pargs->status, CANCELLED);
+    poll_args *pargs = get_poller_locked(pollfds, nsockfds);
+    result = pargs->result;
+    pollcv->next = result->watchers;
+    pollcv->prev = NULL;
+    if (result->watchers) {
+      result->watchers->prev = pollcv;
     }
+    result->watchers = pollcv;
+    result->watchcount++;
+    gpr_ref(&result->refcount);
+
+    pargs->trigger_set = 1;
+    gpr_cv_signal(&pargs->trigger);
+    gpr_cv_wait(&pollcv_cv, &g_cvfds.mu, deadline);
+    res = result->retval;
+    errno = result->err;
+    result->watchcount--;
+    remove_cvn(&result->watchers, pollcv);
   } else if (!skip_poll) {
-    gpr_timespec deadline = gpr_now(GPR_CLOCK_REALTIME);
-    deadline =
-        gpr_time_add(deadline, gpr_time_from_millis(timeout, GPR_TIMESPAN));
-    gpr_cv_wait(pollcv, &g_cvfds.mu, deadline);
+    gpr_cv_wait(&pollcv_cv, &g_cvfds.mu, deadline);
   }
 
   idx = 0;
   for (i = 0; i < nfds; i++) {
     if (fds[i].fd < 0 && (fds[i].events & POLLIN)) {
-      cvn = g_cvfds.cvfds[FD_TO_IDX(fds[i].fd)].cvs;
-      prev = NULL;
-      while (cvn->cv != pollcv) {
-        prev = cvn;
-        cvn = cvn->next;
-        GPR_ASSERT(cvn);
-      }
-      if (!prev) {
-        g_cvfds.cvfds[FD_TO_IDX(fds[i].fd)].cvs = cvn->next;
-      } else {
-        prev->next = cvn->next;
-      }
-      gpr_free(cvn);
-
+      remove_cvn(&g_cvfds.cvfds[FD_TO_IDX(fds[i].fd)].cvs, &(fd_cvs[i]));
       if (g_cvfds.cvfds[FD_TO_IDX(fds[i].fd)].is_set) {
         fds[i].revents = POLLIN;
         if (res >= 0) res++;
       }
-    } else if (!skip_poll && fds[i].fd >= 0 &&
-               gpr_atm_no_barrier_load(&pargs->status) == COMPLETED) {
-      fds[i].revents = pargs->fds[idx].revents;
+    } else if (!skip_poll && fds[i].fd >= 0 && result->completed) {
+      fds[i].revents = result->fds[idx].revents;
       idx++;
     }
   }
 
-  if (pargs) {
-    decref_poll_args(pargs);
-  } else {
-    gpr_cv_destroy(pollcv);
-    gpr_free(pollcv);
+  gpr_free(fd_cvs);
+  gpr_free(pollcv);
+  if (result) {
+    decref_poll_result(result);
   }
+
   gpr_mu_unlock(&g_cvfds.mu);
 
   return res;
@@ -1439,12 +1618,12 @@ static int cvfd_poll(struct pollfd *fds, nfds_t nfds, int timeout) {
 static void global_cv_fd_table_init() {
   gpr_mu_init(&g_cvfds.mu);
   gpr_mu_lock(&g_cvfds.mu);
-  gpr_cv_init(&g_cvfds.shutdown_complete);
-  g_cvfds.shutdown = 0;
-  g_cvfds.pollcount = 0;
+  gpr_cv_init(&g_cvfds.shutdown_cv);
+  gpr_ref_init(&g_cvfds.pollcount, 1);
   g_cvfds.size = CV_DEFAULT_TABLE_SIZE;
   g_cvfds.cvfds = gpr_malloc(sizeof(fd_node) * CV_DEFAULT_TABLE_SIZE);
   g_cvfds.free_fds = NULL;
+  thread_grace = gpr_time_from_millis(POLLCV_THREAD_GRACE_MS, GPR_TIMESPAN);
   for (int i = 0; i < CV_DEFAULT_TABLE_SIZE; i++) {
     g_cvfds.cvfds[i].is_set = 0;
     g_cvfds.cvfds[i].cvs = NULL;
@@ -1454,23 +1633,35 @@ static void global_cv_fd_table_init() {
   // Override the poll function with one that supports cvfds
   g_cvfds.poll = grpc_poll_function;
   grpc_poll_function = &cvfd_poll;
+
+  // Initialize the cache
+  poll_cache.size = 32;
+  poll_cache.count = 0;
+  poll_cache.free_pollers = NULL;
+  poll_cache.active_pollers = gpr_malloc(sizeof(void *) * 32);
+  for (unsigned int i = 0; i < poll_cache.size; i++) {
+    poll_cache.active_pollers[i] = NULL;
+  }
+
   gpr_mu_unlock(&g_cvfds.mu);
 }
 
 static void global_cv_fd_table_shutdown() {
   gpr_mu_lock(&g_cvfds.mu);
-  g_cvfds.shutdown = 1;
   // Attempt to wait for all abandoned poll() threads to terminate
   // Not doing so will result in reported memory leaks
-  if (g_cvfds.pollcount > 0) {
-    int res = gpr_cv_wait(&g_cvfds.shutdown_complete, &g_cvfds.mu,
+  if (!gpr_unref(&g_cvfds.pollcount)) {
+    int res = gpr_cv_wait(&g_cvfds.shutdown_cv, &g_cvfds.mu,
                           gpr_time_add(gpr_now(GPR_CLOCK_REALTIME),
                                        gpr_time_from_seconds(3, GPR_TIMESPAN)));
     GPR_ASSERT(res == 0);
   }
-  gpr_cv_destroy(&g_cvfds.shutdown_complete);
+  gpr_cv_destroy(&g_cvfds.shutdown_cv);
   grpc_poll_function = g_cvfds.poll;
   gpr_free(g_cvfds.cvfds);
+
+  gpr_free(poll_cache.active_pollers);
+
   gpr_mu_unlock(&g_cvfds.mu);
   gpr_mu_destroy(&g_cvfds.mu);
 }
diff --git a/src/core/lib/iomgr/ev_posix.c b/src/core/lib/iomgr/ev_posix.c
index cff77e641c..91f8cd5482 100644
--- a/src/core/lib/iomgr/ev_posix.c
+++ b/src/core/lib/iomgr/ev_posix.c
@@ -170,8 +170,9 @@ int grpc_fd_wrapped_fd(grpc_fd *fd) {
 }
 
 void grpc_fd_orphan(grpc_exec_ctx *exec_ctx, grpc_fd *fd, grpc_closure *on_done,
-                    int *release_fd, const char *reason) {
-  g_event_engine->fd_orphan(exec_ctx, fd, on_done, release_fd, reason);
+                    int *release_fd, bool already_closed, const char *reason) {
+  g_event_engine->fd_orphan(exec_ctx, fd, on_done, release_fd, already_closed,
+                            reason);
 }
 
 void grpc_fd_shutdown(grpc_exec_ctx *exec_ctx, grpc_fd *fd, grpc_error *why) {
diff --git a/src/core/lib/iomgr/ev_posix.h b/src/core/lib/iomgr/ev_posix.h
index 0de7333843..1108e46ef8 100644
--- a/src/core/lib/iomgr/ev_posix.h
+++ b/src/core/lib/iomgr/ev_posix.h
@@ -37,7 +37,7 @@ typedef struct grpc_event_engine_vtable {
   grpc_fd *(*fd_create)(int fd, const char *name);
   int (*fd_wrapped_fd)(grpc_fd *fd);
   void (*fd_orphan)(grpc_exec_ctx *exec_ctx, grpc_fd *fd, grpc_closure *on_done,
-                    int *release_fd, const char *reason);
+                    int *release_fd, bool already_closed, const char *reason);
   void (*fd_shutdown)(grpc_exec_ctx *exec_ctx, grpc_fd *fd, grpc_error *why);
   void (*fd_notify_on_read)(grpc_exec_ctx *exec_ctx, grpc_fd *fd,
                             grpc_closure *closure);
@@ -104,7 +104,7 @@ int grpc_fd_wrapped_fd(grpc_fd *fd);
    notify_on_write.
    MUST NOT be called with a pollset lock taken */
 void grpc_fd_orphan(grpc_exec_ctx *exec_ctx, grpc_fd *fd, grpc_closure *on_done,
-                    int *release_fd, const char *reason);
+                    int *release_fd, bool already_closed, const char *reason);
 
 /* Has grpc_fd_shutdown been called on an fd? */
 bool grpc_fd_is_shutdown(grpc_fd *fd);
diff --git a/src/core/lib/iomgr/exec_ctx.c b/src/core/lib/iomgr/exec_ctx.c
index 833170ceed..41c69add17 100644
--- a/src/core/lib/iomgr/exec_ctx.c
+++ b/src/core/lib/iomgr/exec_ctx.c
@@ -51,33 +51,6 @@ bool grpc_exec_ctx_has_work(grpc_exec_ctx *exec_ctx) {
          !grpc_closure_list_empty(exec_ctx->closure_list);
 }
 
-bool grpc_exec_ctx_flush(grpc_exec_ctx *exec_ctx) {
-  bool did_something = 0;
-  GPR_TIMER_BEGIN("grpc_exec_ctx_flush", 0);
-  for (;;) {
-    if (!grpc_closure_list_empty(exec_ctx->closure_list)) {
-      grpc_closure *c = exec_ctx->closure_list.head;
-      exec_ctx->closure_list.head = exec_ctx->closure_list.tail = NULL;
-      while (c != NULL) {
-        grpc_closure *next = c->next_data.next;
-        grpc_error *error = c->error_data.error;
-        did_something = true;
-#ifndef NDEBUG
-        c->scheduled = false;
-#endif
-        c->cb(exec_ctx, c->cb_arg, error);
-        GRPC_ERROR_UNREF(error);
-        c = next;
-      }
-    } else if (!grpc_combiner_continue_exec_ctx(exec_ctx)) {
-      break;
-    }
-  }
-  GPR_ASSERT(exec_ctx->active_combiner == NULL);
-  GPR_TIMER_END("grpc_exec_ctx_flush", 0);
-  return did_something;
-}
-
 void grpc_exec_ctx_finish(grpc_exec_ctx *exec_ctx) {
   exec_ctx->flags |= GRPC_EXEC_CTX_FLAG_IS_FINISHED;
   grpc_exec_ctx_flush(exec_ctx);
@@ -103,6 +76,29 @@ static void exec_ctx_run(grpc_exec_ctx *exec_ctx, grpc_closure *closure,
   GRPC_ERROR_UNREF(error);
 }
 
+bool grpc_exec_ctx_flush(grpc_exec_ctx *exec_ctx) {
+  bool did_something = 0;
+  GPR_TIMER_BEGIN("grpc_exec_ctx_flush", 0);
+  for (;;) {
+    if (!grpc_closure_list_empty(exec_ctx->closure_list)) {
+      grpc_closure *c = exec_ctx->closure_list.head;
+      exec_ctx->closure_list.head = exec_ctx->closure_list.tail = NULL;
+      while (c != NULL) {
+        grpc_closure *next = c->next_data.next;
+        grpc_error *error = c->error_data.error;
+        did_something = true;
+        exec_ctx_run(exec_ctx, c, error);
+        c = next;
+      }
+    } else if (!grpc_combiner_continue_exec_ctx(exec_ctx)) {
+      break;
+    }
+  }
+  GPR_ASSERT(exec_ctx->active_combiner == NULL);
+  GPR_TIMER_END("grpc_exec_ctx_flush", 0);
+  return did_something;
+}
+
 static void exec_ctx_sched(grpc_exec_ctx *exec_ctx, grpc_closure *closure,
                            grpc_error *error) {
   grpc_closure_list_append(&exec_ctx->closure_list, closure, error);
diff --git a/src/core/lib/iomgr/gethostname.h b/src/core/lib/iomgr/gethostname.h
new file mode 100644
index 0000000000..9c6b9d8d42
--- /dev/null
+++ b/src/core/lib/iomgr/gethostname.h
@@ -0,0 +1,26 @@
+/*
+ *
+ * Copyright 2017 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#ifndef GRPC_CORE_LIB_IOMGR_GETHOSTNAME_H
+#define GRPC_CORE_LIB_IOMGR_GETHOSTNAME_H
+
+// Returns the hostname of the local machine.
+// Caller takes ownership of result.
+char *grpc_gethostname();
+
+#endif /* GRPC_CORE_LIB_IOMGR_GETHOSTNAME_H */
diff --git a/src/core/lib/support/thd_internal.h b/src/core/lib/iomgr/gethostname_fallback.c
index cc468c7846..6229461568 100644
--- a/src/core/lib/support/thd_internal.h
+++ b/src/core/lib/iomgr/gethostname_fallback.c
@@ -1,6 +1,6 @@
 /*
  *
- * Copyright 2015 gRPC authors.
+ * Copyright 2017 gRPC authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -16,9 +16,12 @@
  *
  */
 
-#ifndef GRPC_CORE_LIB_SUPPORT_THD_INTERNAL_H
-#define GRPC_CORE_LIB_SUPPORT_THD_INTERNAL_H
+#include "src/core/lib/iomgr/port.h"
 
-/* Internal interfaces between modules within the gpr support library.  */
+#ifdef GRPC_GETHOSTNAME_FALLBACK
 
-#endif /* GRPC_CORE_LIB_SUPPORT_THD_INTERNAL_H */
+#include <stddef.h>
+
+char *grpc_gethostname() { return NULL; }
+
+#endif  // GRPC_GETHOSTNAME_FALLBACK
diff --git a/src/core/lib/iomgr/gethostname_host_name_max.c b/src/core/lib/iomgr/gethostname_host_name_max.c
new file mode 100644
index 0000000000..4d0511412e
--- /dev/null
+++ b/src/core/lib/iomgr/gethostname_host_name_max.c
@@ -0,0 +1,37 @@
+/*
+ *
+ * Copyright 2017 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#include "src/core/lib/iomgr/port.h"
+
+#ifdef GRPC_POSIX_HOST_NAME_MAX
+
+#include <limits.h>
+#include <unistd.h>
+
+#include <grpc/support/alloc.h>
+
+char *grpc_gethostname() {
+  char *hostname = (char *)gpr_malloc(HOST_NAME_MAX);
+  if (gethostname(hostname, HOST_NAME_MAX) != 0) {
+    gpr_free(hostname);
+    return NULL;
+  }
+  return hostname;
+}
+
+#endif  // GRPC_POSIX_HOST_NAME_MAX
diff --git a/src/core/lib/iomgr/gethostname_sysconf.c b/src/core/lib/iomgr/gethostname_sysconf.c
new file mode 100644
index 0000000000..51bac5d69d
--- /dev/null
+++ b/src/core/lib/iomgr/gethostname_sysconf.c
@@ -0,0 +1,37 @@
+/*
+ *
+ * Copyright 2017 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#include "src/core/lib/iomgr/port.h"
+
+#ifdef GRPC_POSIX_SYSCONF
+
+#include <unistd.h>
+
+#include <grpc/support/alloc.h>
+
+char *grpc_gethostname() {
+  size_t host_name_max = (size_t)sysconf(_SC_HOST_NAME_MAX);
+  char *hostname = (char *)gpr_malloc(host_name_max);
+  if (gethostname(hostname, host_name_max) != 0) {
+    gpr_free(hostname);
+    return NULL;
+  }
+  return hostname;
+}
+
+#endif  // GRPC_POSIX_SYSCONF
diff --git a/src/core/lib/iomgr/nameser.h b/src/core/lib/iomgr/nameser.h
new file mode 100644
index 0000000000..daed6de518
--- /dev/null
+++ b/src/core/lib/iomgr/nameser.h
@@ -0,0 +1,104 @@
+/*
+ *
+ * Copyright 2017 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#ifndef GRPC_CORE_LIB_IOMGR_NAMESER_H
+#define GRPC_CORE_LIB_IOMGR_NAMESER_H
+
+#include "src/core/lib/iomgr/port.h"
+
+#ifdef GRPC_HAVE_ARPA_NAMESER
+
+#include <arpa/nameser.h>
+
+#else /* GRPC_HAVE_ARPA_NAMESER */
+
+typedef enum __ns_class {
+  ns_c_invalid = 0, /* Cookie. */
+  ns_c_in = 1,      /* Internet. */
+  ns_c_2 = 2,       /* unallocated/unsupported. */
+  ns_c_chaos = 3,   /* MIT Chaos-net. */
+  ns_c_hs = 4,      /* MIT Hesiod. */
+  /* Query class values which do not appear in resource records */
+  ns_c_none = 254, /* for prereq. sections in update requests */
+  ns_c_any = 255,  /* Wildcard match. */
+  ns_c_max = 65536
+} ns_class;
+
+typedef enum __ns_type {
+  ns_t_invalid = 0,   /* Cookie. */
+  ns_t_a = 1,         /* Host address. */
+  ns_t_ns = 2,        /* Authoritative server. */
+  ns_t_md = 3,        /* Mail destination. */
+  ns_t_mf = 4,        /* Mail forwarder. */
+  ns_t_cname = 5,     /* Canonical name. */
+  ns_t_soa = 6,       /* Start of authority zone. */
+  ns_t_mb = 7,        /* Mailbox domain name. */
+  ns_t_mg = 8,        /* Mail group member. */
+  ns_t_mr = 9,        /* Mail rename name. */
+  ns_t_null = 10,     /* Null resource record. */
+  ns_t_wks = 11,      /* Well known service. */
+  ns_t_ptr = 12,      /* Domain name pointer. */
+  ns_t_hinfo = 13,    /* Host information. */
+  ns_t_minfo = 14,    /* Mailbox information. */
+  ns_t_mx = 15,       /* Mail routing information. */
+  ns_t_txt = 16,      /* Text strings. */
+  ns_t_rp = 17,       /* Responsible person. */
+  ns_t_afsdb = 18,    /* AFS cell database. */
+  ns_t_x25 = 19,      /* X_25 calling address. */
+  ns_t_isdn = 20,     /* ISDN calling address. */
+  ns_t_rt = 21,       /* Router. */
+  ns_t_nsap = 22,     /* NSAP address. */
+  ns_t_nsap_ptr = 23, /* Reverse NSAP lookup (deprecated). */
+  ns_t_sig = 24,      /* Security signature. */
+  ns_t_key = 25,      /* Security key. */
+  ns_t_px = 26,       /* X.400 mail mapping. */
+  ns_t_gpos = 27,     /* Geographical position (withdrawn). */
+  ns_t_aaaa = 28,     /* Ip6 Address. */
+  ns_t_loc = 29,      /* Location Information. */
+  ns_t_nxt = 30,      /* Next domain (security). */
+  ns_t_eid = 31,      /* Endpoint identifier. */
+  ns_t_nimloc = 32,   /* Nimrod Locator. */
+  ns_t_srv = 33,      /* Server Selection. */
+  ns_t_atma = 34,     /* ATM Address */
+  ns_t_naptr = 35,    /* Naming Authority PoinTeR */
+  ns_t_kx = 36,       /* Key Exchange */
+  ns_t_cert = 37,     /* Certification record */
+  ns_t_a6 = 38,       /* IPv6 address (deprecates AAAA) */
+  ns_t_dname = 39,    /* Non-terminal DNAME (for IPv6) */
+  ns_t_sink = 40,     /* Kitchen sink (experimentatl) */
+  ns_t_opt = 41,      /* EDNS0 option (meta-RR) */
+  ns_t_apl = 42,      /* Address prefix list (RFC3123) */
+  ns_t_ds = 43,       /* Delegation Signer (RFC4034) */
+  ns_t_sshfp = 44,    /* SSH Key Fingerprint (RFC4255) */
+  ns_t_rrsig = 46,    /* Resource Record Signature (RFC4034) */
+  ns_t_nsec = 47,     /* Next Secure (RFC4034) */
+  ns_t_dnskey = 48,   /* DNS Public Key (RFC4034) */
+  ns_t_tkey = 249,    /* Transaction key */
+  ns_t_tsig = 250,    /* Transaction signature. */
+  ns_t_ixfr = 251,    /* Incremental zone transfer. */
+  ns_t_axfr = 252,    /* Transfer zone of authority. */
+  ns_t_mailb = 253,   /* Transfer mailbox records. */
+  ns_t_maila = 254,   /* Transfer mail agent records. */
+  ns_t_any = 255,     /* Wildcard match. */
+  ns_t_zxfr = 256,    /* BIND-specific, nonstandard. */
+  ns_t_max = 65536
+} ns_type;
+
+#endif /* GRPC_HAVE_ARPA_NAMESER */
+
+#endif /* GRPC_CORE_LIB_IOMGR_NAMESER_H */
diff --git a/src/core/lib/iomgr/port.h b/src/core/lib/iomgr/port.h
index f5d15b4850..42033d0ba4 100644
--- a/src/core/lib/iomgr/port.h
+++ b/src/core/lib/iomgr/port.h
@@ -24,6 +24,7 @@
 #if defined(GRPC_UV)
 // Do nothing
 #elif defined(GPR_MANYLINUX1)
+#define GRPC_HAVE_ARPA_NAMESER 1
 #define GRPC_HAVE_IFADDRS 1
 #define GRPC_HAVE_IPV6_RECVPKTINFO 1
 #define GRPC_HAVE_IP_PKTINFO 1
@@ -51,12 +52,14 @@
 #define GRPC_POSIX_WAKEUP_FD 1
 #define GRPC_TIMER_USE_GENERIC 1
 #elif defined(GPR_LINUX)
+#define GRPC_HAVE_ARPA_NAMESER 1
 #define GRPC_HAVE_IFADDRS 1
 #define GRPC_HAVE_IPV6_RECVPKTINFO 1
 #define GRPC_HAVE_IP_PKTINFO 1
 #define GRPC_HAVE_MSG_NOSIGNAL 1
 #define GRPC_HAVE_UNIX_SOCKET 1
 #define GRPC_LINUX_MULTIPOLL_WITH_EPOLL 1
+#define GRPC_POSIX_HOST_NAME_MAX 1
 #define GRPC_POSIX_SOCKET 1
 #define GRPC_POSIX_SOCKETADDR 1
 #define GRPC_POSIX_WAKEUP_FD 1
@@ -82,6 +85,7 @@
 #define GRPC_POSIX_SOCKETUTILS
 #endif
 #elif defined(GPR_APPLE)
+#define GRPC_HAVE_ARPA_NAMESER 1
 #define GRPC_HAVE_IFADDRS 1
 #define GRPC_HAVE_SO_NOSIGPIPE 1
 #define GRPC_HAVE_UNIX_SOCKET 1
@@ -90,9 +94,11 @@
 #define GRPC_POSIX_SOCKET 1
 #define GRPC_POSIX_SOCKETADDR 1
 #define GRPC_POSIX_SOCKETUTILS 1
+#define GRPC_POSIX_SYSCONF 1
 #define GRPC_POSIX_WAKEUP_FD 1
 #define GRPC_TIMER_USE_GENERIC 1
 #elif defined(GPR_FREEBSD)
+#define GRPC_HAVE_ARPA_NAMESER 1
 #define GRPC_HAVE_IFADDRS 1
 #define GRPC_HAVE_IPV6_RECVPKTINFO 1
 #define GRPC_HAVE_SO_NOSIGPIPE 1
@@ -104,6 +110,7 @@
 #define GRPC_POSIX_WAKEUP_FD 1
 #define GRPC_TIMER_USE_GENERIC 1
 #elif defined(GPR_NACL)
+#define GRPC_HAVE_ARPA_NAMESER 1
 #define GRPC_POSIX_NO_SPECIAL_WAKEUP_FD 1
 #define GRPC_POSIX_SOCKET 1
 #define GRPC_POSIX_SOCKETADDR 1
@@ -120,4 +127,11 @@
 #error Must define exactly one of GRPC_POSIX_SOCKET, GRPC_WINSOCK_SOCKET, GPR_CUSTOM_SOCKET
 #endif
 
+#if defined(GRPC_POSIX_HOST_NAME_MAX) && defined(GRPC_POSIX_SYSCONF)
+#error "Cannot define both GRPC_POSIX_HOST_NAME_MAX and GRPC_POSIX_SYSCONF"
+#endif
+#if !defined(GRPC_POSIX_HOST_NAME_MAX) && !defined(GRPC_POSIX_SYSCONF)
+#define GRPC_GETHOSTNAME_FALLBACK 1
+#endif
+
 #endif /* GRPC_CORE_LIB_IOMGR_PORT_H */
diff --git a/src/core/lib/iomgr/tcp_client_posix.c b/src/core/lib/iomgr/tcp_client_posix.c
index 21e320a6e7..a25fba4527 100644
--- a/src/core/lib/iomgr/tcp_client_posix.c
+++ b/src/core/lib/iomgr/tcp_client_posix.c
@@ -209,7 +209,8 @@ static void on_writable(grpc_exec_ctx *exec_ctx, void *acp, grpc_error *error) {
 finish:
   if (fd != NULL) {
     grpc_pollset_set_del_fd(exec_ctx, ac->interested_parties, fd);
-    grpc_fd_orphan(exec_ctx, fd, NULL, NULL, "tcp_client_orphan");
+    grpc_fd_orphan(exec_ctx, fd, NULL, NULL, false /* already_closed */,
+                   "tcp_client_orphan");
     fd = NULL;
   }
   done = (--ac->refs == 0);
@@ -295,7 +296,8 @@ static void tcp_client_connect_impl(grpc_exec_ctx *exec_ctx,
   }
 
   if (errno != EWOULDBLOCK && errno != EINPROGRESS) {
-    grpc_fd_orphan(exec_ctx, fdobj, NULL, NULL, "tcp_client_connect_error");
+    grpc_fd_orphan(exec_ctx, fdobj, NULL, NULL, false /* already_closed */,
+                   "tcp_client_connect_error");
     GRPC_CLOSURE_SCHED(exec_ctx, closure, GRPC_OS_ERROR(errno, "connect"));
     goto done;
   }
diff --git a/src/core/lib/iomgr/tcp_posix.c b/src/core/lib/iomgr/tcp_posix.c
index 9d27de0b1c..1bace788c5 100644
--- a/src/core/lib/iomgr/tcp_posix.c
+++ b/src/core/lib/iomgr/tcp_posix.c
@@ -296,7 +296,7 @@ static void tcp_shutdown(grpc_exec_ctx *exec_ctx, grpc_endpoint *ep,
 
 static void tcp_free(grpc_exec_ctx *exec_ctx, grpc_tcp *tcp) {
   grpc_fd_orphan(exec_ctx, tcp->em_fd, tcp->release_fd_cb, tcp->release_fd,
-                 "tcp_unref_orphan");
+                 false /* already_closed */, "tcp_unref_orphan");
   grpc_slice_buffer_destroy_internal(exec_ctx, &tcp->last_read_buffer);
   grpc_resource_user_unref(exec_ctx, tcp->resource_user);
   gpr_free(tcp->peer_string);
diff --git a/src/core/lib/iomgr/tcp_server_posix.c b/src/core/lib/iomgr/tcp_server_posix.c
index f304642951..0fc5c0fd86 100644
--- a/src/core/lib/iomgr/tcp_server_posix.c
+++ b/src/core/lib/iomgr/tcp_server_posix.c
@@ -166,7 +166,7 @@ static void deactivated_all_ports(grpc_exec_ctx *exec_ctx, grpc_tcp_server *s) {
       GRPC_CLOSURE_INIT(&sp->destroyed_closure, destroyed_port, s,
                         grpc_schedule_on_exec_ctx);
       grpc_fd_orphan(exec_ctx, sp->emfd, &sp->destroyed_closure, NULL,
-                     "tcp_listener_shutdown");
+                     false /* already_closed */, "tcp_listener_shutdown");
     }
     gpr_mu_unlock(&s->mu);
   } else {
diff --git a/src/core/lib/iomgr/tcp_server_utils_posix_common.c b/src/core/lib/iomgr/tcp_server_utils_posix_common.c
index dbb43186bd..ad535bc43e 100644
--- a/src/core/lib/iomgr/tcp_server_utils_posix_common.c
+++ b/src/core/lib/iomgr/tcp_server_utils_posix_common.c
@@ -39,7 +39,7 @@
 
 #define MIN_SAFE_ACCEPT_QUEUE_SIZE 100
 
-static gpr_once s_init_max_accept_queue_size;
+static gpr_once s_init_max_accept_queue_size = GPR_ONCE_INIT;
 static int s_max_accept_queue_size;
 
 /* get max listen queue size on linux */
diff --git a/src/core/lib/iomgr/udp_server.c b/src/core/lib/iomgr/udp_server.c
index 54e7f417a7..88fa34cb7a 100644
--- a/src/core/lib/iomgr/udp_server.c
+++ b/src/core/lib/iomgr/udp_server.c
@@ -214,7 +214,7 @@ static void deactivated_all_ports(grpc_exec_ctx *exec_ctx, grpc_udp_server *s) {
                       sp->server->user_data);
       }
       grpc_fd_orphan(exec_ctx, sp->emfd, &sp->destroyed_closure, NULL,
-                     "udp_listener_shutdown");
+                     false /* already_closed */, "udp_listener_shutdown");
     }
     gpr_mu_unlock(&s->mu);
   } else {
diff --git a/src/core/lib/iomgr/wakeup_fd_cv.h b/src/core/lib/iomgr/wakeup_fd_cv.h
index c5dcdc9746..46e84f5843 100644
--- a/src/core/lib/iomgr/wakeup_fd_cv.h
+++ b/src/core/lib/iomgr/wakeup_fd_cv.h
@@ -43,6 +43,7 @@
 typedef struct cv_node {
   gpr_cv* cv;
   struct cv_node* next;
+  struct cv_node* prev;
 } cv_node;
 
 typedef struct fd_node {
@@ -53,9 +54,8 @@ typedef struct fd_node {
 
 typedef struct cv_fd_table {
   gpr_mu mu;
-  int pollcount;
-  int shutdown;
-  gpr_cv shutdown_complete;
+  gpr_refcount pollcount;
+  gpr_cv shutdown_cv;
   fd_node* cvfds;
   fd_node* free_fds;
   unsigned int size;
diff --git a/src/core/lib/json/json_reader.c b/src/core/lib/json/json_reader.c
index 75f59e0912..094a35176c 100644
--- a/src/core/lib/json/json_reader.c
+++ b/src/core/lib/json/json_reader.c
@@ -178,6 +178,7 @@ grpc_json_reader_status grpc_json_reader_run(grpc_json_reader *reader) {
             json_reader_string_clear(reader);
             reader->state = GRPC_JSON_STATE_VALUE_END;
           /* The missing break here is intentional. */
+          /* fallthrough */
 
           case GRPC_JSON_STATE_VALUE_END:
           case GRPC_JSON_STATE_OBJECT_KEY_BEGIN:
diff --git a/src/core/lib/profiling/timers.h b/src/core/lib/profiling/timers.h
index 58e6659e6d..7f02b4bf84 100644
--- a/src/core/lib/profiling/timers.h
+++ b/src/core/lib/profiling/timers.h
@@ -37,7 +37,8 @@ void gpr_timers_set_log_filename(const char *filename);
 
 void gpr_timer_set_enabled(int enabled);
 
-#if !(defined(GRPC_STAP_PROFILER) + defined(GRPC_BASIC_PROFILER))
+#if !(defined(GRPC_STAP_PROFILER) + defined(GRPC_BASIC_PROFILER) + \
+      defined(GRPC_CUSTOM_PROFILER))
 /* No profiling. No-op all the things. */
 #define GPR_TIMER_MARK(tag, important) \
   do {                                 \
@@ -56,6 +57,12 @@ void gpr_timer_set_enabled(int enabled);
 #if defined(GRPC_STAP_PROFILER) && defined(GRPC_BASIC_PROFILER)
 #error "GRPC_STAP_PROFILER and GRPC_BASIC_PROFILER are mutually exclusive."
 #endif
+#if defined(GRPC_STAP_PROFILER) && defined(GRPC_CUSTOM_PROFILER)
+#error "GRPC_STAP_PROFILER and GRPC_CUSTOM_PROFILER are mutually exclusive."
+#endif
+#if defined(GRPC_CUSTOM_PROFILER) && defined(GRPC_BASIC_PROFILER)
+#error "GRPC_CUSTOM_PROFILER and GRPC_BASIC_PROFILER are mutually exclusive."
+#endif
 
 /* Generic profiling interface. */
 #define GPR_TIMER_MARK(tag, important) \
@@ -80,22 +87,25 @@ void gpr_timer_set_enabled(int enabled);
 #ifdef __cplusplus
 }
 
-#if (defined(GRPC_STAP_PROFILER) + defined(GRPC_BASIC_PROFILER))
+#if (defined(GRPC_STAP_PROFILER) + defined(GRPC_BASIC_PROFILER) + \
+     defined(GRPC_CUSTOM_PROFILER))
 namespace grpc {
 class ProfileScope {
  public:
-  ProfileScope(const char *desc, bool important) : desc_(desc) {
-    GPR_TIMER_BEGIN(desc_, important ? 1 : 0);
+  ProfileScope(const char *desc, bool important, const char *file, int line)
+      : desc_(desc) {
+    gpr_timer_begin(desc_, important ? 1 : 0, file, line);
   }
-  ~ProfileScope() { GPR_TIMER_END(desc_, 0); }
+  ~ProfileScope() { gpr_timer_end(desc_, 0, "n/a", 0); }
 
  private:
   const char *const desc_;
 };
-}
+}  // namespace grpc
 
-#define GPR_TIMER_SCOPE(tag, important) \
-  ::grpc::ProfileScope _profile_scope_##__LINE__((tag), (important))
+#define GPR_TIMER_SCOPE(tag, important)                                        \
+  ::grpc::ProfileScope _profile_scope_##__LINE__((tag), (important), __FILE__, \
+                                                 __LINE__)
 #else
 #define GPR_TIMER_SCOPE(tag, important) \
   do {                                  \
diff --git a/src/core/lib/security/credentials/composite/composite_credentials.c b/src/core/lib/security/credentials/composite/composite_credentials.c
index 77d7b04627..09fd60a12c 100644
--- a/src/core/lib/security/credentials/composite/composite_credentials.c
+++ b/src/core/lib/security/credentials/composite/composite_credentials.c
@@ -32,88 +32,98 @@
 typedef struct {
   grpc_composite_call_credentials *composite_creds;
   size_t creds_index;
-  grpc_credentials_md_store *md_elems;
-  grpc_auth_metadata_context auth_md_context;
-  void *user_data;
   grpc_polling_entity *pollent;
-  grpc_credentials_metadata_cb cb;
+  grpc_auth_metadata_context auth_md_context;
+  grpc_credentials_mdelem_array *md_array;
+  grpc_closure *on_request_metadata;
+  grpc_closure internal_on_request_metadata;
 } grpc_composite_call_credentials_metadata_context;
 
 static void composite_call_destruct(grpc_exec_ctx *exec_ctx,
                                     grpc_call_credentials *creds) {
   grpc_composite_call_credentials *c = (grpc_composite_call_credentials *)creds;
-  size_t i;
-  for (i = 0; i < c->inner.num_creds; i++) {
+  for (size_t i = 0; i < c->inner.num_creds; i++) {
     grpc_call_credentials_unref(exec_ctx, c->inner.creds_array[i]);
   }
   gpr_free(c->inner.creds_array);
 }
 
-static void composite_call_md_context_destroy(
-    grpc_exec_ctx *exec_ctx,
-    grpc_composite_call_credentials_metadata_context *ctx) {
-  grpc_credentials_md_store_unref(exec_ctx, ctx->md_elems);
-  gpr_free(ctx);
-}
-
-static void composite_call_metadata_cb(grpc_exec_ctx *exec_ctx, void *user_data,
-                                       grpc_credentials_md *md_elems,
-                                       size_t num_md,
-                                       grpc_credentials_status status,
-                                       const char *error_details) {
+static void composite_call_metadata_cb(grpc_exec_ctx *exec_ctx, void *arg,
+                                       grpc_error *error) {
   grpc_composite_call_credentials_metadata_context *ctx =
-      (grpc_composite_call_credentials_metadata_context *)user_data;
-  if (status != GRPC_CREDENTIALS_OK) {
-    ctx->cb(exec_ctx, ctx->user_data, NULL, 0, status, error_details);
-    return;
-  }
-
-  /* Copy the metadata in the context. */
-  if (num_md > 0) {
-    size_t i;
-    for (i = 0; i < num_md; i++) {
-      grpc_credentials_md_store_add(ctx->md_elems, md_elems[i].key,
-                                    md_elems[i].value);
+      (grpc_composite_call_credentials_metadata_context *)arg;
+  if (error == GRPC_ERROR_NONE) {
+    /* See if we need to get some more metadata. */
+    if (ctx->creds_index < ctx->composite_creds->inner.num_creds) {
+      grpc_call_credentials *inner_creds =
+          ctx->composite_creds->inner.creds_array[ctx->creds_index++];
+      if (grpc_call_credentials_get_request_metadata(
+              exec_ctx, inner_creds, ctx->pollent, ctx->auth_md_context,
+              ctx->md_array, &ctx->internal_on_request_metadata, &error)) {
+        // Synchronous response, so call ourselves recursively.
+        composite_call_metadata_cb(exec_ctx, arg, error);
+        GRPC_ERROR_UNREF(error);
+      }
+      return;
     }
+    // We're done!
   }
-
-  /* See if we need to get some more metadata. */
-  if (ctx->creds_index < ctx->composite_creds->inner.num_creds) {
-    grpc_call_credentials *inner_creds =
-        ctx->composite_creds->inner.creds_array[ctx->creds_index++];
-    grpc_call_credentials_get_request_metadata(
-        exec_ctx, inner_creds, ctx->pollent, ctx->auth_md_context,
-        composite_call_metadata_cb, ctx);
-    return;
-  }
-
-  /* We're done!. */
-  ctx->cb(exec_ctx, ctx->user_data, ctx->md_elems->entries,
-          ctx->md_elems->num_entries, GRPC_CREDENTIALS_OK, NULL);
-  composite_call_md_context_destroy(exec_ctx, ctx);
+  GRPC_CLOSURE_SCHED(exec_ctx, ctx->on_request_metadata, GRPC_ERROR_REF(error));
+  gpr_free(ctx);
 }
 
-static void composite_call_get_request_metadata(
+static bool composite_call_get_request_metadata(
     grpc_exec_ctx *exec_ctx, grpc_call_credentials *creds,
     grpc_polling_entity *pollent, grpc_auth_metadata_context auth_md_context,
-    grpc_credentials_metadata_cb cb, void *user_data) {
+    grpc_credentials_mdelem_array *md_array, grpc_closure *on_request_metadata,
+    grpc_error **error) {
   grpc_composite_call_credentials *c = (grpc_composite_call_credentials *)creds;
   grpc_composite_call_credentials_metadata_context *ctx;
-
   ctx = gpr_zalloc(sizeof(grpc_composite_call_credentials_metadata_context));
-  ctx->auth_md_context = auth_md_context;
-  ctx->user_data = user_data;
-  ctx->cb = cb;
   ctx->composite_creds = c;
   ctx->pollent = pollent;
-  ctx->md_elems = grpc_credentials_md_store_create(c->inner.num_creds);
-  grpc_call_credentials_get_request_metadata(
-      exec_ctx, c->inner.creds_array[ctx->creds_index++], ctx->pollent,
-      auth_md_context, composite_call_metadata_cb, ctx);
+  ctx->auth_md_context = auth_md_context;
+  ctx->md_array = md_array;
+  ctx->on_request_metadata = on_request_metadata;
+  GRPC_CLOSURE_INIT(&ctx->internal_on_request_metadata,
+                    composite_call_metadata_cb, ctx, grpc_schedule_on_exec_ctx);
+  while (ctx->creds_index < ctx->composite_creds->inner.num_creds) {
+    grpc_call_credentials *inner_creds =
+        ctx->composite_creds->inner.creds_array[ctx->creds_index++];
+    if (grpc_call_credentials_get_request_metadata(
+            exec_ctx, inner_creds, ctx->pollent, ctx->auth_md_context,
+            ctx->md_array, &ctx->internal_on_request_metadata, error)) {
+      if (*error != GRPC_ERROR_NONE) break;
+    } else {
+      break;
+    }
+  }
+  // If we got through all creds synchronously or we got a synchronous
+  // error on one of them, return synchronously.
+  if (ctx->creds_index == ctx->composite_creds->inner.num_creds ||
+      *error != GRPC_ERROR_NONE) {
+    gpr_free(ctx);
+    return true;
+  }
+  // At least one inner cred is returning asynchronously, so we'll
+  // return asynchronously as well.
+  return false;
+}
+
+static void composite_call_cancel_get_request_metadata(
+    grpc_exec_ctx *exec_ctx, grpc_call_credentials *creds,
+    grpc_credentials_mdelem_array *md_array, grpc_error *error) {
+  grpc_composite_call_credentials *c = (grpc_composite_call_credentials *)creds;
+  for (size_t i = 0; i < c->inner.num_creds; ++i) {
+    grpc_call_credentials_cancel_get_request_metadata(
+        exec_ctx, c->inner.creds_array[i], md_array, GRPC_ERROR_REF(error));
+  }
+  GRPC_ERROR_UNREF(error);
 }
 
 static grpc_call_credentials_vtable composite_call_credentials_vtable = {
-    composite_call_destruct, composite_call_get_request_metadata};
+    composite_call_destruct, composite_call_get_request_metadata,
+    composite_call_cancel_get_request_metadata};
 
 static grpc_call_credentials_array get_creds_array(
     grpc_call_credentials **creds_addr) {
diff --git a/src/core/lib/security/credentials/credentials.c b/src/core/lib/security/credentials/credentials.c
index b1f1e82076..8a67c9865b 100644
--- a/src/core/lib/security/credentials/credentials.c
+++ b/src/core/lib/security/credentials/credentials.c
@@ -38,13 +38,10 @@
 /* -- Common. -- */
 
 grpc_credentials_metadata_request *grpc_credentials_metadata_request_create(
-    grpc_call_credentials *creds, grpc_credentials_metadata_cb cb,
-    void *user_data) {
+    grpc_call_credentials *creds) {
   grpc_credentials_metadata_request *r =
       gpr_zalloc(sizeof(grpc_credentials_metadata_request));
   r->creds = grpc_call_credentials_ref(creds);
-  r->cb = cb;
-  r->user_data = user_data;
   return r;
 }
 
