Merge github.com:grpc/grpc into fuzzy-bits

75 files changed, 1117 insertions, 1000 deletions

diff --git a/src/compiler/cpp_generator.cc b/src/compiler/cpp_generator.cc
index 97295bed45..206a6e1fe5 100644
--- a/src/compiler/cpp_generator.cc
+++ b/src/compiler/cpp_generator.cc
@@ -83,6 +83,28 @@ grpc::string FilenameIdentifier(const grpc::string &filename) {
 }
 }  // namespace
 
+template<class T, size_t N>
+T *array_end(T (&array)[N]) { return array + N; }
+
+void PrintIncludes(grpc::protobuf::io::Printer *printer, const std::vector<grpc::string>& headers, const Parameters &params) {
+  std::map<grpc::string, grpc::string> vars;
+
+  vars["l"] = params.use_system_headers ? '<' : '"';
+  vars["r"] = params.use_system_headers ? '>' : '"';
+
+  if (!params.grpc_search_path.empty()) {
+    vars["l"] += params.grpc_search_path;
+    if (params.grpc_search_path.back() != '/') {
+      vars["l"] += '/';
+    }
+  }
+
+  for (auto i = headers.begin(); i != headers.end(); i++) {
+    vars["h"] = *i;
+    printer->Print(vars, "#include $l$$h$$r$\n");
+  }
+}
+
 grpc::string GetHeaderPrologue(const grpc::protobuf::FileDescriptor *file,
                                const Parameters &params) {
   grpc::string output;
@@ -111,36 +133,46 @@ grpc::string GetHeaderPrologue(const grpc::protobuf::FileDescriptor *file,
 
 grpc::string GetHeaderIncludes(const grpc::protobuf::FileDescriptor *file,
                                const Parameters &params) {
-  grpc::string temp =
-      "#include <grpc++/impl/codegen/async_stream.h>\n"
-      "#include <grpc++/impl/codegen/async_unary_call.h>\n"
-      "#include <grpc++/impl/codegen/proto_utils.h>\n"
-      "#include <grpc++/impl/codegen/rpc_method.h>\n"
-      "#include <grpc++/impl/codegen/service_type.h>\n"
-      "#include <grpc++/impl/codegen/status.h>\n"
-      "#include <grpc++/impl/codegen/stub_options.h>\n"
-      "#include <grpc++/impl/codegen/sync_stream.h>\n"
-      "\n"
-      "namespace grpc {\n"
-      "class CompletionQueue;\n"
-      "class RpcService;\n"
-      "class ServerCompletionQueue;\n"
-      "class ServerContext;\n"
-      "}  // namespace grpc\n\n";
+  grpc::string output;
+  {
+    // Scope the output stream so it closes and finalizes output to the string.
+    grpc::protobuf::io::StringOutputStream output_stream(&output);
+    grpc::protobuf::io::Printer printer(&output_stream, '$');
+    std::map<grpc::string, grpc::string> vars;
 
-  if (!file->package().empty()) {
-    std::vector<grpc::string> parts =
-        grpc_generator::tokenize(file->package(), ".");
+    static const char *headers_strs[] = {
+      "grpc++/impl/codegen/async_stream.h",
+      "grpc++/impl/codegen/async_unary_call.h",
+      "grpc++/impl/codegen/proto_utils.h",
+      "grpc++/impl/codegen/rpc_method.h",
+      "grpc++/impl/codegen/service_type.h",
+      "grpc++/impl/codegen/status.h",
+      "grpc++/impl/codegen/stub_options.h",
+      "grpc++/impl/codegen/sync_stream.h"
+    };
+    std::vector<grpc::string> headers(headers_strs, array_end(headers_strs));
+    PrintIncludes(&printer, headers, params);
+    printer.Print(vars, "\n");
+    printer.Print(vars, "namespace grpc {\n");
+    printer.Print(vars, "class CompletionQueue;\n");
+    printer.Print(vars, "class Channel;\n");
+    printer.Print(vars, "class RpcService;\n");
+    printer.Print(vars, "class ServerCompletionQueue;\n");
+    printer.Print(vars, "class ServerContext;\n");
+    printer.Print(vars, "}  // namespace grpc\n\n");
 