@@ -104,18 +101,25 @@ void grpc_call_credentials_release(grpc_call_credentials *creds) {
   grpc_exec_ctx_finish(&exec_ctx);
 }
 
-void grpc_call_credentials_get_request_metadata(
+bool grpc_call_credentials_get_request_metadata(
     grpc_exec_ctx *exec_ctx, grpc_call_credentials *creds,
     grpc_polling_entity *pollent, grpc_auth_metadata_context context,
-    grpc_credentials_metadata_cb cb, void *user_data) {
+    grpc_credentials_mdelem_array *md_array, grpc_closure *on_request_metadata,
+    grpc_error **error) {
   if (creds == NULL || creds->vtable->get_request_metadata == NULL) {
-    if (cb != NULL) {
-      cb(exec_ctx, user_data, NULL, 0, GRPC_CREDENTIALS_OK, NULL);
-    }
+    return true;
+  }
+  return creds->vtable->get_request_metadata(
+      exec_ctx, creds, pollent, context, md_array, on_request_metadata, error);
+}
+
+void grpc_call_credentials_cancel_get_request_metadata(
+    grpc_exec_ctx *exec_ctx, grpc_call_credentials *creds,
+    grpc_credentials_mdelem_array *md_array, grpc_error *error) {
+  if (creds == NULL || creds->vtable->cancel_get_request_metadata == NULL) {
     return;
   }
-  creds->vtable->get_request_metadata(exec_ctx, creds, pollent, context, cb,
-                                      user_data);
+  creds->vtable->cancel_get_request_metadata(exec_ctx, creds, md_array, error);
 }
 
 grpc_security_status grpc_channel_credentials_create_security_connector(
diff --git a/src/core/lib/security/credentials/credentials.h b/src/core/lib/security/credentials/credentials.h
index c45c2e957c..04a54b0ca8 100644
--- a/src/core/lib/security/credentials/credentials.h
+++ b/src/core/lib/security/credentials/credentials.h
@@ -138,48 +138,39 @@ grpc_channel_credentials *grpc_channel_credentials_from_arg(
 grpc_channel_credentials *grpc_channel_credentials_find_in_args(
     const grpc_channel_args *args);
 
-/* --- grpc_credentials_md. --- */
+/* --- grpc_credentials_mdelem_array. --- */
 
 typedef struct {
-  grpc_slice key;
-  grpc_slice value;
-} grpc_credentials_md;
+  grpc_mdelem *md;
+  size_t size;
+} grpc_credentials_mdelem_array;
 
-typedef struct {
-  grpc_credentials_md *entries;
-  size_t num_entries;
-  size_t allocated;
-  gpr_refcount refcount;
-} grpc_credentials_md_store;
+/// Takes a new ref to \a md.
+void grpc_credentials_mdelem_array_add(grpc_credentials_mdelem_array *list,
+                                       grpc_mdelem md);
 
-grpc_credentials_md_store *grpc_credentials_md_store_create(
-    size_t initial_capacity);
+/// Appends all elements from \a src to \a dst, taking a new ref to each one.
+void grpc_credentials_mdelem_array_append(grpc_credentials_mdelem_array *dst,
+                                          grpc_credentials_mdelem_array *src);
 
-/* Will ref key and value. */
-void grpc_credentials_md_store_add(grpc_credentials_md_store *store,
-                                   grpc_slice key, grpc_slice value);
-void grpc_credentials_md_store_add_cstrings(grpc_credentials_md_store *store,
-                                            const char *key, const char *value);
-grpc_credentials_md_store *grpc_credentials_md_store_ref(
-    grpc_credentials_md_store *store);
-void grpc_credentials_md_store_unref(grpc_exec_ctx *exec_ctx,
-                                     grpc_credentials_md_store *store);
+void grpc_credentials_mdelem_array_destroy(grpc_exec_ctx *exec_ctx,
+                                           grpc_credentials_mdelem_array *list);
 
 /* --- grpc_call_credentials. --- */
 
-/* error_details must be NULL if status is GRPC_CREDENTIALS_OK. */
-typedef void (*grpc_credentials_metadata_cb)(
-    grpc_exec_ctx *exec_ctx, void *user_data, grpc_credentials_md *md_elems,
-    size_t num_md, grpc_credentials_status status, const char *error_details);
-
 typedef struct {
   void (*destruct)(grpc_exec_ctx *exec_ctx, grpc_call_credentials *c);
-  void (*get_request_metadata)(grpc_exec_ctx *exec_ctx,
+  bool (*get_request_metadata)(grpc_exec_ctx *exec_ctx,
                                grpc_call_credentials *c,
                                grpc_polling_entity *pollent,
                                grpc_auth_metadata_context context,
-                               grpc_credentials_metadata_cb cb,
-                               void *user_data);
+                               grpc_credentials_mdelem_array *md_array,
+                               grpc_closure *on_request_metadata,
+                               grpc_error **error);
+  void (*cancel_get_request_metadata)(grpc_exec_ctx *exec_ctx,
+                                      grpc_call_credentials *c,
+                                      grpc_credentials_mdelem_array *md_array,
+                                      grpc_error *error);
 } grpc_call_credentials_vtable;
 
 struct grpc_call_credentials {
@@ -191,15 +182,29 @@ struct grpc_call_credentials {
 grpc_call_credentials *grpc_call_credentials_ref(grpc_call_credentials *creds);
 void grpc_call_credentials_unref(grpc_exec_ctx *exec_ctx,
                                  grpc_call_credentials *creds);
-void grpc_call_credentials_get_request_metadata(
+
+/// Returns true if completed synchronously, in which case \a error will
+/// be set to indicate the result.  Otherwise, \a on_request_metadata will
+/// be invoked asynchronously when complete.  \a md_array will be populated
+/// with the resulting metadata once complete.
+bool grpc_call_credentials_get_request_metadata(
     grpc_exec_ctx *exec_ctx, grpc_call_credentials *creds,
     grpc_polling_entity *pollent, grpc_auth_metadata_context context,
-    grpc_credentials_metadata_cb cb, void *user_data);
+    grpc_credentials_mdelem_array *md_array, grpc_closure *on_request_metadata,
+    grpc_error **error);
+
+/// Cancels a pending asynchronous operation started by
+/// grpc_call_credentials_get_request_metadata() with the corresponding
+/// value of \a md_array.
+void grpc_call_credentials_cancel_get_request_metadata(
+    grpc_exec_ctx *exec_ctx, grpc_call_credentials *c,
+    grpc_credentials_mdelem_array *md_array, grpc_error *error);
 
 /* Metadata-only credentials with the specified key and value where
    asynchronicity can be simulated for testing. */
 grpc_call_credentials *grpc_md_only_test_credentials_create(
-    const char *md_key, const char *md_value, int is_async);
+    grpc_exec_ctx *exec_ctx, const char *md_key, const char *md_value,
+    bool is_async);
 
 /* --- grpc_server_credentials. --- */
 
@@ -238,14 +243,11 @@ grpc_server_credentials *grpc_find_server_credentials_in_args(
 
 typedef struct {
   grpc_call_credentials *creds;
-  grpc_credentials_metadata_cb cb;
   grpc_http_response response;
-  void *user_data;
 } grpc_credentials_metadata_request;
 
 grpc_credentials_metadata_request *grpc_credentials_metadata_request_create(
-    grpc_call_credentials *creds, grpc_credentials_metadata_cb cb,
-    void *user_data);
+    grpc_call_credentials *creds);
 
 void grpc_credentials_metadata_request_destroy(
     grpc_exec_ctx *exec_ctx, grpc_credentials_metadata_request *r);
diff --git a/src/core/lib/security/credentials/credentials_metadata.c b/src/core/lib/security/credentials/credentials_metadata.c
index fcfdd52d20..ccd39e610f 100644
--- a/src/core/lib/security/credentials/credentials_metadata.c
+++ b/src/core/lib/security/credentials/credentials_metadata.c
@@ -24,65 +24,36 @@
 
 #include "src/core/lib/slice/slice_internal.h"
 
-static void store_ensure_capacity(grpc_credentials_md_store *store) {
-  if (store->num_entries == store->allocated) {
-    store->allocated = (store->allocated == 0) ? 1 : store->allocated * 2;
-    store->entries = gpr_realloc(
-        store->entries, store->allocated * sizeof(grpc_credentials_md));
+static void mdelem_list_ensure_capacity(grpc_credentials_mdelem_array *list,
+                                        size_t additional_space_needed) {
+  size_t target_size = list->size + additional_space_needed;
+  // Find the next power of two greater than the target size (i.e.,
+  // whenever we add more space, we double what we already have).
+  size_t new_size = 2;
+  while (new_size < target_size) {
+    new_size *= 2;
   }
+  list->md = gpr_realloc(list->md, sizeof(grpc_mdelem) * new_size);
 }
 
-grpc_credentials_md_store *grpc_credentials_md_store_create(
-    size_t initial_capacity) {
-  grpc_credentials_md_store *store =
-      gpr_zalloc(sizeof(grpc_credentials_md_store));
-  if (initial_capacity > 0) {
-    store->entries = gpr_malloc(initial_capacity * sizeof(grpc_credentials_md));
-    store->allocated = initial_capacity;
-  }
-  gpr_ref_init(&store->refcount, 1);
-  return store;
-}
-
-void grpc_credentials_md_store_add(grpc_credentials_md_store *store,
-                                   grpc_slice key, grpc_slice value) {
-  if (store == NULL) return;
-  store_ensure_capacity(store);
-  store->entries[store->num_entries].key = grpc_slice_ref_internal(key);
-  store->entries[store->num_entries].value = grpc_slice_ref_internal(value);
-  store->num_entries++;
+void grpc_credentials_mdelem_array_add(grpc_credentials_mdelem_array *list,
+                                       grpc_mdelem md) {
+  mdelem_list_ensure_capacity(list, 1);
+  list->md[list->size++] = GRPC_MDELEM_REF(md);
 }
 
-void grpc_credentials_md_store_add_cstrings(grpc_credentials_md_store *store,
-                                            const char *key,
-                                            const char *value) {
-  if (store == NULL) return;
-  store_ensure_capacity(store);
-  store->entries[store->num_entries].key = grpc_slice_from_copied_string(key);
-  store->entries[store->num_entries].value =
-      grpc_slice_from_copied_string(value);
-  store->num_entries++;
-}
-
-grpc_credentials_md_store *grpc_credentials_md_store_ref(
-    grpc_credentials_md_store *store) {
-  if (store == NULL) return NULL;
-  gpr_ref(&store->refcount);
-  return store;
+void grpc_credentials_mdelem_array_append(grpc_credentials_mdelem_array *dst,
+                                          grpc_credentials_mdelem_array *src) {
+  mdelem_list_ensure_capacity(dst, src->size);
+  for (size_t i = 0; i < src->size; ++i) {
+    dst->md[dst->size++] = GRPC_MDELEM_REF(src->md[i]);
+  }
 }
 
-void grpc_credentials_md_store_unref(grpc_exec_ctx *exec_ctx,
-                                     grpc_credentials_md_store *store) {
-  if (store == NULL) return;
-  if (gpr_unref(&store->refcount)) {
-    if (store->entries != NULL) {
-      size_t i;
-      for (i = 0; i < store->num_entries; i++) {
-        grpc_slice_unref_internal(exec_ctx, store->entries[i].key);
-        grpc_slice_unref_internal(exec_ctx, store->entries[i].value);
-      }
-      gpr_free(store->entries);
-    }
-    gpr_free(store);
+void grpc_credentials_mdelem_array_destroy(
+    grpc_exec_ctx *exec_ctx, grpc_credentials_mdelem_array *list) {
+  for (size_t i = 0; i < list->size; ++i) {
+    GRPC_MDELEM_UNREF(exec_ctx, list->md[i]);
   }
+  gpr_free(list->md);
 }
diff --git a/src/core/lib/security/credentials/fake/fake_credentials.c b/src/core/lib/security/credentials/fake/fake_credentials.c
index a01dd379e4..ac9017850f 100644
--- a/src/core/lib/security/credentials/fake/fake_credentials.c
+++ b/src/core/lib/security/credentials/fake/fake_credentials.c
@@ -98,50 +98,44 @@ const char *grpc_fake_transport_get_expected_targets(
 static void md_only_test_destruct(grpc_exec_ctx *exec_ctx,
                                   grpc_call_credentials *creds) {
   grpc_md_only_test_credentials *c = (grpc_md_only_test_credentials *)creds;
-  grpc_credentials_md_store_unref(exec_ctx, c->md_store);
+  GRPC_MDELEM_UNREF(exec_ctx, c->md);
 }
 
-static void on_simulated_token_fetch_done(grpc_exec_ctx *exec_ctx,
-                                          void *user_data, grpc_error *error) {
-  grpc_credentials_metadata_request *r =
-      (grpc_credentials_metadata_request *)user_data;
-  grpc_md_only_test_credentials *c = (grpc_md_only_test_credentials *)r->creds;
-  r->cb(exec_ctx, r->user_data, c->md_store->entries, c->md_store->num_entries,
-        GRPC_CREDENTIALS_OK, NULL);
-  grpc_credentials_metadata_request_destroy(exec_ctx, r);
-}
-
-static void md_only_test_get_request_metadata(
+static bool md_only_test_get_request_metadata(
     grpc_exec_ctx *exec_ctx, grpc_call_credentials *creds,
     grpc_polling_entity *pollent, grpc_auth_metadata_context context,
-    grpc_credentials_metadata_cb cb, void *user_data) {
+    grpc_credentials_mdelem_array *md_array, grpc_closure *on_request_metadata,
+    grpc_error **error) {
   grpc_md_only_test_credentials *c = (grpc_md_only_test_credentials *)creds;
-
+  grpc_credentials_mdelem_array_add(md_array, c->md);
   if (c->is_async) {
-    grpc_credentials_metadata_request *cb_arg =
-        grpc_credentials_metadata_request_create(creds, cb, user_data);
-    GRPC_CLOSURE_SCHED(
-        exec_ctx,
-        GRPC_CLOSURE_CREATE(on_simulated_token_fetch_done, cb_arg,
-                            grpc_executor_scheduler(GRPC_EXECUTOR_SHORT)),
-        GRPC_ERROR_NONE);
-  } else {
-    cb(exec_ctx, user_data, c->md_store->entries, 1, GRPC_CREDENTIALS_OK, NULL);
+    GRPC_CLOSURE_SCHED(exec_ctx, on_request_metadata, GRPC_ERROR_NONE);
+    return false;
   }
+  return true;
+}
+
+static void md_only_test_cancel_get_request_metadata(
+    grpc_exec_ctx *exec_ctx, grpc_call_credentials *c,
+    grpc_credentials_mdelem_array *md_array, grpc_error *error) {
+  GRPC_ERROR_UNREF(error);
 }
 
 static grpc_call_credentials_vtable md_only_test_vtable = {
-    md_only_test_destruct, md_only_test_get_request_metadata};
+    md_only_test_destruct, md_only_test_get_request_metadata,
+    md_only_test_cancel_get_request_metadata};
 
 grpc_call_credentials *grpc_md_only_test_credentials_create(
-    const char *md_key, const char *md_value, int is_async) {
+    grpc_exec_ctx *exec_ctx, const char *md_key, const char *md_value,
+    bool is_async) {
   grpc_md_only_test_credentials *c =
       gpr_zalloc(sizeof(grpc_md_only_test_credentials));
   c->base.type = GRPC_CALL_CREDENTIALS_TYPE_OAUTH2;
   c->base.vtable = &md_only_test_vtable;
   gpr_ref_init(&c->base.refcount, 1);
-  c->md_store = grpc_credentials_md_store_create(1);
-  grpc_credentials_md_store_add_cstrings(c->md_store, md_key, md_value);
+  c->md =
+      grpc_mdelem_from_slices(exec_ctx, grpc_slice_from_copied_string(md_key),
+                              grpc_slice_from_copied_string(md_value));
   c->is_async = is_async;
   return &c->base;
 }
diff --git a/src/core/lib/security/credentials/fake/fake_credentials.h b/src/core/lib/security/credentials/fake/fake_credentials.h
index fae7a6a9c4..aa0f3b6e20 100644
--- a/src/core/lib/security/credentials/fake/fake_credentials.h
+++ b/src/core/lib/security/credentials/fake/fake_credentials.h
@@ -52,8 +52,8 @@ const char *grpc_fake_transport_get_expected_targets(
 
 typedef struct {
   grpc_call_credentials base;
-  grpc_credentials_md_store *md_store;
-  int is_async;
+  grpc_mdelem md;
+  bool is_async;
 } grpc_md_only_test_credentials;
 
 #endif /* GRPC_CORE_LIB_SECURITY_CREDENTIALS_FAKE_FAKE_CREDENTIALS_H */
diff --git a/src/core/lib/security/credentials/iam/iam_credentials.c b/src/core/lib/security/credentials/iam/iam_credentials.c
index 4b32c5a047..3de8319d98 100644
--- a/src/core/lib/security/credentials/iam/iam_credentials.c
+++ b/src/core/lib/security/credentials/iam/iam_credentials.c
@@ -30,26 +30,33 @@
 static void iam_destruct(grpc_exec_ctx *exec_ctx,
                          grpc_call_credentials *creds) {
   grpc_google_iam_credentials *c = (grpc_google_iam_credentials *)creds;
-  grpc_credentials_md_store_unref(exec_ctx, c->iam_md);
+  grpc_credentials_mdelem_array_destroy(exec_ctx, &c->md_array);
 }
 
-static void iam_get_request_metadata(grpc_exec_ctx *exec_ctx,
+static bool iam_get_request_metadata(grpc_exec_ctx *exec_ctx,
                                      grpc_call_credentials *creds,
                                      grpc_polling_entity *pollent,
                                      grpc_auth_metadata_context context,
-                                     grpc_credentials_metadata_cb cb,
-                                     void *user_data) {
+                                     grpc_credentials_mdelem_array *md_array,
+                                     grpc_closure *on_request_metadata,
+                                     grpc_error **error) {
   grpc_google_iam_credentials *c = (grpc_google_iam_credentials *)creds;
-  cb(exec_ctx, user_data, c->iam_md->entries, c->iam_md->num_entries,
-     GRPC_CREDENTIALS_OK, NULL);
+  grpc_credentials_mdelem_array_append(md_array, &c->md_array);
+  return true;
 }
 
-static grpc_call_credentials_vtable iam_vtable = {iam_destruct,
-                                                  iam_get_request_metadata};
+static void iam_cancel_get_request_metadata(
+    grpc_exec_ctx *exec_ctx, grpc_call_credentials *c,
+    grpc_credentials_mdelem_array *md_array, grpc_error *error) {
+  GRPC_ERROR_UNREF(error);
+}
+
+static grpc_call_credentials_vtable iam_vtable = {
+    iam_destruct, iam_get_request_metadata, iam_cancel_get_request_metadata};
 
 grpc_call_credentials *grpc_google_iam_credentials_create(
     const char *token, const char *authority_selector, void *reserved) {
-  grpc_google_iam_credentials *c;
+  grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
   GRPC_API_TRACE(
       "grpc_iam_credentials_create(token=%s, authority_selector=%s, "
       "reserved=%p)",
@@ -57,14 +64,22 @@ grpc_call_credentials *grpc_google_iam_credentials_create(
   GPR_ASSERT(reserved == NULL);
   GPR_ASSERT(token != NULL);
   GPR_ASSERT(authority_selector != NULL);
-  c = gpr_zalloc(sizeof(grpc_google_iam_credentials));
+  grpc_google_iam_credentials *c = gpr_zalloc(sizeof(*c));
   c->base.type = GRPC_CALL_CREDENTIALS_TYPE_IAM;
   c->base.vtable = &iam_vtable;
   gpr_ref_init(&c->base.refcount, 1);
-  c->iam_md = grpc_credentials_md_store_create(2);
-  grpc_credentials_md_store_add_cstrings(
-      c->iam_md, GRPC_IAM_AUTHORIZATION_TOKEN_METADATA_KEY, token);
-  grpc_credentials_md_store_add_cstrings(
-      c->iam_md, GRPC_IAM_AUTHORITY_SELECTOR_METADATA_KEY, authority_selector);
+  grpc_mdelem md = grpc_mdelem_from_slices(
+      &exec_ctx,
+      grpc_slice_from_static_string(GRPC_IAM_AUTHORIZATION_TOKEN_METADATA_KEY),
+      grpc_slice_from_copied_string(token));
+  grpc_credentials_mdelem_array_add(&c->md_array, md);
+  GRPC_MDELEM_UNREF(&exec_ctx, md);
+  md = grpc_mdelem_from_slices(
+      &exec_ctx,
+      grpc_slice_from_static_string(GRPC_IAM_AUTHORITY_SELECTOR_METADATA_KEY),
+      grpc_slice_from_copied_string(authority_selector));
+  grpc_credentials_mdelem_array_add(&c->md_array, md);
+  GRPC_MDELEM_UNREF(&exec_ctx, md);
+  grpc_exec_ctx_finish(&exec_ctx);
   return &c->base;
 }
diff --git a/src/core/lib/security/credentials/iam/iam_credentials.h b/src/core/lib/security/credentials/iam/iam_credentials.h
index fff3c6d2ca..5e3cf65bad 100644
--- a/src/core/lib/security/credentials/iam/iam_credentials.h
+++ b/src/core/lib/security/credentials/iam/iam_credentials.h
@@ -23,7 +23,7 @@
 
 typedef struct {
   grpc_call_credentials base;
-  grpc_credentials_md_store *iam_md;
+  grpc_credentials_mdelem_array md_array;
 } grpc_google_iam_credentials;
 
 #endif /* GRPC_CORE_LIB_SECURITY_CREDENTIALS_IAM_IAM_CREDENTIALS_H */
diff --git a/src/core/lib/security/credentials/jwt/jwt_credentials.c b/src/core/lib/security/credentials/jwt/jwt_credentials.c
index 4357657def..02c82e99ba 100644
--- a/src/core/lib/security/credentials/jwt/jwt_credentials.c
+++ b/src/core/lib/security/credentials/jwt/jwt_credentials.c
@@ -29,10 +29,8 @@
 
 static void jwt_reset_cache(grpc_exec_ctx *exec_ctx,
                             grpc_service_account_jwt_access_credentials *c) {
-  if (c->cached.jwt_md != NULL) {
-    grpc_credentials_md_store_unref(exec_ctx, c->cached.jwt_md);
-    c->cached.jwt_md = NULL;
-  }
+  GRPC_MDELEM_UNREF(exec_ctx, c->cached.jwt_md);
+  c->cached.jwt_md = GRPC_MDNULL;
   if (c->cached.service_url != NULL) {
     gpr_free(c->cached.service_url);
     c->cached.service_url = NULL;
@@ -49,33 +47,34 @@ static void jwt_destruct(grpc_exec_ctx *exec_ctx,
   gpr_mu_destroy(&c->cache_mu);
 }
 
-static void jwt_get_request_metadata(grpc_exec_ctx *exec_ctx,
+static bool jwt_get_request_metadata(grpc_exec_ctx *exec_ctx,
                                      grpc_call_credentials *creds,
                                      grpc_polling_entity *pollent,
                                      grpc_auth_metadata_context context,
-                                     grpc_credentials_metadata_cb cb,
-                                     void *user_data) {
+                                     grpc_credentials_mdelem_array *md_array,
+                                     grpc_closure *on_request_metadata,
+                                     grpc_error **error) {
   grpc_service_account_jwt_access_credentials *c =
       (grpc_service_account_jwt_access_credentials *)creds;
   gpr_timespec refresh_threshold = gpr_time_from_seconds(
       GRPC_SECURE_TOKEN_REFRESH_THRESHOLD_SECS, GPR_TIMESPAN);
 
   /* See if we can return a cached jwt. */
-  grpc_credentials_md_store *jwt_md = NULL;
+  grpc_mdelem jwt_md = GRPC_MDNULL;
   {
     gpr_mu_lock(&c->cache_mu);
     if (c->cached.service_url != NULL &&
         strcmp(c->cached.service_url, context.service_url) == 0 &&
-        c->cached.jwt_md != NULL &&
+        !GRPC_MDISNULL(c->cached.jwt_md) &&
         (gpr_time_cmp(gpr_time_sub(c->cached.jwt_expiration,
                                    gpr_now(GPR_CLOCK_REALTIME)),
                       refresh_threshold) > 0)) {
-      jwt_md = grpc_credentials_md_store_ref(c->cached.jwt_md);
+      jwt_md = GRPC_MDELEM_REF(c->cached.jwt_md);
     }
     gpr_mu_unlock(&c->cache_mu);
   }
 
-  if (jwt_md == NULL) {
+  if (GRPC_MDISNULL(jwt_md)) {
     char *jwt = NULL;
     /* Generate a new jwt. */
     gpr_mu_lock(&c->cache_mu);
@@ -89,27 +88,33 @@ static void jwt_get_request_metadata(grpc_exec_ctx *exec_ctx,
       c->cached.jwt_expiration =
           gpr_time_add(gpr_now(GPR_CLOCK_REALTIME), c->jwt_lifetime);
       c->cached.service_url = gpr_strdup(context.service_url);
-      c->cached.jwt_md = grpc_credentials_md_store_create(1);
-      grpc_credentials_md_store_add_cstrings(
-          c->cached.jwt_md, GRPC_AUTHORIZATION_METADATA_KEY, md_value);
+      c->cached.jwt_md = grpc_mdelem_from_slices(
+          exec_ctx,
+          grpc_slice_from_static_string(GRPC_AUTHORIZATION_METADATA_KEY),
+          grpc_slice_from_copied_string(md_value));
       gpr_free(md_value);
-      jwt_md = grpc_credentials_md_store_ref(c->cached.jwt_md);
+      jwt_md = GRPC_MDELEM_REF(c->cached.jwt_md);
     }
     gpr_mu_unlock(&c->cache_mu);
   }
 
-  if (jwt_md != NULL) {
-    cb(exec_ctx, user_data, jwt_md->entries, jwt_md->num_entries,
-       GRPC_CREDENTIALS_OK, NULL);
-    grpc_credentials_md_store_unref(exec_ctx, jwt_md);
+  if (!GRPC_MDISNULL(jwt_md)) {
+    grpc_credentials_mdelem_array_add(md_array, jwt_md);
+    GRPC_MDELEM_UNREF(exec_ctx, jwt_md);
   } else {
-    cb(exec_ctx, user_data, NULL, 0, GRPC_CREDENTIALS_ERROR,
-       "Could not generate JWT.");
+    *error = GRPC_ERROR_CREATE_FROM_STATIC_STRING("Could not generate JWT.");
   }
+  return true;
+}
+
+static void jwt_cancel_get_request_metadata(
+    grpc_exec_ctx *exec_ctx, grpc_call_credentials *c,
+    grpc_credentials_mdelem_array *md_array, grpc_error *error) {
+  GRPC_ERROR_UNREF(error);
 }
 
-static grpc_call_credentials_vtable jwt_vtable = {jwt_destruct,
-                                                  jwt_get_request_metadata};
+static grpc_call_credentials_vtable jwt_vtable = {
+    jwt_destruct, jwt_get_request_metadata, jwt_cancel_get_request_metadata};
 
 grpc_call_credentials *
 grpc_service_account_jwt_access_credentials_create_from_auth_json_key(
diff --git a/src/core/lib/security/credentials/jwt/jwt_credentials.h b/src/core/lib/security/credentials/jwt/jwt_credentials.h
index 6e461f1715..07f4022669 100644
--- a/src/core/lib/security/credentials/jwt/jwt_credentials.h
+++ b/src/core/lib/security/credentials/jwt/jwt_credentials.h
@@ -29,7 +29,7 @@ typedef struct {
   // the service_url for a more sophisticated one.
   gpr_mu cache_mu;
   struct {
-    grpc_credentials_md_store *jwt_md;
+    grpc_mdelem jwt_md;
     char *service_url;
     gpr_timespec jwt_expiration;
   } cached;
diff --git a/src/core/lib/security/credentials/jwt/jwt_verifier.c b/src/core/lib/security/credentials/jwt/jwt_verifier.c
index 6cd558d123..a27284bc50 100644
--- a/src/core/lib/security/credentials/jwt/jwt_verifier.c
+++ b/src/core/lib/security/credentials/jwt/jwt_verifier.c
@@ -442,7 +442,7 @@ static EVP_PKEY *extract_pkey_from_x509(const char *x509_str) {
 
 end:
   BIO_free(bio);
-  if (x509 != NULL) X509_free(x509);
+  X509_free(x509);
   return result;
 }
 
@@ -496,6 +496,8 @@ static EVP_PKEY *pkey_from_jwk(grpc_exec_ctx *exec_ctx, const grpc_json *json,
   const grpc_json *key_prop;
   RSA *rsa = NULL;
   EVP_PKEY *result = NULL;
+  BIGNUM *tmp_n = NULL;
+  BIGNUM *tmp_e = NULL;
 
   GPR_ASSERT(kty != NULL && json != NULL);
   if (strcmp(kty, "RSA") != 0) {
@@ -507,8 +509,6 @@ static EVP_PKEY *pkey_from_jwk(grpc_exec_ctx *exec_ctx, const grpc_json *json,
     gpr_log(GPR_ERROR, "Could not create rsa key.");
     goto end;
   }
-  BIGNUM *tmp_n = NULL;
-  BIGNUM *tmp_e = NULL;
   for (key_prop = json->child; key_prop != NULL; key_prop = key_prop->next) {
     if (strcmp(key_prop->key, "n") == 0) {
       tmp_n =
@@ -528,11 +528,16 @@ static EVP_PKEY *pkey_from_jwk(grpc_exec_ctx *exec_ctx, const grpc_json *json,
     gpr_log(GPR_ERROR, "Cannot set RSA key from inputs.");
     goto end;
   }
+  /* RSA_set0_key takes ownership on success. */
+  tmp_n = NULL;
+  tmp_e = NULL;
   result = EVP_PKEY_new();
   EVP_PKEY_set1_RSA(result, rsa); /* uprefs rsa. */
 
 end:
-  if (rsa != NULL) RSA_free(rsa);
+  RSA_free(rsa);
+  BN_free(tmp_n);
+  BN_free(tmp_e);
   return result;
 }
 
@@ -618,7 +623,7 @@ static int verify_jwt_signature(EVP_PKEY *key, const char *alg,
   result = 1;
 
 end:
-  if (md_ctx != NULL) EVP_MD_CTX_destroy(md_ctx);
+  EVP_MD_CTX_destroy(md_ctx);
   return result;
 }
 
@@ -658,7 +663,7 @@ static void on_keys_retrieved(grpc_exec_ctx *exec_ctx, void *user_data,
 
 end:
   if (json != NULL) grpc_json_destroy(json);
-  if (verification_key != NULL) EVP_PKEY_free(verification_key);
+  EVP_PKEY_free(verification_key);
   ctx->user_cb(exec_ctx, ctx->user_data, status, claims);
   verifier_cb_ctx_destroy(exec_ctx, ctx);
 }
diff --git a/src/core/lib/security/credentials/oauth2/oauth2_credentials.c b/src/core/lib/security/credentials/oauth2/oauth2_credentials.c
index 9de561b310..10b270c49c 100644
--- a/src/core/lib/security/credentials/oauth2/oauth2_credentials.c
+++ b/src/core/lib/security/credentials/oauth2/oauth2_credentials.c
@@ -107,15 +107,17 @@ static void oauth2_token_fetcher_destruct(grpc_exec_ctx *exec_ctx,
                                           grpc_call_credentials *creds) {
   grpc_oauth2_token_fetcher_credentials *c =
       (grpc_oauth2_token_fetcher_credentials *)creds;
-  grpc_credentials_md_store_unref(exec_ctx, c->access_token_md);
+  GRPC_MDELEM_UNREF(exec_ctx, c->access_token_md);
   gpr_mu_destroy(&c->mu);
+  grpc_pollset_set_destroy(exec_ctx,
+                           grpc_polling_entity_pollset_set(&c->pollent));
   grpc_httpcli_context_destroy(exec_ctx, &c->httpcli_context);
 }
 
 grpc_credentials_status
 grpc_oauth2_token_fetcher_credentials_parse_server_response(
     grpc_exec_ctx *exec_ctx, const grpc_http_response *response,
-    grpc_credentials_md_store **token_md, gpr_timespec *token_lifetime) {
+    grpc_mdelem *token_md, gpr_timespec *token_lifetime) {
   char *null_terminated_body = NULL;
   char *new_access_token = NULL;
   grpc_credentials_status status = GRPC_CREDENTIALS_OK;
@@ -184,17 +186,18 @@ grpc_oauth2_token_fetcher_credentials_parse_server_response(
     token_lifetime->tv_sec = strtol(expires_in->value, NULL, 10);
     token_lifetime->tv_nsec = 0;
     token_lifetime->clock_type = GPR_TIMESPAN;
-    if (*token_md != NULL) grpc_credentials_md_store_unref(exec_ctx, *token_md);
-    *token_md = grpc_credentials_md_store_create(1);
-    grpc_credentials_md_store_add_cstrings(
-        *token_md, GRPC_AUTHORIZATION_METADATA_KEY, new_access_token);
+    if (!GRPC_MDISNULL(*token_md)) GRPC_MDELEM_UNREF(exec_ctx, *token_md);
+    *token_md = grpc_mdelem_from_slices(
+        exec_ctx,
+        grpc_slice_from_static_string(GRPC_AUTHORIZATION_METADATA_KEY),
+        grpc_slice_from_copied_string(new_access_token));
     status = GRPC_CREDENTIALS_OK;
   }
 
 end:
-  if (status != GRPC_CREDENTIALS_OK && (*token_md != NULL)) {
-    grpc_credentials_md_store_unref(exec_ctx, *token_md);
-    *token_md = NULL;
+  if (status != GRPC_CREDENTIALS_OK && !GRPC_MDISNULL(*token_md)) {
+    GRPC_MDELEM_UNREF(exec_ctx, *token_md);
+    *token_md = GRPC_MDNULL;
   }
   if (null_terminated_body != NULL) gpr_free(null_terminated_body);
   if (new_access_token != NULL) gpr_free(new_access_token);
@@ -205,63 +208,130 @@ end:
 static void on_oauth2_token_fetcher_http_response(grpc_exec_ctx *exec_ctx,
                                                   void *user_data,
                                                   grpc_error *error) {
+  GRPC_LOG_IF_ERROR("oauth_fetch", GRPC_ERROR_REF(error));
   grpc_credentials_metadata_request *r =
       (grpc_credentials_metadata_request *)user_data;
   grpc_oauth2_token_fetcher_credentials *c =
       (grpc_oauth2_token_fetcher_credentials *)r->creds;
+  grpc_mdelem access_token_md = GRPC_MDNULL;
   gpr_timespec token_lifetime;
-  grpc_credentials_status status;
-
-  GRPC_LOG_IF_ERROR("oauth_fetch", GRPC_ERROR_REF(error));
-
+  grpc_credentials_status status =
+      grpc_oauth2_token_fetcher_credentials_parse_server_response(
+          exec_ctx, &r->response, &access_token_md, &token_lifetime);
+  // Update cache and grab list of pending requests.
   gpr_mu_lock(&c->mu);
-  status = grpc_oauth2_token_fetcher_credentials_parse_server_response(
-      exec_ctx, &r->response, &c->access_token_md, &token_lifetime);
-  if (status == GRPC_CREDENTIALS_OK) {
-    c->token_expiration =
-        gpr_time_add(gpr_now(GPR_CLOCK_REALTIME), token_lifetime);
-    r->cb(exec_ctx, r->user_data, c->access_token_md->entries,
-          c->access_token_md->num_entries, GRPC_CREDENTIALS_OK, NULL);
-  } else {
-    c->token_expiration = gpr_inf_past(GPR_CLOCK_REALTIME);
-    r->cb(exec_ctx, r->user_data, NULL, 0, status,
-          "Error occured when fetching oauth2 token.");
-  }
+  c->token_fetch_pending = false;
+  c->access_token_md = GRPC_MDELEM_REF(access_token_md);
+  c->token_expiration =
+      status == GRPC_CREDENTIALS_OK
+          ? gpr_time_add(gpr_now(GPR_CLOCK_REALTIME), token_lifetime)
+          : gpr_inf_past(GPR_CLOCK_REALTIME);
+  grpc_oauth2_pending_get_request_metadata *pending_request =
+      c->pending_requests;
+  c->pending_requests = NULL;
   gpr_mu_unlock(&c->mu);
+  // Invoke callbacks for all pending requests.
+  while (pending_request != NULL) {
+    if (status == GRPC_CREDENTIALS_OK) {
+      grpc_credentials_mdelem_array_add(pending_request->md_array,
+                                        access_token_md);
+    } else {
+      error = GRPC_ERROR_CREATE_REFERENCING_FROM_STATIC_STRING(
+          "Error occured when fetching oauth2 token.", &error, 1);
+    }
+    GRPC_CLOSURE_SCHED(exec_ctx, pending_request->on_request_metadata, error);
+    grpc_polling_entity_del_from_pollset_set(
+        exec_ctx, pending_request->pollent,
+        grpc_polling_entity_pollset_set(&c->pollent));
+    grpc_oauth2_pending_get_request_metadata *prev = pending_request;
+    pending_request = pending_request->next;
+    gpr_free(prev);
+  }
+  GRPC_MDELEM_UNREF(exec_ctx, access_token_md);
+  grpc_call_credentials_unref(exec_ctx, r->creds);
   grpc_credentials_metadata_request_destroy(exec_ctx, r);
 }
 
-static void oauth2_token_fetcher_get_request_metadata(
+static bool oauth2_token_fetcher_get_request_metadata(
     grpc_exec_ctx *exec_ctx, grpc_call_credentials *creds,
     grpc_polling_entity *pollent, grpc_auth_metadata_context context,
-    grpc_credentials_metadata_cb cb, void *user_data) {
+    grpc_credentials_mdelem_array *md_array, grpc_closure *on_request_metadata,
+    grpc_error **error) {
   grpc_oauth2_token_fetcher_credentials *c =
       (grpc_oauth2_token_fetcher_credentials *)creds;
+  // Check if we can use the cached token.
   gpr_timespec refresh_threshold = gpr_time_from_seconds(
       GRPC_SECURE_TOKEN_REFRESH_THRESHOLD_SECS, GPR_TIMESPAN);
-  grpc_credentials_md_store *cached_access_token_md = NULL;
-  {
-    gpr_mu_lock(&c->mu);
-    if (c->access_token_md != NULL &&
-        (gpr_time_cmp(
-             gpr_time_sub(c->token_expiration, gpr_now(GPR_CLOCK_REALTIME)),
-             refresh_threshold) > 0)) {
-      cached_access_token_md =
-          grpc_credentials_md_store_ref(c->access_token_md);
-    }
+  grpc_mdelem cached_access_token_md = GRPC_MDNULL;
+  gpr_mu_lock(&c->mu);
+  if (!GRPC_MDISNULL(c->access_token_md) &&
+      (gpr_time_cmp(
+           gpr_time_sub(c->token_expiration, gpr_now(GPR_CLOCK_REALTIME)),
+           refresh_threshold) > 0)) {
+    cached_access_token_md = GRPC_MDELEM_REF(c->access_token_md);
+  }
+  if (!GRPC_MDISNULL(cached_access_token_md)) {
     gpr_mu_unlock(&c->mu);
+    grpc_credentials_mdelem_array_add(md_array, cached_access_token_md);
+    GRPC_MDELEM_UNREF(exec_ctx, cached_access_token_md);
+    return true;
   }
-  if (cached_access_token_md != NULL) {
-    cb(exec_ctx, user_data, cached_access_token_md->entries,
-       cached_access_token_md->num_entries, GRPC_CREDENTIALS_OK, NULL);
-    grpc_credentials_md_store_unref(exec_ctx, cached_access_token_md);
-  } else {
+  // Couldn't get the token from the cache.
+  // Add request to c->pending_requests and start a new fetch if needed.
+  grpc_oauth2_pending_get_request_metadata *pending_request =
+      (grpc_oauth2_pending_get_request_metadata *)gpr_malloc(
+          sizeof(*pending_request));
+  pending_request->md_array = md_array;
+  pending_request->on_request_metadata = on_request_metadata;
+  pending_request->pollent = pollent;
+  grpc_polling_entity_add_to_pollset_set(
+      exec_ctx, pollent, grpc_polling_entity_pollset_set(&c->pollent));
+  pending_request->next = c->pending_requests;
+  c->pending_requests = pending_request;
+  bool start_fetch = false;
+  if (!c->token_fetch_pending) {
+    c->token_fetch_pending = true;
+    start_fetch = true;
+  }
+  gpr_mu_unlock(&c->mu);
+  if (start_fetch) {
+    grpc_call_credentials_ref(creds);
     c->fetch_func(
-        exec_ctx,
-        grpc_credentials_metadata_request_create(creds, cb, user_data),
-        &c->httpcli_context, pollent, on_oauth2_token_fetcher_http_response,
-        gpr_time_add(gpr_now(GPR_CLOCK_REALTIME), refresh_threshold));
+        exec_ctx, grpc_credentials_metadata_request_create(creds),
+        &c->httpcli_context, &c->pollent, on_oauth2_token_fetcher_http_response,
+        gpr_time_add(gpr_now(GPR_CLOCK_MONOTONIC), refresh_threshold));
   }
+  return false;
+}
+
+static void oauth2_token_fetcher_cancel_get_request_metadata(
+    grpc_exec_ctx *exec_ctx, grpc_call_credentials *creds,
+    grpc_credentials_mdelem_array *md_array, grpc_error *error) {
+  grpc_oauth2_token_fetcher_credentials *c =
+      (grpc_oauth2_token_fetcher_credentials *)creds;
+  gpr_mu_lock(&c->mu);
+  grpc_oauth2_pending_get_request_metadata *prev = NULL;
+  grpc_oauth2_pending_get_request_metadata *pending_request =
+      c->pending_requests;
+  while (pending_request != NULL) {
+    if (pending_request->md_array == md_array) {
+      // Remove matching pending request from the list.
+      if (prev != NULL) {
+        prev->next = pending_request->next;
+      } else {
+        c->pending_requests = pending_request->next;
+      }
+      // Invoke the callback immediately with an error.
+      GRPC_CLOSURE_SCHED(exec_ctx, pending_request->on_request_metadata,
+                         GRPC_ERROR_REF(error));
+      gpr_free(pending_request);
+      break;
+    }
+    prev = pending_request;
+    pending_request = pending_request->next;
+  }
+  gpr_mu_unlock(&c->mu);
+  GRPC_ERROR_UNREF(error);
 }
 
 static void init_oauth2_token_fetcher(grpc_oauth2_token_fetcher_credentials *c,
@@ -272,6 +342,8 @@ static void init_oauth2_token_fetcher(grpc_oauth2_token_fetcher_credentials *c,
   gpr_mu_init(&c->mu);
   c->token_expiration = gpr_inf_past(GPR_CLOCK_REALTIME);
   c->fetch_func = fetch_func;
+  c->pollent =
+      grpc_polling_entity_create_from_pollset_set(grpc_pollset_set_create());
   grpc_httpcli_context_init(&c->httpcli_context);
 }
 