-    for (auto part = parts.begin(); part != parts.end(); part++) {
-      temp.append("namespace ");
-      temp.append(*part);
-      temp.append(" {\n");
+    if (!file->package().empty()) {
+      std::vector<grpc::string> parts =
+          grpc_generator::tokenize(file->package(), ".");
+
+      for (auto part = parts.begin(); part != parts.end(); part++) {
+        vars["part"] = *part;
+        printer.Print(vars, "namespace $part$ {\n");
+      }
+      printer.Print(vars, "\n");
     }
-    temp.append("\n");
   }
-
-  return temp;
+  return output;
 }
 
 void PrintHeaderClientMethodInterfaces(
@@ -852,7 +884,7 @@ grpc::string GetSourcePrologue(const grpc::protobuf::FileDescriptor *file,
 }
 
 grpc::string GetSourceIncludes(const grpc::protobuf::FileDescriptor *file,
-                               const Parameters &param) {
+                               const Parameters &params) {
   grpc::string output;
   {
     // Scope the output stream so it closes and finalizes output to the string.
@@ -860,16 +892,18 @@ grpc::string GetSourceIncludes(const grpc::protobuf::FileDescriptor *file,
     grpc::protobuf::io::Printer printer(&output_stream, '$');
     std::map<grpc::string, grpc::string> vars;
 
-    printer.Print(vars, "#include <grpc++/impl/codegen/async_stream.h>\n");
-    printer.Print(vars, "#include <grpc++/impl/codegen/async_unary_call.h>\n");
-    printer.Print(vars, "#include <grpc++/impl/codegen/channel_interface.h>\n");
-    printer.Print(vars, "#include <grpc++/impl/codegen/client_unary_call.h>\n");
-    printer.Print(vars,
-                  "#include <grpc++/impl/codegen/method_handler_impl.h>\n");
-    printer.Print(vars,
-                  "#include <grpc++/impl/codegen/rpc_service_method.h>\n");
-    printer.Print(vars, "#include <grpc++/impl/codegen/service_type.h>\n");
-    printer.Print(vars, "#include <grpc++/impl/codegen/sync_stream.h>\n");
+    static const char *headers_strs[] = {
+      "grpc++/impl/codegen/async_stream.h",
+      "grpc++/impl/codegen/async_unary_call.h",
+      "grpc++/impl/codegen/channel_interface.h",
+      "grpc++/impl/codegen/client_unary_call.h",
+      "grpc++/impl/codegen/method_handler_impl.h",
+      "grpc++/impl/codegen/rpc_service_method.h",
+      "grpc++/impl/codegen/service_type.h",
+      "grpc++/impl/codegen/sync_stream.h"
+    };
+    std::vector<grpc::string> headers(headers_strs, array_end(headers_strs));
+    PrintIncludes(&printer, headers, params);
 
     if (!file->package().empty()) {
       std::vector<grpc::string> parts =
diff --git a/src/compiler/cpp_generator.h b/src/compiler/cpp_generator.h
index 70c2e985f6..4f9de9d11a 100644
--- a/src/compiler/cpp_generator.h
+++ b/src/compiler/cpp_generator.h
@@ -1,6 +1,6 @@
 /*
  *
- * Copyright 2015, Google Inc.
+ * Copyright 2015-2016, Google Inc.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -42,6 +42,10 @@ namespace grpc_cpp_generator {
 struct Parameters {
   // Puts the service into a namespace
   grpc::string services_namespace;
+  // Use system includes (<>) or local includes ("")
+  bool use_system_headers;
+  // Prefix to any grpc include
+  grpc::string grpc_search_path;
 };
 
 // Return the prologue of the generated header file.
diff --git a/src/compiler/cpp_plugin.cc b/src/compiler/cpp_plugin.cc
index 88c704948e..d8ada4835c 100644
--- a/src/compiler/cpp_plugin.cc
+++ b/src/compiler/cpp_plugin.cc
@@ -1,6 +1,6 @@
 /*
  *
- * Copyright 2015, Google Inc.
+ * Copyright 2015-2016, Google Inc.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -59,6 +59,7 @@ class CppGrpcGenerator : public grpc::protobuf::compiler::CodeGenerator {
     }
 
     grpc_cpp_generator::Parameters generator_parameters;
+    generator_parameters.use_system_headers = true;
 