@@ -280,7 +352,8 @@ static void init_oauth2_token_fetcher(grpc_oauth2_token_fetcher_credentials *c,
 //
 
 static grpc_call_credentials_vtable compute_engine_vtable = {
-    oauth2_token_fetcher_destruct, oauth2_token_fetcher_get_request_metadata};
+    oauth2_token_fetcher_destruct, oauth2_token_fetcher_get_request_metadata,
+    oauth2_token_fetcher_cancel_get_request_metadata};
 
 static void compute_engine_fetch_oauth2(
     grpc_exec_ctx *exec_ctx, grpc_credentials_metadata_request *metadata_req,
@@ -301,7 +374,6 @@ static void compute_engine_fetch_oauth2(
   grpc_httpcli_get(
       exec_ctx, httpcli_context, pollent, resource_quota, &request, deadline,
       GRPC_CLOSURE_CREATE(response_cb, metadata_req, grpc_schedule_on_exec_ctx),
-
       &metadata_req->response);
   grpc_resource_quota_unref_internal(exec_ctx, resource_quota);
 }
@@ -331,7 +403,8 @@ static void refresh_token_destruct(grpc_exec_ctx *exec_ctx,
 }
 
 static grpc_call_credentials_vtable refresh_token_vtable = {
-    refresh_token_destruct, oauth2_token_fetcher_get_request_metadata};
+    refresh_token_destruct, oauth2_token_fetcher_get_request_metadata,
+    oauth2_token_fetcher_cancel_get_request_metadata};
 
 static void refresh_token_fetch_oauth2(
     grpc_exec_ctx *exec_ctx, grpc_credentials_metadata_request *metadata_req,
@@ -416,26 +489,33 @@ grpc_call_credentials *grpc_google_refresh_token_credentials_create(
 static void access_token_destruct(grpc_exec_ctx *exec_ctx,
                                   grpc_call_credentials *creds) {
   grpc_access_token_credentials *c = (grpc_access_token_credentials *)creds;
-  grpc_credentials_md_store_unref(exec_ctx, c->access_token_md);
+  GRPC_MDELEM_UNREF(exec_ctx, c->access_token_md);
 }
 
-static void access_token_get_request_metadata(
+static bool access_token_get_request_metadata(
     grpc_exec_ctx *exec_ctx, grpc_call_credentials *creds,
     grpc_polling_entity *pollent, grpc_auth_metadata_context context,
-    grpc_credentials_metadata_cb cb, void *user_data) {
+    grpc_credentials_mdelem_array *md_array, grpc_closure *on_request_metadata,
+    grpc_error **error) {
   grpc_access_token_credentials *c = (grpc_access_token_credentials *)creds;
-  cb(exec_ctx, user_data, c->access_token_md->entries, 1, GRPC_CREDENTIALS_OK,
-     NULL);
+  grpc_credentials_mdelem_array_add(md_array, c->access_token_md);
+  return true;
+}
+
+static void access_token_cancel_get_request_metadata(
+    grpc_exec_ctx *exec_ctx, grpc_call_credentials *c,
+    grpc_credentials_mdelem_array *md_array, grpc_error *error) {
+  GRPC_ERROR_UNREF(error);
 }
 
 static grpc_call_credentials_vtable access_token_vtable = {
-    access_token_destruct, access_token_get_request_metadata};
+    access_token_destruct, access_token_get_request_metadata,
+    access_token_cancel_get_request_metadata};
 
 grpc_call_credentials *grpc_access_token_credentials_create(
     const char *access_token, void *reserved) {
   grpc_access_token_credentials *c =
       gpr_zalloc(sizeof(grpc_access_token_credentials));
-  char *token_md_value;
   GRPC_API_TRACE(
       "grpc_access_token_credentials_create(access_token=<redacted>, "
       "reserved=%p)",
@@ -444,10 +524,13 @@ grpc_call_credentials *grpc_access_token_credentials_create(
   c->base.type = GRPC_CALL_CREDENTIALS_TYPE_OAUTH2;
   c->base.vtable = &access_token_vtable;
   gpr_ref_init(&c->base.refcount, 1);
-  c->access_token_md = grpc_credentials_md_store_create(1);
+  char *token_md_value;
   gpr_asprintf(&token_md_value, "Bearer %s", access_token);
-  grpc_credentials_md_store_add_cstrings(
-      c->access_token_md, GRPC_AUTHORIZATION_METADATA_KEY, token_md_value);
+  grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
+  c->access_token_md = grpc_mdelem_from_slices(
+      &exec_ctx, grpc_slice_from_static_string(GRPC_AUTHORIZATION_METADATA_KEY),
+      grpc_slice_from_copied_string(token_md_value));
+  grpc_exec_ctx_finish(&exec_ctx);
   gpr_free(token_md_value);
   return &c->base;
 }
diff --git a/src/core/lib/security/credentials/oauth2/oauth2_credentials.h b/src/core/lib/security/credentials/oauth2/oauth2_credentials.h
index 72093afe9e..d9ad6691b8 100644
--- a/src/core/lib/security/credentials/oauth2/oauth2_credentials.h
+++ b/src/core/lib/security/credentials/oauth2/oauth2_credentials.h
@@ -58,13 +58,24 @@ typedef void (*grpc_fetch_oauth2_func)(grpc_exec_ctx *exec_ctx,
                                        grpc_polling_entity *pollent,
                                        grpc_iomgr_cb_func cb,
                                        gpr_timespec deadline);
+
+typedef struct grpc_oauth2_pending_get_request_metadata {
+  grpc_credentials_mdelem_array *md_array;
+  grpc_closure *on_request_metadata;
+  grpc_polling_entity *pollent;
+  struct grpc_oauth2_pending_get_request_metadata *next;
+} grpc_oauth2_pending_get_request_metadata;
+
 typedef struct {
   grpc_call_credentials base;
   gpr_mu mu;
-  grpc_credentials_md_store *access_token_md;
+  grpc_mdelem access_token_md;
   gpr_timespec token_expiration;
+  bool token_fetch_pending;
+  grpc_oauth2_pending_get_request_metadata *pending_requests;
   grpc_httpcli_context httpcli_context;
   grpc_fetch_oauth2_func fetch_func;
+  grpc_polling_entity pollent;
 } grpc_oauth2_token_fetcher_credentials;
 
 // Google refresh token credentials.
@@ -76,7 +87,7 @@ typedef struct {
 // Access token credentials.
 typedef struct {
   grpc_call_credentials base;
-  grpc_credentials_md_store *access_token_md;
+  grpc_mdelem access_token_md;
 } grpc_access_token_credentials;
 
 // Private constructor for refresh token credentials from an already parsed
@@ -89,6 +100,6 @@ grpc_refresh_token_credentials_create_from_auth_refresh_token(
 grpc_credentials_status
 grpc_oauth2_token_fetcher_credentials_parse_server_response(
     grpc_exec_ctx *exec_ctx, const struct grpc_http_response *response,
-    grpc_credentials_md_store **token_md, gpr_timespec *token_lifetime);
+    grpc_mdelem *token_md, gpr_timespec *token_lifetime);
 
 #endif /* GRPC_CORE_LIB_SECURITY_CREDENTIALS_OAUTH2_OAUTH2_CREDENTIALS_H */
diff --git a/src/core/lib/security/credentials/plugin/plugin_credentials.c b/src/core/lib/security/credentials/plugin/plugin_credentials.c
index 96ebfb4d0d..73e0c23e0f 100644
--- a/src/core/lib/security/credentials/plugin/plugin_credentials.c
+++ b/src/core/lib/security/credentials/plugin/plugin_credentials.c
@@ -31,19 +31,28 @@
 #include "src/core/lib/surface/api_trace.h"
 #include "src/core/lib/surface/validate_metadata.h"
 
-typedef struct {
-  void *user_data;
-  grpc_credentials_metadata_cb cb;
-} grpc_metadata_plugin_request;
-
 static void plugin_destruct(grpc_exec_ctx *exec_ctx,
                             grpc_call_credentials *creds) {
   grpc_plugin_credentials *c = (grpc_plugin_credentials *)creds;
+  gpr_mu_destroy(&c->mu);
   if (c->plugin.state != NULL && c->plugin.destroy != NULL) {
     c->plugin.destroy(c->plugin.state);
   }
 }
 
+static void pending_request_remove_locked(
+    grpc_plugin_credentials *c,
+    grpc_plugin_credentials_pending_request *pending_request) {
+  if (pending_request->prev == NULL) {
+    c->pending_requests = pending_request->next;
+  } else {
+    pending_request->prev->next = pending_request->next;
+  }
+  if (pending_request->next != NULL) {
+    pending_request->next->prev = pending_request->prev;
+  }
+}
+
 static void plugin_md_request_metadata_ready(void *request,
                                              const grpc_metadata *md,
                                              size_t num_md,
@@ -53,76 +62,117 @@ static void plugin_md_request_metadata_ready(void *request,
   grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INITIALIZER(
       GRPC_EXEC_CTX_FLAG_IS_FINISHED | GRPC_EXEC_CTX_FLAG_THREAD_RESOURCE_LOOP,
       NULL, NULL);
-  grpc_metadata_plugin_request *r = (grpc_metadata_plugin_request *)request;
-  if (status != GRPC_STATUS_OK) {
-    if (error_details != NULL) {
-      gpr_log(GPR_ERROR, "Getting metadata from plugin failed with error: %s",
-              error_details);
-    }
-    r->cb(&exec_ctx, r->user_data, NULL, 0, GRPC_CREDENTIALS_ERROR,
-          error_details);
-  } else {
-    size_t i;
-    bool seen_illegal_header = false;
-    grpc_credentials_md *md_array = NULL;
-    for (i = 0; i < num_md; i++) {
-      if (!GRPC_LOG_IF_ERROR("validate_metadata_from_plugin",
-                             grpc_validate_header_key_is_legal(md[i].key))) {
-        seen_illegal_header = true;
-        break;
-      } else if (!grpc_is_binary_header(md[i].key) &&
-                 !GRPC_LOG_IF_ERROR(
-                     "validate_metadata_from_plugin",
-                     grpc_validate_header_nonbin_value_is_legal(md[i].value))) {
-        gpr_log(GPR_ERROR, "Plugin added invalid metadata value.");
-        seen_illegal_header = true;
-        break;
+  grpc_plugin_credentials_pending_request *r =
+      (grpc_plugin_credentials_pending_request *)request;
+  // Check if the request has been cancelled.
+  // If not, remove it from the pending list, so that it cannot be
+  // cancelled out from under us.
+  gpr_mu_lock(&r->creds->mu);
+  if (!r->cancelled) pending_request_remove_locked(r->creds, r);
+  gpr_mu_unlock(&r->creds->mu);
+  grpc_call_credentials_unref(&exec_ctx, &r->creds->base);
+  // If it has not been cancelled, process it.
+  if (!r->cancelled) {
+    if (status != GRPC_STATUS_OK) {
+      char *msg;
+      gpr_asprintf(&msg, "Getting metadata from plugin failed with error: %s",
+                   error_details);
+      GRPC_CLOSURE_SCHED(&exec_ctx, r->on_request_metadata,
+                         GRPC_ERROR_CREATE_FROM_COPIED_STRING(msg));
+      gpr_free(msg);
+    } else {
+      bool seen_illegal_header = false;
+      for (size_t i = 0; i < num_md; ++i) {
+        if (!GRPC_LOG_IF_ERROR("validate_metadata_from_plugin",
+                               grpc_validate_header_key_is_legal(md[i].key))) {
+          seen_illegal_header = true;
+          break;
+        } else if (!grpc_is_binary_header(md[i].key) &&
+                   !GRPC_LOG_IF_ERROR(
+                       "validate_metadata_from_plugin",
+                       grpc_validate_header_nonbin_value_is_legal(
+                           md[i].value))) {
+          gpr_log(GPR_ERROR, "Plugin added invalid metadata value.");
+          seen_illegal_header = true;
+          break;
+        }
       }
-    }
-    if (seen_illegal_header) {
-      r->cb(&exec_ctx, r->user_data, NULL, 0, GRPC_CREDENTIALS_ERROR,
-            "Illegal metadata");
-    } else if (num_md > 0) {
-      md_array = gpr_malloc(num_md * sizeof(grpc_credentials_md));
-      for (i = 0; i < num_md; i++) {
-        md_array[i].key = grpc_slice_ref_internal(md[i].key);
-        md_array[i].value = grpc_slice_ref_internal(md[i].value);
+      if (seen_illegal_header) {
+        GRPC_CLOSURE_SCHED(
+            &exec_ctx, r->on_request_metadata,
+            GRPC_ERROR_CREATE_FROM_STATIC_STRING("Illegal metadata"));
+      } else {
+        for (size_t i = 0; i < num_md; ++i) {
+          grpc_mdelem mdelem = grpc_mdelem_from_slices(
+              &exec_ctx, grpc_slice_ref_internal(md[i].key),
+              grpc_slice_ref_internal(md[i].value));
+          grpc_credentials_mdelem_array_add(r->md_array, mdelem);
+          GRPC_MDELEM_UNREF(&exec_ctx, mdelem);
+        }
+        GRPC_CLOSURE_SCHED(&exec_ctx, r->on_request_metadata, GRPC_ERROR_NONE);
       }
-      r->cb(&exec_ctx, r->user_data, md_array, num_md, GRPC_CREDENTIALS_OK,
-            NULL);
-      for (i = 0; i < num_md; i++) {
-        grpc_slice_unref_internal(&exec_ctx, md_array[i].key);
-        grpc_slice_unref_internal(&exec_ctx, md_array[i].value);
-      }
-      gpr_free(md_array);
-    } else if (num_md == 0) {
-      r->cb(&exec_ctx, r->user_data, NULL, 0, GRPC_CREDENTIALS_OK, NULL);
     }
   }
   gpr_free(r);
   grpc_exec_ctx_finish(&exec_ctx);
 }
 
-static void plugin_get_request_metadata(grpc_exec_ctx *exec_ctx,
+static bool plugin_get_request_metadata(grpc_exec_ctx *exec_ctx,
                                         grpc_call_credentials *creds,
                                         grpc_polling_entity *pollent,
                                         grpc_auth_metadata_context context,
-                                        grpc_credentials_metadata_cb cb,
-                                        void *user_data) {
+                                        grpc_credentials_mdelem_array *md_array,
+                                        grpc_closure *on_request_metadata,
+                                        grpc_error **error) {
   grpc_plugin_credentials *c = (grpc_plugin_credentials *)creds;
   if (c->plugin.get_metadata != NULL) {
-    grpc_metadata_plugin_request *request = gpr_zalloc(sizeof(*request));
-    request->user_data = user_data;
-    request->cb = cb;
+    // Create pending_request object.
+    grpc_plugin_credentials_pending_request *pending_request =
+        (grpc_plugin_credentials_pending_request *)gpr_zalloc(
+            sizeof(*pending_request));
+    pending_request->creds = c;
+    pending_request->md_array = md_array;
+    pending_request->on_request_metadata = on_request_metadata;
+    // Add it to the pending list.
+    gpr_mu_lock(&c->mu);
+    if (c->pending_requests != NULL) {
+      c->pending_requests->prev = pending_request;
+    }
+    pending_request->next = c->pending_requests;
+    c->pending_requests = pending_request;
+    gpr_mu_unlock(&c->mu);
+    // Invoke the plugin.  The callback holds a ref to us.
+    grpc_call_credentials_ref(creds);
     c->plugin.get_metadata(c->plugin.state, context,
-                           plugin_md_request_metadata_ready, request);
-  } else {
-    cb(exec_ctx, user_data, NULL, 0, GRPC_CREDENTIALS_OK, NULL);
+                           plugin_md_request_metadata_ready, pending_request);
+    return false;
+  }
+  return true;
+}
+
+static void plugin_cancel_get_request_metadata(
+    grpc_exec_ctx *exec_ctx, grpc_call_credentials *creds,
+    grpc_credentials_mdelem_array *md_array, grpc_error *error) {
+  grpc_plugin_credentials *c = (grpc_plugin_credentials *)creds;
+  gpr_mu_lock(&c->mu);
+  for (grpc_plugin_credentials_pending_request *pending_request =
+           c->pending_requests;
+       pending_request != NULL; pending_request = pending_request->next) {
+    if (pending_request->md_array == md_array) {
+      pending_request->cancelled = true;
+      GRPC_CLOSURE_SCHED(exec_ctx, pending_request->on_request_metadata,
+                         GRPC_ERROR_REF(error));
+      pending_request_remove_locked(c, pending_request);
+      break;
+    }
   }
+  gpr_mu_unlock(&c->mu);
+  GRPC_ERROR_UNREF(error);
 }
 
 static grpc_call_credentials_vtable plugin_vtable = {
-    plugin_destruct, plugin_get_request_metadata};
+    plugin_destruct, plugin_get_request_metadata,
+    plugin_cancel_get_request_metadata};
 
 grpc_call_credentials *grpc_metadata_credentials_create_from_plugin(
     grpc_metadata_credentials_plugin plugin, void *reserved) {
@@ -134,5 +184,6 @@ grpc_call_credentials *grpc_metadata_credentials_create_from_plugin(
   c->base.vtable = &plugin_vtable;
   gpr_ref_init(&c->base.refcount, 1);
   c->plugin = plugin;
+  gpr_mu_init(&c->mu);
   return &c->base;
 }
diff --git a/src/core/lib/security/credentials/plugin/plugin_credentials.h b/src/core/lib/security/credentials/plugin/plugin_credentials.h
index ba3dd76859..57266d589a 100644
--- a/src/core/lib/security/credentials/plugin/plugin_credentials.h
+++ b/src/core/lib/security/credentials/plugin/plugin_credentials.h
@@ -21,10 +21,22 @@
 
 #include "src/core/lib/security/credentials/credentials.h"
 
-typedef struct {
+struct grpc_plugin_credentials;
+
+typedef struct grpc_plugin_credentials_pending_request {
+  bool cancelled;
+  struct grpc_plugin_credentials *creds;
+  grpc_credentials_mdelem_array *md_array;
+  grpc_closure *on_request_metadata;
+  struct grpc_plugin_credentials_pending_request *prev;
+  struct grpc_plugin_credentials_pending_request *next;
+} grpc_plugin_credentials_pending_request;
+
+typedef struct grpc_plugin_credentials {
   grpc_call_credentials base;
   grpc_metadata_credentials_plugin plugin;
-  grpc_credentials_md_store *plugin_md;
+  gpr_mu mu;
+  grpc_plugin_credentials_pending_request *pending_requests;
 } grpc_plugin_credentials;
 
 #endif /* GRPC_CORE_LIB_SECURITY_CREDENTIALS_PLUGIN_PLUGIN_CREDENTIALS_H */
diff --git a/src/core/lib/security/transport/client_auth_filter.c b/src/core/lib/security/transport/client_auth_filter.c
index 50a51b31cd..531a88434f 100644
--- a/src/core/lib/security/transport/client_auth_filter.c
+++ b/src/core/lib/security/transport/client_auth_filter.c
@@ -51,8 +51,15 @@ typedef struct {
   grpc_polling_entity *pollent;
   gpr_atm security_context_set;
   gpr_mu security_context_mu;
+  grpc_credentials_mdelem_array md_array;
   grpc_linked_mdelem md_links[MAX_CREDENTIALS_METADATA_COUNT];
   grpc_auth_metadata_context auth_md_context;
+  grpc_closure closure;
+  // Either 0 (no cancellation and no async operation in flight),
+  // a grpc_closure* (if the lowest bit is 0),
+  // or a grpc_error* (if the lowest bit is 1).
+  gpr_atm cancellation_state;
+  grpc_closure cancel_closure;
 } call_data;
 
 /* We can have a per-channel credentials. */
@@ -61,6 +68,43 @@ typedef struct {
   grpc_auth_context *auth_context;
 } channel_data;
 
+static void decode_cancel_state(gpr_atm cancel_state, grpc_closure **func,
+                                grpc_error **error) {
+  // If the lowest bit is 1, the value is a grpc_error*.
+  // Otherwise, if non-zdero, the value is a grpc_closure*.
+  if (cancel_state & 1) {
+    *error = (grpc_error *)(cancel_state & ~(gpr_atm)1);
+  } else if (cancel_state != 0) {
+    *func = (grpc_closure *)cancel_state;
+  }
+}
+
+static gpr_atm encode_cancel_state_error(grpc_error *error) {
+  // Set the lowest bit to 1 to indicate that it's an error.
+  return (gpr_atm)1 | (gpr_atm)error;
+}
+
+// Returns an error if the call has been cancelled.  Otherwise, sets the
+// cancellation function to be called upon cancellation.
+static grpc_error *set_cancel_func(grpc_call_element *elem,
+                                   grpc_iomgr_cb_func func) {
+  call_data *calld = (call_data *)elem->call_data;
+  // Decode original state.
+  gpr_atm original_state = gpr_atm_acq_load(&calld->cancellation_state);
+  grpc_error *original_error = GRPC_ERROR_NONE;
+  grpc_closure *original_func = NULL;
+  decode_cancel_state(original_state, &original_func, &original_error);
+  // If error is set, return it.
+  if (original_error != GRPC_ERROR_NONE) return GRPC_ERROR_REF(original_error);
+  // Otherwise, store func.
+  GRPC_CLOSURE_INIT(&calld->cancel_closure, func, elem,
+                    grpc_schedule_on_exec_ctx);
+  GPR_ASSERT(((gpr_atm)&calld->cancel_closure & (gpr_atm)1) == 0);
+  gpr_atm_rel_store(&calld->cancellation_state,
+                    (gpr_atm)&calld->cancel_closure);
+  return GRPC_ERROR_NONE;
+}
+
 static void reset_auth_metadata_context(
     grpc_auth_metadata_context *auth_md_context) {
   if (auth_md_context->service_url != NULL) {
@@ -86,41 +130,29 @@ static void add_error(grpc_error **combined, grpc_error *error) {
   *combined = grpc_error_add_child(*combined, error);
 }
 
-static void on_credentials_metadata(grpc_exec_ctx *exec_ctx, void *user_data,
-                                    grpc_credentials_md *md_elems,
-                                    size_t num_md,
-                                    grpc_credentials_status status,
-                                    const char *error_details) {
-  grpc_transport_stream_op_batch *batch =
-      (grpc_transport_stream_op_batch *)user_data;
+static void on_credentials_metadata(grpc_exec_ctx *exec_ctx, void *arg,
+                                    grpc_error *input_error) {
+  grpc_transport_stream_op_batch *batch = (grpc_transport_stream_op_batch *)arg;
   grpc_call_element *elem = batch->handler_private.extra_arg;
   call_data *calld = elem->call_data;
   reset_auth_metadata_context(&calld->auth_md_context);
-  grpc_error *error = GRPC_ERROR_NONE;
-  if (status != GRPC_CREDENTIALS_OK) {
-    error = grpc_error_set_int(
-        GRPC_ERROR_CREATE_FROM_COPIED_STRING(
-            error_details != NULL && strlen(error_details) > 0
-                ? error_details
-                : "Credentials failed to get metadata."),
-        GRPC_ERROR_INT_GRPC_STATUS, GRPC_STATUS_UNAUTHENTICATED);
-  } else {
-    GPR_ASSERT(num_md <= MAX_CREDENTIALS_METADATA_COUNT);
+  grpc_error *error = GRPC_ERROR_REF(input_error);
+  if (error == GRPC_ERROR_NONE) {
+    GPR_ASSERT(calld->md_array.size <= MAX_CREDENTIALS_METADATA_COUNT);
     GPR_ASSERT(batch->send_initial_metadata);
     grpc_metadata_batch *mdb =
         batch->payload->send_initial_metadata.send_initial_metadata;
-    for (size_t i = 0; i < num_md; i++) {
-      add_error(&error,
-                grpc_metadata_batch_add_tail(
-                    exec_ctx, mdb, &calld->md_links[i],
-                    grpc_mdelem_from_slices(
-                        exec_ctx, grpc_slice_ref_internal(md_elems[i].key),
-                        grpc_slice_ref_internal(md_elems[i].value))));
+    for (size_t i = 0; i < calld->md_array.size; ++i) {
+      add_error(&error, grpc_metadata_batch_add_tail(
+                            exec_ctx, mdb, &calld->md_links[i],
+                            GRPC_MDELEM_REF(calld->md_array.md[i])));
     }
   }
   if (error == GRPC_ERROR_NONE) {
     grpc_call_next_op(exec_ctx, elem, batch);
   } else {
+    error = grpc_error_set_int(error, GRPC_ERROR_INT_GRPC_STATUS,
+                               GRPC_STATUS_UNAUTHENTICATED);
     grpc_transport_stream_op_batch_finish_with_failure(exec_ctx, batch, error);
   }
 }
@@ -155,6 +187,14 @@ void build_auth_metadata_context(grpc_security_connector *sc,
   gpr_free(host);
 }
 
+static void cancel_get_request_metadata(grpc_exec_ctx *exec_ctx, void *arg,
+                                        grpc_error *error) {
+  grpc_call_element *elem = (grpc_call_element *)arg;
+  call_data *calld = (call_data *)elem->call_data;
+  grpc_call_credentials_cancel_get_request_metadata(
+      exec_ctx, calld->creds, &calld->md_array, GRPC_ERROR_REF(error));
+}
+
 static void send_security_metadata(grpc_exec_ctx *exec_ctx,
                                    grpc_call_element *elem,
                                    grpc_transport_stream_op_batch *batch) {
@@ -193,20 +233,33 @@ static void send_security_metadata(grpc_exec_ctx *exec_ctx,
 
   build_auth_metadata_context(&chand->security_connector->base,
                               chand->auth_context, calld);
+
+  grpc_error *cancel_error = set_cancel_func(elem, cancel_get_request_metadata);
+  if (cancel_error != GRPC_ERROR_NONE) {
+    grpc_transport_stream_op_batch_finish_with_failure(exec_ctx, batch,
+                                                       cancel_error);
+    return;
+  }
   GPR_ASSERT(calld->pollent != NULL);
-  grpc_call_credentials_get_request_metadata(
-      exec_ctx, calld->creds, calld->pollent, calld->auth_md_context,
-      on_credentials_metadata, batch);
+  GRPC_CLOSURE_INIT(&calld->closure, on_credentials_metadata, batch,
+                    grpc_schedule_on_exec_ctx);
+  grpc_error *error = GRPC_ERROR_NONE;
+  if (grpc_call_credentials_get_request_metadata(
+          exec_ctx, calld->creds, calld->pollent, calld->auth_md_context,
+          &calld->md_array, &calld->closure, &error)) {
+    // Synchronous return; invoke on_credentials_metadata() directly.
+    on_credentials_metadata(exec_ctx, batch, error);
+    GRPC_ERROR_UNREF(error);
+  }
 }
 
-static void on_host_checked(grpc_exec_ctx *exec_ctx, void *user_data,
-                            grpc_security_status status) {
-  grpc_transport_stream_op_batch *batch =
-      (grpc_transport_stream_op_batch *)user_data;
+static void on_host_checked(grpc_exec_ctx *exec_ctx, void *arg,
+                            grpc_error *error) {
+  grpc_transport_stream_op_batch *batch = (grpc_transport_stream_op_batch *)arg;
   grpc_call_element *elem = batch->handler_private.extra_arg;
   call_data *calld = elem->call_data;
 
-  if (status == GRPC_SECURITY_OK) {
+  if (error == GRPC_ERROR_NONE) {
     send_security_metadata(exec_ctx, elem, batch);
   } else {
     char *error_msg;
@@ -223,6 +276,16 @@ static void on_host_checked(grpc_exec_ctx *exec_ctx, void *user_data,
   }
 }
 
+static void cancel_check_call_host(grpc_exec_ctx *exec_ctx, void *arg,
+                                   grpc_error *error) {
+  grpc_call_element *elem = (grpc_call_element *)arg;
+  call_data *calld = (call_data *)elem->call_data;
+  channel_data *chand = (channel_data *)elem->channel_data;
+  grpc_channel_security_connector_cancel_check_call_host(
+      exec_ctx, chand->security_connector, &calld->closure,
+      GRPC_ERROR_REF(error));
+}
+
 static void auth_start_transport_stream_op_batch(
     grpc_exec_ctx *exec_ctx, grpc_call_element *elem,
     grpc_transport_stream_op_batch *batch) {
@@ -232,7 +295,32 @@ static void auth_start_transport_stream_op_batch(
   call_data *calld = elem->call_data;
   channel_data *chand = elem->channel_data;
 
-  if (!batch->cancel_stream) {
+  if (batch->cancel_stream) {
+    while (true) {
+      // Decode the original cancellation state.
+      gpr_atm original_state = gpr_atm_acq_load(&calld->cancellation_state);
+      grpc_error *cancel_error = GRPC_ERROR_NONE;
+      grpc_closure *func = NULL;
+      decode_cancel_state(original_state, &func, &cancel_error);
+      // If we had already set a cancellation error, there's nothing
+      // more to do.
+      if (cancel_error != GRPC_ERROR_NONE) break;
+      // If there's a cancel func, call it.
+      // Note that even if the cancel func has been changed by some
+      // other thread between when we decoded it and now, it will just
+      // be a no-op.
+      cancel_error = GRPC_ERROR_REF(batch->payload->cancel_stream.cancel_error);
+      if (func != NULL) {
+        GRPC_CLOSURE_SCHED(exec_ctx, func, GRPC_ERROR_REF(cancel_error));
+      }
+      // Encode the new error into cancellation state.
+      if (gpr_atm_full_cas(&calld->cancellation_state, original_state,
+                           encode_cancel_state_error(cancel_error))) {
+        break;  // Success.
+      }
+      // The cas failed, so try again.
+    }
+  } else {
     /* double checked lock over security context to ensure it's set once */
     if (gpr_atm_acq_load(&calld->security_context_set) == 0) {
       gpr_mu_lock(&calld->security_context_mu);
@@ -277,12 +365,26 @@ static void auth_start_transport_stream_op_batch(
       }
     }
     if (calld->have_host) {
-      char *call_host = grpc_slice_to_c_string(calld->host);
-      batch->handler_private.extra_arg = elem;
-      grpc_channel_security_connector_check_call_host(
-          exec_ctx, chand->security_connector, call_host, chand->auth_context,
-          on_host_checked, batch);
-      gpr_free(call_host);
+      grpc_error *cancel_error = set_cancel_func(elem, cancel_check_call_host);
+      if (cancel_error != GRPC_ERROR_NONE) {
+        grpc_transport_stream_op_batch_finish_with_failure(exec_ctx, batch,
+                                                           cancel_error);
+      } else {
+        char *call_host = grpc_slice_to_c_string(calld->host);
+        batch->handler_private.extra_arg = elem;
+        grpc_error *error = GRPC_ERROR_NONE;
+        if (grpc_channel_security_connector_check_call_host(
+                exec_ctx, chand->security_connector, call_host,
+                chand->auth_context,
+                GRPC_CLOSURE_INIT(&calld->closure, on_host_checked, batch,
+                                  grpc_schedule_on_exec_ctx),
+                &error)) {
+          // Synchronous return; invoke on_host_checked() directly.
+          on_host_checked(exec_ctx, batch, error);
+          GRPC_ERROR_UNREF(error);
+        }
+        gpr_free(call_host);
+      }
       GPR_TIMER_END("auth_start_transport_stream_op_batch", 0);
       return; /* early exit */
     }
@@ -315,6 +417,7 @@ static void destroy_call_elem(grpc_exec_ctx *exec_ctx, grpc_call_element *elem,
                               const grpc_call_final_info *final_info,
                               grpc_closure *ignored) {
   call_data *calld = elem->call_data;
+  grpc_credentials_mdelem_array_destroy(exec_ctx, &calld->md_array);
   grpc_call_credentials_unref(exec_ctx, calld->creds);
   if (calld->have_host) {
     grpc_slice_unref_internal(exec_ctx, calld->host);
@@ -324,6 +427,11 @@ static void destroy_call_elem(grpc_exec_ctx *exec_ctx, grpc_call_element *elem,
   }
   reset_auth_metadata_context(&calld->auth_md_context);
   gpr_mu_destroy(&calld->security_context_mu);
+  gpr_atm cancel_state = gpr_atm_acq_load(&calld->cancellation_state);
+  grpc_error *cancel_error = GRPC_ERROR_NONE;
+  grpc_closure *cancel_func = NULL;
+  decode_cancel_state(cancel_state, &cancel_func, &cancel_error);
+  GRPC_ERROR_UNREF(cancel_error);
 }
 
 /* Constructor for channel_data */
diff --git a/src/core/lib/security/transport/security_connector.c b/src/core/lib/security/transport/security_connector.c
index 6788126769..a7568b995f 100644
--- a/src/core/lib/security/transport/security_connector.c
+++ b/src/core/lib/security/transport/security_connector.c
@@ -136,15 +136,27 @@ void grpc_security_connector_check_peer(grpc_exec_ctx *exec_ctx,
   }
 }
 
-void grpc_channel_security_connector_check_call_host(
+bool grpc_channel_security_connector_check_call_host(
     grpc_exec_ctx *exec_ctx, grpc_channel_security_connector *sc,
     const char *host, grpc_auth_context *auth_context,
-    grpc_security_call_host_check_cb cb, void *user_data) {
+    grpc_closure *on_call_host_checked, grpc_error **error) {
   if (sc == NULL || sc->check_call_host == NULL) {
-    cb(exec_ctx, user_data, GRPC_SECURITY_ERROR);
-  } else {
-    sc->check_call_host(exec_ctx, sc, host, auth_context, cb, user_data);
+    *error = GRPC_ERROR_CREATE_FROM_STATIC_STRING(
+        "cannot check call host -- no security connector");
+    return true;
   }
+  return sc->check_call_host(exec_ctx, sc, host, auth_context,
+                             on_call_host_checked, error);
+}
+
+void grpc_channel_security_connector_cancel_check_call_host(
+    grpc_exec_ctx *exec_ctx, grpc_channel_security_connector *sc,
+    grpc_closure *on_call_host_checked, grpc_error *error) {
+  if (sc == NULL || sc->cancel_check_call_host == NULL) {
+    GRPC_ERROR_UNREF(error);
+    return;
+  }
+  sc->cancel_check_call_host(exec_ctx, sc, on_call_host_checked, error);
 }
 
 #ifndef NDEBUG
@@ -368,13 +380,19 @@ static void fake_server_check_peer(grpc_exec_ctx *exec_ctx,
   fake_check_peer(exec_ctx, sc, peer, auth_context, on_peer_checked);
 }
 
-static void fake_channel_check_call_host(grpc_exec_ctx *exec_ctx,
+static bool fake_channel_check_call_host(grpc_exec_ctx *exec_ctx,
                                          grpc_channel_security_connector *sc,
                                          const char *host,
                                          grpc_auth_context *auth_context,
-                                         grpc_security_call_host_check_cb cb,
-                                         void *user_data) {
-  cb(exec_ctx, user_data, GRPC_SECURITY_OK);
+                                         grpc_closure *on_call_host_checked,
+                                         grpc_error **error) {
+  return true;
+}
+
+static void fake_channel_cancel_check_call_host(
+    grpc_exec_ctx *exec_ctx, grpc_channel_security_connector *sc,
+    grpc_closure *on_call_host_checked, grpc_error *error) {
+  GRPC_ERROR_UNREF(error);
 }
 
 static void fake_channel_add_handshakers(
@@ -413,6 +431,7 @@ grpc_channel_security_connector *grpc_fake_channel_security_connector_create(
   c->base.request_metadata_creds =
       grpc_call_credentials_ref(request_metadata_creds);
   c->base.check_call_host = fake_channel_check_call_host;
+  c->base.cancel_check_call_host = fake_channel_cancel_check_call_host;
   c->base.add_handshakers = fake_channel_add_handshakers;
   c->target = gpr_strdup(target);
   const char *expected_targets = grpc_fake_transport_get_expected_targets(args);
@@ -663,26 +682,35 @@ void tsi_shallow_peer_destruct(tsi_peer *peer) {
   if (peer->properties != NULL) gpr_free(peer->properties);
 }
 
-static void ssl_channel_check_call_host(grpc_exec_ctx *exec_ctx,
+static bool ssl_channel_check_call_host(grpc_exec_ctx *exec_ctx,
                                         grpc_channel_security_connector *sc,
                                         const char *host,
                                         grpc_auth_context *auth_context,
-                                        grpc_security_call_host_check_cb cb,
-                                        void *user_data) {
+                                        grpc_closure *on_call_host_checked,
+                                        grpc_error **error) {
   grpc_ssl_channel_security_connector *c =
       (grpc_ssl_channel_security_connector *)sc;
   grpc_security_status status = GRPC_SECURITY_ERROR;
   tsi_peer peer = tsi_shallow_peer_from_ssl_auth_context(auth_context);
   if (ssl_host_matches_name(&peer, host)) status = GRPC_SECURITY_OK;
-
   /* If the target name was overridden, then the original target_name was
      'checked' transitively during the previous peer check at the end of the
      handshake. */
   if (c->overridden_target_name != NULL && strcmp(host, c->target_name) == 0) {
     status = GRPC_SECURITY_OK;
   }
-  cb(exec_ctx, user_data, status);
+  if (status != GRPC_SECURITY_OK) {
+    *error = GRPC_ERROR_CREATE_FROM_STATIC_STRING(
+        "call host does not match SSL server name");
+  }
   tsi_shallow_peer_destruct(&peer);
+  return true;
+}
+
+static void ssl_channel_cancel_check_call_host(
+    grpc_exec_ctx *exec_ctx, grpc_channel_security_connector *sc,
+    grpc_closure *on_call_host_checked, grpc_error *error) {
+  GRPC_ERROR_UNREF(error);
 }
 
 static grpc_security_connector_vtable ssl_channel_vtable = {
@@ -811,6 +839,7 @@ grpc_security_status grpc_ssl_channel_security_connector_create(
   c->base.request_metadata_creds =
       grpc_call_credentials_ref(request_metadata_creds);
   c->base.check_call_host = ssl_channel_check_call_host;
+  c->base.cancel_check_call_host = ssl_channel_cancel_check_call_host;
   c->base.add_handshakers = ssl_channel_add_handshakers;
   gpr_split_host_port(target_name, &c->target_name, &port);
   gpr_free(port);
diff --git a/src/core/lib/security/transport/security_connector.h b/src/core/lib/security/transport/security_connector.h
index 1c0fe40045..4f9b63ad20 100644
--- a/src/core/lib/security/transport/security_connector.h
+++ b/src/core/lib/security/transport/security_connector.h
@@ -117,27 +117,38 @@ grpc_security_connector *grpc_security_connector_find_in_args(
 
 typedef struct grpc_channel_security_connector grpc_channel_security_connector;
 
-typedef void (*grpc_security_call_host_check_cb)(grpc_exec_ctx *exec_ctx,
-                                                 void *user_data,
-                                                 grpc_security_status status);
-
 struct grpc_channel_security_connector {
   grpc_security_connector base;
   grpc_call_credentials *request_metadata_creds;
-  void (*check_call_host)(grpc_exec_ctx *exec_ctx,
+  bool (*check_call_host)(grpc_exec_ctx *exec_ctx,
                           grpc_channel_security_connector *sc, const char *host,
                           grpc_auth_context *auth_context,
-                          grpc_security_call_host_check_cb cb, void *user_data);
+                          grpc_closure *on_call_host_checked,
+                          grpc_error **error);
+  void (*cancel_check_call_host)(grpc_exec_ctx *exec_ctx,
+                                 grpc_channel_security_connector *sc,
+                                 grpc_closure *on_call_host_checked,
+                                 grpc_error *error);
   void (*add_handshakers)(grpc_exec_ctx *exec_ctx,
                           grpc_channel_security_connector *sc,
                           grpc_handshake_manager *handshake_mgr);
 };
 
-/* Checks that the host that will be set for a call is acceptable. */
-void grpc_channel_security_connector_check_call_host(
+/// Checks that the host that will be set for a call is acceptable.
+/// Returns true if completed synchronously, in which case \a error will
+/// be set to indicate the result.  Otherwise, \a on_call_host_checked
+/// will be invoked when complete.
+bool grpc_channel_security_connector_check_call_host(
     grpc_exec_ctx *exec_ctx, grpc_channel_security_connector *sc,
     const char *host, grpc_auth_context *auth_context,
-    grpc_security_call_host_check_cb cb, void *user_data);
+    grpc_closure *on_call_host_checked, grpc_error **error);
+
+/// Cancels a pending asychronous call to
+/// grpc_channel_security_connector_check_call_host() with
+/// \a on_call_host_checked as its callback.
+void grpc_channel_security_connector_cancel_check_call_host(
+    grpc_exec_ctx *exec_ctx, grpc_channel_security_connector *sc,
+    grpc_closure *on_call_host_checked, grpc_error *error);
 
 /* Registers handshakers with \a handshake_mgr. */
 void grpc_channel_security_connector_add_handshakers(
diff --git a/src/core/lib/security/transport/security_handshaker.c b/src/core/lib/security/transport/security_handshaker.c
index 628800fd6e..bf7a5272cb 100644
--- a/src/core/lib/security/transport/security_handshaker.c
+++ b/src/core/lib/security/transport/security_handshaker.c
@@ -145,7 +145,7 @@ static void on_peer_checked_inner(grpc_exec_ctx *exec_ctx,
     return;
   }
   // Get unused bytes.
-  unsigned char *unused_bytes = NULL;
+  const unsigned char *unused_bytes = NULL;
   size_t unused_bytes_size = 0;
   result = tsi_handshaker_result_get_unused_bytes(
       h->handshaker_result, &unused_bytes, &unused_bytes_size);
@@ -265,7 +265,7 @@ static grpc_error *do_handshaker_next_locked(
     grpc_exec_ctx *exec_ctx, security_handshaker *h,
     const unsigned char *bytes_received, size_t bytes_received_size) {
   // Invoke TSI handshaker.
-  unsigned char *bytes_to_send = NULL;
+  const unsigned char *bytes_to_send = NULL;
   size_t bytes_to_send_size = 0;
   tsi_handshaker_result *handshaker_result = NULL;
   tsi_result result = tsi_handshaker_next(
diff --git a/src/core/lib/support/avl.c b/src/core/lib/support/avl.c
index a6178fdbce..0e28b24c98 100644
--- a/src/core/lib/support/avl.c
+++ b/src/core/lib/support/avl.c
@@ -39,15 +39,16 @@ static gpr_avl_node *ref_node(gpr_avl_node *node) {
   return node;
 }
 
-static void unref_node(const gpr_avl_vtable *vtable, gpr_avl_node *node) {
+static void unref_node(const gpr_avl_vtable *vtable, gpr_avl_node *node,
+                       void *user_data) {
   if (node == NULL) {
     return;
   }
   if (gpr_unref(&node->refs)) {
-    vtable->destroy_key(node->key);
-    vtable->destroy_value(node->value);
-    unref_node(vtable, node->left);
-    unref_node(vtable, node->right);
+    vtable->destroy_key(node->key, user_data);
+    vtable->destroy_value(node->value, user_data);
+    unref_node(vtable, node->left, user_data);
+    unref_node(vtable, node->right, user_data);
     gpr_free(node);
   }
 }
@@ -87,30 +88,30 @@ gpr_avl_node *new_node(void *key, void *value, gpr_avl_node *left,
 }
 
 static gpr_avl_node *get(const gpr_avl_vtable *vtable, gpr_avl_node *node,
-                         void *key) {
+                         void *key, void *user_data) {
   long cmp;
 
   if (node == NULL) {
     return NULL;
   }
 
-  cmp = vtable->compare_keys(node->key, key);
+  cmp = vtable->compare_keys(node->key, key, user_data);
   if (cmp == 0) {
     return node;
   } else if (cmp > 0) {
-    return get(vtable, node->left, key);
+    return get(vtable, node->left, key, user_data);
   } else {
-    return get(vtable, node->right, key);
+    return get(vtable, node->right, key, user_data);
   }
 }
 
-void *gpr_avl_get(gpr_avl avl, void *key) {
-  gpr_avl_node *node = get(avl.vtable, avl.root, key);
+void *gpr_avl_get(gpr_avl avl, void *key, void *user_data) {
+  gpr_avl_node *node = get(avl.vtable, avl.root, key, user_data);
   return node ? node->value : NULL;
 }
 
-int gpr_avl_maybe_get(gpr_avl avl, void *key, void **value) {
-  gpr_avl_node *node = get(avl.vtable, avl.root, key);
+int gpr_avl_maybe_get(gpr_avl avl, void *key, void **value, void *user_data) {
+  gpr_avl_node *node = get(avl.vtable, avl.root, key, user_data);
   if (node != NULL) {
     *value = node->value;
     return 1;
@@ -120,70 +121,75 @@ int gpr_avl_maybe_get(gpr_avl avl, void *key, void **value) {
 
 static gpr_avl_node *rotate_left(const gpr_avl_vtable *vtable, void *key,
                                  void *value, gpr_avl_node *left,
-                                 gpr_avl_node *right) {
-  gpr_avl_node *n =
-      new_node(vtable->copy_key(right->key), vtable->copy_value(right->value),
-               new_node(key, value, left, ref_node(right->left)),
-               ref_node(right->right));
-  unref_node(vtable, right);
+                                 gpr_avl_node *right, void *user_data) {
+  gpr_avl_node *n = new_node(vtable->copy_key(right->key, user_data),
+                             vtable->copy_value(right->value, user_data),
+                             new_node(key, value, left, ref_node(right->left)),
+                             ref_node(right->right));
+  unref_node(vtable, right, user_data);
   return n;
 }
 
 static gpr_avl_node *rotate_right(const gpr_avl_vtable *vtable, void *key,
                                   void *value, gpr_avl_node *left,
-                                  gpr_avl_node *right) {
-  gpr_avl_node *n = new_node(
-      vtable->copy_key(left->key), vtable->copy_value(left->value),
-      ref_node(left->left), new_node(key, value, ref_node(left->right), right));
-  unref_node(vtable, left);
+                                  gpr_avl_node *right, void *user_data) {
+  gpr_avl_node *n =
+      new_node(vtable->copy_key(left->key, user_data),
+               vtable->copy_value(left->value, user_data), ref_node(left->left),
+               new_node(key, value, ref_node(left->right), right));
+  unref_node(vtable, left, user_data);
   return n;
 }
 
 static gpr_avl_node *rotate_left_right(const gpr_avl_vtable *vtable, void *key,
                                        void *value, gpr_avl_node *left,
-                                       gpr_avl_node *right) {
+                                       gpr_avl_node *right, void *user_data) {
   /* rotate_right(..., rotate_left(left), right) */
-  gpr_avl_node *n = new_node(
-      vtable->copy_key(left->right->key),
-      vtable->copy_value(left->right->value),
-      new_node(vtable->copy_key(left->key), vtable->copy_value(left->value),
-               ref_node(left->left), ref_node(left->right->left)),
-      new_node(key, value, ref_node(left->right->right), right));
-  unref_node(vtable, left);
+  gpr_avl_node *n =
+      new_node(vtable->copy_key(left->right->key, user_data),
+               vtable->copy_value(left->right->value, user_data),
+               new_node(vtable->copy_key(left->key, user_data),
+                        vtable->copy_value(left->value, user_data),
+                        ref_node(left->left), ref_node(left->right->left)),
+               new_node(key, value, ref_node(left->right->right), right));
+  unref_node(vtable, left, user_data);
   return n;
 }
 
 static gpr_avl_node *rotate_right_left(const gpr_avl_vtable *vtable, void *key,
                                        void *value, gpr_avl_node *left,
-                                       gpr_avl_node *right) {
+                                       gpr_avl_node *right, void *user_data) {
   /* rotate_left(..., left, rotate_right(right)) */
-  gpr_avl_node *n = new_node(
-      vtable->copy_key(right->left->key),
-      vtable->copy_value(right->left->value),
-      new_node(key, value, left, ref_node(right->left->left)),
-      new_node(vtable->copy_key(right->key), vtable->copy_value(right->value),
-               ref_node(right->left->right), ref_node(right->right)));
-  unref_node(vtable, right);
+  gpr_avl_node *n =
+      new_node(vtable->copy_key(right->left->key, user_data),
+               vtable->copy_value(right->left->value, user_data),
+               new_node(key, value, left, ref_node(right->left->left)),
+               new_node(vtable->copy_key(right->key, user_data),
+                        vtable->copy_value(right->value, user_data),
+                        ref_node(right->left->right), ref_node(right->right)));
+  unref_node(vtable, right, user_data);
   return n;
 }
 
 static gpr_avl_node *rebalance(const gpr_avl_vtable *vtable, void *key,
                                void *value, gpr_avl_node *left,
-                               gpr_avl_node *right) {
+                               gpr_avl_node *right, void *user_data) {
   switch (node_height(left) - node_height(right)) {
     case 2:
       if (node_height(left->left) - node_height(left->right) == -1) {
         return assert_invariants(
-            rotate_left_right(vtable, key, value, left, right));
+            rotate_left_right(vtable, key, value, left, right, user_data));
       } else {
-        return assert_invariants(rotate_right(vtable, key, value, left, right));
+        return assert_invariants(
+            rotate_right(vtable, key, value, left, right, user_data));
       }
     case -2:
       if (node_height(right->left) - node_height(right->right) == 1) {
         return assert_invariants(
-            rotate_right_left(vtable, key, value, left, right));
+            rotate_right_left(vtable, key, value, left, right, user_data));
       } else {
-        return assert_invariants(rotate_left(vtable, key, value, left, right));
+        return assert_invariants(
+            rotate_left(vtable, key, value, left, right, user_data));
       }
     default:
       return assert_invariants(new_node(key, value, left, right));
@@ -191,30 +197,32 @@ static gpr_avl_node *rebalance(const gpr_avl_vtable *vtable, void *key,
 }
 
 static gpr_avl_node *add_key(const gpr_avl_vtable *vtable, gpr_avl_node *node,
-                             void *key, void *value) {
+                             void *key, void *value, void *user_data) {
   long cmp;
   if (node == NULL) {
     return new_node(key, value, NULL, NULL);
   }
-  cmp = vtable->compare_keys(node->key, key);
+  cmp = vtable->compare_keys(node->key, key, user_data);
   if (cmp == 0) {
     return new_node(key, value, ref_node(node->left), ref_node(node->right));
   } else if (cmp > 0) {
-    return rebalance(
-        vtable, vtable->copy_key(node->key), vtable->copy_value(node->value),
-        add_key(vtable, node->left, key, value), ref_node(node->right));
+    return rebalance(vtable, vtable->copy_key(node->key, user_data),
+                     vtable->copy_value(node->value, user_data),
+                     add_key(vtable, node->left, key, value, user_data),
+                     ref_node(node->right), user_data);
   } else {
-    return rebalance(vtable, vtable->copy_key(node->key),
-                     vtable->copy_value(node->value), ref_node(node->left),
-                     add_key(vtable, node->right, key, value));
+    return rebalance(
+        vtable, vtable->copy_key(node->key, user_data),
+        vtable->copy_value(node->value, user_data), ref_node(node->left),
+        add_key(vtable, node->right, key, value, user_data), user_data);
   }
 }
 
-gpr_avl gpr_avl_add(gpr_avl avl, void *key, void *value) {
+gpr_avl gpr_avl_add(gpr_avl avl, void *key, void *value, void *user_data) {
   gpr_avl_node *old_root = avl.root;
-  avl.root = add_key(avl.vtable, avl.root, key, value);
+  avl.root = add_key(avl.vtable, avl.root, key, value, user_data);
   assert_invariants(avl.root);
-  unref_node(avl.vtable, old_root);
+  unref_node(avl.vtable, old_root, user_data);
   return avl;
 }
 
@@ -233,12 +241,13 @@ static gpr_avl_node *in_order_tail(gpr_avl_node *node) {
 }
 
 static gpr_avl_node *remove_key(const gpr_avl_vtable *vtable,
-                                gpr_avl_node *node, void *key) {
+                                gpr_avl_node *node, void *key,
+                                void *user_data) {
   long cmp;
   if (node == NULL) {
     return NULL;
   }
-  cmp = vtable->compare_keys(node->key, key);
+  cmp = vtable->compare_keys(node->key, key, user_data);
   if (cmp == 0) {
     if (node->left == NULL) {
       return ref_node(node->right);
@@ -246,39 +255,45 @@ static gpr_avl_node *remove_key(const gpr_avl_vtable *vtable,
       return ref_node(node->left);
     } else if (node->left->height < node->right->height) {
       gpr_avl_node *h = in_order_head(node->right);
-      return rebalance(vtable, vtable->copy_key(h->key),
-                       vtable->copy_value(h->value), ref_node(node->left),
-                       remove_key(vtable, node->right, h->key));
+      return rebalance(
+          vtable, vtable->copy_key(h->key, user_data),
+          vtable->copy_value(h->value, user_data), ref_node(node->left),
+          remove_key(vtable, node->right, h->key, user_data), user_data);
     } else {
       gpr_avl_node *h = in_order_tail(node->left);
-      return rebalance(
-          vtable, vtable->copy_key(h->key), vtable->copy_value(h->value),
-          remove_key(vtable, node->left, h->key), ref_node(node->right));
+      return rebalance(vtable, vtable->copy_key(h->key, user_data),
+                       vtable->copy_value(h->value, user_data),
+                       remove_key(vtable, node->left, h->key, user_data),
+                       ref_node(node->right), user_data);
     }
   } else if (cmp > 0) {
-    return rebalance(
-        vtable, vtable->copy_key(node->key), vtable->copy_value(node->value),
-        remove_key(vtable, node->left, key), ref_node(node->right));
+    return rebalance(vtable, vtable->copy_key(node->key, user_data),
+                     vtable->copy_value(node->value, user_data),
+                     remove_key(vtable, node->left, key, user_data),
+                     ref_node(node->right), user_data);
   } else {
-    return rebalance(vtable, vtable->copy_key(node->key),
-                     vtable->copy_value(node->value), ref_node(node->left),
-                     remove_key(vtable, node->right, key));
+    return rebalance(
+        vtable, vtable->copy_key(node->key, user_data),
+        vtable->copy_value(node->value, user_data), ref_node(node->left),
+        remove_key(vtable, node->right, key, user_data), user_data);
   }
 }
 
-gpr_avl gpr_avl_remove(gpr_avl avl, void *key) {
+gpr_avl gpr_avl_remove(gpr_avl avl, void *key, void *user_data) {
   gpr_avl_node *old_root = avl.root;
-  avl.root = remove_key(avl.vtable, avl.root, key);
+  avl.root = remove_key(avl.vtable, avl.root, key, user_data);
   assert_invariants(avl.root);
-  unref_node(avl.vtable, old_root);
+  unref_node(avl.vtable, old_root, user_data);
   return avl;
 }
 
-gpr_avl gpr_avl_ref(gpr_avl avl) {
+gpr_avl gpr_avl_ref(gpr_avl avl, void *user_data) {
   ref_node(avl.root);
   return avl;
 }
 
-void gpr_avl_unref(gpr_avl avl) { unref_node(avl.vtable, avl.root); }
+void gpr_avl_unref(gpr_avl avl, void *user_data) {
+  unref_node(avl.vtable, avl.root, user_data);
+}
 
 int gpr_avl_is_empty(gpr_avl avl) { return avl.root == NULL; }
diff --git a/src/core/lib/support/block_annotate.h b/src/core/lib/support/block_annotate.h
index 0a2cb45018..8e3ef7df65 100644
--- a/src/core/lib/support/block_annotate.h
+++ b/src/core/lib/support/block_annotate.h
@@ -19,15 +19,37 @@
 #ifndef GRPC_CORE_LIB_SUPPORT_BLOCK_ANNOTATE_H
 #define GRPC_CORE_LIB_SUPPORT_BLOCK_ANNOTATE_H
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+void gpr_thd_start_blocking_region();
+void gpr_thd_end_blocking_region();
+
+#ifdef __cplusplus
+}
+#endif
+
 /* These annotations identify the beginning and end of regions where
    the code may block for reasons other than synchronization functions.
    These include poll, epoll, and getaddrinfo. */
 
+#ifdef GRPC_SCHEDULING_MARK_BLOCKING_REGION
+#define GRPC_SCHEDULING_START_BLOCKING_REGION \
+  do {                                        \
+    gpr_thd_start_blocking_region();          \
+  } while (0)
+#define GRPC_SCHEDULING_END_BLOCKING_REGION \
+  do {                                      \
+    gpr_thd_end_blocking_region();          \
+  } while (0)
+#else
 #define GRPC_SCHEDULING_START_BLOCKING_REGION \
   do {                                        \
   } while (0)
 #define GRPC_SCHEDULING_END_BLOCKING_REGION \
   do {                                      \
   } while (0)
+#endif
 
 #endif /* GRPC_CORE_LIB_SUPPORT_BLOCK_ANNOTATE_H */
diff --git a/src/core/lib/support/murmur_hash.c b/src/core/lib/support/murmur_hash.c
index f329611818..f06b970de7 100644
--- a/src/core/lib/support/murmur_hash.c
+++ b/src/core/lib/support/murmur_hash.c
@@ -62,8 +62,10 @@ uint32_t gpr_murmur_hash3(const void *key, size_t len, uint32_t seed) {
   switch (len & 3) {
     case 3:
       k1 ^= ((uint32_t)tail[2]) << 16;
+    /* fallthrough */
     case 2:
       k1 ^= ((uint32_t)tail[1]) << 8;
+    /* fallthrough */
     case 1:
       k1 ^= tail[0];
       k1 *= c1;
diff --git a/src/core/lib/surface/alarm.c b/src/core/lib/surface/alarm.c
index ef8405cca8..7d60b1de17 100644
--- a/src/core/lib/surface/alarm.c
+++ b/src/core/lib/surface/alarm.c
@@ -15,13 +15,21 @@
  * limitations under the License.
  *
  */
+#include "src/core/lib/surface/alarm_internal.h"
 
 #include <grpc/grpc.h>
 #include <grpc/support/alloc.h>
+#include <grpc/support/log.h>
 #include "src/core/lib/iomgr/timer.h"
 #include "src/core/lib/surface/completion_queue.h"
 
+#ifndef NDEBUG
+grpc_tracer_flag grpc_trace_alarm_refcount =
+    GRPC_TRACER_INITIALIZER(false, "alarm_refcount");
+#endif
+
 struct grpc_alarm {
+  gpr_refcount refs;
   grpc_timer alarm;
   grpc_closure on_alarm;
   grpc_cq_completion completion;
@@ -31,13 +39,58 @@ struct grpc_alarm {
   void *tag;
 };
 
-static void do_nothing_end_completion(grpc_exec_ctx *exec_ctx, void *arg,
-                                      grpc_cq_completion *c) {}
+static void alarm_ref(grpc_alarm *alarm) { gpr_ref(&alarm->refs); }
+
+static void alarm_unref(grpc_alarm *alarm) {
+  if (gpr_unref(&alarm->refs)) {
+    grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
+    GRPC_CQ_INTERNAL_UNREF(&exec_ctx, alarm->cq, "alarm");
+    grpc_exec_ctx_finish(&exec_ctx);
+    gpr_free(alarm);
+  }
+}
+
+#ifndef NDEBUG
+static void alarm_ref_dbg(grpc_alarm *alarm, const char *reason,
+                          const char *file, int line) {
+  if (GRPC_TRACER_ON(grpc_trace_alarm_refcount)) {
+    gpr_atm val = gpr_atm_no_barrier_load(&alarm->refs.count);
+    gpr_log(file, line, GPR_LOG_SEVERITY_DEBUG,
+            "Alarm:%p  ref %" PRIdPTR " -> %" PRIdPTR " %s", alarm, val,
+            val + 1, reason);
+  }
+
+  alarm_ref(alarm);
+}
+
+static void alarm_unref_dbg(grpc_alarm *alarm, const char *reason,
+                            const char *file, int line) {
+  if (GRPC_TRACER_ON(grpc_trace_alarm_refcount)) {
+    gpr_atm val = gpr_atm_no_barrier_load(&alarm->refs.count);
+    gpr_log(file, line, GPR_LOG_SEVERITY_DEBUG,
+            "Alarm:%p  Unref %" PRIdPTR " -> %" PRIdPTR " %s", alarm, val,
+            val - 1, reason);
+  }
+
+  alarm_unref(alarm);
+}
+#endif
+
+static void alarm_end_completion(grpc_exec_ctx *exec_ctx, void *arg,
+                                 grpc_cq_completion *c) {
+  grpc_alarm *alarm = arg;
+  GRPC_ALARM_UNREF(alarm, "dequeue-end-op");
+}
 
 static void alarm_cb(grpc_exec_ctx *exec_ctx, void *arg, grpc_error *error) {
   grpc_alarm *alarm = arg;
-  grpc_cq_end_op(exec_ctx, alarm->cq, alarm->tag, error,
-                 do_nothing_end_completion, NULL, &alarm->completion);
+
+  /* We are queuing an op on completion queue. This means, the alarm's structure
+     cannot be destroyed until the op is dequeued. Adding an extra ref
+     here and unref'ing when the op is dequeued will achieve this */
+  GRPC_ALARM_REF(alarm, "queue-end-op");
+  grpc_cq_end_op(exec_ctx, alarm->cq, alarm->tag, error, alarm_end_completion,
+                 (void *)alarm, &alarm->completion);
 }
 
 grpc_alarm *grpc_alarm_create(grpc_completion_queue *cq, gpr_timespec deadline,
@@ -45,11 +98,19 @@ grpc_alarm *grpc_alarm_create(grpc_completion_queue *cq, gpr_timespec deadline,
   grpc_alarm *alarm = gpr_malloc(sizeof(grpc_alarm));
   grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
 
+  gpr_ref_init(&alarm->refs, 1);
+
+#ifndef NDEBUG
+  if (GRPC_TRACER_ON(grpc_trace_alarm_refcount)) {
+    gpr_log(GPR_DEBUG, "Alarm:%p created (ref: 1)", alarm);
+  }
+#endif
+
   GRPC_CQ_INTERNAL_REF(cq, "alarm");
   alarm->cq = cq;
   alarm->tag = tag;
 
-  grpc_cq_begin_op(cq, tag);
+  GPR_ASSERT(grpc_cq_begin_op(cq, tag));
   GRPC_CLOSURE_INIT(&alarm->on_alarm, alarm_cb, alarm,
                     grpc_schedule_on_exec_ctx);
   grpc_timer_init(&exec_ctx, &alarm->alarm,
@@ -66,9 +127,6 @@ void grpc_alarm_cancel(grpc_alarm *alarm) {
 }
 
 void grpc_alarm_destroy(grpc_alarm *alarm) {
-  grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
   grpc_alarm_cancel(alarm);
-  GRPC_CQ_INTERNAL_UNREF(&exec_ctx, alarm->cq, "alarm");
-  gpr_free(alarm);
-  grpc_exec_ctx_finish(&exec_ctx);
+  GRPC_ALARM_UNREF(alarm, "alarm_destroy");
 }
diff --git a/src/core/lib/surface/alarm_internal.h b/src/core/lib/surface/alarm_internal.h
new file mode 100644
index 0000000000..7f2126c5c9
--- /dev/null
+++ b/src/core/lib/surface/alarm_internal.h
@@ -0,0 +1,40 @@
+/*
+ *
+ * Copyright 2015-2017 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#ifndef GRPC_CORE_LIB_SURFACE_ALARM_INTERNAL_H
+#define GRPC_CORE_LIB_SURFACE_ALARM_INTERNAL_H
+
+#include <grpc/support/log.h>
+#include "src/core/lib/debug/trace.h"
+
+#ifndef NDEBUG
+
+extern grpc_tracer_flag grpc_trace_alarm_refcount;
+
+#define GRPC_ALARM_REF(a, reason) alarm_ref_dbg(a, reason, __FILE__, __LINE__)
+#define GRPC_ALARM_UNREF(a, reason) \
+  alarm_unref_dbg(a, reason, __FILE__, __LINE__)
+
+#else /* !defined(NDEBUG) */
+
+#define GRPC_ALARM_REF(a, reason) alarm_ref(a)
+#define GRPC_ALARM_UNREF(a, reason) alarm_unref(a)
+
+#endif /* defined(NDEBUG) */
+
+#endif /* GRPC_CORE_LIB_SURFACE_ALARM_INTERNAL_H */
diff --git a/src/core/lib/surface/call.c b/src/core/lib/surface/call.c
index 2365d27307..62d542d2c5 100644
--- a/src/core/lib/surface/call.c
+++ b/src/core/lib/surface/call.c
@@ -144,6 +144,9 @@ typedef struct {
   grpc_call *sibling_prev;
 } child_call;
 
+#define RECV_NONE ((gpr_atm)0)
+#define RECV_INITIAL_METADATA_FIRST ((gpr_atm)1)
+
 struct grpc_call {
   gpr_refcount ext_ref;
   gpr_arena *arena;
@@ -170,9 +173,6 @@ struct grpc_call {
   gpr_atm any_ops_sent_atm;
   gpr_atm received_final_op_atm;
 
-  /* have we received initial metadata */
-  bool has_initial_md_been_received;
-
   batch_control *active_batches[MAX_CONCURRENT_BATCHES];
   grpc_transport_stream_op_batch_payload stream_op_payload;
 
@@ -192,8 +192,12 @@ struct grpc_call {
 
   /* Compression algorithm for *incoming* data */
   grpc_compression_algorithm incoming_compression_algorithm;
+  /* Stream compression algorithm for *incoming* data */
+  grpc_stream_compression_algorithm incoming_stream_compression_algorithm;
   /* Supported encodings (compression algorithms), a bitset */
   uint32_t encodings_accepted_by_peer;
+  /* Supported stream encodings (stream compression algorithms), a bitset */
+  uint32_t stream_encodings_accepted_by_peer;
 
   /* Contexts for various subsystems (security, tracing, ...). */
   grpc_call_context_element context[GRPC_CONTEXT_COUNT];
@@ -226,7 +230,23 @@ struct grpc_call {
     } server;
   } final_op;
 
-  void *saved_receiving_stream_ready_bctlp;
+  /* recv_state can contain one of the following values:
+     RECV_NONE :                 :  no initial metadata and messages received
+     RECV_INITIAL_METADATA_FIRST :  received initial metadata first
+     a batch_control*            :  received messages first
+
+                 +------1------RECV_NONE------3-----+
+                 |                                  |
+                 |                                  |
+                 v                                  v
+     RECV_INITIAL_METADATA_FIRST        receiving_stream_ready_bctlp
+           |           ^                      |           ^
+           |           |                      |           |
+           +-----2-----+                      +-----4-----+
+
+    For 1, 4: See receiving_initial_metadata_ready() function
+    For 2, 3: See receiving_stream_ready() function */
+  gpr_atm recv_state;
 };
 
 grpc_tracer_flag grpc_call_error_trace =
@@ -644,6 +664,8 @@ static void cancel_with_error(grpc_exec_ctx *exec_ctx, grpc_call *c,
 
 static grpc_error *error_from_status(grpc_status_code status,
                                      const char *description) {
+  // copying 'description' is needed to ensure the grpc_call_cancel_with_status
+  // guarantee that can be short-lived.
   return grpc_error_set_int(
       grpc_error_set_str(GRPC_ERROR_CREATE_FROM_COPIED_STRING(description),
                          GRPC_ERROR_STR_GRPC_MESSAGE,
@@ -750,6 +772,12 @@ static void set_incoming_compression_algorithm(
   call->incoming_compression_algorithm = algo;
 }
 
+static void set_incoming_stream_compression_algorithm(
+    grpc_call *call, grpc_stream_compression_algorithm algo) {
+  GPR_ASSERT(algo < GRPC_STREAM_COMPRESS_ALGORITHMS_COUNT);
+  call->incoming_stream_compression_algorithm = algo;
+}
+
 grpc_compression_algorithm grpc_call_test_only_get_compression_algorithm(
     grpc_call *call) {
   grpc_compression_algorithm algorithm;
@@ -763,6 +791,13 @@ static grpc_compression_algorithm compression_algorithm_for_level_locked(
                                               call->encodings_accepted_by_peer);
 }
 
+static grpc_stream_compression_algorithm
+stream_compression_algorithm_for_level_locked(
+    grpc_call *call, grpc_stream_compression_level level) {
+  return grpc_stream_compression_algorithm_for_level(
+      level, call->stream_encodings_accepted_by_peer);
+}
+
 uint32_t grpc_call_test_only_get_message_flags(grpc_call *call) {
   uint32_t flags;
   flags = call->test_only_last_message_flags;
@@ -817,13 +852,71 @@ static void set_encodings_accepted_by_peer(grpc_exec_ctx *exec_ctx,
       (void *)(((uintptr_t)call->encodings_accepted_by_peer) + 1));
 }
 
+static void set_stream_encodings_accepted_by_peer(grpc_exec_ctx *exec_ctx,
+                                                  grpc_call *call,
+                                                  grpc_mdelem mdel) {
+  size_t i;
+  grpc_stream_compression_algorithm algorithm;
+  grpc_slice_buffer accept_encoding_parts;
+  grpc_slice accept_encoding_slice;
+  void *accepted_user_data;
+
+  accepted_user_data =
+      grpc_mdelem_get_user_data(mdel, destroy_encodings_accepted_by_peer);
+  if (accepted_user_data != NULL) {
+    call->stream_encodings_accepted_by_peer =
+        (uint32_t)(((uintptr_t)accepted_user_data) - 1);
+    return;
+  }
+
+  accept_encoding_slice = GRPC_MDVALUE(mdel);
+  grpc_slice_buffer_init(&accept_encoding_parts);
+  grpc_slice_split(accept_encoding_slice, ",", &accept_encoding_parts);
+
+  /* Always support no compression */
+  GPR_BITSET(&call->stream_encodings_accepted_by_peer,
+             GRPC_STREAM_COMPRESS_NONE);
+  for (i = 0; i < accept_encoding_parts.count; i++) {
+    grpc_slice accept_encoding_entry_slice = accept_encoding_parts.slices[i];
+    if (grpc_stream_compression_algorithm_parse(accept_encoding_entry_slice,
+                                                &algorithm)) {
+      GPR_BITSET(&call->stream_encodings_accepted_by_peer, algorithm);
+    } else {
+      char *accept_encoding_entry_str =
+          grpc_slice_to_c_string(accept_encoding_entry_slice);
+      gpr_log(GPR_ERROR,
+              "Invalid entry in accept encoding metadata: '%s'. Ignoring.",
+              accept_encoding_entry_str);
+      gpr_free(accept_encoding_entry_str);
+    }
+  }
+
+  grpc_slice_buffer_destroy_internal(exec_ctx, &accept_encoding_parts);
+
+  grpc_mdelem_set_user_data(
+      mdel, destroy_encodings_accepted_by_peer,
+      (void *)(((uintptr_t)call->stream_encodings_accepted_by_peer) + 1));
+}
+
 uint32_t grpc_call_test_only_get_encodings_accepted_by_peer(grpc_call *call) {
   uint32_t encodings_accepted_by_peer;
   encodings_accepted_by_peer = call->encodings_accepted_by_peer;
   return encodings_accepted_by_peer;
 }
 
-static grpc_linked_mdelem *linked_from_md(grpc_metadata *md) {
+uint32_t grpc_call_test_only_get_stream_encodings_accepted_by_peer(
+    grpc_call *call) {
+  uint32_t stream_encodings_accepted_by_peer;
+  stream_encodings_accepted_by_peer = call->stream_encodings_accepted_by_peer;
+  return stream_encodings_accepted_by_peer;
+}
+
+grpc_stream_compression_algorithm
+grpc_call_test_only_get_incoming_stream_encodings(grpc_call *call) {
+  return call->incoming_stream_compression_algorithm;
+}
+
+static grpc_linked_mdelem *linked_from_md(const grpc_metadata *md) {
   return (grpc_linked_mdelem *)&md->internal_data;
 }
 
@@ -847,7 +940,7 @@ static int prepare_application_metadata(
   for (i = 0; i < total_count; i++) {
     const grpc_metadata *md =
         get_md_elem(metadata, additional_metadata, i, count);
-    grpc_linked_mdelem *l = (grpc_linked_mdelem *)&md->internal_data;
+    grpc_linked_mdelem *l = linked_from_md(md);
     GPR_ASSERT(sizeof(grpc_linked_mdelem) == sizeof(md->internal_data));
     if (!GRPC_LOG_IF_ERROR("validate_metadata",
                            grpc_validate_header_key_is_legal(md->key))) {
@@ -864,7 +957,7 @@ static int prepare_application_metadata(
     for (int j = 0; j < i; j++) {
       const grpc_metadata *md =
           get_md_elem(metadata, additional_metadata, j, count);
-      grpc_linked_mdelem *l = (grpc_linked_mdelem *)&md->internal_data;
+      grpc_linked_mdelem *l = linked_from_md(md);
       GRPC_MDELEM_UNREF(exec_ctx, l->md);
     }
     return 0;
@@ -882,9 +975,12 @@ static int prepare_application_metadata(
   }
   for (i = 0; i < total_count; i++) {
     grpc_metadata *md = get_md_elem(metadata, additional_metadata, i, count);
-    GRPC_LOG_IF_ERROR(
-        "prepare_application_metadata",
-        grpc_metadata_batch_link_tail(exec_ctx, batch, linked_from_md(md)));
+    grpc_linked_mdelem *l = linked_from_md(md);
+    grpc_error *error = grpc_metadata_batch_link_tail(exec_ctx, batch, l);
+    if (error != GRPC_ERROR_NONE) {
+      GRPC_MDELEM_UNREF(exec_ctx, l->md);
+    }
+    GRPC_LOG_IF_ERROR("prepare_application_metadata", error);
   }
   call->send_extra_metadata_count = 0;
 
@@ -931,6 +1027,22 @@ static grpc_compression_algorithm decode_compression(grpc_mdelem md) {
   return algorithm;
 }
 
+static grpc_stream_compression_algorithm decode_stream_compression(
+    grpc_mdelem md) {
+  grpc_stream_compression_algorithm algorithm =
+      grpc_stream_compression_algorithm_from_slice(GRPC_MDVALUE(md));
+  if (algorithm == GRPC_STREAM_COMPRESS_ALGORITHMS_COUNT) {
+    char *md_c_str = grpc_slice_to_c_string(GRPC_MDVALUE(md));
+    gpr_log(GPR_ERROR,
+            "Invalid incoming stream compression algorithm: '%s'. Interpreting "
+            "incoming data as uncompressed.",
+            md_c_str);
+    gpr_free(md_c_str);
+    return GRPC_STREAM_COMPRESS_NONE;
+  }
+  return algorithm;
+}
+
 static void publish_app_metadata(grpc_call *call, grpc_metadata_batch *b,
                                  int is_trailing) {
   if (b->list.count == 0) return;
@@ -955,7 +1067,19 @@ static void publish_app_metadata(grpc_call *call, grpc_metadata_batch *b,
 
 static void recv_initial_filter(grpc_exec_ctx *exec_ctx, grpc_call *call,
                                 grpc_metadata_batch *b) {
-  if (b->idx.named.grpc_encoding != NULL) {
+  if (b->idx.named.content_encoding != NULL) {
+    if (b->idx.named.grpc_encoding != NULL) {
+      gpr_log(GPR_ERROR,
+              "Received both content-encoding and grpc-encoding header. "
+              "Ignoring grpc-encoding.");
+      grpc_metadata_batch_remove(exec_ctx, b, b->idx.named.grpc_encoding);
+    }
+    GPR_TIMER_BEGIN("incoming_stream_compression_algorithm", 0);
+    set_incoming_stream_compression_algorithm(
+        call, decode_stream_compression(b->idx.named.content_encoding->md));
+    GPR_TIMER_END("incoming_stream_compression_algorithm", 0);
+    grpc_metadata_batch_remove(exec_ctx, b, b->idx.named.content_encoding);
+  } else if (b->idx.named.grpc_encoding != NULL) {
     GPR_TIMER_BEGIN("incoming_compression_algorithm", 0);
     set_incoming_compression_algorithm(
         call, decode_compression(b->idx.named.grpc_encoding->md));
@@ -969,6 +1093,13 @@ static void recv_initial_filter(grpc_exec_ctx *exec_ctx, grpc_call *call,
     grpc_metadata_batch_remove(exec_ctx, b, b->idx.named.grpc_accept_encoding);
     GPR_TIMER_END("encodings_accepted_by_peer", 0);
   }
+  if (b->idx.named.accept_encoding != NULL) {
+    GPR_TIMER_BEGIN("stream_encodings_accepted_by_peer", 0);
+    set_stream_encodings_accepted_by_peer(exec_ctx, call,
+                                          b->idx.named.accept_encoding->md);
+    grpc_metadata_batch_remove(exec_ctx, b, b->idx.named.accept_encoding);
+    GPR_TIMER_END("stream_encodings_accepted_by_peer", 0);
+  }
   publish_app_metadata(call, b, false);
 }
 
@@ -1285,19 +1416,61 @@ static void receiving_stream_ready(grpc_exec_ctx *exec_ctx, void *bctlp,
     cancel_with_error(exec_ctx, call, STATUS_FROM_SURFACE,
                       GRPC_ERROR_REF(error));
   }
-  if (call->has_initial_md_been_received || error != GRPC_ERROR_NONE ||
-      call->receiving_stream == NULL) {
+  /* If recv_state is RECV_NONE, we will save the batch_control
+   * object with rel_cas, and will not use it after the cas. Its corresponding
+   * acq_load is in receiving_initial_metadata_ready() */
+  if (error != GRPC_ERROR_NONE || call->receiving_stream == NULL ||
+      !gpr_atm_rel_cas(&call->recv_state, RECV_NONE, (gpr_atm)bctlp)) {
     process_data_after_md(exec_ctx, bctlp);
-  } else {
-    call->saved_receiving_stream_ready_bctlp = bctlp;
   }
 }
 
 static void validate_filtered_metadata(grpc_exec_ctx *exec_ctx,
                                        batch_control *bctl) {
   grpc_call *call = bctl->call;
-  /* validate call->incoming_compression_algorithm */
-  if (call->incoming_compression_algorithm != GRPC_COMPRESS_NONE) {
+  /* validate compression algorithms */
+  if (call->incoming_stream_compression_algorithm !=
+      GRPC_STREAM_COMPRESS_NONE) {
+    const grpc_stream_compression_algorithm algo =
+        call->incoming_stream_compression_algorithm;
+    char *error_msg = NULL;
+    const grpc_compression_options compression_options =
+        grpc_channel_compression_options(call->channel);
+    if (algo >= GRPC_STREAM_COMPRESS_ALGORITHMS_COUNT) {
+      gpr_asprintf(&error_msg,
+                   "Invalid stream compression algorithm value '%d'.", algo);
+      gpr_log(GPR_ERROR, "%s", error_msg);
+      cancel_with_status(exec_ctx, call, STATUS_FROM_SURFACE,
+                         GRPC_STATUS_UNIMPLEMENTED, error_msg);
+    } else if (grpc_compression_options_is_stream_compression_algorithm_enabled(
+                   &compression_options, algo) == 0) {
+      /* check if algorithm is supported by current channel config */
+      char *algo_name = NULL;
+      grpc_stream_compression_algorithm_name(algo, &algo_name);
+      gpr_asprintf(&error_msg, "Stream compression algorithm '%s' is disabled.",
+                   algo_name);
+      gpr_log(GPR_ERROR, "%s", error_msg);
+      cancel_with_status(exec_ctx, call, STATUS_FROM_SURFACE,
+                         GRPC_STATUS_UNIMPLEMENTED, error_msg);
+    }
+    gpr_free(error_msg);
+
+    GPR_ASSERT(call->stream_encodings_accepted_by_peer != 0);
+    if (!GPR_BITGET(call->stream_encodings_accepted_by_peer,
+                    call->incoming_stream_compression_algorithm)) {
+      if (GRPC_TRACER_ON(grpc_compression_trace)) {
+        char *algo_name = NULL;
+        grpc_stream_compression_algorithm_name(
+            call->incoming_stream_compression_algorithm, &algo_name);
+        gpr_log(
+            GPR_ERROR,
+            "Stream compression algorithm (content-encoding = '%s') not "
+            "present in the bitset of accepted encodings (accept-encodings: "
+            "'0x%x')",
+            algo_name, call->stream_encodings_accepted_by_peer);
+      }
+    }
+  } else if (call->incoming_compression_algorithm != GRPC_COMPRESS_NONE) {
     const grpc_compression_algorithm algo =
         call->incoming_compression_algorithm;
     char *error_msg = NULL;
@@ -1324,22 +1497,20 @@ static void validate_filtered_metadata(grpc_exec_ctx *exec_ctx,
       call->incoming_compression_algorithm = algo;
     }
     gpr_free(error_msg);
-  }
 
-  /* make sure the received grpc-encoding is amongst the ones listed in
-   * grpc-accept-encoding */
-  GPR_ASSERT(call->encodings_accepted_by_peer != 0);
-  if (!GPR_BITGET(call->encodings_accepted_by_peer,
-                  call->incoming_compression_algorithm)) {
-    if (GRPC_TRACER_ON(grpc_compression_trace)) {
-      char *algo_name = NULL;
-      grpc_compression_algorithm_name(call->incoming_compression_algorithm,
-                                      &algo_name);
-      gpr_log(GPR_ERROR,
-              "Compression algorithm (grpc-encoding = '%s') not present in "
-              "the bitset of accepted encodings (grpc-accept-encodings: "
-              "'0x%x')",
-              algo_name, call->encodings_accepted_by_peer);
+    GPR_ASSERT(call->encodings_accepted_by_peer != 0);
+    if (!GPR_BITGET(call->encodings_accepted_by_peer,
+                    call->incoming_compression_algorithm)) {
+      if (GRPC_TRACER_ON(grpc_compression_trace)) {
+        char *algo_name = NULL;
+        grpc_compression_algorithm_name(call->incoming_compression_algorithm,
+                                        &algo_name);
+        gpr_log(GPR_ERROR,
+                "Compression algorithm (grpc-encoding = '%s') not present in "
+                "the bitset of accepted encodings (grpc-accept-encodings: "
+                "'0x%x')",
+                algo_name, call->encodings_accepted_by_peer);
+      }
     }
   }
 }
@@ -1379,12 +1550,31 @@ static void receiving_initial_metadata_ready(grpc_exec_ctx *exec_ctx,
     }
   }
 