     if (!parameter.empty()) {
       std::vector<grpc::string> parameters_list =
@@ -70,6 +71,17 @@ class CppGrpcGenerator : public grpc::protobuf::compiler::CodeGenerator {
           grpc_generator::tokenize(*parameter_string, "=");
         if (param[0] == "services_namespace") {
           generator_parameters.services_namespace = param[1];
+        } else if (param[0] == "use_system_headers") {
+          if (param[1] == "true") {
+            generator_parameters.use_system_headers = true;
+          } else if (param[1] == "false") {
+            generator_parameters.use_system_headers = false;
+          } else {
+            *error = grpc::string("Invalid parameter: ") + *parameter_string;
+            return false;
+          }
+        } else if (param[0] == "grpc_search_path") {
+          generator_parameters.grpc_search_path = param[1];
         } else {
           *error = grpc::string("Unknown parameter: ") + *parameter_string;
           return false;
diff --git a/src/compiler/python_generator.cc b/src/compiler/python_generator.cc
index 4fd5dfbecb..5a2ecce1d4 100644
--- a/src/compiler/python_generator.cc
+++ b/src/compiler/python_generator.cc
@@ -190,11 +190,10 @@ bool PrintBetaServicer(const ServiceDescriptor* service,
         "Documentation", doc,
       });
   out->Print("\n");
-  out->Print(dict, "class Beta$Service$Servicer(object):\n");
+  out->Print(dict, "class Beta$Service$Servicer(six.with_metaclass(abc.ABCMeta, object)):\n");
   {
     IndentScope raii_class_indent(out);
     out->Print(dict, "\"\"\"$Documentation$\"\"\"\n");
-    out->Print("__metaclass__ = abc.ABCMeta\n");
     for (int i = 0; i < service->method_count(); ++i) {
       auto meth = service->method(i);
       grpc::string arg_name = meth->client_streaming() ?
@@ -219,11 +218,10 @@ bool PrintBetaStub(const ServiceDescriptor* service,
         "Documentation", doc,
       });
   out->Print("\n");
-  out->Print(dict, "class Beta$Service$Stub(object):\n");
+  out->Print(dict, "class Beta$Service$Stub(six.with_metaclass(abc.ABCMeta, object)):\n");
   {
     IndentScope raii_class_indent(out);
     out->Print(dict, "\"\"\"$Documentation$\"\"\"\n");
-    out->Print("__metaclass__ = abc.ABCMeta\n");
     for (int i = 0; i < service->method_count(); ++i) {
       const MethodDescriptor* meth = service->method(i);
       grpc::string arg_name = meth->client_streaming() ?
@@ -449,6 +447,7 @@ bool PrintBetaStubFactory(const grpc::string& package_qualified_service_name,
 bool PrintPreamble(const FileDescriptor* file,
                    const GeneratorConfiguration& config, Printer* out) {
   out->Print("import abc\n");
+  out->Print("import six\n");
   out->Print("from $Package$ import implementations as beta_implementations\n",
              "Package", config.beta_package_root);
   out->Print("from grpc.framework.common import cardinality\n");
diff --git a/src/core/census/grpc_plugin.c b/src/core/census/grpc_plugin.c
index 3be2a48eb8..8d60a5197e 100644
--- a/src/core/census/grpc_plugin.c
+++ b/src/core/census/grpc_plugin.c
@@ -63,8 +63,6 @@ void census_grpc_plugin_init(void) {
   }
   grpc_channel_init_register_stage(GRPC_CLIENT_CHANNEL, INT_MAX,
                                    maybe_add_census_filter, NULL);
-  grpc_channel_init_register_stage(GRPC_CLIENT_UCHANNEL, INT_MAX,
-                                   maybe_add_census_filter, NULL);
   grpc_channel_init_register_stage(GRPC_SERVER_CHANNEL, INT_MAX,
                                    maybe_add_census_filter, NULL);
 }
diff --git a/src/core/channel/channel_stack_builder.c b/src/core/channel/channel_stack_builder.c
index 80e2e393f9..1b1004e5f9 100644
--- a/src/core/channel/channel_stack_builder.c
+++ b/src/core/channel/channel_stack_builder.c
@@ -216,7 +216,6 @@ void *grpc_channel_stack_builder_finish(grpc_exec_ctx *exec_ctx,
   // count the number of filters
   size_t num_filters = 0;
   for (filter_node *p = builder->begin.next; p != &builder->end; p = p->next) {
-    gpr_log(GPR_DEBUG, "%d: %s", num_filters, p->filter->name);
     num_filters++;
   }
 
diff --git a/src/core/channel/client_uchannel.c b/src/core/channel/client_uchannel.c
deleted file mode 100644
index d32327206e..0000000000
--- a/src/core/channel/client_uchannel.c
+++ /dev/null
@@ -1,233 +0,0 @@
-/*
- *
- * Copyright 2015-2016, Google Inc.
- * All rights reserved.
- *
- * Redistribution and use in source and binary forms, with or without
- * modification, are permitted provided that the following conditions are
- * met:
- *
- *     * Redistributions of source code must retain the above copyright
- * notice, this list of conditions and the following disclaimer.
- *     * Redistributions in binary form must reproduce the above
- * copyright notice, this list of conditions and the following disclaimer
- * in the documentation and/or other materials provided with the
- * distribution.
- *     * Neither the name of Google Inc. nor the names of its
- * contributors may be used to endorse or promote products derived from
- * this software without specific prior written permission.
- *
- * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
- * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
- * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
- * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
- * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
- * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
- * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
- * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
- * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
- * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
- * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
- *
- */
-
-#include "src/core/channel/client_uchannel.h"
-
-#include <string.h>
-
-#include "src/core/census/grpc_filter.h"
-#include "src/core/channel/channel_args.h"
-#include "src/core/channel/client_channel.h"
-#include "src/core/channel/compress_filter.h"
-#include "src/core/channel/subchannel_call_holder.h"
-#include "src/core/iomgr/iomgr.h"
-#include "src/core/support/string.h"
-#include "src/core/surface/channel.h"
-#include "src/core/transport/connectivity_state.h"
-
-#include <grpc/support/alloc.h>
-#include <grpc/support/log.h>
-#include <grpc/support/sync.h>
-#include <grpc/support/useful.h>
-
-/** Microchannel (uchannel) implementation: a lightweight channel without any
- * load-balancing mechanisms meant for communication from within the core. */
-
-typedef struct client_uchannel_channel_data {
-  /** master channel - the grpc_channel instance that ultimately owns
-      this channel_data via its channel stack.
-      We occasionally use this to bump the refcount on the master channel
-      to keep ourselves alive through an asynchronous operation. */
-  grpc_channel_stack *owning_stack;
-
-  /** connectivity state being tracked */
-  grpc_connectivity_state_tracker state_tracker;
-
-  /** the subchannel wrapped by the microchannel */
-  grpc_connected_subchannel *connected_subchannel;
-
-  /** the callback used to stay subscribed to subchannel connectivity
-   * notifications */
-  grpc_closure connectivity_cb;
-
-  /** the current connectivity state of the wrapped subchannel */
-  grpc_connectivity_state subchannel_connectivity;
-
-  gpr_mu mu_state;
-} channel_data;
-
-typedef grpc_subchannel_call_holder call_data;
-
-static void monitor_subchannel(grpc_exec_ctx *exec_ctx, void *arg,
-                               bool iomgr_success) {
-  channel_data *chand = arg;
-  grpc_connectivity_state_set(exec_ctx, &chand->state_tracker,
-                              chand->subchannel_connectivity,
-                              "uchannel_monitor_subchannel");
-  grpc_connected_subchannel_notify_on_state_change(
-      exec_ctx, chand->connected_subchannel, NULL,
-      &chand->subchannel_connectivity, &chand->connectivity_cb);
-}
-
-static char *cuc_get_peer(grpc_exec_ctx *exec_ctx, grpc_call_element *elem) {
-  return grpc_subchannel_call_holder_get_peer(exec_ctx, elem->call_data);
-}
-
-static void cuc_start_transport_stream_op(grpc_exec_ctx *exec_ctx,
-                                          grpc_call_element *elem,
-                                          grpc_transport_stream_op *op) {
-  GRPC_CALL_LOG_OP(GPR_INFO, elem, op);
-  grpc_subchannel_call_holder_perform_op(exec_ctx, elem->call_data, op);
-}
-
-static void cuc_start_transport_op(grpc_exec_ctx *exec_ctx,
-                                   grpc_channel_element *elem,
-                                   grpc_transport_op *op) {
-  channel_data *chand = elem->channel_data;
-
-  grpc_exec_ctx_enqueue(exec_ctx, op->on_consumed, true, NULL);
-
-  GPR_ASSERT(op->set_accept_stream == false);
-  GPR_ASSERT(op->bind_pollset == NULL);
-
-  if (op->on_connectivity_state_change != NULL) {
-    grpc_connectivity_state_notify_on_state_change(
-        exec_ctx, &chand->state_tracker, op->connectivity_state,
-        op->on_connectivity_state_change);
-    op->on_connectivity_state_change = NULL;
-    op->connectivity_state = NULL;
-  }
-
-  if (op->disconnect) {