-  call->has_initial_md_been_received = true;
-  if (call->saved_receiving_stream_ready_bctlp != NULL) {
-    grpc_closure *saved_rsr_closure = GRPC_CLOSURE_CREATE(
-        receiving_stream_ready, call->saved_receiving_stream_ready_bctlp,
-        grpc_schedule_on_exec_ctx);
-    call->saved_receiving_stream_ready_bctlp = NULL;
+  grpc_closure *saved_rsr_closure = NULL;
+  while (true) {
+    gpr_atm rsr_bctlp = gpr_atm_acq_load(&call->recv_state);
+    /* Should only receive initial metadata once */
+    GPR_ASSERT(rsr_bctlp != 1);
+    if (rsr_bctlp == 0) {
+      /* We haven't seen initial metadata and messages before, thus initial
+       * metadata is received first.
+       * no_barrier_cas is used, as this function won't access the batch_control
+       * object saved by receiving_stream_ready() if the initial metadata is
+       * received first. */
+      if (gpr_atm_no_barrier_cas(&call->recv_state, RECV_NONE,
+                                 RECV_INITIAL_METADATA_FIRST)) {
+        break;
+      }
+    } else {
+      /* Already received messages */
+      saved_rsr_closure = GRPC_CLOSURE_CREATE(receiving_stream_ready,
+                                              (batch_control *)rsr_bctlp,
+                                              grpc_schedule_on_exec_ctx);
+      /* No need to modify recv_state */
+      break;
+    }
+  }
+  if (saved_rsr_closure != NULL) {
     GRPC_CLOSURE_RUN(exec_ctx, saved_rsr_closure, GRPC_ERROR_REF(error));
   }
 
@@ -1422,7 +1612,7 @@ static grpc_call_error call_start_batch(grpc_exec_ctx *exec_ctx,
 
   if (nops == 0) {
     if (!is_notify_tag_closure) {
-      grpc_cq_begin_op(call->cq, notify_tag);
+      GPR_ASSERT(grpc_cq_begin_op(call->cq, notify_tag));
       grpc_cq_end_op(exec_ctx, call->cq, notify_tag, GRPC_ERROR_NONE,
                      free_no_op_completion, NULL,
                      gpr_malloc(sizeof(grpc_cq_completion)));
@@ -1466,29 +1656,56 @@ static grpc_call_error call_start_batch(grpc_exec_ctx *exec_ctx,
         /* process compression level */
         memset(&compression_md, 0, sizeof(compression_md));
         size_t additional_metadata_count = 0;
-        grpc_compression_level effective_compression_level;
+        grpc_compression_level effective_compression_level =
+            GRPC_COMPRESS_LEVEL_NONE;
+        grpc_stream_compression_level effective_stream_compression_level =
+            GRPC_STREAM_COMPRESS_LEVEL_NONE;
         bool level_set = false;
-        if (op->data.send_initial_metadata.maybe_compression_level.is_set) {
+        bool stream_compression = false;
+        if (op->data.send_initial_metadata.maybe_stream_compression_level
+                .is_set) {
+          effective_stream_compression_level =
+              op->data.send_initial_metadata.maybe_stream_compression_level
+                  .level;
+          level_set = true;
+          stream_compression = true;
+        } else if (op->data.send_initial_metadata.maybe_compression_level
+                       .is_set) {
           effective_compression_level =
               op->data.send_initial_metadata.maybe_compression_level.level;
           level_set = true;
         } else {
           const grpc_compression_options copts =
               grpc_channel_compression_options(call->channel);
-          level_set = copts.default_level.is_set;
-          if (level_set) {
+          if (copts.default_stream_compression_level.is_set) {
+            level_set = true;
+            effective_stream_compression_level =
+                copts.default_stream_compression_level.level;
+            stream_compression = true;
+          } else if (copts.default_level.is_set) {
+            level_set = true;
             effective_compression_level = copts.default_level.level;
           }
         }
         if (level_set && !call->is_client) {
-          const grpc_compression_algorithm calgo =
-              compression_algorithm_for_level_locked(
-                  call, effective_compression_level);
-          // the following will be picked up by the compress filter and used as
-          // the call's compression algorithm.
-          compression_md.key = GRPC_MDSTR_GRPC_INTERNAL_ENCODING_REQUEST;
-          compression_md.value = grpc_compression_algorithm_slice(calgo);
-          additional_metadata_count++;
+          if (stream_compression) {
+            const grpc_stream_compression_algorithm calgo =
+                stream_compression_algorithm_for_level_locked(
+                    call, effective_stream_compression_level);
+            compression_md.key =
+                GRPC_MDSTR_GRPC_INTERNAL_STREAM_ENCODING_REQUEST;
+            compression_md.value =
+                grpc_stream_compression_algorithm_slice(calgo);
+          } else {
+            const grpc_compression_algorithm calgo =
+                compression_algorithm_for_level_locked(
+                    call, effective_compression_level);
+            /* the following will be picked up by the compress filter and used
+             * as the call's compression algorithm. */
+            compression_md.key = GRPC_MDSTR_GRPC_INTERNAL_ENCODING_REQUEST;
+            compression_md.value = grpc_compression_algorithm_slice(calgo);
+            additional_metadata_count++;
+          }
         }
 
         if (op->data.send_initial_metadata.count + additional_metadata_count >
@@ -1723,7 +1940,7 @@ static grpc_call_error call_start_batch(grpc_exec_ctx *exec_ctx,
 
   GRPC_CALL_INTERNAL_REF(call, "completion");
   if (!is_notify_tag_closure) {
-    grpc_cq_begin_op(call->cq, notify_tag);
+    GPR_ASSERT(grpc_cq_begin_op(call->cq, notify_tag));
   }
   gpr_ref_init(&bctl->steps_to_complete, num_completion_callbacks_needed);
 
@@ -1844,6 +2061,8 @@ const char *grpc_call_error_to_string(grpc_call_error error) {
       return "GRPC_CALL_ERROR_PAYLOAD_TYPE_MISMATCH";
     case GRPC_CALL_ERROR_TOO_MANY_OPERATIONS:
       return "GRPC_CALL_ERROR_TOO_MANY_OPERATIONS";
+    case GRPC_CALL_ERROR_COMPLETION_QUEUE_SHUTDOWN:
+      return "GRPC_CALL_ERROR_COMPLETION_QUEUE_SHUTDOWN";
     case GRPC_CALL_OK:
       return "GRPC_CALL_OK";
   }
diff --git a/src/core/lib/surface/call_test_only.h b/src/core/lib/surface/call_test_only.h
index 2f1b80bfd7..a5a01b3679 100644
--- a/src/core/lib/surface/call_test_only.h
+++ b/src/core/lib/surface/call_test_only.h
@@ -42,6 +42,18 @@ uint32_t grpc_call_test_only_get_message_flags(grpc_call *call);
  * To be indexed by grpc_compression_algorithm enum values. */
 uint32_t grpc_call_test_only_get_encodings_accepted_by_peer(grpc_call *call);
 
+/** Returns a bitset for the stream encodings (stream compression algorithms)
+ * supported by \a call's peer.
+ *
+ * To be indexed by grpc_stream_compression_algorithm enum values. */
+uint32_t grpc_call_test_only_get_stream_encodings_accepted_by_peer(
+    grpc_call *call);
+
+/** Returns the incoming stream compression algorithm (content-encoding header)
+ * received by a call. */
+grpc_stream_compression_algorithm
+grpc_call_test_only_get_incoming_stream_encodings(grpc_call *call);
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/src/core/lib/surface/channel.c b/src/core/lib/surface/channel.c
index 5780a18ce8..850fbe6a69 100644
--- a/src/core/lib/surface/channel.c
+++ b/src/core/lib/surface/channel.c
@@ -142,6 +142,16 @@ grpc_channel *grpc_channel_create_with_builder(
                                      GRPC_COMPRESS_LEVEL_NONE,
                                      GRPC_COMPRESS_LEVEL_COUNT - 1});
     } else if (0 == strcmp(args->args[i].key,
+                           GRPC_STREAM_COMPRESSION_CHANNEL_DEFAULT_LEVEL)) {
+      channel->compression_options.default_stream_compression_level.is_set =
+          true;
+      channel->compression_options.default_stream_compression_level.level =
+          (grpc_stream_compression_level)grpc_channel_arg_get_integer(
+              &args->args[i],
+              (grpc_integer_options){GRPC_STREAM_COMPRESS_LEVEL_NONE,
+                                     GRPC_STREAM_COMPRESS_LEVEL_NONE,
+                                     GRPC_STREAM_COMPRESS_LEVEL_COUNT - 1});
+    } else if (0 == strcmp(args->args[i].key,
                            GRPC_COMPRESSION_CHANNEL_DEFAULT_ALGORITHM)) {
       channel->compression_options.default_algorithm.is_set = true;
       channel->compression_options.default_algorithm.algorithm =
@@ -149,12 +159,31 @@ grpc_channel *grpc_channel_create_with_builder(
               &args->args[i],
               (grpc_integer_options){GRPC_COMPRESS_NONE, GRPC_COMPRESS_NONE,
                                      GRPC_COMPRESS_ALGORITHMS_COUNT - 1});
+    } else if (0 == strcmp(args->args[i].key,
+                           GRPC_STREAM_COMPRESSION_CHANNEL_DEFAULT_ALGORITHM)) {
+      channel->compression_options.default_stream_compression_algorithm.is_set =
+          true;
+      channel->compression_options.default_stream_compression_algorithm
+          .algorithm =
+          (grpc_stream_compression_algorithm)grpc_channel_arg_get_integer(
+              &args->args[i],
+              (grpc_integer_options){
+                  GRPC_STREAM_COMPRESS_NONE, GRPC_STREAM_COMPRESS_NONE,
+                  GRPC_STREAM_COMPRESS_ALGORITHMS_COUNT - 1});
     } else if (0 ==
                strcmp(args->args[i].key,
                       GRPC_COMPRESSION_CHANNEL_ENABLED_ALGORITHMS_BITSET)) {
       channel->compression_options.enabled_algorithms_bitset =
           (uint32_t)args->args[i].value.integer |
           0x1; /* always support no compression */
+    } else if (0 ==
+               strcmp(
+                   args->args[i].key,
+                   GRPC_STREAM_COMPRESSION_CHANNEL_ENABLED_ALGORITHMS_BITSET)) {
+      channel->compression_options
+          .enabled_stream_compression_algorithms_bitset =
+          (uint32_t)args->args[i].value.integer |
+          0x1; /* always support no compression */
     }
   }
 
diff --git a/src/core/lib/surface/channel_ping.c b/src/core/lib/surface/channel_ping.c
index 80eb80af78..e85b308850 100644
--- a/src/core/lib/surface/channel_ping.c
+++ b/src/core/lib/surface/channel_ping.c
@@ -59,7 +59,7 @@ void grpc_channel_ping(grpc_channel *channel, grpc_completion_queue *cq,
   GRPC_CLOSURE_INIT(&pr->closure, ping_done, pr, grpc_schedule_on_exec_ctx);
   op->send_ping = &pr->closure;
   op->bind_pollset = grpc_cq_pollset(cq);
-  grpc_cq_begin_op(cq, tag);
+  GPR_ASSERT(grpc_cq_begin_op(cq, tag));
   top_elem->filter->start_transport_op(&exec_ctx, top_elem, op);
   grpc_exec_ctx_finish(&exec_ctx);
 }
diff --git a/src/core/lib/surface/completion_queue.c b/src/core/lib/surface/completion_queue.c
index 978d7b4171..10e4e5ab0c 100644
--- a/src/core/lib/surface/completion_queue.c
+++ b/src/core/lib/surface/completion_queue.c
@@ -196,7 +196,7 @@ typedef struct cq_vtable {
   void (*init)(void *data);
   void (*shutdown)(grpc_exec_ctx *exec_ctx, grpc_completion_queue *cq);
   void (*destroy)(void *data);
-  void (*begin_op)(grpc_completion_queue *cq, void *tag);
+  bool (*begin_op)(grpc_completion_queue *cq, void *tag);
   void (*end_op)(grpc_exec_ctx *exec_ctx, grpc_completion_queue *cq, void *tag,
                  grpc_error *error,
                  void (*done)(grpc_exec_ctx *exec_ctx, void *done_arg,
@@ -235,7 +235,8 @@ typedef struct cq_next_data {
   /* Number of outstanding events (+1 if not shut down) */
   gpr_atm pending_events;
 
-  int shutdown_called;
+  /** 0 initially. 1 once we initiated shutdown */
+  bool shutdown_called;
 } cq_next_data;
 
 typedef struct cq_pluck_data {
@@ -244,15 +245,20 @@ typedef struct cq_pluck_data {
   grpc_cq_completion *completed_tail;
 
   /** Number of pending events (+1 if we're not shutdown) */
-  gpr_refcount pending_events;
+  gpr_atm pending_events;
 
   /** Counter of how many things have ever been queued on this completion queue
       useful for avoiding locks to check the queue */
   gpr_atm things_queued_ever;
 
-  /** 0 initially, 1 once we've begun shutting down */
+  /** 0 initially. 1 once we completed shutting */
+  /* TODO: (sreek) This is not needed since (shutdown == 1) if and only if
+   * (pending_events == 0). So consider removing this in future and use
+   * pending_events */
   gpr_atm shutdown;
-  int shutdown_called;
+
+  /** 0 initially. 1 once we initiated shutdown */
+  bool shutdown_called;
 
   int num_pluckers;
   plucker pluckers[GRPC_MAX_COMPLETION_QUEUE_PLUCKERS];
@@ -288,8 +294,8 @@ static void cq_shutdown_next(grpc_exec_ctx *exec_ctx,
 static void cq_shutdown_pluck(grpc_exec_ctx *exec_ctx,
                               grpc_completion_queue *cq);
 
-static void cq_begin_op_for_next(grpc_completion_queue *cq, void *tag);
-static void cq_begin_op_for_pluck(grpc_completion_queue *cq, void *tag);
+static bool cq_begin_op_for_next(grpc_completion_queue *cq, void *tag);
+static bool cq_begin_op_for_pluck(grpc_completion_queue *cq, void *tag);
 
 static void cq_end_op_for_next(grpc_exec_ctx *exec_ctx,
                                grpc_completion_queue *cq, void *tag,
@@ -436,7 +442,7 @@ grpc_completion_queue *grpc_completion_queue_create_internal(
 
 static void cq_init_next(void *ptr) {
   cq_next_data *cqd = ptr;
-  /* Initial ref is dropped by grpc_completion_queue_shutdown */
+  /* Initial count is dropped by grpc_completion_queue_shutdown */
   gpr_atm_no_barrier_store(&cqd->pending_events, 1);
   cqd->shutdown_called = false;
   gpr_atm_no_barrier_store(&cqd->things_queued_ever, 0);
@@ -451,12 +457,12 @@ static void cq_destroy_next(void *ptr) {
 
 static void cq_init_pluck(void *ptr) {
   cq_pluck_data *cqd = ptr;
-  /* Initial ref is dropped by grpc_completion_queue_shutdown */
-  gpr_ref_init(&cqd->pending_events, 1);
+  /* Initial count is dropped by grpc_completion_queue_shutdown */
+  gpr_atm_no_barrier_store(&cqd->pending_events, 1);
   cqd->completed_tail = &cqd->completed_head;
   cqd->completed_head.next = (uintptr_t)cqd->completed_tail;
   gpr_atm_no_barrier_store(&cqd->shutdown, 0);
-  cqd->shutdown_called = 0;
+  cqd->shutdown_called = false;
   cqd->num_pluckers = 0;
   gpr_atm_no_barrier_store(&cqd->things_queued_ever, 0);
 }
@@ -522,33 +528,6 @@ void grpc_cq_internal_unref(grpc_exec_ctx *exec_ctx,
   }
 }
 
-static void cq_begin_op_for_next(grpc_completion_queue *cq, void *tag) {
-  cq_next_data *cqd = DATA_FROM_CQ(cq);
-  GPR_ASSERT(!cqd->shutdown_called);
-  gpr_atm_no_barrier_fetch_add(&cqd->pending_events, 1);
-}
-
-static void cq_begin_op_for_pluck(grpc_completion_queue *cq, void *tag) {
-  cq_pluck_data *cqd = DATA_FROM_CQ(cq);
-  GPR_ASSERT(!cqd->shutdown_called);
-  gpr_ref(&cqd->pending_events);
-}
-
-void grpc_cq_begin_op(grpc_completion_queue *cq, void *tag) {
-#ifndef NDEBUG
-  gpr_mu_lock(cq->mu);
-  if (cq->outstanding_tag_count == cq->outstanding_tag_capacity) {
-    cq->outstanding_tag_capacity = GPR_MAX(4, 2 * cq->outstanding_tag_capacity);
-    cq->outstanding_tags =
-        gpr_realloc(cq->outstanding_tags, sizeof(*cq->outstanding_tags) *
-                                              cq->outstanding_tag_capacity);
-  }
-  cq->outstanding_tags[cq->outstanding_tag_count++] = tag;
-  gpr_mu_unlock(cq->mu);
-#endif
-  cq->vtable->begin_op(cq, tag);
-}
-
 #ifndef NDEBUG
 static void cq_check_tag(grpc_completion_queue *cq, void *tag, bool lock_cq) {
   int found = 0;
@@ -576,6 +555,49 @@ static void cq_check_tag(grpc_completion_queue *cq, void *tag, bool lock_cq) {
 static void cq_check_tag(grpc_completion_queue *cq, void *tag, bool lock_cq) {}
 #endif
 
+/* Atomically increments a counter only if the counter is not zero. Returns
+ * true if the increment was successful; false if the counter is zero */
+static bool atm_inc_if_nonzero(gpr_atm *counter) {
+  while (true) {
+    gpr_atm count = gpr_atm_no_barrier_load(counter);
+    /* If zero, we are done. If not, we must to a CAS (instead of an atomic
+     * increment) to maintain the contract: do not increment the counter if it
+     * is zero. */
+    if (count == 0) {
+      return false;
+    } else if (gpr_atm_no_barrier_cas(counter, count, count + 1)) {
+      break;
+    }
+  }
+
+  return true;
+}
+
+static bool cq_begin_op_for_next(grpc_completion_queue *cq, void *tag) {
+  cq_next_data *cqd = DATA_FROM_CQ(cq);
+  return atm_inc_if_nonzero(&cqd->pending_events);
+}
+
+static bool cq_begin_op_for_pluck(grpc_completion_queue *cq, void *tag) {
+  cq_pluck_data *cqd = DATA_FROM_CQ(cq);
+  return atm_inc_if_nonzero(&cqd->pending_events);
+}
+
+bool grpc_cq_begin_op(grpc_completion_queue *cq, void *tag) {
+#ifndef NDEBUG
+  gpr_mu_lock(cq->mu);
+  if (cq->outstanding_tag_count == cq->outstanding_tag_capacity) {
+    cq->outstanding_tag_capacity = GPR_MAX(4, 2 * cq->outstanding_tag_capacity);
+    cq->outstanding_tags =
+        gpr_realloc(cq->outstanding_tags, sizeof(*cq->outstanding_tags) *
+                                              cq->outstanding_tag_capacity);
+  }
+  cq->outstanding_tags[cq->outstanding_tag_count++] = tag;
+  gpr_mu_unlock(cq->mu);
+#endif
+  return cq->vtable->begin_op(cq, tag);
+}
+
 /* Queue a GRPC_OP_COMPLETED operation to a completion queue (with a
  * completion
  * type of GRPC_CQ_NEXT) */
@@ -696,8 +718,10 @@ static void cq_end_op_for_pluck(grpc_exec_ctx *exec_ctx,
       ((uintptr_t)storage) | (1u & (uintptr_t)cqd->completed_tail->next);
   cqd->completed_tail = storage;
 
-  int shutdown = gpr_unref(&cqd->pending_events);
-  if (!shutdown) {
+  if (gpr_atm_full_fetch_add(&cqd->pending_events, -1) == 1) {
+    cq_finish_shutdown_pluck(exec_ctx, cq);
+    gpr_mu_unlock(cq->mu);
+  } else {
     grpc_pollset_worker *pluck_worker = NULL;
     for (int i = 0; i < cqd->num_pluckers; i++) {
       if (cqd->pluckers[i].tag == tag) {
@@ -717,9 +741,6 @@ static void cq_end_op_for_pluck(grpc_exec_ctx *exec_ctx,
 
       GRPC_ERROR_UNREF(kick_error);
     }
-  } else {
-    cq_finish_shutdown_pluck(exec_ctx, cq);
-    gpr_mu_unlock(cq->mu);
   }
 
   GPR_TIMER_END("cq_end_op_for_pluck", 0);
@@ -855,8 +876,7 @@ static grpc_event cq_next(grpc_completion_queue *cq, gpr_timespec deadline,
          inconsistent state. If it is the latter, we shold do a 0-timeout poll
          so that the thread comes back quickly from poll to make a second
          attempt at popping. Not doing this can potentially deadlock this
-         thread
-         forever (if the deadline is infinity) */
+         thread forever (if the deadline is infinity) */
       if (cq_event_queue_num_items(&cqd->queue) > 0) {
         iteration_deadline = gpr_time_0(GPR_CLOCK_MONOTONIC);
       }
@@ -869,10 +889,8 @@ static grpc_event cq_next(grpc_completion_queue *cq, gpr_timespec deadline,
       if (cq_event_queue_num_items(&cqd->queue) > 0) {
         /* Go to the beginning of the loop. No point doing a poll because
            (cq->shutdown == true) is only possible when there is no pending
-           work
-           (i.e cq->pending_events == 0) and any outstanding
-           grpc_cq_completion
-           events are already queued on this cq */
+           work (i.e cq->pending_events == 0) and any outstanding completion
+           events should have already been queued on this cq */
         continue;
       }
 
@@ -909,11 +927,6 @@ static grpc_event cq_next(grpc_completion_queue *cq, gpr_timespec deadline,
     is_finished_arg.first_loop = false;
   }
 
-  GRPC_SURFACE_TRACE_RETURNED_EVENT(cq, &ret);
-  GRPC_CQ_INTERNAL_UNREF(&exec_ctx, cq, "next");
-  grpc_exec_ctx_finish(&exec_ctx);
-  GPR_ASSERT(is_finished_arg.stolen_completion == NULL);
-
   if (cq_event_queue_num_items(&cqd->queue) > 0 &&
       gpr_atm_no_barrier_load(&cqd->pending_events) > 0) {
     gpr_mu_lock(cq->mu);
@@ -921,6 +934,11 @@ static grpc_event cq_next(grpc_completion_queue *cq, gpr_timespec deadline,
     gpr_mu_unlock(cq->mu);
   }
 
+  GRPC_SURFACE_TRACE_RETURNED_EVENT(cq, &ret);
+  GRPC_CQ_INTERNAL_UNREF(&exec_ctx, cq, "next");
+  grpc_exec_ctx_finish(&exec_ctx);
+  GPR_ASSERT(is_finished_arg.stolen_completion == NULL);
+
   GPR_TIMER_END("grpc_completion_queue_next", 0);
 
   return ret;
@@ -947,15 +965,20 @@ static void cq_shutdown_next(grpc_exec_ctx *exec_ctx,
                              grpc_completion_queue *cq) {
   cq_next_data *cqd = DATA_FROM_CQ(cq);
 
+  /* Need an extra ref for cq here because:
+   * We call cq_finish_shutdown_next() below, that would call pollset shutdown.
+   * Pollset shutdown decrements the cq ref count which can potentially destroy
+   * the cq (if that happens to be the last ref).
+   * Creating an extra ref here prevents the cq from getting destroyed while
+   * this function is still active */
   GRPC_CQ_INTERNAL_REF(cq, "shutting_down");
   gpr_mu_lock(cq->mu);
   if (cqd->shutdown_called) {
     gpr_mu_unlock(cq->mu);
     GRPC_CQ_INTERNAL_UNREF(exec_ctx, cq, "shutting_down");
-    GPR_TIMER_END("grpc_completion_queue_shutdown", 0);
     return;
   }
-  cqd->shutdown_called = 1;
+  cqd->shutdown_called = true;
   if (gpr_atm_full_fetch_add(&cqd->pending_events, -1) == 1) {
     cq_finish_shutdown_next(exec_ctx, cq);
   }
@@ -1167,21 +1190,31 @@ static void cq_finish_shutdown_pluck(grpc_exec_ctx *exec_ctx,
                               &cq->pollset_shutdown_done);
 }
 
+/* NOTE: This function is almost exactly identical to cq_shutdown_next() but
+ * merging them is a bit tricky and probably not worth it */
 static void cq_shutdown_pluck(grpc_exec_ctx *exec_ctx,
                               grpc_completion_queue *cq) {
   cq_pluck_data *cqd = DATA_FROM_CQ(cq);
 
+  /* Need an extra ref for cq here because:
+   * We call cq_finish_shutdown_pluck() below, that would call pollset shutdown.
+   * Pollset shutdown decrements the cq ref count which can potentially destroy
+   * the cq (if that happens to be the last ref).
+   * Creating an extra ref here prevents the cq from getting destroyed while
+   * this function is still active */
+  GRPC_CQ_INTERNAL_REF(cq, "shutting_down (pluck cq)");
   gpr_mu_lock(cq->mu);
   if (cqd->shutdown_called) {
     gpr_mu_unlock(cq->mu);
-    GPR_TIMER_END("grpc_completion_queue_shutdown", 0);
+    GRPC_CQ_INTERNAL_UNREF(exec_ctx, cq, "shutting_down (pluck cq)");
     return;
   }
-  cqd->shutdown_called = 1;
-  if (gpr_unref(&cqd->pending_events)) {
+  cqd->shutdown_called = true;
+  if (gpr_atm_full_fetch_add(&cqd->pending_events, -1) == 1) {
     cq_finish_shutdown_pluck(exec_ctx, cq);
   }
   gpr_mu_unlock(cq->mu);
+  GRPC_CQ_INTERNAL_UNREF(exec_ctx, cq, "shutting_down (pluck cq)");
 }
 
 /* Shutdown simply drops a ref that we reserved at creation time; if we drop
diff --git a/src/core/lib/surface/completion_queue.h b/src/core/lib/surface/completion_queue.h
index af44482513..69d144bd95 100644
--- a/src/core/lib/surface/completion_queue.h
+++ b/src/core/lib/surface/completion_queue.h
@@ -72,8 +72,9 @@ void grpc_cq_internal_unref(grpc_exec_ctx *exec_ctx, grpc_completion_queue *cc);
 
 /* Flag that an operation is beginning: the completion channel will not finish
    shutdown until a corrensponding grpc_cq_end_* call is made.
-   \a tag is currently used only in debug builds. */
-void grpc_cq_begin_op(grpc_completion_queue *cc, void *tag);
+   \a tag is currently used only in debug builds. Return true on success, and
+   false if completion_queue has been shutdown. */
+bool grpc_cq_begin_op(grpc_completion_queue *cc, void *tag);
 
 /* Queue a GRPC_OP_COMPLETED operation; tag must correspond to the tag passed to
    grpc_cq_begin_op */
diff --git a/src/core/lib/surface/init.c b/src/core/lib/surface/init.c
index db111e597f..d199ac060e 100644
--- a/src/core/lib/surface/init.c
+++ b/src/core/lib/surface/init.c
@@ -36,6 +36,7 @@
 #include "src/core/lib/iomgr/resource_quota.h"
 #include "src/core/lib/profiling/timers.h"
 #include "src/core/lib/slice/slice_internal.h"
+#include "src/core/lib/surface/alarm_internal.h"
 #include "src/core/lib/surface/api_trace.h"
 #include "src/core/lib/surface/call.h"
 #include "src/core/lib/surface/channel_init.h"
@@ -135,6 +136,7 @@ void grpc_init(void) {
     grpc_register_tracer(&grpc_call_error_trace);
 #ifndef NDEBUG
     grpc_register_tracer(&grpc_trace_pending_tags);
+    grpc_register_tracer(&grpc_trace_alarm_refcount);
     grpc_register_tracer(&grpc_trace_cq_refcount);
     grpc_register_tracer(&grpc_trace_closure);
     grpc_register_tracer(&grpc_trace_error_refcount);
diff --git a/src/core/lib/surface/server.c b/src/core/lib/surface/server.c
index 4bdc03052f..f8c84fb4a8 100644
--- a/src/core/lib/surface/server.c
+++ b/src/core/lib/surface/server.c
@@ -1261,7 +1261,7 @@ void grpc_server_shutdown_and_notify(grpc_server *server,
   }
 
   /* stay locked, and gather up some stuff to do */
-  grpc_cq_begin_op(cq, tag);
+  GPR_ASSERT(grpc_cq_begin_op(cq, tag));
   if (server->shutdown_published) {
     grpc_cq_end_op(&exec_ctx, cq, tag, GRPC_ERROR_NONE, done_published_shutdown,
                    NULL, gpr_malloc(sizeof(grpc_cq_completion)));
@@ -1448,7 +1448,11 @@ grpc_call_error grpc_server_request_call(
     error = GRPC_CALL_ERROR_NOT_SERVER_COMPLETION_QUEUE;
     goto done;
   }
-  grpc_cq_begin_op(cq_for_notification, tag);
+  if (grpc_cq_begin_op(cq_for_notification, tag) == false) {
+    gpr_free(rc);
+    error = GRPC_CALL_ERROR_COMPLETION_QUEUE_SHUTDOWN;
+    goto done;
+  }
   details->reserved = NULL;
   rc->cq_idx = cq_idx;
   rc->type = BATCH_CALL;
@@ -1498,7 +1502,11 @@ grpc_call_error grpc_server_request_registered_call(
     error = GRPC_CALL_ERROR_PAYLOAD_TYPE_MISMATCH;
     goto done;
   }
-  grpc_cq_begin_op(cq_for_notification, tag);
+  if (grpc_cq_begin_op(cq_for_notification, tag) == false) {
+    gpr_free(rc);
+    error = GRPC_CALL_ERROR_COMPLETION_QUEUE_SHUTDOWN;
+    goto done;
+  }
   rc->cq_idx = cq_idx;
   rc->type = REGISTERED_CALL;
   rc->server = server;
diff --git a/src/core/lib/surface/version.c b/src/core/lib/surface/version.c
index 8cef15da80..96c16105e7 100644
--- a/src/core/lib/surface/version.c
+++ b/src/core/lib/surface/version.c
@@ -23,4 +23,4 @@
 
 const char *grpc_version_string(void) { return "4.0.0-dev"; }
 
-const char *grpc_g_stands_for(void) { return "gregarious"; }
+const char *grpc_g_stands_for(void) { return "gambit"; }
diff --git a/src/core/lib/transport/bdp_estimator.c b/src/core/lib/transport/bdp_estimator.c
index 311ae6390d..8b57693413 100644
--- a/src/core/lib/transport/bdp_estimator.c
+++ b/src/core/lib/transport/bdp_estimator.c
@@ -33,20 +33,24 @@ void grpc_bdp_estimator_init(grpc_bdp_estimator *estimator, const char *name) {
   estimator->bw_est = 0;
 }
 
-bool grpc_bdp_estimator_get_estimate(grpc_bdp_estimator *estimator,
+bool grpc_bdp_estimator_get_estimate(const grpc_bdp_estimator *estimator,
                                      int64_t *estimate) {
   *estimate = estimator->estimate;
   return true;
 }
 
-bool grpc_bdp_estimator_get_bw(grpc_bdp_estimator *estimator, double *bw) {
+bool grpc_bdp_estimator_get_bw(const grpc_bdp_estimator *estimator,
+                               double *bw) {
   *bw = estimator->bw_est;
   return true;
 }
 
-bool grpc_bdp_estimator_add_incoming_bytes(grpc_bdp_estimator *estimator,
+void grpc_bdp_estimator_add_incoming_bytes(grpc_bdp_estimator *estimator,
                                            int64_t num_bytes) {
   estimator->accumulator += num_bytes;
+}
+
+bool grpc_bdp_estimator_need_ping(const grpc_bdp_estimator *estimator) {
   switch (estimator->ping_state) {
     case GRPC_BDP_PING_UNSCHEDULED:
       return true;
diff --git a/src/core/lib/transport/bdp_estimator.h b/src/core/lib/transport/bdp_estimator.h
index a232d1f87f..1ef0dc99dd 100644
--- a/src/core/lib/transport/bdp_estimator.h
+++ b/src/core/lib/transport/bdp_estimator.h
@@ -47,13 +47,15 @@ typedef struct grpc_bdp_estimator {
 void grpc_bdp_estimator_init(grpc_bdp_estimator *estimator, const char *name);
 
 // Returns true if a reasonable estimate could be obtained
-bool grpc_bdp_estimator_get_estimate(grpc_bdp_estimator *estimator,
+bool grpc_bdp_estimator_get_estimate(const grpc_bdp_estimator *estimator,
                                      int64_t *estimate);
-// Returns true if a reasonable estimate could be obtained
-bool grpc_bdp_estimator_get_bw(grpc_bdp_estimator *estimator, double *bw);
+// Tracks new bytes read.
+bool grpc_bdp_estimator_get_bw(const grpc_bdp_estimator *estimator, double *bw);
 // Returns true if the user should schedule a ping
-bool grpc_bdp_estimator_add_incoming_bytes(grpc_bdp_estimator *estimator,
+void grpc_bdp_estimator_add_incoming_bytes(grpc_bdp_estimator *estimator,
                                            int64_t num_bytes);
+// Returns true if the user should schedule a ping
+bool grpc_bdp_estimator_need_ping(const grpc_bdp_estimator *estimator);
 // Schedule a ping: call in response to receiving a true from
 // grpc_bdp_estimator_add_incoming_bytes once a ping has been scheduled by a
 // transport (but not necessarily started)
diff --git a/src/core/lib/transport/byte_stream.c b/src/core/lib/transport/byte_stream.c
index 3355814017..fb03a10315 100644
--- a/src/core/lib/transport/byte_stream.c
+++ b/src/core/lib/transport/byte_stream.c
@@ -19,29 +19,37 @@
 #include "src/core/lib/transport/byte_stream.h"
 
 #include <stdlib.h>
+#include <string.h>
 
 #include <grpc/support/log.h>
 
 #include "src/core/lib/slice/slice_internal.h"
 
-int grpc_byte_stream_next(grpc_exec_ctx *exec_ctx,
-                          grpc_byte_stream *byte_stream, size_t max_size_hint,
-                          grpc_closure *on_complete) {
-  return byte_stream->next(exec_ctx, byte_stream, max_size_hint, on_complete);
+bool grpc_byte_stream_next(grpc_exec_ctx *exec_ctx,
+                           grpc_byte_stream *byte_stream, size_t max_size_hint,
+                           grpc_closure *on_complete) {
+  return byte_stream->vtable->next(exec_ctx, byte_stream, max_size_hint,
+                                   on_complete);
 }
 
 grpc_error *grpc_byte_stream_pull(grpc_exec_ctx *exec_ctx,
                                   grpc_byte_stream *byte_stream,
                                   grpc_slice *slice) {
-  return byte_stream->pull(exec_ctx, byte_stream, slice);
+  return byte_stream->vtable->pull(exec_ctx, byte_stream, slice);
+}
+
+void grpc_byte_stream_shutdown(grpc_exec_ctx *exec_ctx,
+                               grpc_byte_stream *byte_stream,
+                               grpc_error *error) {
+  byte_stream->vtable->shutdown(exec_ctx, byte_stream, error);
 }
 
 void grpc_byte_stream_destroy(grpc_exec_ctx *exec_ctx,
                               grpc_byte_stream *byte_stream) {
-  byte_stream->destroy(exec_ctx, byte_stream);
+  byte_stream->vtable->destroy(exec_ctx, byte_stream);
 }
 
-/* slice_buffer_stream */
+// grpc_slice_buffer_stream
 
 static bool slice_buffer_stream_next(grpc_exec_ctx *exec_ctx,
                                      grpc_byte_stream *byte_stream,
@@ -56,6 +64,9 @@ static grpc_error *slice_buffer_stream_pull(grpc_exec_ctx *exec_ctx,
                                             grpc_byte_stream *byte_stream,
                                             grpc_slice *slice) {
   grpc_slice_buffer_stream *stream = (grpc_slice_buffer_stream *)byte_stream;
+  if (stream->shutdown_error != GRPC_ERROR_NONE) {
+    return GRPC_ERROR_REF(stream->shutdown_error);
+  }
   GPR_ASSERT(stream->cursor < stream->backing_buffer->count);
   *slice =
       grpc_slice_ref_internal(stream->backing_buffer->slices[stream->cursor]);
@@ -63,8 +74,23 @@ static grpc_error *slice_buffer_stream_pull(grpc_exec_ctx *exec_ctx,
   return GRPC_ERROR_NONE;
 }
 
+static void slice_buffer_stream_shutdown(grpc_exec_ctx *exec_ctx,
+                                         grpc_byte_stream *byte_stream,
+                                         grpc_error *error) {
+  grpc_slice_buffer_stream *stream = (grpc_slice_buffer_stream *)byte_stream;
+  GRPC_ERROR_UNREF(stream->shutdown_error);
+  stream->shutdown_error = error;
+}
+
 static void slice_buffer_stream_destroy(grpc_exec_ctx *exec_ctx,
-                                        grpc_byte_stream *byte_stream) {}
+                                        grpc_byte_stream *byte_stream) {
+  grpc_slice_buffer_stream *stream = (grpc_slice_buffer_stream *)byte_stream;
+  GRPC_ERROR_UNREF(stream->shutdown_error);
+}
+
+static const grpc_byte_stream_vtable slice_buffer_stream_vtable = {
+    slice_buffer_stream_next, slice_buffer_stream_pull,
+    slice_buffer_stream_shutdown, slice_buffer_stream_destroy};
 
 void grpc_slice_buffer_stream_init(grpc_slice_buffer_stream *stream,
                                    grpc_slice_buffer *slice_buffer,
@@ -72,9 +98,89 @@ void grpc_slice_buffer_stream_init(grpc_slice_buffer_stream *stream,
   GPR_ASSERT(slice_buffer->length <= UINT32_MAX);
   stream->base.length = (uint32_t)slice_buffer->length;
   stream->base.flags = flags;
-  stream->base.next = slice_buffer_stream_next;
-  stream->base.pull = slice_buffer_stream_pull;
-  stream->base.destroy = slice_buffer_stream_destroy;
+  stream->base.vtable = &slice_buffer_stream_vtable;
   stream->backing_buffer = slice_buffer;
   stream->cursor = 0;
+  stream->shutdown_error = GRPC_ERROR_NONE;
+}
+
+// grpc_caching_byte_stream
+
+void grpc_byte_stream_cache_init(grpc_byte_stream_cache *cache,
+                                 grpc_byte_stream *underlying_stream) {
+  cache->underlying_stream = underlying_stream;
+  grpc_slice_buffer_init(&cache->cache_buffer);
+}
+
+void grpc_byte_stream_cache_destroy(grpc_exec_ctx *exec_ctx,
+                                    grpc_byte_stream_cache *cache) {
+  grpc_byte_stream_destroy(exec_ctx, cache->underlying_stream);
+  grpc_slice_buffer_destroy_internal(exec_ctx, &cache->cache_buffer);
+}
+
+static bool caching_byte_stream_next(grpc_exec_ctx *exec_ctx,
+                                     grpc_byte_stream *byte_stream,
+                                     size_t max_size_hint,
+                                     grpc_closure *on_complete) {
+  grpc_caching_byte_stream *stream = (grpc_caching_byte_stream *)byte_stream;
+  if (stream->shutdown_error != GRPC_ERROR_NONE) return true;
+  if (stream->cursor < stream->cache->cache_buffer.count) return true;
+  return grpc_byte_stream_next(exec_ctx, stream->cache->underlying_stream,
+                               max_size_hint, on_complete);
+}
+
+static grpc_error *caching_byte_stream_pull(grpc_exec_ctx *exec_ctx,
+                                            grpc_byte_stream *byte_stream,
+                                            grpc_slice *slice) {
+  grpc_caching_byte_stream *stream = (grpc_caching_byte_stream *)byte_stream;
+  if (stream->shutdown_error != GRPC_ERROR_NONE) {
+    return GRPC_ERROR_REF(stream->shutdown_error);
+  }
+  if (stream->cursor < stream->cache->cache_buffer.count) {
+    *slice = grpc_slice_ref_internal(
+        stream->cache->cache_buffer.slices[stream->cursor]);
+    ++stream->cursor;
+    return GRPC_ERROR_NONE;
+  }
+  grpc_error *error =
+      grpc_byte_stream_pull(exec_ctx, stream->cache->underlying_stream, slice);
+  if (error == GRPC_ERROR_NONE) {
+    ++stream->cursor;
+    grpc_slice_buffer_add(&stream->cache->cache_buffer,
+                          grpc_slice_ref_internal(*slice));
+  }
+  return error;
+}
+
+static void caching_byte_stream_shutdown(grpc_exec_ctx *exec_ctx,
+                                         grpc_byte_stream *byte_stream,
+                                         grpc_error *error) {
+  grpc_caching_byte_stream *stream = (grpc_caching_byte_stream *)byte_stream;
+  GRPC_ERROR_UNREF(stream->shutdown_error);
+  stream->shutdown_error = GRPC_ERROR_REF(error);
+  grpc_byte_stream_shutdown(exec_ctx, stream->cache->underlying_stream, error);
+}
+
+static void caching_byte_stream_destroy(grpc_exec_ctx *exec_ctx,
+                                        grpc_byte_stream *byte_stream) {
+  grpc_caching_byte_stream *stream = (grpc_caching_byte_stream *)byte_stream;
+  GRPC_ERROR_UNREF(stream->shutdown_error);
+}
+
+static const grpc_byte_stream_vtable caching_byte_stream_vtable = {
+    caching_byte_stream_next, caching_byte_stream_pull,
+    caching_byte_stream_shutdown, caching_byte_stream_destroy};
+
+void grpc_caching_byte_stream_init(grpc_caching_byte_stream *stream,
+                                   grpc_byte_stream_cache *cache) {
+  memset(stream, 0, sizeof(*stream));
+  stream->base.length = cache->underlying_stream->length;
+  stream->base.flags = cache->underlying_stream->flags;
+  stream->base.vtable = &caching_byte_stream_vtable;
+  stream->cache = cache;
+  stream->shutdown_error = GRPC_ERROR_NONE;
+}
+
+void grpc_caching_byte_stream_reset(grpc_caching_byte_stream *stream) {
+  stream->cursor = 0;
 }
diff --git a/src/core/lib/transport/byte_stream.h b/src/core/lib/transport/byte_stream.h
index f172296e4b..1e1e8310b8 100644
--- a/src/core/lib/transport/byte_stream.h
+++ b/src/core/lib/transport/byte_stream.h
@@ -28,52 +28,109 @@
 /** Mask of all valid internal flags. */
 #define GRPC_WRITE_INTERNAL_USED_MASK (GRPC_WRITE_INTERNAL_COMPRESS)
 