-    grpc_connectivity_state_set(exec_ctx, &chand->state_tracker,
-                                GRPC_CHANNEL_FATAL_FAILURE, "disconnect");
-  }
-}
-
-static int cuc_pick_subchannel(grpc_exec_ctx *exec_ctx, void *arg,
-                               grpc_metadata_batch *initial_metadata,
-                               grpc_connected_subchannel **connected_subchannel,
-                               grpc_closure *on_ready) {
-  channel_data *chand = arg;
-  GPR_ASSERT(initial_metadata != NULL);
-  *connected_subchannel = chand->connected_subchannel;
-  return 1;
-}
-
-/* Constructor for call_data */
-static void cuc_init_call_elem(grpc_exec_ctx *exec_ctx, grpc_call_element *elem,
-                               grpc_call_element_args *args) {
-  grpc_subchannel_call_holder_init(elem->call_data, cuc_pick_subchannel,
-                                   elem->channel_data, args->call_stack);
-}
-
-/* Destructor for call_data */
-static void cuc_destroy_call_elem(grpc_exec_ctx *exec_ctx,
-                                  grpc_call_element *elem) {
-  grpc_subchannel_call_holder_destroy(exec_ctx, elem->call_data);
-}
-
-/* Constructor for channel_data */
-static void cuc_init_channel_elem(grpc_exec_ctx *exec_ctx,
-                                  grpc_channel_element *elem,
-                                  grpc_channel_element_args *args) {
-  channel_data *chand = elem->channel_data;
-  memset(chand, 0, sizeof(*chand));
-  grpc_closure_init(&chand->connectivity_cb, monitor_subchannel, chand);
-  GPR_ASSERT(args->is_last);
-  GPR_ASSERT(elem->filter == &grpc_client_uchannel_filter);
-  chand->owning_stack = args->channel_stack;
-  grpc_connectivity_state_init(&chand->state_tracker, GRPC_CHANNEL_IDLE,
-                               "client_uchannel");
-  gpr_mu_init(&chand->mu_state);
-}
-
-/* Destructor for channel_data */
-static void cuc_destroy_channel_elem(grpc_exec_ctx *exec_ctx,
-                                     grpc_channel_element *elem) {
-  channel_data *chand = elem->channel_data;
-  /* cancel subscription */
-  grpc_connected_subchannel_notify_on_state_change(
-      exec_ctx, chand->connected_subchannel, NULL, NULL,
-      &chand->connectivity_cb);
-  grpc_connectivity_state_destroy(exec_ctx, &chand->state_tracker);
-  gpr_mu_destroy(&chand->mu_state);
-  GRPC_CONNECTED_SUBCHANNEL_UNREF(exec_ctx, chand->connected_subchannel,
-                                  "uchannel");
-}
-
-static void cuc_set_pollset(grpc_exec_ctx *exec_ctx, grpc_call_element *elem,
-                            grpc_pollset *pollset) {
-  call_data *calld = elem->call_data;
-  calld->pollset = pollset;
-}
-
-const grpc_channel_filter grpc_client_uchannel_filter = {
-    cuc_start_transport_stream_op, cuc_start_transport_op, sizeof(call_data),
-    cuc_init_call_elem, cuc_set_pollset, cuc_destroy_call_elem,
-    sizeof(channel_data), cuc_init_channel_elem, cuc_destroy_channel_elem,
-    cuc_get_peer, "client-uchannel",
-};
-
-grpc_connectivity_state grpc_client_uchannel_check_connectivity_state(
-    grpc_exec_ctx *exec_ctx, grpc_channel_element *elem, int try_to_connect) {
-  channel_data *chand = elem->channel_data;
-  grpc_connectivity_state out;
-  gpr_mu_lock(&chand->mu_state);
-  out = grpc_connectivity_state_check(&chand->state_tracker);
-  gpr_mu_unlock(&chand->mu_state);
-  return out;
-}
-
-void grpc_client_uchannel_watch_connectivity_state(
-    grpc_exec_ctx *exec_ctx, grpc_channel_element *elem, grpc_pollset *pollset,
-    grpc_connectivity_state *state, grpc_closure *on_complete) {
-  channel_data *chand = elem->channel_data;
-  gpr_mu_lock(&chand->mu_state);
-  grpc_connectivity_state_notify_on_state_change(
-      exec_ctx, &chand->state_tracker, state, on_complete);
-  gpr_mu_unlock(&chand->mu_state);
-}
-
-grpc_channel *grpc_client_uchannel_create(grpc_subchannel *subchannel,
-                                          grpc_channel_args *args) {
-  grpc_channel *channel = NULL;
-  grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
-
-  channel =
-      grpc_channel_create(&exec_ctx, NULL, args, GRPC_CLIENT_UCHANNEL, NULL);
-
-  return channel;
-}
-
-void grpc_client_uchannel_set_connected_subchannel(
-    grpc_channel *uchannel, grpc_connected_subchannel *connected_subchannel) {
-  grpc_channel_element *elem =
-      grpc_channel_stack_last_element(grpc_channel_get_channel_stack(uchannel));
-  channel_data *chand = elem->channel_data;
-  GPR_ASSERT(elem->filter == &grpc_client_uchannel_filter);
-  gpr_mu_lock(&chand->mu_state);
-  chand->connected_subchannel = connected_subchannel;
-  GRPC_CONNECTED_SUBCHANNEL_REF(connected_subchannel, "uchannel");
-  gpr_mu_unlock(&chand->mu_state);
-}
diff --git a/src/core/channel/subchannel_call_holder.h b/src/core/channel/subchannel_call_holder.h
index 9086cdc882..84b4657db4 100644
--- a/src/core/channel/subchannel_call_holder.h
+++ b/src/core/channel/subchannel_call_holder.h
@@ -55,15 +55,14 @@ typedef enum {
     for initial metadata before trying to create a call object,
     and handling cancellation gracefully.
 
-    Both the channel and uchannel filter use this as their call_data. */
+    The channel filter uses this as their call_data. */
 typedef struct grpc_subchannel_call_holder {
   /** either 0 for no call, 1 for cancelled, or a pointer to a
       grpc_subchannel_call */
   gpr_atm subchannel_call;
   /** Helper function to choose the subchannel on which to create
       the call object. Channel filter delegates to the load
-      balancing policy (once it's ready); uchannel returns
-      immediately */
+      balancing policy (once it's ready). */
   grpc_subchannel_call_holder_pick_subchannel pick_subchannel;
   void *pick_subchannel_arg;
 
diff --git a/src/core/client_config/resolvers/dns_resolver.c b/src/core/client_config/resolvers/dns_resolver.c
index e28e4757a1..2b2ee97e12 100644
--- a/src/core/client_config/resolvers/dns_resolver.c
+++ b/src/core/client_config/resolvers/dns_resolver.c
@@ -42,8 +42,14 @@
 #include "src/core/client_config/lb_policy_registry.h"
 #include "src/core/iomgr/resolve_address.h"
 #include "src/core/iomgr/timer.h"
+#include "src/core/support/backoff.h"
 #include "src/core/support/string.h"
 
+#define BACKOFF_MULTIPLIER 1.6
+#define BACKOFF_JITTER 0.2
+#define BACKOFF_MIN_SECONDS 1
+#define BACKOFF_MAX_SECONDS 120
+
 typedef struct {
   /** base class: must be first */
   grpc_resolver base;
@@ -75,6 +81,8 @@ typedef struct {
   /** retry timer */
   bool have_retry_timer;
   grpc_timer retry_timer;
+  /** retry backoff state */
+  gpr_backoff backoff_state;
 } dns_resolver;
 