-struct grpc_byte_stream;
 typedef struct grpc_byte_stream grpc_byte_stream;
 
-struct grpc_byte_stream {
-  uint32_t length;
-  uint32_t flags;
+typedef struct {
   bool (*next)(grpc_exec_ctx *exec_ctx, grpc_byte_stream *byte_stream,
                size_t max_size_hint, grpc_closure *on_complete);
   grpc_error *(*pull)(grpc_exec_ctx *exec_ctx, grpc_byte_stream *byte_stream,
                       grpc_slice *slice);
+  void (*shutdown)(grpc_exec_ctx *exec_ctx, grpc_byte_stream *byte_stream,
+                   grpc_error *error);
   void (*destroy)(grpc_exec_ctx *exec_ctx, grpc_byte_stream *byte_stream);
+} grpc_byte_stream_vtable;
+
+struct grpc_byte_stream {
+  uint32_t length;
+  uint32_t flags;
+  const grpc_byte_stream_vtable *vtable;
 };
 
-/* returns 1 if the bytes are available immediately (in which case
- * on_complete will not be called), 0 if the bytes will be available
- * asynchronously.
- *
- * max_size_hint can be set as a hint as to the maximum number
- * of bytes that would be acceptable to read.
- */
-int grpc_byte_stream_next(grpc_exec_ctx *exec_ctx,
-                          grpc_byte_stream *byte_stream, size_t max_size_hint,
-                          grpc_closure *on_complete);
+// Returns true if the bytes are available immediately (in which case
+// on_complete will not be called), false if the bytes will be available
+// asynchronously.
+//
+// max_size_hint can be set as a hint as to the maximum number
+// of bytes that would be acceptable to read.
+bool grpc_byte_stream_next(grpc_exec_ctx *exec_ctx,
+                           grpc_byte_stream *byte_stream, size_t max_size_hint,
+                           grpc_closure *on_complete);
 
-/* returns the next slice in the byte stream when it is ready (indicated by
- * either grpc_byte_stream_next returning 1 or on_complete passed to
- * grpc_byte_stream_next is called).
- *
- * once a slice is returned into *slice, it is owned by the caller.
- */
+// Returns the next slice in the byte stream when it is ready (indicated by
+// either grpc_byte_stream_next returning true or on_complete passed to
+// grpc_byte_stream_next is called).
+//
+// Once a slice is returned into *slice, it is owned by the caller.
 grpc_error *grpc_byte_stream_pull(grpc_exec_ctx *exec_ctx,
                                   grpc_byte_stream *byte_stream,
                                   grpc_slice *slice);
 
+// Shuts down the byte stream.
+//
+// If there is a pending call to on_complete from grpc_byte_stream_next(),
+// it will be invoked with the error passed to grpc_byte_stream_shutdown().
+//
+// The next call to grpc_byte_stream_pull() (if any) will return the error
+// passed to grpc_byte_stream_shutdown().
+void grpc_byte_stream_shutdown(grpc_exec_ctx *exec_ctx,
+                               grpc_byte_stream *byte_stream,
+                               grpc_error *error);
+
 void grpc_byte_stream_destroy(grpc_exec_ctx *exec_ctx,
                               grpc_byte_stream *byte_stream);
 
-/* grpc_byte_stream that wraps a slice buffer */
+// grpc_slice_buffer_stream
+//
+// A grpc_byte_stream that wraps a slice buffer.
+
 typedef struct grpc_slice_buffer_stream {
   grpc_byte_stream base;
   grpc_slice_buffer *backing_buffer;
   size_t cursor;
+  grpc_error *shutdown_error;
 } grpc_slice_buffer_stream;
 
 void grpc_slice_buffer_stream_init(grpc_slice_buffer_stream *stream,
                                    grpc_slice_buffer *slice_buffer,
                                    uint32_t flags);
 
+// grpc_caching_byte_stream
+//
+// A grpc_byte_stream that that wraps an underlying byte stream but caches
+// the resulting slices in a slice buffer.  If an initial attempt fails
+// without fully draining the underlying stream, a new caching stream
+// can be created from the same underlying cache, in which case it will
+// return whatever is in the backing buffer before continuing to read the
+// underlying stream.
+//
+// NOTE: No synchronization is done, so it is not safe to have multiple
+// grpc_caching_byte_streams simultaneously drawing from the same underlying
+// grpc_byte_stream_cache at the same time.
+
+typedef struct {
+  grpc_byte_stream *underlying_stream;
+  grpc_slice_buffer cache_buffer;
+} grpc_byte_stream_cache;
+
+// Takes ownership of underlying_stream.
+void grpc_byte_stream_cache_init(grpc_byte_stream_cache *cache,
+                                 grpc_byte_stream *underlying_stream);
+
+// Must not be called while still in use by a grpc_caching_byte_stream.
+void grpc_byte_stream_cache_destroy(grpc_exec_ctx *exec_ctx,
+                                    grpc_byte_stream_cache *cache);
+
+typedef struct {
+  grpc_byte_stream base;
+  grpc_byte_stream_cache *cache;
+  size_t cursor;
+  grpc_error *shutdown_error;
+} grpc_caching_byte_stream;
+
+void grpc_caching_byte_stream_init(grpc_caching_byte_stream *stream,
+                                   grpc_byte_stream_cache *cache);
+
+// Resets the byte stream to the start of the underlying stream.
+void grpc_caching_byte_stream_reset(grpc_caching_byte_stream *stream);
+
 #endif /* GRPC_CORE_LIB_TRANSPORT_BYTE_STREAM_H */
diff --git a/src/core/lib/transport/static_metadata.c b/src/core/lib/transport/static_metadata.c
index 2388f19f81..28f05d5c44 100644
--- a/src/core/lib/transport/static_metadata.c
+++ b/src/core/lib/transport/static_metadata.c
@@ -40,65 +40,68 @@ static uint8_t g_bytes[] = {
     114, 45,  115, 116, 97,  116, 115, 45,  98,  105, 110, 103, 114, 112, 99,
     45,  116, 97,  103, 115, 45,  98,  105, 110, 103, 114, 112, 99,  45,  116,
     114, 97,  99,  101, 45,  98,  105, 110, 99,  111, 110, 116, 101, 110, 116,
-    45,  116, 121, 112, 101, 103, 114, 112, 99,  45,  105, 110, 116, 101, 114,
-    110, 97,  108, 45,  101, 110, 99,  111, 100, 105, 110, 103, 45,  114, 101,
-    113, 117, 101, 115, 116, 117, 115, 101, 114, 45,  97,  103, 101, 110, 116,
-    104, 111, 115, 116, 108, 98,  45,  116, 111, 107, 101, 110, 103, 114, 112,
-    99,  45,  116, 105, 109, 101, 111, 117, 116, 103, 114, 112, 99,  46,  119,
-    97,  105, 116, 95,  102, 111, 114, 95,  114, 101, 97,  100, 121, 103, 114,
-    112, 99,  46,  116, 105, 109, 101, 111, 117, 116, 103, 114, 112, 99,  46,
-    109, 97,  120, 95,  114, 101, 113, 117, 101, 115, 116, 95,  109, 101, 115,
-    115, 97,  103, 101, 95,  98,  121, 116, 101, 115, 103, 114, 112, 99,  46,
-    109, 97,  120, 95,  114, 101, 115, 112, 111, 110, 115, 101, 95,  109, 101,
-    115, 115, 97,  103, 101, 95,  98,  121, 116, 101, 115, 47,  103, 114, 112,
-    99,  46,  108, 98,  46,  118, 49,  46,  76,  111, 97,  100, 66,  97,  108,
-    97,  110, 99,  101, 114, 47,  66,  97,  108, 97,  110, 99,  101, 76,  111,
-    97,  100, 48,  49,  50,  105, 100, 101, 110, 116, 105, 116, 121, 103, 122,
-    105, 112, 100, 101, 102, 108, 97,  116, 101, 116, 114, 97,  105, 108, 101,
-    114, 115, 97,  112, 112, 108, 105, 99,  97,  116, 105, 111, 110, 47,  103,
-    114, 112, 99,  80,  79,  83,  84,  50,  48,  48,  52,  48,  52,  104, 116,
-    116, 112, 104, 116, 116, 112, 115, 103, 114, 112, 99,  71,  69,  84,  80,
-    85,  84,  47,  47,  105, 110, 100, 101, 120, 46,  104, 116, 109, 108, 50,
-    48,  52,  50,  48,  54,  51,  48,  52,  52,  48,  48,  53,  48,  48,  97,
-    99,  99,  101, 112, 116, 45,  99,  104, 97,  114, 115, 101, 116, 97,  99,
-    99,  101, 112, 116, 45,  101, 110, 99,  111, 100, 105, 110, 103, 103, 122,
-    105, 112, 44,  32,  100, 101, 102, 108, 97,  116, 101, 97,  99,  99,  101,
-    112, 116, 45,  108, 97,  110, 103, 117, 97,  103, 101, 97,  99,  99,  101,
-    112, 116, 45,  114, 97,  110, 103, 101, 115, 97,  99,  99,  101, 112, 116,
-    97,  99,  99,  101, 115, 115, 45,  99,  111, 110, 116, 114, 111, 108, 45,
-    97,  108, 108, 111, 119, 45,  111, 114, 105, 103, 105, 110, 97,  103, 101,
-    97,  108, 108, 111, 119, 97,  117, 116, 104, 111, 114, 105, 122, 97,  116,
-    105, 111, 110, 99,  97,  99,  104, 101, 45,  99,  111, 110, 116, 114, 111,
-    108, 99,  111, 110, 116, 101, 110, 116, 45,  100, 105, 115, 112, 111, 115,
-    105, 116, 105, 111, 110, 99,  111, 110, 116, 101, 110, 116, 45,  101, 110,
-    99,  111, 100, 105, 110, 103, 99,  111, 110, 116, 101, 110, 116, 45,  108,
-    97,  110, 103, 117, 97,  103, 101, 99,  111, 110, 116, 101, 110, 116, 45,
-    108, 101, 110, 103, 116, 104, 99,  111, 110, 116, 101, 110, 116, 45,  108,
-    111, 99,  97,  116, 105, 111, 110, 99,  111, 110, 116, 101, 110, 116, 45,
-    114, 97,  110, 103, 101, 99,  111, 111, 107, 105, 101, 100, 97,  116, 101,
-    101, 116, 97,  103, 101, 120, 112, 101, 99,  116, 101, 120, 112, 105, 114,
-    101, 115, 102, 114, 111, 109, 105, 102, 45,  109, 97,  116, 99,  104, 105,
-    102, 45,  109, 111, 100, 105, 102, 105, 101, 100, 45,  115, 105, 110, 99,
-    101, 105, 102, 45,  110, 111, 110, 101, 45,  109, 97,  116, 99,  104, 105,
-    102, 45,  114, 97,  110, 103, 101, 105, 102, 45,  117, 110, 109, 111, 100,
-    105, 102, 105, 101, 100, 45,  115, 105, 110, 99,  101, 108, 97,  115, 116,
-    45,  109, 111, 100, 105, 102, 105, 101, 100, 108, 98,  45,  99,  111, 115,
-    116, 45,  98,  105, 110, 108, 105, 110, 107, 108, 111, 99,  97,  116, 105,
-    111, 110, 109, 97,  120, 45,  102, 111, 114, 119, 97,  114, 100, 115, 112,
-    114, 111, 120, 121, 45,  97,  117, 116, 104, 101, 110, 116, 105, 99,  97,
-    116, 101, 112, 114, 111, 120, 121, 45,  97,  117, 116, 104, 111, 114, 105,
-    122, 97,  116, 105, 111, 110, 114, 97,  110, 103, 101, 114, 101, 102, 101,
-    114, 101, 114, 114, 101, 102, 114, 101, 115, 104, 114, 101, 116, 114, 121,
-    45,  97,  102, 116, 101, 114, 115, 101, 114, 118, 101, 114, 115, 101, 116,
-    45,  99,  111, 111, 107, 105, 101, 115, 116, 114, 105, 99,  116, 45,  116,
-    114, 97,  110, 115, 112, 111, 114, 116, 45,  115, 101, 99,  117, 114, 105,
-    116, 121, 116, 114, 97,  110, 115, 102, 101, 114, 45,  101, 110, 99,  111,
-    100, 105, 110, 103, 118, 97,  114, 121, 118, 105, 97,  119, 119, 119, 45,
-    97,  117, 116, 104, 101, 110, 116, 105, 99,  97,  116, 101, 105, 100, 101,
-    110, 116, 105, 116, 121, 44,  100, 101, 102, 108, 97,  116, 101, 105, 100,
-    101, 110, 116, 105, 116, 121, 44,  103, 122, 105, 112, 100, 101, 102, 108,
-    97,  116, 101, 44,  103, 122, 105, 112, 105, 100, 101, 110, 116, 105, 116,
-    121, 44,  100, 101, 102, 108, 97,  116, 101, 44,  103, 122, 105, 112};
+    45,  116, 121, 112, 101, 99,  111, 110, 116, 101, 110, 116, 45,  101, 110,
+    99,  111, 100, 105, 110, 103, 97,  99,  99,  101, 112, 116, 45,  101, 110,
+    99,  111, 100, 105, 110, 103, 103, 114, 112, 99,  45,  105, 110, 116, 101,
+    114, 110, 97,  108, 45,  101, 110, 99,  111, 100, 105, 110, 103, 45,  114,
+    101, 113, 117, 101, 115, 116, 103, 114, 112, 99,  45,  105, 110, 116, 101,
+    114, 110, 97,  108, 45,  115, 116, 114, 101, 97,  109, 45,  101, 110, 99,
+    111, 100, 105, 110, 103, 45,  114, 101, 113, 117, 101, 115, 116, 117, 115,
+    101, 114, 45,  97,  103, 101, 110, 116, 104, 111, 115, 116, 108, 98,  45,
+    116, 111, 107, 101, 110, 103, 114, 112, 99,  45,  116, 105, 109, 101, 111,
+    117, 116, 103, 114, 112, 99,  46,  119, 97,  105, 116, 95,  102, 111, 114,
+    95,  114, 101, 97,  100, 121, 103, 114, 112, 99,  46,  116, 105, 109, 101,
+    111, 117, 116, 103, 114, 112, 99,  46,  109, 97,  120, 95,  114, 101, 113,
+    117, 101, 115, 116, 95,  109, 101, 115, 115, 97,  103, 101, 95,  98,  121,
+    116, 101, 115, 103, 114, 112, 99,  46,  109, 97,  120, 95,  114, 101, 115,
+    112, 111, 110, 115, 101, 95,  109, 101, 115, 115, 97,  103, 101, 95,  98,
+    121, 116, 101, 115, 47,  103, 114, 112, 99,  46,  108, 98,  46,  118, 49,
+    46,  76,  111, 97,  100, 66,  97,  108, 97,  110, 99,  101, 114, 47,  66,
+    97,  108, 97,  110, 99,  101, 76,  111, 97,  100, 48,  49,  50,  105, 100,
+    101, 110, 116, 105, 116, 121, 103, 122, 105, 112, 100, 101, 102, 108, 97,
+    116, 101, 116, 114, 97,  105, 108, 101, 114, 115, 97,  112, 112, 108, 105,
+    99,  97,  116, 105, 111, 110, 47,  103, 114, 112, 99,  80,  79,  83,  84,
+    50,  48,  48,  52,  48,  52,  104, 116, 116, 112, 104, 116, 116, 112, 115,
+    103, 114, 112, 99,  71,  69,  84,  80,  85,  84,  47,  47,  105, 110, 100,
+    101, 120, 46,  104, 116, 109, 108, 50,  48,  52,  50,  48,  54,  51,  48,
+    52,  52,  48,  48,  53,  48,  48,  97,  99,  99,  101, 112, 116, 45,  99,
+    104, 97,  114, 115, 101, 116, 103, 122, 105, 112, 44,  32,  100, 101, 102,
+    108, 97,  116, 101, 97,  99,  99,  101, 112, 116, 45,  108, 97,  110, 103,
+    117, 97,  103, 101, 97,  99,  99,  101, 112, 116, 45,  114, 97,  110, 103,
+    101, 115, 97,  99,  99,  101, 112, 116, 97,  99,  99,  101, 115, 115, 45,
+    99,  111, 110, 116, 114, 111, 108, 45,  97,  108, 108, 111, 119, 45,  111,
+    114, 105, 103, 105, 110, 97,  103, 101, 97,  108, 108, 111, 119, 97,  117,
+    116, 104, 111, 114, 105, 122, 97,  116, 105, 111, 110, 99,  97,  99,  104,
+    101, 45,  99,  111, 110, 116, 114, 111, 108, 99,  111, 110, 116, 101, 110,
+    116, 45,  100, 105, 115, 112, 111, 115, 105, 116, 105, 111, 110, 99,  111,
+    110, 116, 101, 110, 116, 45,  108, 97,  110, 103, 117, 97,  103, 101, 99,
+    111, 110, 116, 101, 110, 116, 45,  108, 101, 110, 103, 116, 104, 99,  111,
+    110, 116, 101, 110, 116, 45,  108, 111, 99,  97,  116, 105, 111, 110, 99,
+    111, 110, 116, 101, 110, 116, 45,  114, 97,  110, 103, 101, 99,  111, 111,
+    107, 105, 101, 100, 97,  116, 101, 101, 116, 97,  103, 101, 120, 112, 101,
+    99,  116, 101, 120, 112, 105, 114, 101, 115, 102, 114, 111, 109, 105, 102,
+    45,  109, 97,  116, 99,  104, 105, 102, 45,  109, 111, 100, 105, 102, 105,
+    101, 100, 45,  115, 105, 110, 99,  101, 105, 102, 45,  110, 111, 110, 101,
+    45,  109, 97,  116, 99,  104, 105, 102, 45,  114, 97,  110, 103, 101, 105,
+    102, 45,  117, 110, 109, 111, 100, 105, 102, 105, 101, 100, 45,  115, 105,
+    110, 99,  101, 108, 97,  115, 116, 45,  109, 111, 100, 105, 102, 105, 101,
+    100, 108, 98,  45,  99,  111, 115, 116, 45,  98,  105, 110, 108, 105, 110,
+    107, 108, 111, 99,  97,  116, 105, 111, 110, 109, 97,  120, 45,  102, 111,
+    114, 119, 97,  114, 100, 115, 112, 114, 111, 120, 121, 45,  97,  117, 116,
+    104, 101, 110, 116, 105, 99,  97,  116, 101, 112, 114, 111, 120, 121, 45,
+    97,  117, 116, 104, 111, 114, 105, 122, 97,  116, 105, 111, 110, 114, 97,
+    110, 103, 101, 114, 101, 102, 101, 114, 101, 114, 114, 101, 102, 114, 101,
+    115, 104, 114, 101, 116, 114, 121, 45,  97,  102, 116, 101, 114, 115, 101,
+    114, 118, 101, 114, 115, 101, 116, 45,  99,  111, 111, 107, 105, 101, 115,
+    116, 114, 105, 99,  116, 45,  116, 114, 97,  110, 115, 112, 111, 114, 116,
+    45,  115, 101, 99,  117, 114, 105, 116, 121, 116, 114, 97,  110, 115, 102,
+    101, 114, 45,  101, 110, 99,  111, 100, 105, 110, 103, 118, 97,  114, 121,
+    118, 105, 97,  119, 119, 119, 45,  97,  117, 116, 104, 101, 110, 116, 105,
+    99,  97,  116, 101, 105, 100, 101, 110, 116, 105, 116, 121, 44,  100, 101,
+    102, 108, 97,  116, 101, 105, 100, 101, 110, 116, 105, 116, 121, 44,  103,
+    122, 105, 112, 100, 101, 102, 108, 97,  116, 101, 44,  103, 122, 105, 112,
+    105, 100, 101, 110, 116, 105, 116, 121, 44,  100, 101, 102, 108, 97,  116,
+    101, 44,  103, 122, 105, 112};
 
 static void static_ref(void *unused) {}
 static void static_unref(grpc_exec_ctx *exec_ctx, void *unused) {}
@@ -209,6 +212,7 @@ grpc_slice_refcount grpc_static_metadata_refcounts[GRPC_STATIC_MDSTR_COUNT] = {
     {&grpc_static_metadata_vtable, &static_sub_refcnt},
     {&grpc_static_metadata_vtable, &static_sub_refcnt},
     {&grpc_static_metadata_vtable, &static_sub_refcnt},
+    {&grpc_static_metadata_vtable, &static_sub_refcnt},
 };
 
 const grpc_slice grpc_static_slice_table[GRPC_STATIC_MDSTR_COUNT] = {
@@ -243,193 +247,194 @@ const grpc_slice grpc_static_slice_table[GRPC_STATIC_MDSTR_COUNT] = {
     {.refcount = &grpc_static_metadata_refcounts[14],
      .data.refcounted = {g_bytes + 158, 12}},
     {.refcount = &grpc_static_metadata_refcounts[15],
-     .data.refcounted = {g_bytes + 170, 30}},
+     .data.refcounted = {g_bytes + 170, 16}},
     {.refcount = &grpc_static_metadata_refcounts[16],
-     .data.refcounted = {g_bytes + 200, 10}},
+     .data.refcounted = {g_bytes + 186, 15}},
     {.refcount = &grpc_static_metadata_refcounts[17],
-     .data.refcounted = {g_bytes + 210, 4}},
+     .data.refcounted = {g_bytes + 201, 30}},
     {.refcount = &grpc_static_metadata_refcounts[18],
-     .data.refcounted = {g_bytes + 214, 8}},
+     .data.refcounted = {g_bytes + 231, 37}},
     {.refcount = &grpc_static_metadata_refcounts[19],
-     .data.refcounted = {g_bytes + 222, 12}},
+     .data.refcounted = {g_bytes + 268, 10}},
     {.refcount = &grpc_static_metadata_refcounts[20],
-     .data.refcounted = {g_bytes + 234, 0}},
+     .data.refcounted = {g_bytes + 278, 4}},
     {.refcount = &grpc_static_metadata_refcounts[21],
-     .data.refcounted = {g_bytes + 234, 19}},
+     .data.refcounted = {g_bytes + 282, 8}},
     {.refcount = &grpc_static_metadata_refcounts[22],
-     .data.refcounted = {g_bytes + 253, 12}},
+     .data.refcounted = {g_bytes + 290, 12}},
     {.refcount = &grpc_static_metadata_refcounts[23],
-     .data.refcounted = {g_bytes + 265, 30}},
+     .data.refcounted = {g_bytes + 302, 0}},
     {.refcount = &grpc_static_metadata_refcounts[24],
-     .data.refcounted = {g_bytes + 295, 31}},
+     .data.refcounted = {g_bytes + 302, 19}},
     {.refcount = &grpc_static_metadata_refcounts[25],
-     .data.refcounted = {g_bytes + 326, 36}},
+     .data.refcounted = {g_bytes + 321, 12}},
     {.refcount = &grpc_static_metadata_refcounts[26],
-     .data.refcounted = {g_bytes + 362, 1}},
+     .data.refcounted = {g_bytes + 333, 30}},
     {.refcount = &grpc_static_metadata_refcounts[27],
-     .data.refcounted = {g_bytes + 363, 1}},
+     .data.refcounted = {g_bytes + 363, 31}},
     {.refcount = &grpc_static_metadata_refcounts[28],
-     .data.refcounted = {g_bytes + 364, 1}},
+     .data.refcounted = {g_bytes + 394, 36}},
     {.refcount = &grpc_static_metadata_refcounts[29],
-     .data.refcounted = {g_bytes + 365, 8}},
+     .data.refcounted = {g_bytes + 430, 1}},
     {.refcount = &grpc_static_metadata_refcounts[30],
-     .data.refcounted = {g_bytes + 373, 4}},
+     .data.refcounted = {g_bytes + 431, 1}},
     {.refcount = &grpc_static_metadata_refcounts[31],
-     .data.refcounted = {g_bytes + 377, 7}},
+     .data.refcounted = {g_bytes + 432, 1}},
     {.refcount = &grpc_static_metadata_refcounts[32],
-     .data.refcounted = {g_bytes + 384, 8}},
+     .data.refcounted = {g_bytes + 433, 8}},
     {.refcount = &grpc_static_metadata_refcounts[33],
-     .data.refcounted = {g_bytes + 392, 16}},
+     .data.refcounted = {g_bytes + 441, 4}},
     {.refcount = &grpc_static_metadata_refcounts[34],
-     .data.refcounted = {g_bytes + 408, 4}},
+     .data.refcounted = {g_bytes + 445, 7}},
     {.refcount = &grpc_static_metadata_refcounts[35],
-     .data.refcounted = {g_bytes + 412, 3}},
+     .data.refcounted = {g_bytes + 452, 8}},
     {.refcount = &grpc_static_metadata_refcounts[36],
-     .data.refcounted = {g_bytes + 415, 3}},
+     .data.refcounted = {g_bytes + 460, 16}},
     {.refcount = &grpc_static_metadata_refcounts[37],
-     .data.refcounted = {g_bytes + 418, 4}},
+     .data.refcounted = {g_bytes + 476, 4}},
     {.refcount = &grpc_static_metadata_refcounts[38],
-     .data.refcounted = {g_bytes + 422, 5}},
+     .data.refcounted = {g_bytes + 480, 3}},
     {.refcount = &grpc_static_metadata_refcounts[39],
-     .data.refcounted = {g_bytes + 427, 4}},
+     .data.refcounted = {g_bytes + 483, 3}},
     {.refcount = &grpc_static_metadata_refcounts[40],
-     .data.refcounted = {g_bytes + 431, 3}},
+     .data.refcounted = {g_bytes + 486, 4}},
     {.refcount = &grpc_static_metadata_refcounts[41],
-     .data.refcounted = {g_bytes + 434, 3}},
+     .data.refcounted = {g_bytes + 490, 5}},
     {.refcount = &grpc_static_metadata_refcounts[42],
-     .data.refcounted = {g_bytes + 437, 1}},
+     .data.refcounted = {g_bytes + 495, 4}},
     {.refcount = &grpc_static_metadata_refcounts[43],
-     .data.refcounted = {g_bytes + 438, 11}},
+     .data.refcounted = {g_bytes + 499, 3}},
     {.refcount = &grpc_static_metadata_refcounts[44],
-     .data.refcounted = {g_bytes + 449, 3}},
+     .data.refcounted = {g_bytes + 502, 3}},
     {.refcount = &grpc_static_metadata_refcounts[45],
-     .data.refcounted = {g_bytes + 452, 3}},
+     .data.refcounted = {g_bytes + 505, 1}},
     {.refcount = &grpc_static_metadata_refcounts[46],
-     .data.refcounted = {g_bytes + 455, 3}},
+     .data.refcounted = {g_bytes + 506, 11}},
     {.refcount = &grpc_static_metadata_refcounts[47],
-     .data.refcounted = {g_bytes + 458, 3}},
+     .data.refcounted = {g_bytes + 517, 3}},
     {.refcount = &grpc_static_metadata_refcounts[48],
-     .data.refcounted = {g_bytes + 461, 3}},
+     .data.refcounted = {g_bytes + 520, 3}},
     {.refcount = &grpc_static_metadata_refcounts[49],
-     .data.refcounted = {g_bytes + 464, 14}},
+     .data.refcounted = {g_bytes + 523, 3}},
     {.refcount = &grpc_static_metadata_refcounts[50],
-     .data.refcounted = {g_bytes + 478, 15}},
+     .data.refcounted = {g_bytes + 526, 3}},
     {.refcount = &grpc_static_metadata_refcounts[51],
-     .data.refcounted = {g_bytes + 493, 13}},
+     .data.refcounted = {g_bytes + 529, 3}},
     {.refcount = &grpc_static_metadata_refcounts[52],
-     .data.refcounted = {g_bytes + 506, 15}},
+     .data.refcounted = {g_bytes + 532, 14}},
     {.refcount = &grpc_static_metadata_refcounts[53],
-     .data.refcounted = {g_bytes + 521, 13}},
+     .data.refcounted = {g_bytes + 546, 13}},
     {.refcount = &grpc_static_metadata_refcounts[54],
-     .data.refcounted = {g_bytes + 534, 6}},
+     .data.refcounted = {g_bytes + 559, 15}},
     {.refcount = &grpc_static_metadata_refcounts[55],
-     .data.refcounted = {g_bytes + 540, 27}},
+     .data.refcounted = {g_bytes + 574, 13}},
     {.refcount = &grpc_static_metadata_refcounts[56],
-     .data.refcounted = {g_bytes + 567, 3}},
+     .data.refcounted = {g_bytes + 587, 6}},
     {.refcount = &grpc_static_metadata_refcounts[57],
-     .data.refcounted = {g_bytes + 570, 5}},
+     .data.refcounted = {g_bytes + 593, 27}},
     {.refcount = &grpc_static_metadata_refcounts[58],
-     .data.refcounted = {g_bytes + 575, 13}},
+     .data.refcounted = {g_bytes + 620, 3}},
     {.refcount = &grpc_static_metadata_refcounts[59],
-     .data.refcounted = {g_bytes + 588, 13}},
+     .data.refcounted = {g_bytes + 623, 5}},
     {.refcount = &grpc_static_metadata_refcounts[60],
-     .data.refcounted = {g_bytes + 601, 19}},
+     .data.refcounted = {g_bytes + 628, 13}},
     {.refcount = &grpc_static_metadata_refcounts[61],
-     .data.refcounted = {g_bytes + 620, 16}},
+     .data.refcounted = {g_bytes + 641, 13}},
     {.refcount = &grpc_static_metadata_refcounts[62],
-     .data.refcounted = {g_bytes + 636, 16}},
+     .data.refcounted = {g_bytes + 654, 19}},
     {.refcount = &grpc_static_metadata_refcounts[63],
-     .data.refcounted = {g_bytes + 652, 14}},
+     .data.refcounted = {g_bytes + 673, 16}},
     {.refcount = &grpc_static_metadata_refcounts[64],
-     .data.refcounted = {g_bytes + 666, 16}},
+     .data.refcounted = {g_bytes + 689, 14}},
     {.refcount = &grpc_static_metadata_refcounts[65],
-     .data.refcounted = {g_bytes + 682, 13}},
+     .data.refcounted = {g_bytes + 703, 16}},
     {.refcount = &grpc_static_metadata_refcounts[66],
-     .data.refcounted = {g_bytes + 695, 6}},
+     .data.refcounted = {g_bytes + 719, 13}},
     {.refcount = &grpc_static_metadata_refcounts[67],
-     .data.refcounted = {g_bytes + 701, 4}},
+     .data.refcounted = {g_bytes + 732, 6}},
     {.refcount = &grpc_static_metadata_refcounts[68],
-     .data.refcounted = {g_bytes + 705, 4}},
+     .data.refcounted = {g_bytes + 738, 4}},
     {.refcount = &grpc_static_metadata_refcounts[69],
-     .data.refcounted = {g_bytes + 709, 6}},
+     .data.refcounted = {g_bytes + 742, 4}},
     {.refcount = &grpc_static_metadata_refcounts[70],
-     .data.refcounted = {g_bytes + 715, 7}},
+     .data.refcounted = {g_bytes + 746, 6}},
     {.refcount = &grpc_static_metadata_refcounts[71],
-     .data.refcounted = {g_bytes + 722, 4}},
+     .data.refcounted = {g_bytes + 752, 7}},
     {.refcount = &grpc_static_metadata_refcounts[72],
-     .data.refcounted = {g_bytes + 726, 8}},
+     .data.refcounted = {g_bytes + 759, 4}},
     {.refcount = &grpc_static_metadata_refcounts[73],
-     .data.refcounted = {g_bytes + 734, 17}},
+     .data.refcounted = {g_bytes + 763, 8}},
     {.refcount = &grpc_static_metadata_refcounts[74],
-     .data.refcounted = {g_bytes + 751, 13}},
+     .data.refcounted = {g_bytes + 771, 17}},
     {.refcount = &grpc_static_metadata_refcounts[75],
-     .data.refcounted = {g_bytes + 764, 8}},
+     .data.refcounted = {g_bytes + 788, 13}},
     {.refcount = &grpc_static_metadata_refcounts[76],
-     .data.refcounted = {g_bytes + 772, 19}},
+     .data.refcounted = {g_bytes + 801, 8}},
     {.refcount = &grpc_static_metadata_refcounts[77],
-     .data.refcounted = {g_bytes + 791, 13}},
+     .data.refcounted = {g_bytes + 809, 19}},
     {.refcount = &grpc_static_metadata_refcounts[78],
-     .data.refcounted = {g_bytes + 804, 11}},
+     .data.refcounted = {g_bytes + 828, 13}},
     {.refcount = &grpc_static_metadata_refcounts[79],
-     .data.refcounted = {g_bytes + 815, 4}},
+     .data.refcounted = {g_bytes + 841, 11}},
     {.refcount = &grpc_static_metadata_refcounts[80],
-     .data.refcounted = {g_bytes + 819, 8}},
+     .data.refcounted = {g_bytes + 852, 4}},
     {.refcount = &grpc_static_metadata_refcounts[81],
-     .data.refcounted = {g_bytes + 827, 12}},
+     .data.refcounted = {g_bytes + 856, 8}},
     {.refcount = &grpc_static_metadata_refcounts[82],
-     .data.refcounted = {g_bytes + 839, 18}},
+     .data.refcounted = {g_bytes + 864, 12}},
     {.refcount = &grpc_static_metadata_refcounts[83],
-     .data.refcounted = {g_bytes + 857, 19}},
+     .data.refcounted = {g_bytes + 876, 18}},
     {.refcount = &grpc_static_metadata_refcounts[84],
-     .data.refcounted = {g_bytes + 876, 5}},
+     .data.refcounted = {g_bytes + 894, 19}},
     {.refcount = &grpc_static_metadata_refcounts[85],
-     .data.refcounted = {g_bytes + 881, 7}},
+     .data.refcounted = {g_bytes + 913, 5}},
     {.refcount = &grpc_static_metadata_refcounts[86],
-     .data.refcounted = {g_bytes + 888, 7}},
+     .data.refcounted = {g_bytes + 918, 7}},
     {.refcount = &grpc_static_metadata_refcounts[87],
-     .data.refcounted = {g_bytes + 895, 11}},
+     .data.refcounted = {g_bytes + 925, 7}},
     {.refcount = &grpc_static_metadata_refcounts[88],
-     .data.refcounted = {g_bytes + 906, 6}},
+     .data.refcounted = {g_bytes + 932, 11}},
     {.refcount = &grpc_static_metadata_refcounts[89],
-     .data.refcounted = {g_bytes + 912, 10}},
+     .data.refcounted = {g_bytes + 943, 6}},
     {.refcount = &grpc_static_metadata_refcounts[90],
-     .data.refcounted = {g_bytes + 922, 25}},
+     .data.refcounted = {g_bytes + 949, 10}},
     {.refcount = &grpc_static_metadata_refcounts[91],
-     .data.refcounted = {g_bytes + 947, 17}},
+     .data.refcounted = {g_bytes + 959, 25}},
     {.refcount = &grpc_static_metadata_refcounts[92],
-     .data.refcounted = {g_bytes + 964, 4}},
+     .data.refcounted = {g_bytes + 984, 17}},
     {.refcount = &grpc_static_metadata_refcounts[93],
-     .data.refcounted = {g_bytes + 968, 3}},
+     .data.refcounted = {g_bytes + 1001, 4}},
     {.refcount = &grpc_static_metadata_refcounts[94],
-     .data.refcounted = {g_bytes + 971, 16}},
+     .data.refcounted = {g_bytes + 1005, 3}},
     {.refcount = &grpc_static_metadata_refcounts[95],
-     .data.refcounted = {g_bytes + 987, 16}},
+     .data.refcounted = {g_bytes + 1008, 16}},
     {.refcount = &grpc_static_metadata_refcounts[96],
-     .data.refcounted = {g_bytes + 1003, 13}},
+     .data.refcounted = {g_bytes + 1024, 16}},
     {.refcount = &grpc_static_metadata_refcounts[97],
-     .data.refcounted = {g_bytes + 1016, 12}},
+     .data.refcounted = {g_bytes + 1040, 13}},
     {.refcount = &grpc_static_metadata_refcounts[98],
-     .data.refcounted = {g_bytes + 1028, 21}},
+     .data.refcounted = {g_bytes + 1053, 12}},
+    {.refcount = &grpc_static_metadata_refcounts[99],
+     .data.refcounted = {g_bytes + 1065, 21}},
 };
 
 uintptr_t grpc_static_mdelem_user_data[GRPC_STATIC_MDELEM_COUNT] = {
-    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
-    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
-    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
-    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2, 4, 4, 6, 6, 8, 8};
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2, 4, 4, 6, 6, 8, 8, 2, 4, 4};
 
 static const int8_t elems_r[] = {
-    10,  8,   -3,  0,   9,  21, -77, 22,  0,   10, -7,  0,   0,   0,
-    14,  0,   13,  12,  11, 0,  0,   0,   0,   0,  0,   0,   0,   0,
-    0,   0,   0,   0,   0,  0,  0,   0,   0,   0,  0,   0,   0,   0,
-    0,   0,   0,   0,   0,  0,  0,   -50, -51, 16, -53, -54, -55, -56,
-    -56, -57, -58, -59, 0,  37, 36,  35,  34,  33, 32,  31,  30,  29,
-    28,  27,  26,  25,  24, 23, 22,  21,  20,  19, 18,  17,  16,  15,
-    14,  13,  12,  11,  10, 13, 12,  11,  10,  9,  8,   7,   0};
+    11, 9,   -3, 0,   10,  27,  -74, 28,  0,   14, -7, 0,  0,  0,  18, 8,  -2,
+    0,  0,   13, 12,  11,  0,   0,   0,   0,   0,  0,  0,  0,  0,  0,  0,  0,
+    0,  0,   0,  0,   0,   0,   0,   0,   0,   0,  0,  0,  0,  0,  0,  0,  0,
+    0,  -50, 0,  -33, -55, -56, -57, -58, -57, 0,  40, 39, 38, 37, 36, 35, 34,
+    33, 32,  31, 30,  29,  28,  28,  27,  26,  25, 24, 23, 22, 21, 20, 19, 22,
+    21, 20,  19, 18,  17,  16,  15,  14,  13,  12, 12, 11, 0};
 static uint32_t elems_phash(uint32_t i) {
-  i -= 42;
-  uint32_t x = i % 97;
-  uint32_t y = i / 97;
+  i -= 45;
+  uint32_t x = i % 98;
+  uint32_t y = i / 98;
   uint32_t h = x;
   if (y < GPR_ARRAY_SIZE(elems_r)) {
     uint32_t delta = (uint32_t)elems_r[y];
@@ -439,30 +444,31 @@ static uint32_t elems_phash(uint32_t i) {
 }
 