 static void dns_destroy(grpc_exec_ctx *exec_ctx, grpc_resolver *r);
@@ -111,6 +119,7 @@ static void dns_channel_saw_error(grpc_exec_ctx *exec_ctx,
   dns_resolver *r = (dns_resolver *)resolver;
   gpr_mu_lock(&r->mu);
   if (!r->resolving) {
+    gpr_backoff_reset(&r->backoff_state);
     dns_start_resolving_locked(r);
   }
   gpr_mu_unlock(&r->mu);
@@ -125,6 +134,7 @@ static void dns_next(grpc_exec_ctx *exec_ctx, grpc_resolver *resolver,
   r->next_completion = on_complete;
   r->target_config = target_config;
   if (r->resolved_version == 0 && !r->resolving) {
+    gpr_backoff_reset(&r->backoff_state);
     dns_start_resolving_locked(r);
   } else {
     dns_maybe_finish_next_locked(exec_ctx, r);
@@ -185,17 +195,16 @@ static void dns_on_resolved(grpc_exec_ctx *exec_ctx, void *arg,
     grpc_resolved_addresses_destroy(addresses);
     gpr_free(subchannels);
   } else {
-    int retry_seconds = 15;
-    gpr_log(GPR_DEBUG, "dns resolution failed: retrying in %d seconds",
-            retry_seconds);
+    gpr_timespec now = gpr_now(GPR_CLOCK_MONOTONIC);
+    gpr_timespec next_try = gpr_backoff_step(&r->backoff_state, now);
+    gpr_timespec timeout = gpr_time_sub(next_try, now);
+    gpr_log(GPR_DEBUG, "dns resolution failed: retrying in %d.%09d seconds",
+            timeout.tv_sec, timeout.tv_nsec);
     GPR_ASSERT(!r->have_retry_timer);
     r->have_retry_timer = true;
-    gpr_timespec now = gpr_now(GPR_CLOCK_MONOTONIC);
     GRPC_RESOLVER_REF(&r->base, "retry-timer");
-    grpc_timer_init(
-        exec_ctx, &r->retry_timer,
-        gpr_time_add(now, gpr_time_from_seconds(retry_seconds, GPR_TIMESPAN)),
-        dns_on_retry_timer, r, now);
+    grpc_timer_init(exec_ctx, &r->retry_timer, next_try, dns_on_retry_timer, r,
+                    now);
   }
   if (r->resolved_config) {
     grpc_client_config_unref(exec_ctx, r->resolved_config);
@@ -263,6 +272,8 @@ static grpc_resolver *dns_create(grpc_resolver_args *args,
   r->name = gpr_strdup(path);
   r->default_port = gpr_strdup(default_port);
   r->subchannel_factory = args->subchannel_factory;
+  gpr_backoff_init(&r->backoff_state, BACKOFF_MULTIPLIER, BACKOFF_JITTER,
+                   BACKOFF_MIN_SECONDS * 1000, BACKOFF_MAX_SECONDS * 1000);
   grpc_subchannel_factory_ref(r->subchannel_factory);
   r->lb_policy_name = gpr_strdup(lb_policy_name);
   return &r->base;
diff --git a/src/core/client_config/resolvers/sockaddr_resolver.c b/src/core/client_config/resolvers/sockaddr_resolver.c
index 68910ad975..3cb7d79b67 100644
--- a/src/core/client_config/resolvers/sockaddr_resolver.c
+++ b/src/core/client_config/resolvers/sockaddr_resolver.c
@@ -37,9 +37,6 @@
 
 #include <stdio.h>
 #include <string.h>
-#ifdef GPR_POSIX_SOCKET
-#include <sys/un.h>
-#endif
 
 #include <grpc/support/alloc.h>
 #include <grpc/support/host_port.h>
@@ -47,6 +44,7 @@
 
 #include "src/core/client_config/lb_policy_registry.h"
 #include "src/core/iomgr/resolve_address.h"
+#include "src/core/iomgr/unix_sockets_posix.h"
 #include "src/core/support/string.h"
 
 typedef struct {
@@ -168,24 +166,6 @@ static void sockaddr_destroy(grpc_exec_ctx *exec_ctx, grpc_resolver *gr) {
   gpr_free(r);
 }
 
-#ifdef GPR_POSIX_SOCKET
-static int parse_unix(grpc_uri *uri, struct sockaddr_storage *addr,
-                      size_t *len) {
-  struct sockaddr_un *un = (struct sockaddr_un *)addr;
-
-  un->sun_family = AF_UNIX;
-  strcpy(un->sun_path, uri->path);
-  *len = strlen(un->sun_path) + sizeof(un->sun_family) + 1;
-
-  return 1;
-}
-
-static char *unix_get_default_authority(grpc_resolver_factory *factory,
-                                        grpc_uri *uri) {
-  return gpr_strdup("localhost");
-}
-#endif
-
 static char *ip_get_default_authority(grpc_uri *uri) {
   const char *path = uri->path;
   if (path[0] == '/') ++path;
@@ -371,21 +351,22 @@ static void sockaddr_factory_ref(grpc_resolver_factory *factory) {}
 
 static void sockaddr_factory_unref(grpc_resolver_factory *factory) {}
 
-#define DECL_FACTORY(name)                                                  \
+#define DECL_FACTORY(name, prefix)                                          \
   static grpc_resolver *name##_factory_create_resolver(                     \
       grpc_resolver_factory *factory, grpc_resolver_args *args) {           \
-    return sockaddr_create(args, "pick_first", parse_##name);               \
+    return sockaddr_create(args, "pick_first", prefix##parse_##name);       \
   }                                                                         \
   static const grpc_resolver_factory_vtable name##_factory_vtable = {       \
       sockaddr_factory_ref, sockaddr_factory_unref,                         \
-      name##_factory_create_resolver, name##_get_default_authority, #name}; \
+      name##_factory_create_resolver, prefix##name##_get_default_authority, \
+      #name};                                                               \
   static grpc_resolver_factory name##_resolver_factory = {                  \
       &name##_factory_vtable};                                              \
   grpc_resolver_factory *grpc_##name##_resolver_factory_create() {          \
     return &name##_resolver_factory;                                        \
   }
 