 static const uint16_t elem_keys[] = {
-    1019, 1020, 1021, 242,  243,  244,  245,  246,  139,  140,  42,   43,
-    433,  434,  435,  920,  921,  922,  719,  720,  1406, 527,  721,  1604,
-    1703, 1802, 4871, 4970, 5001, 5168, 5267, 5366, 5465, 1419, 5564, 5663,
-    5762, 5861, 5960, 6059, 6158, 6257, 6356, 6455, 6554, 6653, 6752, 6851,
-    6950, 7049, 7148, 7247, 7346, 7445, 7544, 7643, 7742, 7841, 7940, 8039,
-    8138, 8237, 8336, 8435, 8534, 8633, 1085, 1086, 1087, 1088, 8732, 8831,
-    8930, 9029, 9128, 9227, 9326, 0,    317,  0,    0,    0,    0,    0,
+    1032, 1033, 1034, 247,  248,  249,  250,  251,  1623, 143,  144,  45,
+    46,   440,  441,  442,  1523, 1632, 1633, 932,  933,  934,  729,  730,
+    1423, 1532, 1533, 535,  731,  1923, 2023, 2123, 5223, 5523, 5623, 5723,
+    5823, 1436, 1653, 5923, 6023, 6123, 6223, 6323, 6423, 6523, 6623, 6723,
+    6823, 6923, 7023, 7123, 7223, 5423, 7323, 7423, 7523, 7623, 7723, 7823,
+    7923, 8023, 8123, 8223, 1096, 1097, 1098, 1099, 8323, 8423, 8523, 8623,
+    8723, 8823, 8923, 9023, 9123, 9223, 9323, 323,  9423, 9523, 1697, 0,
     0,    0,    0,    0,    0,    0,    0,    0,    0,    0,    0,    0,
-    0,    0,    0,    0,    0,    133,  233,  234,  0,    0,    0,    0,
+    0,    0,    0,    0,    0,    0,    0,    137,  238,  239,  0,    0,
     0,    0,    0,    0,    0,    0,    0,    0,    0,    0,    0,    0,
     0,    0,    0,    0,    0,    0,    0,    0,    0,    0,    0,    0,
-    0};
+    0,    0,    0,    0,    0};
 static const uint8_t elem_idxs[] = {
-    74,  77,  75,  19,  20,  21,  22,  23,  15,  16,  17,  18,  11,  12,  13,
-    3,   4,   5,   0,   1,   41,  6,   2,   70,  48,  55,  24,  25,  26,  27,
-    28,  29,  30,  7,   31,  32,  33,  34,  35,  36,  37,  38,  39,  40,  42,
-    43,  44,  45,  46,  47,  49,  50,  51,  52,  53,  54,  56,  57,  58,  59,
-    60,  61,  62,  63,  64,  65,  76,  78,  79,  80,  66,  67,  68,  69,  71,
-    72,  73,  255, 14,  255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
-    255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 8,   9,   10};
+    76,  79,  77,  19,  20,  21,  22,  23,  25,  15,  16,  17,  18,  11,
+    12,  13,  38,  83,  84,  3,   4,   5,   0,   1,   43,  36,  37,  6,
+    2,   72,  50,  57,  24,  28,  29,  30,  31,  7,   26,  32,  33,  34,
+    35,  39,  40,  41,  42,  44,  45,  46,  47,  48,  49,  27,  51,  52,
+    53,  54,  55,  56,  58,  59,  60,  61,  78,  80,  81,  82,  62,  63,
+    64,  65,  66,  67,  68,  69,  70,  71,  73,  14,  74,  75,  85,  255,
+    255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
+    255, 255, 255, 255, 255, 8,   9,   10};
 
 grpc_mdelem grpc_static_mdelem_for_static_strings(int a, int b) {
   if (a == -1 || b == -1) return GRPC_MDNULL;
-  uint32_t k = (uint32_t)(a * 99 + b);
+  uint32_t k = (uint32_t)(a * 100 + b);
   uint32_t h = elems_phash(k);
   return h < GPR_ARRAY_SIZE(elem_keys) && elem_keys[h] == k &&
                  elem_idxs[h] != 255
@@ -474,328 +480,350 @@ grpc_mdelem grpc_static_mdelem_for_static_strings(int a, int b) {
 grpc_mdelem_data grpc_static_mdelem_table[GRPC_STATIC_MDELEM_COUNT] = {
     {{.refcount = &grpc_static_metadata_refcounts[7],
       .data.refcounted = {g_bytes + 50, 11}},
-     {.refcount = &grpc_static_metadata_refcounts[26],
-      .data.refcounted = {g_bytes + 362, 1}}},
+     {.refcount = &grpc_static_metadata_refcounts[29],
+      .data.refcounted = {g_bytes + 430, 1}}},
     {{.refcount = &grpc_static_metadata_refcounts[7],
       .data.refcounted = {g_bytes + 50, 11}},
-     {.refcount = &grpc_static_metadata_refcounts[27],
-      .data.refcounted = {g_bytes + 363, 1}}},
+     {.refcount = &grpc_static_metadata_refcounts[30],
+      .data.refcounted = {g_bytes + 431, 1}}},
     {{.refcount = &grpc_static_metadata_refcounts[7],
       .data.refcounted = {g_bytes + 50, 11}},
-     {.refcount = &grpc_static_metadata_refcounts[28],
-      .data.refcounted = {g_bytes + 364, 1}}},
+     {.refcount = &grpc_static_metadata_refcounts[31],
+      .data.refcounted = {g_bytes + 432, 1}}},
     {{.refcount = &grpc_static_metadata_refcounts[9],
       .data.refcounted = {g_bytes + 77, 13}},
-     {.refcount = &grpc_static_metadata_refcounts[29],
-      .data.refcounted = {g_bytes + 365, 8}}},
+     {.refcount = &grpc_static_metadata_refcounts[32],
+      .data.refcounted = {g_bytes + 433, 8}}},
     {{.refcount = &grpc_static_metadata_refcounts[9],
       .data.refcounted = {g_bytes + 77, 13}},
-     {.refcount = &grpc_static_metadata_refcounts[30],
-      .data.refcounted = {g_bytes + 373, 4}}},
+     {.refcount = &grpc_static_metadata_refcounts[33],
+      .data.refcounted = {g_bytes + 441, 4}}},
     {{.refcount = &grpc_static_metadata_refcounts[9],
       .data.refcounted = {g_bytes + 77, 13}},
-     {.refcount = &grpc_static_metadata_refcounts[31],
-      .data.refcounted = {g_bytes + 377, 7}}},
+     {.refcount = &grpc_static_metadata_refcounts[34],
+      .data.refcounted = {g_bytes + 445, 7}}},
     {{.refcount = &grpc_static_metadata_refcounts[5],
       .data.refcounted = {g_bytes + 36, 2}},
-     {.refcount = &grpc_static_metadata_refcounts[32],
-      .data.refcounted = {g_bytes + 384, 8}}},
+     {.refcount = &grpc_static_metadata_refcounts[35],
+      .data.refcounted = {g_bytes + 452, 8}}},
     {{.refcount = &grpc_static_metadata_refcounts[14],
       .data.refcounted = {g_bytes + 158, 12}},
-     {.refcount = &grpc_static_metadata_refcounts[33],
-      .data.refcounted = {g_bytes + 392, 16}}},
+     {.refcount = &grpc_static_metadata_refcounts[36],
+      .data.refcounted = {g_bytes + 460, 16}}},
     {{.refcount = &grpc_static_metadata_refcounts[1],
       .data.refcounted = {g_bytes + 5, 7}},
-     {.refcount = &grpc_static_metadata_refcounts[34],
-      .data.refcounted = {g_bytes + 408, 4}}},
+     {.refcount = &grpc_static_metadata_refcounts[37],
+      .data.refcounted = {g_bytes + 476, 4}}},
     {{.refcount = &grpc_static_metadata_refcounts[2],
       .data.refcounted = {g_bytes + 12, 7}},
-     {.refcount = &grpc_static_metadata_refcounts[35],
-      .data.refcounted = {g_bytes + 412, 3}}},
+     {.refcount = &grpc_static_metadata_refcounts[38],
+      .data.refcounted = {g_bytes + 480, 3}}},
     {{.refcount = &grpc_static_metadata_refcounts[2],
       .data.refcounted = {g_bytes + 12, 7}},
-     {.refcount = &grpc_static_metadata_refcounts[36],
-      .data.refcounted = {g_bytes + 415, 3}}},
+     {.refcount = &grpc_static_metadata_refcounts[39],
+      .data.refcounted = {g_bytes + 483, 3}}},
     {{.refcount = &grpc_static_metadata_refcounts[4],
       .data.refcounted = {g_bytes + 29, 7}},
-     {.refcount = &grpc_static_metadata_refcounts[37],
-      .data.refcounted = {g_bytes + 418, 4}}},
+     {.refcount = &grpc_static_metadata_refcounts[40],
+      .data.refcounted = {g_bytes + 486, 4}}},
     {{.refcount = &grpc_static_metadata_refcounts[4],
       .data.refcounted = {g_bytes + 29, 7}},
-     {.refcount = &grpc_static_metadata_refcounts[38],
-      .data.refcounted = {g_bytes + 422, 5}}},
+     {.refcount = &grpc_static_metadata_refcounts[41],
+      .data.refcounted = {g_bytes + 490, 5}}},
     {{.refcount = &grpc_static_metadata_refcounts[4],
       .data.refcounted = {g_bytes + 29, 7}},
-     {.refcount = &grpc_static_metadata_refcounts[39],
-      .data.refcounted = {g_bytes + 427, 4}}},
+     {.refcount = &grpc_static_metadata_refcounts[42],
+      .data.refcounted = {g_bytes + 495, 4}}},
     {{.refcount = &grpc_static_metadata_refcounts[3],
       .data.refcounted = {g_bytes + 19, 10}},
-     {.refcount = &grpc_static_metadata_refcounts[20],
-      .data.refcounted = {g_bytes + 234, 0}}},
+     {.refcount = &grpc_static_metadata_refcounts[23],
+      .data.refcounted = {g_bytes + 302, 0}}},
     {{.refcount = &grpc_static_metadata_refcounts[1],
       .data.refcounted = {g_bytes + 5, 7}},
-     {.refcount = &grpc_static_metadata_refcounts[40],
-      .data.refcounted = {g_bytes + 431, 3}}},
+     {.refcount = &grpc_static_metadata_refcounts[43],
+      .data.refcounted = {g_bytes + 499, 3}}},
     {{.refcount = &grpc_static_metadata_refcounts[1],
       .data.refcounted = {g_bytes + 5, 7}},
-     {.refcount = &grpc_static_metadata_refcounts[41],
-      .data.refcounted = {g_bytes + 434, 3}}},
+     {.refcount = &grpc_static_metadata_refcounts[44],
+      .data.refcounted = {g_bytes + 502, 3}}},
     {{.refcount = &grpc_static_metadata_refcounts[0],
       .data.refcounted = {g_bytes + 0, 5}},
-     {.refcount = &grpc_static_metadata_refcounts[42],
-      .data.refcounted = {g_bytes + 437, 1}}},
+     {.refcount = &grpc_static_metadata_refcounts[45],
+      .data.refcounted = {g_bytes + 505, 1}}},
     {{.refcount = &grpc_static_metadata_refcounts[0],
       .data.refcounted = {g_bytes + 0, 5}},
-     {.refcount = &grpc_static_metadata_refcounts[43],
-      .data.refcounted = {g_bytes + 438, 11}}},
+     {.refcount = &grpc_static_metadata_refcounts[46],
+      .data.refcounted = {g_bytes + 506, 11}}},
     {{.refcount = &grpc_static_metadata_refcounts[2],
       .data.refcounted = {g_bytes + 12, 7}},
-     {.refcount = &grpc_static_metadata_refcounts[44],
-      .data.refcounted = {g_bytes + 449, 3}}},
+     {.refcount = &grpc_static_metadata_refcounts[47],
+      .data.refcounted = {g_bytes + 517, 3}}},
     {{.refcount = &grpc_static_metadata_refcounts[2],
       .data.refcounted = {g_bytes + 12, 7}},
-     {.refcount = &grpc_static_metadata_refcounts[45],
-      .data.refcounted = {g_bytes + 452, 3}}},
+     {.refcount = &grpc_static_metadata_refcounts[48],
+      .data.refcounted = {g_bytes + 520, 3}}},
     {{.refcount = &grpc_static_metadata_refcounts[2],
       .data.refcounted = {g_bytes + 12, 7}},
-     {.refcount = &grpc_static_metadata_refcounts[46],
-      .data.refcounted = {g_bytes + 455, 3}}},
+     {.refcount = &grpc_static_metadata_refcounts[49],
+      .data.refcounted = {g_bytes + 523, 3}}},
     {{.refcount = &grpc_static_metadata_refcounts[2],
       .data.refcounted = {g_bytes + 12, 7}},
-     {.refcount = &grpc_static_metadata_refcounts[47],
-      .data.refcounted = {g_bytes + 458, 3}}},
+     {.refcount = &grpc_static_metadata_refcounts[50],
+      .data.refcounted = {g_bytes + 526, 3}}},
     {{.refcount = &grpc_static_metadata_refcounts[2],
       .data.refcounted = {g_bytes + 12, 7}},
-     {.refcount = &grpc_static_metadata_refcounts[48],
-      .data.refcounted = {g_bytes + 461, 3}}},
-    {{.refcount = &grpc_static_metadata_refcounts[49],
-      .data.refcounted = {g_bytes + 464, 14}},
-     {.refcount = &grpc_static_metadata_refcounts[20],
-      .data.refcounted = {g_bytes + 234, 0}}},
-    {{.refcount = &grpc_static_metadata_refcounts[50],
-      .data.refcounted = {g_bytes + 478, 15}},
-     {.refcount = &grpc_static_metadata_refcounts[20],
-      .data.refcounted = {g_bytes + 234, 0}}},
-    {{.refcount = &grpc_static_metadata_refcounts[50],
-      .data.refcounted = {g_bytes + 478, 15}},
      {.refcount = &grpc_static_metadata_refcounts[51],
-      .data.refcounted = {g_bytes + 493, 13}}},
+      .data.refcounted = {g_bytes + 529, 3}}},
     {{.refcount = &grpc_static_metadata_refcounts[52],
-      .data.refcounted = {g_bytes + 506, 15}},
-     {.refcount = &grpc_static_metadata_refcounts[20],
-      .data.refcounted = {g_bytes + 234, 0}}},
-    {{.refcount = &grpc_static_metadata_refcounts[53],
-      .data.refcounted = {g_bytes + 521, 13}},
-     {.refcount = &grpc_static_metadata_refcounts[20],
-      .data.refcounted = {g_bytes + 234, 0}}},
+      .data.refcounted = {g_bytes + 532, 14}},
+     {.refcount = &grpc_static_metadata_refcounts[23],
+      .data.refcounted = {g_bytes + 302, 0}}},
+    {{.refcount = &grpc_static_metadata_refcounts[16],
+      .data.refcounted = {g_bytes + 186, 15}},
+     {.refcount = &grpc_static_metadata_refcounts[23],
+      .data.refcounted = {g_bytes + 302, 0}}},
+    {{.refcount = &grpc_static_metadata_refcounts[16],
+      .data.refcounted = {g_bytes + 186, 15}},
+     {.refcount = &grpc_static_metadata_refcounts[53],
+      .data.refcounted = {g_bytes + 546, 13}}},
     {{.refcount = &grpc_static_metadata_refcounts[54],
-      .data.refcounted = {g_bytes + 534, 6}},
-     {.refcount = &grpc_static_metadata_refcounts[20],
-      .data.refcounted = {g_bytes + 234, 0}}},
+      .data.refcounted = {g_bytes + 559, 15}},
+     {.refcount = &grpc_static_metadata_refcounts[23],
+      .data.refcounted = {g_bytes + 302, 0}}},
     {{.refcount = &grpc_static_metadata_refcounts[55],
-      .data.refcounted = {g_bytes + 540, 27}},
-     {.refcount = &grpc_static_metadata_refcounts[20],
-      .data.refcounted = {g_bytes + 234, 0}}},
+      .data.refcounted = {g_bytes + 574, 13}},
+     {.refcount = &grpc_static_metadata_refcounts[23],
+      .data.refcounted = {g_bytes + 302, 0}}},
     {{.refcount = &grpc_static_metadata_refcounts[56],
-      .data.refcounted = {g_bytes + 567, 3}},
-     {.refcount = &grpc_static_metadata_refcounts[20],
-      .data.refcounted = {g_bytes + 234, 0}}},
+      .data.refcounted = {g_bytes + 587, 6}},
+     {.refcount = &grpc_static_metadata_refcounts[23],
+      .data.refcounted = {g_bytes + 302, 0}}},
     {{.refcount = &grpc_static_metadata_refcounts[57],
-      .data.refcounted = {g_bytes + 570, 5}},
-     {.refcount = &grpc_static_metadata_refcounts[20],
-      .data.refcounted = {g_bytes + 234, 0}}},
+      .data.refcounted = {g_bytes + 593, 27}},
+     {.refcount = &grpc_static_metadata_refcounts[23],
+      .data.refcounted = {g_bytes + 302, 0}}},
     {{.refcount = &grpc_static_metadata_refcounts[58],
-      .data.refcounted = {g_bytes + 575, 13}},
-     {.refcount = &grpc_static_metadata_refcounts[20],
-      .data.refcounted = {g_bytes + 234, 0}}},
+      .data.refcounted = {g_bytes + 620, 3}},
+     {.refcount = &grpc_static_metadata_refcounts[23],
+      .data.refcounted = {g_bytes + 302, 0}}},
     {{.refcount = &grpc_static_metadata_refcounts[59],
-      .data.refcounted = {g_bytes + 588, 13}},
-     {.refcount = &grpc_static_metadata_refcounts[20],
-      .data.refcounted = {g_bytes + 234, 0}}},
+      .data.refcounted = {g_bytes + 623, 5}},
+     {.refcount = &grpc_static_metadata_refcounts[23],
+      .data.refcounted = {g_bytes + 302, 0}}},
     {{.refcount = &grpc_static_metadata_refcounts[60],
-      .data.refcounted = {g_bytes + 601, 19}},
-     {.refcount = &grpc_static_metadata_refcounts[20],
-      .data.refcounted = {g_bytes + 234, 0}}},
+      .data.refcounted = {g_bytes + 628, 13}},
+     {.refcount = &grpc_static_metadata_refcounts[23],
+      .data.refcounted = {g_bytes + 302, 0}}},
     {{.refcount = &grpc_static_metadata_refcounts[61],
-      .data.refcounted = {g_bytes + 620, 16}},
-     {.refcount = &grpc_static_metadata_refcounts[20],
-      .data.refcounted = {g_bytes + 234, 0}}},
+      .data.refcounted = {g_bytes + 641, 13}},
+     {.refcount = &grpc_static_metadata_refcounts[23],
+      .data.refcounted = {g_bytes + 302, 0}}},
     {{.refcount = &grpc_static_metadata_refcounts[62],
-      .data.refcounted = {g_bytes + 636, 16}},
-     {.refcount = &grpc_static_metadata_refcounts[20],
-      .data.refcounted = {g_bytes + 234, 0}}},
+      .data.refcounted = {g_bytes + 654, 19}},
+     {.refcount = &grpc_static_metadata_refcounts[23],
+      .data.refcounted = {g_bytes + 302, 0}}},
+    {{.refcount = &grpc_static_metadata_refcounts[15],
+      .data.refcounted = {g_bytes + 170, 16}},
+     {.refcount = &grpc_static_metadata_refcounts[32],
+      .data.refcounted = {g_bytes + 433, 8}}},
+    {{.refcount = &grpc_static_metadata_refcounts[15],
+      .data.refcounted = {g_bytes + 170, 16}},
+     {.refcount = &grpc_static_metadata_refcounts[33],
+      .data.refcounted = {g_bytes + 441, 4}}},
+    {{.refcount = &grpc_static_metadata_refcounts[15],
+      .data.refcounted = {g_bytes + 170, 16}},
+     {.refcount = &grpc_static_metadata_refcounts[23],
+      .data.refcounted = {g_bytes + 302, 0}}},
     {{.refcount = &grpc_static_metadata_refcounts[63],
-      .data.refcounted = {g_bytes + 652, 14}},
-     {.refcount = &grpc_static_metadata_refcounts[20],
-      .data.refcounted = {g_bytes + 234, 0}}},
+      .data.refcounted = {g_bytes + 673, 16}},
+     {.refcount = &grpc_static_metadata_refcounts[23],
+      .data.refcounted = {g_bytes + 302, 0}}},
     {{.refcount = &grpc_static_metadata_refcounts[64],
-      .data.refcounted = {g_bytes + 666, 16}},
-     {.refcount = &grpc_static_metadata_refcounts[20],
-      .data.refcounted = {g_bytes + 234, 0}}},
+      .data.refcounted = {g_bytes + 689, 14}},
+     {.refcount = &grpc_static_metadata_refcounts[23],
+      .data.refcounted = {g_bytes + 302, 0}}},
     {{.refcount = &grpc_static_metadata_refcounts[65],
-      .data.refcounted = {g_bytes + 682, 13}},
-     {.refcount = &grpc_static_metadata_refcounts[20],
-      .data.refcounted = {g_bytes + 234, 0}}},
+      .data.refcounted = {g_bytes + 703, 16}},
+     {.refcount = &grpc_static_metadata_refcounts[23],
+      .data.refcounted = {g_bytes + 302, 0}}},
+    {{.refcount = &grpc_static_metadata_refcounts[66],
+      .data.refcounted = {g_bytes + 719, 13}},
+     {.refcount = &grpc_static_metadata_refcounts[23],
+      .data.refcounted = {g_bytes + 302, 0}}},
     {{.refcount = &grpc_static_metadata_refcounts[14],
       .data.refcounted = {g_bytes + 158, 12}},
-     {.refcount = &grpc_static_metadata_refcounts[20],
-      .data.refcounted = {g_bytes + 234, 0}}},
-    {{.refcount = &grpc_static_metadata_refcounts[66],
-      .data.refcounted = {g_bytes + 695, 6}},
-     {.refcount = &grpc_static_metadata_refcounts[20],
-      .data.refcounted = {g_bytes + 234, 0}}},
+     {.refcount = &grpc_static_metadata_refcounts[23],
+      .data.refcounted = {g_bytes + 302, 0}}},
     {{.refcount = &grpc_static_metadata_refcounts[67],
-      .data.refcounted = {g_bytes + 701, 4}},
-     {.refcount = &grpc_static_metadata_refcounts[20],
-      .data.refcounted = {g_bytes + 234, 0}}},
+      .data.refcounted = {g_bytes + 732, 6}},
+     {.refcount = &grpc_static_metadata_refcounts[23],
+      .data.refcounted = {g_bytes + 302, 0}}},
     {{.refcount = &grpc_static_metadata_refcounts[68],
-      .data.refcounted = {g_bytes + 705, 4}},
-     {.refcount = &grpc_static_metadata_refcounts[20],
-      .data.refcounted = {g_bytes + 234, 0}}},
+      .data.refcounted = {g_bytes + 738, 4}},
+     {.refcount = &grpc_static_metadata_refcounts[23],
+      .data.refcounted = {g_bytes + 302, 0}}},
     {{.refcount = &grpc_static_metadata_refcounts[69],
-      .data.refcounted = {g_bytes + 709, 6}},
-     {.refcount = &grpc_static_metadata_refcounts[20],
-      .data.refcounted = {g_bytes + 234, 0}}},
+      .data.refcounted = {g_bytes + 742, 4}},
+     {.refcount = &grpc_static_metadata_refcounts[23],
+      .data.refcounted = {g_bytes + 302, 0}}},
     {{.refcount = &grpc_static_metadata_refcounts[70],
-      .data.refcounted = {g_bytes + 715, 7}},
-     {.refcount = &grpc_static_metadata_refcounts[20],
-      .data.refcounted = {g_bytes + 234, 0}}},
+      .data.refcounted = {g_bytes + 746, 6}},
+     {.refcount = &grpc_static_metadata_refcounts[23],
+      .data.refcounted = {g_bytes + 302, 0}}},
     {{.refcount = &grpc_static_metadata_refcounts[71],
-      .data.refcounted = {g_bytes + 722, 4}},
-     {.refcount = &grpc_static_metadata_refcounts[20],
-      .data.refcounted = {g_bytes + 234, 0}}},
-    {{.refcount = &grpc_static_metadata_refcounts[17],
-      .data.refcounted = {g_bytes + 210, 4}},
-     {.refcount = &grpc_static_metadata_refcounts[20],
-      .data.refcounted = {g_bytes + 234, 0}}},
+      .data.refcounted = {g_bytes + 752, 7}},
+     {.refcount = &grpc_static_metadata_refcounts[23],
+      .data.refcounted = {g_bytes + 302, 0}}},
     {{.refcount = &grpc_static_metadata_refcounts[72],
-      .data.refcounted = {g_bytes + 726, 8}},
-     {.refcount = &grpc_static_metadata_refcounts[20],
-      .data.refcounted = {g_bytes + 234, 0}}},
+      .data.refcounted = {g_bytes + 759, 4}},
+     {.refcount = &grpc_static_metadata_refcounts[23],
+      .data.refcounted = {g_bytes + 302, 0}}},
+    {{.refcount = &grpc_static_metadata_refcounts[20],
+      .data.refcounted = {g_bytes + 278, 4}},
+     {.refcount = &grpc_static_metadata_refcounts[23],
+      .data.refcounted = {g_bytes + 302, 0}}},
     {{.refcount = &grpc_static_metadata_refcounts[73],
-      .data.refcounted = {g_bytes + 734, 17}},
-     {.refcount = &grpc_static_metadata_refcounts[20],
-      .data.refcounted = {g_bytes + 234, 0}}},
+      .data.refcounted = {g_bytes + 763, 8}},
+     {.refcount = &grpc_static_metadata_refcounts[23],
+      .data.refcounted = {g_bytes + 302, 0}}},
     {{.refcount = &grpc_static_metadata_refcounts[74],
-      .data.refcounted = {g_bytes + 751, 13}},
-     {.refcount = &grpc_static_metadata_refcounts[20],
-      .data.refcounted = {g_bytes + 234, 0}}},
+      .data.refcounted = {g_bytes + 771, 17}},
+     {.refcount = &grpc_static_metadata_refcounts[23],
+      .data.refcounted = {g_bytes + 302, 0}}},
     {{.refcount = &grpc_static_metadata_refcounts[75],
-      .data.refcounted = {g_bytes + 764, 8}},
-     {.refcount = &grpc_static_metadata_refcounts[20],
-      .data.refcounted = {g_bytes + 234, 0}}},
+      .data.refcounted = {g_bytes + 788, 13}},
+     {.refcount = &grpc_static_metadata_refcounts[23],
+      .data.refcounted = {g_bytes + 302, 0}}},
     {{.refcount = &grpc_static_metadata_refcounts[76],
-      .data.refcounted = {g_bytes + 772, 19}},
-     {.refcount = &grpc_static_metadata_refcounts[20],
-      .data.refcounted = {g_bytes + 234, 0}}},
+      .data.refcounted = {g_bytes + 801, 8}},
+     {.refcount = &grpc_static_metadata_refcounts[23],
+      .data.refcounted = {g_bytes + 302, 0}}},
     {{.refcount = &grpc_static_metadata_refcounts[77],
-      .data.refcounted = {g_bytes + 791, 13}},
-     {.refcount = &grpc_static_metadata_refcounts[20],
-      .data.refcounted = {g_bytes + 234, 0}}},
-    {{.refcount = &grpc_static_metadata_refcounts[18],
-      .data.refcounted = {g_bytes + 214, 8}},
-     {.refcount = &grpc_static_metadata_refcounts[20],
-      .data.refcounted = {g_bytes + 234, 0}}},
+      .data.refcounted = {g_bytes + 809, 19}},
+     {.refcount = &grpc_static_metadata_refcounts[23],
+      .data.refcounted = {g_bytes + 302, 0}}},
     {{.refcount = &grpc_static_metadata_refcounts[78],
-      .data.refcounted = {g_bytes + 804, 11}},
-     {.refcount = &grpc_static_metadata_refcounts[20],
-      .data.refcounted = {g_bytes + 234, 0}}},
+      .data.refcounted = {g_bytes + 828, 13}},
+     {.refcount = &grpc_static_metadata_refcounts[23],
+      .data.refcounted = {g_bytes + 302, 0}}},
+    {{.refcount = &grpc_static_metadata_refcounts[21],
+      .data.refcounted = {g_bytes + 282, 8}},
+     {.refcount = &grpc_static_metadata_refcounts[23],
+      .data.refcounted = {g_bytes + 302, 0}}},
     {{.refcount = &grpc_static_metadata_refcounts[79],
-      .data.refcounted = {g_bytes + 815, 4}},
-     {.refcount = &grpc_static_metadata_refcounts[20],
-      .data.refcounted = {g_bytes + 234, 0}}},
+      .data.refcounted = {g_bytes + 841, 11}},
+     {.refcount = &grpc_static_metadata_refcounts[23],
+      .data.refcounted = {g_bytes + 302, 0}}},
     {{.refcount = &grpc_static_metadata_refcounts[80],
-      .data.refcounted = {g_bytes + 819, 8}},
-     {.refcount = &grpc_static_metadata_refcounts[20],
-      .data.refcounted = {g_bytes + 234, 0}}},
+      .data.refcounted = {g_bytes + 852, 4}},
+     {.refcount = &grpc_static_metadata_refcounts[23],
+      .data.refcounted = {g_bytes + 302, 0}}},
     {{.refcount = &grpc_static_metadata_refcounts[81],
-      .data.refcounted = {g_bytes + 827, 12}},
-     {.refcount = &grpc_static_metadata_refcounts[20],
-      .data.refcounted = {g_bytes + 234, 0}}},
+      .data.refcounted = {g_bytes + 856, 8}},
+     {.refcount = &grpc_static_metadata_refcounts[23],
+      .data.refcounted = {g_bytes + 302, 0}}},
     {{.refcount = &grpc_static_metadata_refcounts[82],
-      .data.refcounted = {g_bytes + 839, 18}},
-     {.refcount = &grpc_static_metadata_refcounts[20],
-      .data.refcounted = {g_bytes + 234, 0}}},
+      .data.refcounted = {g_bytes + 864, 12}},
+     {.refcount = &grpc_static_metadata_refcounts[23],
+      .data.refcounted = {g_bytes + 302, 0}}},
     {{.refcount = &grpc_static_metadata_refcounts[83],
-      .data.refcounted = {g_bytes + 857, 19}},
-     {.refcount = &grpc_static_metadata_refcounts[20],
-      .data.refcounted = {g_bytes + 234, 0}}},
+      .data.refcounted = {g_bytes + 876, 18}},
+     {.refcount = &grpc_static_metadata_refcounts[23],
+      .data.refcounted = {g_bytes + 302, 0}}},
     {{.refcount = &grpc_static_metadata_refcounts[84],
-      .data.refcounted = {g_bytes + 876, 5}},
-     {.refcount = &grpc_static_metadata_refcounts[20],
-      .data.refcounted = {g_bytes + 234, 0}}},
+      .data.refcounted = {g_bytes + 894, 19}},
+     {.refcount = &grpc_static_metadata_refcounts[23],
+      .data.refcounted = {g_bytes + 302, 0}}},
     {{.refcount = &grpc_static_metadata_refcounts[85],
-      .data.refcounted = {g_bytes + 881, 7}},
-     {.refcount = &grpc_static_metadata_refcounts[20],
-      .data.refcounted = {g_bytes + 234, 0}}},
+      .data.refcounted = {g_bytes + 913, 5}},
+     {.refcount = &grpc_static_metadata_refcounts[23],
+      .data.refcounted = {g_bytes + 302, 0}}},
     {{.refcount = &grpc_static_metadata_refcounts[86],
-      .data.refcounted = {g_bytes + 888, 7}},
-     {.refcount = &grpc_static_metadata_refcounts[20],
-      .data.refcounted = {g_bytes + 234, 0}}},
+      .data.refcounted = {g_bytes + 918, 7}},
+     {.refcount = &grpc_static_metadata_refcounts[23],
+      .data.refcounted = {g_bytes + 302, 0}}},
     {{.refcount = &grpc_static_metadata_refcounts[87],
-      .data.refcounted = {g_bytes + 895, 11}},
-     {.refcount = &grpc_static_metadata_refcounts[20],
-      .data.refcounted = {g_bytes + 234, 0}}},
+      .data.refcounted = {g_bytes + 925, 7}},
+     {.refcount = &grpc_static_metadata_refcounts[23],
+      .data.refcounted = {g_bytes + 302, 0}}},
     {{.refcount = &grpc_static_metadata_refcounts[88],
-      .data.refcounted = {g_bytes + 906, 6}},
-     {.refcount = &grpc_static_metadata_refcounts[20],
-      .data.refcounted = {g_bytes + 234, 0}}},
+      .data.refcounted = {g_bytes + 932, 11}},
+     {.refcount = &grpc_static_metadata_refcounts[23],
+      .data.refcounted = {g_bytes + 302, 0}}},
     {{.refcount = &grpc_static_metadata_refcounts[89],
-      .data.refcounted = {g_bytes + 912, 10}},
-     {.refcount = &grpc_static_metadata_refcounts[20],
-      .data.refcounted = {g_bytes + 234, 0}}},
+      .data.refcounted = {g_bytes + 943, 6}},
+     {.refcount = &grpc_static_metadata_refcounts[23],
+      .data.refcounted = {g_bytes + 302, 0}}},
     {{.refcount = &grpc_static_metadata_refcounts[90],
-      .data.refcounted = {g_bytes + 922, 25}},
-     {.refcount = &grpc_static_metadata_refcounts[20],
-      .data.refcounted = {g_bytes + 234, 0}}},
+      .data.refcounted = {g_bytes + 949, 10}},
+     {.refcount = &grpc_static_metadata_refcounts[23],
+      .data.refcounted = {g_bytes + 302, 0}}},
     {{.refcount = &grpc_static_metadata_refcounts[91],
-      .data.refcounted = {g_bytes + 947, 17}},
-     {.refcount = &grpc_static_metadata_refcounts[20],
-      .data.refcounted = {g_bytes + 234, 0}}},
-    {{.refcount = &grpc_static_metadata_refcounts[16],
-      .data.refcounted = {g_bytes + 200, 10}},
-     {.refcount = &grpc_static_metadata_refcounts[20],
-      .data.refcounted = {g_bytes + 234, 0}}},
+      .data.refcounted = {g_bytes + 959, 25}},
+     {.refcount = &grpc_static_metadata_refcounts[23],
+      .data.refcounted = {g_bytes + 302, 0}}},
     {{.refcount = &grpc_static_metadata_refcounts[92],
-      .data.refcounted = {g_bytes + 964, 4}},
-     {.refcount = &grpc_static_metadata_refcounts[20],
-      .data.refcounted = {g_bytes + 234, 0}}},
+      .data.refcounted = {g_bytes + 984, 17}},
+     {.refcount = &grpc_static_metadata_refcounts[23],
+      .data.refcounted = {g_bytes + 302, 0}}},
+    {{.refcount = &grpc_static_metadata_refcounts[19],
+      .data.refcounted = {g_bytes + 268, 10}},
+     {.refcount = &grpc_static_metadata_refcounts[23],
+      .data.refcounted = {g_bytes + 302, 0}}},
     {{.refcount = &grpc_static_metadata_refcounts[93],
-      .data.refcounted = {g_bytes + 968, 3}},
-     {.refcount = &grpc_static_metadata_refcounts[20],
-      .data.refcounted = {g_bytes + 234, 0}}},
+      .data.refcounted = {g_bytes + 1001, 4}},
+     {.refcount = &grpc_static_metadata_refcounts[23],
+      .data.refcounted = {g_bytes + 302, 0}}},
     {{.refcount = &grpc_static_metadata_refcounts[94],
-      .data.refcounted = {g_bytes + 971, 16}},
-     {.refcount = &grpc_static_metadata_refcounts[20],
-      .data.refcounted = {g_bytes + 234, 0}}},
-    {{.refcount = &grpc_static_metadata_refcounts[10],
-      .data.refcounted = {g_bytes + 90, 20}},
-     {.refcount = &grpc_static_metadata_refcounts[29],
-      .data.refcounted = {g_bytes + 365, 8}}},
+      .data.refcounted = {g_bytes + 1005, 3}},
+     {.refcount = &grpc_static_metadata_refcounts[23],
+      .data.refcounted = {g_bytes + 302, 0}}},
+    {{.refcount = &grpc_static_metadata_refcounts[95],
+      .data.refcounted = {g_bytes + 1008, 16}},
+     {.refcount = &grpc_static_metadata_refcounts[23],
+      .data.refcounted = {g_bytes + 302, 0}}},
     {{.refcount = &grpc_static_metadata_refcounts[10],
       .data.refcounted = {g_bytes + 90, 20}},
-     {.refcount = &grpc_static_metadata_refcounts[31],
-      .data.refcounted = {g_bytes + 377, 7}}},
+     {.refcount = &grpc_static_metadata_refcounts[32],
+      .data.refcounted = {g_bytes + 433, 8}}},
     {{.refcount = &grpc_static_metadata_refcounts[10],
       .data.refcounted = {g_bytes + 90, 20}},
-     {.refcount = &grpc_static_metadata_refcounts[95],
-      .data.refcounted = {g_bytes + 987, 16}}},
+     {.refcount = &grpc_static_metadata_refcounts[34],
+      .data.refcounted = {g_bytes + 445, 7}}},
     {{.refcount = &grpc_static_metadata_refcounts[10],
       .data.refcounted = {g_bytes + 90, 20}},
-     {.refcount = &grpc_static_metadata_refcounts[30],
-      .data.refcounted = {g_bytes + 373, 4}}},
+     {.refcount = &grpc_static_metadata_refcounts[96],
+      .data.refcounted = {g_bytes + 1024, 16}}},
     {{.refcount = &grpc_static_metadata_refcounts[10],
       .data.refcounted = {g_bytes + 90, 20}},
-     {.refcount = &grpc_static_metadata_refcounts[96],
-      .data.refcounted = {g_bytes + 1003, 13}}},
+     {.refcount = &grpc_static_metadata_refcounts[33],
+      .data.refcounted = {g_bytes + 441, 4}}},
     {{.refcount = &grpc_static_metadata_refcounts[10],
       .data.refcounted = {g_bytes + 90, 20}},
      {.refcount = &grpc_static_metadata_refcounts[97],
-      .data.refcounted = {g_bytes + 1016, 12}}},
+      .data.refcounted = {g_bytes + 1040, 13}}},
     {{.refcount = &grpc_static_metadata_refcounts[10],
       .data.refcounted = {g_bytes + 90, 20}},
      {.refcount = &grpc_static_metadata_refcounts[98],
-      .data.refcounted = {g_bytes + 1028, 21}}},
+      .data.refcounted = {g_bytes + 1053, 12}}},
+    {{.refcount = &grpc_static_metadata_refcounts[10],
+      .data.refcounted = {g_bytes + 90, 20}},
+     {.refcount = &grpc_static_metadata_refcounts[99],
+      .data.refcounted = {g_bytes + 1065, 21}}},
+    {{.refcount = &grpc_static_metadata_refcounts[16],
+      .data.refcounted = {g_bytes + 186, 15}},
+     {.refcount = &grpc_static_metadata_refcounts[32],
+      .data.refcounted = {g_bytes + 433, 8}}},
+    {{.refcount = &grpc_static_metadata_refcounts[16],
+      .data.refcounted = {g_bytes + 186, 15}},
+     {.refcount = &grpc_static_metadata_refcounts[33],
+      .data.refcounted = {g_bytes + 441, 4}}},
+    {{.refcount = &grpc_static_metadata_refcounts[16],
+      .data.refcounted = {g_bytes + 186, 15}},
+     {.refcount = &grpc_static_metadata_refcounts[97],
+      .data.refcounted = {g_bytes + 1040, 13}}},
 };
-const uint8_t grpc_static_accept_encoding_metadata[8] = {0,  74, 75, 76,
-                                                         77, 78, 79, 80};
+const uint8_t grpc_static_accept_encoding_metadata[8] = {0,  76, 77, 78,
+                                                         79, 80, 81, 82};
+
+const uint8_t grpc_static_accept_stream_encoding_metadata[4] = {0, 83, 84, 85};
diff --git a/src/core/lib/transport/static_metadata.h b/src/core/lib/transport/static_metadata.h
index baa86de142..93ab90dff8 100644
--- a/src/core/lib/transport/static_metadata.h
+++ b/src/core/lib/transport/static_metadata.h
@@ -29,7 +29,7 @@
 
 #include "src/core/lib/transport/metadata.h"
 
-#define GRPC_STATIC_MDSTR_COUNT 99
+#define GRPC_STATIC_MDSTR_COUNT 100
 extern const grpc_slice grpc_static_slice_table[GRPC_STATIC_MDSTR_COUNT];
 /* ":path" */
 #define GRPC_MDSTR_PATH (grpc_static_slice_table[0])
@@ -61,178 +61,181 @@ extern const grpc_slice grpc_static_slice_table[GRPC_STATIC_MDSTR_COUNT];
 #define GRPC_MDSTR_GRPC_TRACE_BIN (grpc_static_slice_table[13])
 /* "content-type" */
 #define GRPC_MDSTR_CONTENT_TYPE (grpc_static_slice_table[14])
+/* "content-encoding" */
+#define GRPC_MDSTR_CONTENT_ENCODING (grpc_static_slice_table[15])
+/* "accept-encoding" */
+#define GRPC_MDSTR_ACCEPT_ENCODING (grpc_static_slice_table[16])
 /* "grpc-internal-encoding-request" */
-#define GRPC_MDSTR_GRPC_INTERNAL_ENCODING_REQUEST (grpc_static_slice_table[15])
+#define GRPC_MDSTR_GRPC_INTERNAL_ENCODING_REQUEST (grpc_static_slice_table[17])
+/* "grpc-internal-stream-encoding-request" */
+#define GRPC_MDSTR_GRPC_INTERNAL_STREAM_ENCODING_REQUEST \
+  (grpc_static_slice_table[18])
 /* "user-agent" */
-#define GRPC_MDSTR_USER_AGENT (grpc_static_slice_table[16])
+#define GRPC_MDSTR_USER_AGENT (grpc_static_slice_table[19])
 /* "host" */
-#define GRPC_MDSTR_HOST (grpc_static_slice_table[17])
+#define GRPC_MDSTR_HOST (grpc_static_slice_table[20])
 /* "lb-token" */
-#define GRPC_MDSTR_LB_TOKEN (grpc_static_slice_table[18])
+#define GRPC_MDSTR_LB_TOKEN (grpc_static_slice_table[21])
 /* "grpc-timeout" */
-#define GRPC_MDSTR_GRPC_TIMEOUT (grpc_static_slice_table[19])
+#define GRPC_MDSTR_GRPC_TIMEOUT (grpc_static_slice_table[22])
 /* "" */
-#define GRPC_MDSTR_EMPTY (grpc_static_slice_table[20])
+#define GRPC_MDSTR_EMPTY (grpc_static_slice_table[23])
 /* "grpc.wait_for_ready" */
-#define GRPC_MDSTR_GRPC_DOT_WAIT_FOR_READY (grpc_static_slice_table[21])
+#define GRPC_MDSTR_GRPC_DOT_WAIT_FOR_READY (grpc_static_slice_table[24])
 /* "grpc.timeout" */
-#define GRPC_MDSTR_GRPC_DOT_TIMEOUT (grpc_static_slice_table[22])
+#define GRPC_MDSTR_GRPC_DOT_TIMEOUT (grpc_static_slice_table[25])
 /* "grpc.max_request_message_bytes" */
 #define GRPC_MDSTR_GRPC_DOT_MAX_REQUEST_MESSAGE_BYTES \
-  (grpc_static_slice_table[23])
+  (grpc_static_slice_table[26])
 /* "grpc.max_response_message_bytes" */
 #define GRPC_MDSTR_GRPC_DOT_MAX_RESPONSE_MESSAGE_BYTES \
-  (grpc_static_slice_table[24])
+  (grpc_static_slice_table[27])
 /* "/grpc.lb.v1.LoadBalancer/BalanceLoad" */
 #define GRPC_MDSTR_SLASH_GRPC_DOT_LB_DOT_V1_DOT_LOADBALANCER_SLASH_BALANCELOAD \
-  (grpc_static_slice_table[25])
+  (grpc_static_slice_table[28])
 /* "0" */
-#define GRPC_MDSTR_0 (grpc_static_slice_table[26])
+#define GRPC_MDSTR_0 (grpc_static_slice_table[29])
 /* "1" */
-#define GRPC_MDSTR_1 (grpc_static_slice_table[27])
+#define GRPC_MDSTR_1 (grpc_static_slice_table[30])
 /* "2" */
-#define GRPC_MDSTR_2 (grpc_static_slice_table[28])
+#define GRPC_MDSTR_2 (grpc_static_slice_table[31])
 /* "identity" */
-#define GRPC_MDSTR_IDENTITY (grpc_static_slice_table[29])
+#define GRPC_MDSTR_IDENTITY (grpc_static_slice_table[32])
 /* "gzip" */
-#define GRPC_MDSTR_GZIP (grpc_static_slice_table[30])
+#define GRPC_MDSTR_GZIP (grpc_static_slice_table[33])
 /* "deflate" */
-#define GRPC_MDSTR_DEFLATE (grpc_static_slice_table[31])
+#define GRPC_MDSTR_DEFLATE (grpc_static_slice_table[34])
 /* "trailers" */
-#define GRPC_MDSTR_TRAILERS (grpc_static_slice_table[32])
+#define GRPC_MDSTR_TRAILERS (grpc_static_slice_table[35])
 /* "application/grpc" */
-#define GRPC_MDSTR_APPLICATION_SLASH_GRPC (grpc_static_slice_table[33])
+#define GRPC_MDSTR_APPLICATION_SLASH_GRPC (grpc_static_slice_table[36])
 /* "POST" */
-#define GRPC_MDSTR_POST (grpc_static_slice_table[34])
+#define GRPC_MDSTR_POST (grpc_static_slice_table[37])
 /* "200" */
-#define GRPC_MDSTR_200 (grpc_static_slice_table[35])
+#define GRPC_MDSTR_200 (grpc_static_slice_table[38])
 /* "404" */
-#define GRPC_MDSTR_404 (grpc_static_slice_table[36])
+#define GRPC_MDSTR_404 (grpc_static_slice_table[39])
 /* "http" */
-#define GRPC_MDSTR_HTTP (grpc_static_slice_table[37])
+#define GRPC_MDSTR_HTTP (grpc_static_slice_table[40])
 /* "https" */
-#define GRPC_MDSTR_HTTPS (grpc_static_slice_table[38])
+#define GRPC_MDSTR_HTTPS (grpc_static_slice_table[41])
 /* "grpc" */
-#define GRPC_MDSTR_GRPC (grpc_static_slice_table[39])
+#define GRPC_MDSTR_GRPC (grpc_static_slice_table[42])
 /* "GET" */
-#define GRPC_MDSTR_GET (grpc_static_slice_table[40])
+#define GRPC_MDSTR_GET (grpc_static_slice_table[43])
 /* "PUT" */
-#define GRPC_MDSTR_PUT (grpc_static_slice_table[41])
+#define GRPC_MDSTR_PUT (grpc_static_slice_table[44])
 /* "/" */
-#define GRPC_MDSTR_SLASH (grpc_static_slice_table[42])
+#define GRPC_MDSTR_SLASH (grpc_static_slice_table[45])
 /* "/index.html" */
-#define GRPC_MDSTR_SLASH_INDEX_DOT_HTML (grpc_static_slice_table[43])
+#define GRPC_MDSTR_SLASH_INDEX_DOT_HTML (grpc_static_slice_table[46])
 /* "204" */
-#define GRPC_MDSTR_204 (grpc_static_slice_table[44])
+#define GRPC_MDSTR_204 (grpc_static_slice_table[47])
 /* "206" */
-#define GRPC_MDSTR_206 (grpc_static_slice_table[45])
+#define GRPC_MDSTR_206 (grpc_static_slice_table[48])
 /* "304" */
-#define GRPC_MDSTR_304 (grpc_static_slice_table[46])
+#define GRPC_MDSTR_304 (grpc_static_slice_table[49])
 /* "400" */
-#define GRPC_MDSTR_400 (grpc_static_slice_table[47])
+#define GRPC_MDSTR_400 (grpc_static_slice_table[50])
 /* "500" */
-#define GRPC_MDSTR_500 (grpc_static_slice_table[48])
+#define GRPC_MDSTR_500 (grpc_static_slice_table[51])
 /* "accept-charset" */
-#define GRPC_MDSTR_ACCEPT_CHARSET (grpc_static_slice_table[49])
-/* "accept-encoding" */
-#define GRPC_MDSTR_ACCEPT_ENCODING (grpc_static_slice_table[50])
+#define GRPC_MDSTR_ACCEPT_CHARSET (grpc_static_slice_table[52])
 /* "gzip, deflate" */
-#define GRPC_MDSTR_GZIP_COMMA_DEFLATE (grpc_static_slice_table[51])
+#define GRPC_MDSTR_GZIP_COMMA_DEFLATE (grpc_static_slice_table[53])
 /* "accept-language" */
-#define GRPC_MDSTR_ACCEPT_LANGUAGE (grpc_static_slice_table[52])
+#define GRPC_MDSTR_ACCEPT_LANGUAGE (grpc_static_slice_table[54])
 /* "accept-ranges" */
-#define GRPC_MDSTR_ACCEPT_RANGES (grpc_static_slice_table[53])
+#define GRPC_MDSTR_ACCEPT_RANGES (grpc_static_slice_table[55])
 /* "accept" */
-#define GRPC_MDSTR_ACCEPT (grpc_static_slice_table[54])
+#define GRPC_MDSTR_ACCEPT (grpc_static_slice_table[56])
 /* "access-control-allow-origin" */
-#define GRPC_MDSTR_ACCESS_CONTROL_ALLOW_ORIGIN (grpc_static_slice_table[55])
+#define GRPC_MDSTR_ACCESS_CONTROL_ALLOW_ORIGIN (grpc_static_slice_table[57])
 /* "age" */
-#define GRPC_MDSTR_AGE (grpc_static_slice_table[56])
+#define GRPC_MDSTR_AGE (grpc_static_slice_table[58])
 /* "allow" */
-#define GRPC_MDSTR_ALLOW (grpc_static_slice_table[57])
+#define GRPC_MDSTR_ALLOW (grpc_static_slice_table[59])
 /* "authorization" */
-#define GRPC_MDSTR_AUTHORIZATION (grpc_static_slice_table[58])
+#define GRPC_MDSTR_AUTHORIZATION (grpc_static_slice_table[60])
 /* "cache-control" */
-#define GRPC_MDSTR_CACHE_CONTROL (grpc_static_slice_table[59])
+#define GRPC_MDSTR_CACHE_CONTROL (grpc_static_slice_table[61])
 /* "content-disposition" */
-#define GRPC_MDSTR_CONTENT_DISPOSITION (grpc_static_slice_table[60])
-/* "content-encoding" */
-#define GRPC_MDSTR_CONTENT_ENCODING (grpc_static_slice_table[61])
+#define GRPC_MDSTR_CONTENT_DISPOSITION (grpc_static_slice_table[62])
 /* "content-language" */
-#define GRPC_MDSTR_CONTENT_LANGUAGE (grpc_static_slice_table[62])
+#define GRPC_MDSTR_CONTENT_LANGUAGE (grpc_static_slice_table[63])
 /* "content-length" */
-#define GRPC_MDSTR_CONTENT_LENGTH (grpc_static_slice_table[63])
+#define GRPC_MDSTR_CONTENT_LENGTH (grpc_static_slice_table[64])
 /* "content-location" */
-#define GRPC_MDSTR_CONTENT_LOCATION (grpc_static_slice_table[64])
+#define GRPC_MDSTR_CONTENT_LOCATION (grpc_static_slice_table[65])
 /* "content-range" */
-#define GRPC_MDSTR_CONTENT_RANGE (grpc_static_slice_table[65])
+#define GRPC_MDSTR_CONTENT_RANGE (grpc_static_slice_table[66])
 /* "cookie" */
-#define GRPC_MDSTR_COOKIE (grpc_static_slice_table[66])
+#define GRPC_MDSTR_COOKIE (grpc_static_slice_table[67])
 /* "date" */
-#define GRPC_MDSTR_DATE (grpc_static_slice_table[67])
+#define GRPC_MDSTR_DATE (grpc_static_slice_table[68])
 /* "etag" */
-#define GRPC_MDSTR_ETAG (grpc_static_slice_table[68])
+#define GRPC_MDSTR_ETAG (grpc_static_slice_table[69])
 /* "expect" */
-#define GRPC_MDSTR_EXPECT (grpc_static_slice_table[69])
+#define GRPC_MDSTR_EXPECT (grpc_static_slice_table[70])
 /* "expires" */
-#define GRPC_MDSTR_EXPIRES (grpc_static_slice_table[70])
+#define GRPC_MDSTR_EXPIRES (grpc_static_slice_table[71])
 /* "from" */
-#define GRPC_MDSTR_FROM (grpc_static_slice_table[71])
+#define GRPC_MDSTR_FROM (grpc_static_slice_table[72])
 /* "if-match" */
-#define GRPC_MDSTR_IF_MATCH (grpc_static_slice_table[72])
+#define GRPC_MDSTR_IF_MATCH (grpc_static_slice_table[73])
 /* "if-modified-since" */
-#define GRPC_MDSTR_IF_MODIFIED_SINCE (grpc_static_slice_table[73])
+#define GRPC_MDSTR_IF_MODIFIED_SINCE (grpc_static_slice_table[74])
 /* "if-none-match" */
-#define GRPC_MDSTR_IF_NONE_MATCH (grpc_static_slice_table[74])
+#define GRPC_MDSTR_IF_NONE_MATCH (grpc_static_slice_table[75])
 /* "if-range" */
-#define GRPC_MDSTR_IF_RANGE (grpc_static_slice_table[75])
+#define GRPC_MDSTR_IF_RANGE (grpc_static_slice_table[76])
 /* "if-unmodified-since" */
-#define GRPC_MDSTR_IF_UNMODIFIED_SINCE (grpc_static_slice_table[76])
+#define GRPC_MDSTR_IF_UNMODIFIED_SINCE (grpc_static_slice_table[77])
 /* "last-modified" */
-#define GRPC_MDSTR_LAST_MODIFIED (grpc_static_slice_table[77])
+#define GRPC_MDSTR_LAST_MODIFIED (grpc_static_slice_table[78])
 /* "lb-cost-bin" */
-#define GRPC_MDSTR_LB_COST_BIN (grpc_static_slice_table[78])
+#define GRPC_MDSTR_LB_COST_BIN (grpc_static_slice_table[79])
 /* "link" */
-#define GRPC_MDSTR_LINK (grpc_static_slice_table[79])
+#define GRPC_MDSTR_LINK (grpc_static_slice_table[80])
 /* "location" */
-#define GRPC_MDSTR_LOCATION (grpc_static_slice_table[80])
+#define GRPC_MDSTR_LOCATION (grpc_static_slice_table[81])
 /* "max-forwards" */
-#define GRPC_MDSTR_MAX_FORWARDS (grpc_static_slice_table[81])
+#define GRPC_MDSTR_MAX_FORWARDS (grpc_static_slice_table[82])
 /* "proxy-authenticate" */
-#define GRPC_MDSTR_PROXY_AUTHENTICATE (grpc_static_slice_table[82])
+#define GRPC_MDSTR_PROXY_AUTHENTICATE (grpc_static_slice_table[83])
 /* "proxy-authorization" */
-#define GRPC_MDSTR_PROXY_AUTHORIZATION (grpc_static_slice_table[83])
+#define GRPC_MDSTR_PROXY_AUTHORIZATION (grpc_static_slice_table[84])
 /* "range" */
-#define GRPC_MDSTR_RANGE (grpc_static_slice_table[84])
+#define GRPC_MDSTR_RANGE (grpc_static_slice_table[85])
 /* "referer" */
-#define GRPC_MDSTR_REFERER (grpc_static_slice_table[85])
+#define GRPC_MDSTR_REFERER (grpc_static_slice_table[86])
 /* "refresh" */
-#define GRPC_MDSTR_REFRESH (grpc_static_slice_table[86])
+#define GRPC_MDSTR_REFRESH (grpc_static_slice_table[87])
 /* "retry-after" */
-#define GRPC_MDSTR_RETRY_AFTER (grpc_static_slice_table[87])
+#define GRPC_MDSTR_RETRY_AFTER (grpc_static_slice_table[88])
 /* "server" */
-#define GRPC_MDSTR_SERVER (grpc_static_slice_table[88])
+#define GRPC_MDSTR_SERVER (grpc_static_slice_table[89])
 /* "set-cookie" */
-#define GRPC_MDSTR_SET_COOKIE (grpc_static_slice_table[89])
+#define GRPC_MDSTR_SET_COOKIE (grpc_static_slice_table[90])
 /* "strict-transport-security" */
-#define GRPC_MDSTR_STRICT_TRANSPORT_SECURITY (grpc_static_slice_table[90])
+#define GRPC_MDSTR_STRICT_TRANSPORT_SECURITY (grpc_static_slice_table[91])
 /* "transfer-encoding" */
-#define GRPC_MDSTR_TRANSFER_ENCODING (grpc_static_slice_table[91])
+#define GRPC_MDSTR_TRANSFER_ENCODING (grpc_static_slice_table[92])
 /* "vary" */
-#define GRPC_MDSTR_VARY (grpc_static_slice_table[92])
+#define GRPC_MDSTR_VARY (grpc_static_slice_table[93])
 /* "via" */
-#define GRPC_MDSTR_VIA (grpc_static_slice_table[93])
+#define GRPC_MDSTR_VIA (grpc_static_slice_table[94])
 /* "www-authenticate" */
-#define GRPC_MDSTR_WWW_AUTHENTICATE (grpc_static_slice_table[94])
+#define GRPC_MDSTR_WWW_AUTHENTICATE (grpc_static_slice_table[95])
 /* "identity,deflate" */
-#define GRPC_MDSTR_IDENTITY_COMMA_DEFLATE (grpc_static_slice_table[95])
+#define GRPC_MDSTR_IDENTITY_COMMA_DEFLATE (grpc_static_slice_table[96])
 /* "identity,gzip" */
-#define GRPC_MDSTR_IDENTITY_COMMA_GZIP (grpc_static_slice_table[96])
+#define GRPC_MDSTR_IDENTITY_COMMA_GZIP (grpc_static_slice_table[97])
 /* "deflate,gzip" */
-#define GRPC_MDSTR_DEFLATE_COMMA_GZIP (grpc_static_slice_table[97])
+#define GRPC_MDSTR_DEFLATE_COMMA_GZIP (grpc_static_slice_table[98])
 /* "identity,deflate,gzip" */
 #define GRPC_MDSTR_IDENTITY_COMMA_DEFLATE_COMMA_GZIP \
-  (grpc_static_slice_table[98])
+  (grpc_static_slice_table[99])
 
 extern const grpc_slice_refcount_vtable grpc_static_metadata_vtable;
 extern grpc_slice_refcount
@@ -244,7 +247,7 @@ extern grpc_slice_refcount
 #define GRPC_STATIC_METADATA_INDEX(static_slice) \
   ((int)((static_slice).refcount - grpc_static_metadata_refcounts))
 
-#define GRPC_STATIC_MDELEM_COUNT 81
+#define GRPC_STATIC_MDELEM_COUNT 86
 extern grpc_mdelem_data grpc_static_mdelem_table[GRPC_STATIC_MDELEM_COUNT];
 extern uintptr_t grpc_static_mdelem_user_data[GRPC_STATIC_MDELEM_COUNT];
 /* "grpc-status": "0" */
@@ -355,141 +358,156 @@ extern uintptr_t grpc_static_mdelem_user_data[GRPC_STATIC_MDELEM_COUNT];
 /* "content-disposition": "" */
 #define GRPC_MDELEM_CONTENT_DISPOSITION_EMPTY \
   (GRPC_MAKE_MDELEM(&grpc_static_mdelem_table[35], GRPC_MDELEM_STORAGE_STATIC))
+/* "content-encoding": "identity" */
+#define GRPC_MDELEM_CONTENT_ENCODING_IDENTITY \
+  (GRPC_MAKE_MDELEM(&grpc_static_mdelem_table[36], GRPC_MDELEM_STORAGE_STATIC))
+/* "content-encoding": "gzip" */
+#define GRPC_MDELEM_CONTENT_ENCODING_GZIP \
+  (GRPC_MAKE_MDELEM(&grpc_static_mdelem_table[37], GRPC_MDELEM_STORAGE_STATIC))
 /* "content-encoding": "" */
 #define GRPC_MDELEM_CONTENT_ENCODING_EMPTY \
-  (GRPC_MAKE_MDELEM(&grpc_static_mdelem_table[36], GRPC_MDELEM_STORAGE_STATIC))
+  (GRPC_MAKE_MDELEM(&grpc_static_mdelem_table[38], GRPC_MDELEM_STORAGE_STATIC))
 /* "content-language": "" */
 #define GRPC_MDELEM_CONTENT_LANGUAGE_EMPTY \
-  (GRPC_MAKE_MDELEM(&grpc_static_mdelem_table[37], GRPC_MDELEM_STORAGE_STATIC))
+  (GRPC_MAKE_MDELEM(&grpc_static_mdelem_table[39], GRPC_MDELEM_STORAGE_STATIC))
 /* "content-length": "" */
 #define GRPC_MDELEM_CONTENT_LENGTH_EMPTY \
-  (GRPC_MAKE_MDELEM(&grpc_static_mdelem_table[38], GRPC_MDELEM_STORAGE_STATIC))
+  (GRPC_MAKE_MDELEM(&grpc_static_mdelem_table[40], GRPC_MDELEM_STORAGE_STATIC))
 /* "content-location": "" */
 #define GRPC_MDELEM_CONTENT_LOCATION_EMPTY \
-  (GRPC_MAKE_MDELEM(&grpc_static_mdelem_table[39], GRPC_MDELEM_STORAGE_STATIC))
+  (GRPC_MAKE_MDELEM(&grpc_static_mdelem_table[41], GRPC_MDELEM_STORAGE_STATIC))
 /* "content-range": "" */
 #define GRPC_MDELEM_CONTENT_RANGE_EMPTY \
-  (GRPC_MAKE_MDELEM(&grpc_static_mdelem_table[40], GRPC_MDELEM_STORAGE_STATIC))
+  (GRPC_MAKE_MDELEM(&grpc_static_mdelem_table[42], GRPC_MDELEM_STORAGE_STATIC))
 /* "content-type": "" */
 #define GRPC_MDELEM_CONTENT_TYPE_EMPTY \
-  (GRPC_MAKE_MDELEM(&grpc_static_mdelem_table[41], GRPC_MDELEM_STORAGE_STATIC))
+  (GRPC_MAKE_MDELEM(&grpc_static_mdelem_table[43], GRPC_MDELEM_STORAGE_STATIC))
 /* "cookie": "" */
 #define GRPC_MDELEM_COOKIE_EMPTY \
-  (GRPC_MAKE_MDELEM(&grpc_static_mdelem_table[42], GRPC_MDELEM_STORAGE_STATIC))
+  (GRPC_MAKE_MDELEM(&grpc_static_mdelem_table[44], GRPC_MDELEM_STORAGE_STATIC))
 /* "date": "" */
 #define GRPC_MDELEM_DATE_EMPTY \
-  (GRPC_MAKE_MDELEM(&grpc_static_mdelem_table[43], GRPC_MDELEM_STORAGE_STATIC))
+  (GRPC_MAKE_MDELEM(&grpc_static_mdelem_table[45], GRPC_MDELEM_STORAGE_STATIC))
 /* "etag": "" */
 #define GRPC_MDELEM_ETAG_EMPTY \
-  (GRPC_MAKE_MDELEM(&grpc_static_mdelem_table[44], GRPC_MDELEM_STORAGE_STATIC))
+  (GRPC_MAKE_MDELEM(&grpc_static_mdelem_table[46], GRPC_MDELEM_STORAGE_STATIC))
 /* "expect": "" */
 #define GRPC_MDELEM_EXPECT_EMPTY \
-  (GRPC_MAKE_MDELEM(&grpc_static_mdelem_table[45], GRPC_MDELEM_STORAGE_STATIC))
+  (GRPC_MAKE_MDELEM(&grpc_static_mdelem_table[47], GRPC_MDELEM_STORAGE_STATIC))
 /* "expires": "" */
 #define GRPC_MDELEM_EXPIRES_EMPTY \
-  (GRPC_MAKE_MDELEM(&grpc_static_mdelem_table[46], GRPC_MDELEM_STORAGE_STATIC))
+  (GRPC_MAKE_MDELEM(&grpc_static_mdelem_table[48], GRPC_MDELEM_STORAGE_STATIC))
 /* "from": "" */
 #define GRPC_MDELEM_FROM_EMPTY \
-  (GRPC_MAKE_MDELEM(&grpc_static_mdelem_table[47], GRPC_MDELEM_STORAGE_STATIC))
+  (GRPC_MAKE_MDELEM(&grpc_static_mdelem_table[49], GRPC_MDELEM_STORAGE_STATIC))
 /* "host": "" */
 #define GRPC_MDELEM_HOST_EMPTY \
-  (GRPC_MAKE_MDELEM(&grpc_static_mdelem_table[48], GRPC_MDELEM_STORAGE_STATIC))
+  (GRPC_MAKE_MDELEM(&grpc_static_mdelem_table[50], GRPC_MDELEM_STORAGE_STATIC))
 /* "if-match": "" */
 #define GRPC_MDELEM_IF_MATCH_EMPTY \
-  (GRPC_MAKE_MDELEM(&grpc_static_mdelem_table[49], GRPC_MDELEM_STORAGE_STATIC))
+  (GRPC_MAKE_MDELEM(&grpc_static_mdelem_table[51], GRPC_MDELEM_STORAGE_STATIC))
 /* "if-modified-since": "" */
 #define GRPC_MDELEM_IF_MODIFIED_SINCE_EMPTY \
-  (GRPC_MAKE_MDELEM(&grpc_static_mdelem_table[50], GRPC_MDELEM_STORAGE_STATIC))
+  (GRPC_MAKE_MDELEM(&grpc_static_mdelem_table[52], GRPC_MDELEM_STORAGE_STATIC))
 /* "if-none-match": "" */
 #define GRPC_MDELEM_IF_NONE_MATCH_EMPTY \
-  (GRPC_MAKE_MDELEM(&grpc_static_mdelem_table[51], GRPC_MDELEM_STORAGE_STATIC))
+  (GRPC_MAKE_MDELEM(&grpc_static_mdelem_table[53], GRPC_MDELEM_STORAGE_STATIC))
 /* "if-range": "" */
 #define GRPC_MDELEM_IF_RANGE_EMPTY \
-  (GRPC_MAKE_MDELEM(&grpc_static_mdelem_table[52], GRPC_MDELEM_STORAGE_STATIC))
+  (GRPC_MAKE_MDELEM(&grpc_static_mdelem_table[54], GRPC_MDELEM_STORAGE_STATIC))
 /* "if-unmodified-since": "" */
 #define GRPC_MDELEM_IF_UNMODIFIED_SINCE_EMPTY \
-  (GRPC_MAKE_MDELEM(&grpc_static_mdelem_table[53], GRPC_MDELEM_STORAGE_STATIC))
+  (GRPC_MAKE_MDELEM(&grpc_static_mdelem_table[55], GRPC_MDELEM_STORAGE_STATIC))
 /* "last-modified": "" */
 #define GRPC_MDELEM_LAST_MODIFIED_EMPTY \
-  (GRPC_MAKE_MDELEM(&grpc_static_mdelem_table[54], GRPC_MDELEM_STORAGE_STATIC))
+  (GRPC_MAKE_MDELEM(&grpc_static_mdelem_table[56], GRPC_MDELEM_STORAGE_STATIC))
 /* "lb-token": "" */
 #define GRPC_MDELEM_LB_TOKEN_EMPTY \
-  (GRPC_MAKE_MDELEM(&grpc_static_mdelem_table[55], GRPC_MDELEM_STORAGE_STATIC))
+  (GRPC_MAKE_MDELEM(&grpc_static_mdelem_table[57], GRPC_MDELEM_STORAGE_STATIC))
 /* "lb-cost-bin": "" */
 #define GRPC_MDELEM_LB_COST_BIN_EMPTY \
-  (GRPC_MAKE_MDELEM(&grpc_static_mdelem_table[56], GRPC_MDELEM_STORAGE_STATIC))
+  (GRPC_MAKE_MDELEM(&grpc_static_mdelem_table[58], GRPC_MDELEM_STORAGE_STATIC))
 /* "link": "" */
 #define GRPC_MDELEM_LINK_EMPTY \
-  (GRPC_MAKE_MDELEM(&grpc_static_mdelem_table[57], GRPC_MDELEM_STORAGE_STATIC))
+  (GRPC_MAKE_MDELEM(&grpc_static_mdelem_table[59], GRPC_MDELEM_STORAGE_STATIC))
 /* "location": "" */
 #define GRPC_MDELEM_LOCATION_EMPTY \
-  (GRPC_MAKE_MDELEM(&grpc_static_mdelem_table[58], GRPC_MDELEM_STORAGE_STATIC))
+  (GRPC_MAKE_MDELEM(&grpc_static_mdelem_table[60], GRPC_MDELEM_STORAGE_STATIC))
 /* "max-forwards": "" */
 #define GRPC_MDELEM_MAX_FORWARDS_EMPTY \
-  (GRPC_MAKE_MDELEM(&grpc_static_mdelem_table[59], GRPC_MDELEM_STORAGE_STATIC))
+  (GRPC_MAKE_MDELEM(&grpc_static_mdelem_table[61], GRPC_MDELEM_STORAGE_STATIC))
 /* "proxy-authenticate": "" */
 #define GRPC_MDELEM_PROXY_AUTHENTICATE_EMPTY \
-  (GRPC_MAKE_MDELEM(&grpc_static_mdelem_table[60], GRPC_MDELEM_STORAGE_STATIC))
+  (GRPC_MAKE_MDELEM(&grpc_static_mdelem_table[62], GRPC_MDELEM_STORAGE_STATIC))
 /* "proxy-authorization": "" */
 #define GRPC_MDELEM_PROXY_AUTHORIZATION_EMPTY \
-  (GRPC_MAKE_MDELEM(&grpc_static_mdelem_table[61], GRPC_MDELEM_STORAGE_STATIC))
+  (GRPC_MAKE_MDELEM(&grpc_static_mdelem_table[63], GRPC_MDELEM_STORAGE_STATIC))
 /* "range": "" */
 #define GRPC_MDELEM_RANGE_EMPTY \
-  (GRPC_MAKE_MDELEM(&grpc_static_mdelem_table[62], GRPC_MDELEM_STORAGE_STATIC))
+  (GRPC_MAKE_MDELEM(&grpc_static_mdelem_table[64], GRPC_MDELEM_STORAGE_STATIC))
 /* "referer": "" */
 #define GRPC_MDELEM_REFERER_EMPTY \
-  (GRPC_MAKE_MDELEM(&grpc_static_mdelem_table[63], GRPC_MDELEM_STORAGE_STATIC))
+  (GRPC_MAKE_MDELEM(&grpc_static_mdelem_table[65], GRPC_MDELEM_STORAGE_STATIC))
 /* "refresh": "" */
 #define GRPC_MDELEM_REFRESH_EMPTY \
-  (GRPC_MAKE_MDELEM(&grpc_static_mdelem_table[64], GRPC_MDELEM_STORAGE_STATIC))
+  (GRPC_MAKE_MDELEM(&grpc_static_mdelem_table[66], GRPC_MDELEM_STORAGE_STATIC))
 /* "retry-after": "" */
 #define GRPC_MDELEM_RETRY_AFTER_EMPTY \
-  (GRPC_MAKE_MDELEM(&grpc_static_mdelem_table[65], GRPC_MDELEM_STORAGE_STATIC))
+  (GRPC_MAKE_MDELEM(&grpc_static_mdelem_table[67], GRPC_MDELEM_STORAGE_STATIC))
 /* "server": "" */
 #define GRPC_MDELEM_SERVER_EMPTY \
-  (GRPC_MAKE_MDELEM(&grpc_static_mdelem_table[66], GRPC_MDELEM_STORAGE_STATIC))
+  (GRPC_MAKE_MDELEM(&grpc_static_mdelem_table[68], GRPC_MDELEM_STORAGE_STATIC))
 /* "set-cookie": "" */
 #define GRPC_MDELEM_SET_COOKIE_EMPTY \
-  (GRPC_MAKE_MDELEM(&grpc_static_mdelem_table[67], GRPC_MDELEM_STORAGE_STATIC))
+  (GRPC_MAKE_MDELEM(&grpc_static_mdelem_table[69], GRPC_MDELEM_STORAGE_STATIC))
 /* "strict-transport-security": "" */
 #define GRPC_MDELEM_STRICT_TRANSPORT_SECURITY_EMPTY \
-  (GRPC_MAKE_MDELEM(&grpc_static_mdelem_table[68], GRPC_MDELEM_STORAGE_STATIC))
+  (GRPC_MAKE_MDELEM(&grpc_static_mdelem_table[70], GRPC_MDELEM_STORAGE_STATIC))
 /* "transfer-encoding": "" */
 #define GRPC_MDELEM_TRANSFER_ENCODING_EMPTY \
-  (GRPC_MAKE_MDELEM(&grpc_static_mdelem_table[69], GRPC_MDELEM_STORAGE_STATIC))
+  (GRPC_MAKE_MDELEM(&grpc_static_mdelem_table[71], GRPC_MDELEM_STORAGE_STATIC))
 /* "user-agent": "" */
 #define GRPC_MDELEM_USER_AGENT_EMPTY \
-  (GRPC_MAKE_MDELEM(&grpc_static_mdelem_table[70], GRPC_MDELEM_STORAGE_STATIC))
+  (GRPC_MAKE_MDELEM(&grpc_static_mdelem_table[72], GRPC_MDELEM_STORAGE_STATIC))
 /* "vary": "" */
 #define GRPC_MDELEM_VARY_EMPTY \
-  (GRPC_MAKE_MDELEM(&grpc_static_mdelem_table[71], GRPC_MDELEM_STORAGE_STATIC))
+  (GRPC_MAKE_MDELEM(&grpc_static_mdelem_table[73], GRPC_MDELEM_STORAGE_STATIC))
 /* "via": "" */
 #define GRPC_MDELEM_VIA_EMPTY \
-  (GRPC_MAKE_MDELEM(&grpc_static_mdelem_table[72], GRPC_MDELEM_STORAGE_STATIC))
+  (GRPC_MAKE_MDELEM(&grpc_static_mdelem_table[74], GRPC_MDELEM_STORAGE_STATIC))
 /* "www-authenticate": "" */
 #define GRPC_MDELEM_WWW_AUTHENTICATE_EMPTY \
-  (GRPC_MAKE_MDELEM(&grpc_static_mdelem_table[73], GRPC_MDELEM_STORAGE_STATIC))
+  (GRPC_MAKE_MDELEM(&grpc_static_mdelem_table[75], GRPC_MDELEM_STORAGE_STATIC))
 /* "grpc-accept-encoding": "identity" */
 #define GRPC_MDELEM_GRPC_ACCEPT_ENCODING_IDENTITY \
-  (GRPC_MAKE_MDELEM(&grpc_static_mdelem_table[74], GRPC_MDELEM_STORAGE_STATIC))
+  (GRPC_MAKE_MDELEM(&grpc_static_mdelem_table[76], GRPC_MDELEM_STORAGE_STATIC))
 /* "grpc-accept-encoding": "deflate" */
 #define GRPC_MDELEM_GRPC_ACCEPT_ENCODING_DEFLATE \
-  (GRPC_MAKE_MDELEM(&grpc_static_mdelem_table[75], GRPC_MDELEM_STORAGE_STATIC))
+  (GRPC_MAKE_MDELEM(&grpc_static_mdelem_table[77], GRPC_MDELEM_STORAGE_STATIC))
 /* "grpc-accept-encoding": "identity,deflate" */
 #define GRPC_MDELEM_GRPC_ACCEPT_ENCODING_IDENTITY_COMMA_DEFLATE \
-  (GRPC_MAKE_MDELEM(&grpc_static_mdelem_table[76], GRPC_MDELEM_STORAGE_STATIC))
+  (GRPC_MAKE_MDELEM(&grpc_static_mdelem_table[78], GRPC_MDELEM_STORAGE_STATIC))
 /* "grpc-accept-encoding": "gzip" */
 #define GRPC_MDELEM_GRPC_ACCEPT_ENCODING_GZIP \
-  (GRPC_MAKE_MDELEM(&grpc_static_mdelem_table[77], GRPC_MDELEM_STORAGE_STATIC))
+  (GRPC_MAKE_MDELEM(&grpc_static_mdelem_table[79], GRPC_MDELEM_STORAGE_STATIC))
 /* "grpc-accept-encoding": "identity,gzip" */
 #define GRPC_MDELEM_GRPC_ACCEPT_ENCODING_IDENTITY_COMMA_GZIP \
-  (GRPC_MAKE_MDELEM(&grpc_static_mdelem_table[78], GRPC_MDELEM_STORAGE_STATIC))
+  (GRPC_MAKE_MDELEM(&grpc_static_mdelem_table[80], GRPC_MDELEM_STORAGE_STATIC))
 /* "grpc-accept-encoding": "deflate,gzip" */
 #define GRPC_MDELEM_GRPC_ACCEPT_ENCODING_DEFLATE_COMMA_GZIP \
-  (GRPC_MAKE_MDELEM(&grpc_static_mdelem_table[79], GRPC_MDELEM_STORAGE_STATIC))
+  (GRPC_MAKE_MDELEM(&grpc_static_mdelem_table[81], GRPC_MDELEM_STORAGE_STATIC))
 /* "grpc-accept-encoding": "identity,deflate,gzip" */
 #define GRPC_MDELEM_GRPC_ACCEPT_ENCODING_IDENTITY_COMMA_DEFLATE_COMMA_GZIP \
-  (GRPC_MAKE_MDELEM(&grpc_static_mdelem_table[80], GRPC_MDELEM_STORAGE_STATIC))
+  (GRPC_MAKE_MDELEM(&grpc_static_mdelem_table[82], GRPC_MDELEM_STORAGE_STATIC))
+/* "accept-encoding": "identity" */
+#define GRPC_MDELEM_ACCEPT_ENCODING_IDENTITY \
+  (GRPC_MAKE_MDELEM(&grpc_static_mdelem_table[83], GRPC_MDELEM_STORAGE_STATIC))
+/* "accept-encoding": "gzip" */
+#define GRPC_MDELEM_ACCEPT_ENCODING_GZIP \
+  (GRPC_MAKE_MDELEM(&grpc_static_mdelem_table[84], GRPC_MDELEM_STORAGE_STATIC))
+/* "accept-encoding": "identity,gzip" */
+#define GRPC_MDELEM_ACCEPT_ENCODING_IDENTITY_COMMA_GZIP \
+  (GRPC_MAKE_MDELEM(&grpc_static_mdelem_table[85], GRPC_MDELEM_STORAGE_STATIC))
 
 grpc_mdelem grpc_static_mdelem_for_static_strings(int a, int b);
 typedef enum {
@@ -508,7 +526,10 @@ typedef enum {
   GRPC_BATCH_GRPC_TAGS_BIN,
   GRPC_BATCH_GRPC_TRACE_BIN,
   GRPC_BATCH_CONTENT_TYPE,
+  GRPC_BATCH_CONTENT_ENCODING,
+  GRPC_BATCH_ACCEPT_ENCODING,
   GRPC_BATCH_GRPC_INTERNAL_ENCODING_REQUEST,
+  GRPC_BATCH_GRPC_INTERNAL_STREAM_ENCODING_REQUEST,
   GRPC_BATCH_USER_AGENT,
   GRPC_BATCH_HOST,
   GRPC_BATCH_LB_TOKEN,
@@ -533,7 +554,10 @@ typedef union {
     struct grpc_linked_mdelem *grpc_tags_bin;
     struct grpc_linked_mdelem *grpc_trace_bin;
     struct grpc_linked_mdelem *content_type;
+    struct grpc_linked_mdelem *content_encoding;
+    struct grpc_linked_mdelem *accept_encoding;
     struct grpc_linked_mdelem *grpc_internal_encoding_request;
+    struct grpc_linked_mdelem *grpc_internal_stream_encoding_request;
     struct grpc_linked_mdelem *user_agent;
     struct grpc_linked_mdelem *host;
     struct grpc_linked_mdelem *lb_token;
@@ -552,4 +576,10 @@ extern const uint8_t grpc_static_accept_encoding_metadata[8];
   (GRPC_MAKE_MDELEM(                                                           \
       &grpc_static_mdelem_table[grpc_static_accept_encoding_metadata[(algs)]], \
       GRPC_MDELEM_STORAGE_STATIC))
+
+extern const uint8_t grpc_static_accept_stream_encoding_metadata[4];
+#define GRPC_MDELEM_ACCEPT_STREAM_ENCODING_FOR_ALGORITHMS(algs)                \
+  (GRPC_MAKE_MDELEM(&grpc_static_mdelem_table                                  \
+                        [grpc_static_accept_stream_encoding_metadata[(algs)]], \
+                    GRPC_MDELEM_STORAGE_STATIC))
 #endif /* GRPC_CORE_LIB_TRANSPORT_STATIC_METADATA_H */
diff --git a/src/core/lib/transport/transport.c b/src/core/lib/transport/transport.c
index 3c69279537..0ca7688ca4 100644
--- a/src/core/lib/transport/transport.c
+++ b/src/core/lib/transport/transport.c
@@ -208,27 +208,35 @@ grpc_endpoint *grpc_transport_get_endpoint(grpc_exec_ctx *exec_ctx,
   return transport->vtable->get_endpoint(exec_ctx, transport);
 }
 
+// This comment should be sung to the tune of
+// "Supercalifragilisticexpialidocious":
+//
 // grpc_transport_stream_op_batch_finish_with_failure
 // is a function that must always unref cancel_error
 // though it lives in lib, it handles transport stream ops sure
 // it's grpc_transport_stream_op_batch_finish_with_failure
 
 void grpc_transport_stream_op_batch_finish_with_failure(
-    grpc_exec_ctx *exec_ctx, grpc_transport_stream_op_batch *op,
+    grpc_exec_ctx *exec_ctx, grpc_transport_stream_op_batch *batch,
     grpc_error *error) {
-  if (op->recv_message) {
-    GRPC_CLOSURE_SCHED(exec_ctx, op->payload->recv_message.recv_message_ready,
+  if (batch->send_message) {
+    grpc_byte_stream_destroy(exec_ctx,
+                             batch->payload->send_message.send_message);
+  }
+  if (batch->recv_message) {
+    GRPC_CLOSURE_SCHED(exec_ctx,
+                       batch->payload->recv_message.recv_message_ready,
                        GRPC_ERROR_REF(error));
   }
-  if (op->recv_initial_metadata) {
+  if (batch->recv_initial_metadata) {
     GRPC_CLOSURE_SCHED(
         exec_ctx,
-        op->payload->recv_initial_metadata.recv_initial_metadata_ready,
+        batch->payload->recv_initial_metadata.recv_initial_metadata_ready,
         GRPC_ERROR_REF(error));
   }
-  GRPC_CLOSURE_SCHED(exec_ctx, op->on_complete, error);
-  if (op->cancel_stream) {
-    GRPC_ERROR_UNREF(op->payload->cancel_stream.cancel_error);
+  GRPC_CLOSURE_SCHED(exec_ctx, batch->on_complete, error);
+  if (batch->cancel_stream) {
+    GRPC_ERROR_UNREF(batch->payload->cancel_stream.cancel_error);
   }
 }
 
diff --git a/src/core/lib/transport/transport.h b/src/core/lib/transport/transport.h
index 84e53e683a..099138ea14 100644
--- a/src/core/lib/transport/transport.h
+++ b/src/core/lib/transport/transport.h
@@ -159,6 +159,11 @@ struct grpc_transport_stream_op_batch_payload {
   } send_trailing_metadata;
 
   struct {
+    // The transport (or a filter that decides to return a failure before
+    // the op gets down to the transport) is responsible for calling
+    // grpc_byte_stream_destroy() on this.
+    // The batch's on_complete will not be called until after the byte
+    // stream is destroyed.
     grpc_byte_stream *send_message;
   } send_message;
 
@@ -174,6 +179,10 @@ struct grpc_transport_stream_op_batch_payload {
   } recv_initial_metadata;
 
   struct {
+    // Will be set by the transport to point to the byte stream
+    // containing a received message.
+    // The caller is responsible for calling grpc_byte_stream_destroy()
+    // on this byte stream.
     grpc_byte_stream **recv_message;
     /** Should be enqueued when one message is ready to be processed. */
     grpc_closure *recv_message_ready;