-#ifdef GPR_POSIX_SOCKET
-DECL_FACTORY(unix)
+#ifdef GPR_HAVE_UNIX_SOCKET
+DECL_FACTORY(unix, grpc_)
 #endif
-DECL_FACTORY(ipv4) DECL_FACTORY(ipv6)
+DECL_FACTORY(ipv4, ) DECL_FACTORY(ipv6, )
diff --git a/src/core/httpcli/format_request.c b/src/core/http/format_request.c
index 04f2a2d99a..60179297bf 100644
--- a/src/core/httpcli/format_request.c
+++ b/src/core/http/format_request.c
@@ -1,6 +1,6 @@
 /*
  *
- * Copyright 2015, Google Inc.
+ * Copyright 2015-2016, Google Inc.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -31,7 +31,7 @@
  *
  */
 
-#include "src/core/httpcli/format_request.h"
+#include "src/core/http/format_request.h"
 
 #include <stdarg.h>
 #include <stdio.h>
@@ -46,7 +46,7 @@
 static void fill_common_header(const grpc_httpcli_request *request,
                                gpr_strvec *buf) {
   size_t i;
-  gpr_strvec_add(buf, gpr_strdup(request->path));
+  gpr_strvec_add(buf, gpr_strdup(request->http.path));
   gpr_strvec_add(buf, gpr_strdup(" HTTP/1.0\r\n"));
   /* just in case some crazy server really expects HTTP/1.1 */
   gpr_strvec_add(buf, gpr_strdup("Host: "));
@@ -56,10 +56,10 @@ static void fill_common_header(const grpc_httpcli_request *request,
   gpr_strvec_add(buf,
                  gpr_strdup("User-Agent: " GRPC_HTTPCLI_USER_AGENT "\r\n"));
   /* user supplied headers */
-  for (i = 0; i < request->hdr_count; i++) {
-    gpr_strvec_add(buf, gpr_strdup(request->hdrs[i].key));
+  for (i = 0; i < request->http.hdr_count; i++) {
+    gpr_strvec_add(buf, gpr_strdup(request->http.hdrs[i].key));
     gpr_strvec_add(buf, gpr_strdup(": "));
-    gpr_strvec_add(buf, gpr_strdup(request->hdrs[i].value));
+    gpr_strvec_add(buf, gpr_strdup(request->http.hdrs[i].value));
     gpr_strvec_add(buf, gpr_strdup("\r\n"));
   }
 }
@@ -94,8 +94,8 @@ gpr_slice grpc_httpcli_format_post_request(const grpc_httpcli_request *request,
   fill_common_header(request, &out);
   if (body_bytes) {
     uint8_t has_content_type = 0;
-    for (i = 0; i < request->hdr_count; i++) {
-      if (strcmp(request->hdrs[i].key, "Content-Type") == 0) {
+    for (i = 0; i < request->http.hdr_count; i++) {
+      if (strcmp(request->http.hdrs[i].key, "Content-Type") == 0) {
         has_content_type = 1;
         break;
       }
diff --git a/src/core/httpcli/format_request.h b/src/core/http/format_request.h
index eb47cc90ca..49593b695c 100644
--- a/src/core/httpcli/format_request.h
+++ b/src/core/http/format_request.h
@@ -31,10 +31,10 @@
  *
  */
 
-#ifndef GRPC_CORE_HTTPCLI_FORMAT_REQUEST_H
-#define GRPC_CORE_HTTPCLI_FORMAT_REQUEST_H
+#ifndef GRPC_CORE_HTTP_FORMAT_REQUEST_H
+#define GRPC_CORE_HTTP_FORMAT_REQUEST_H
 
-#include "src/core/httpcli/httpcli.h"
+#include "src/core/http/httpcli.h"
 #include <grpc/support/slice.h>
 
 gpr_slice grpc_httpcli_format_get_request(const grpc_httpcli_request *request);
@@ -42,4 +42,4 @@ gpr_slice grpc_httpcli_format_post_request(const grpc_httpcli_request *request,
                                            const char *body_bytes,
                                            size_t body_size);
 
-#endif /* GRPC_CORE_HTTPCLI_FORMAT_REQUEST_H */
+#endif /* GRPC_CORE_HTTP_FORMAT_REQUEST_H */
diff --git a/src/core/httpcli/httpcli.c b/src/core/http/httpcli.c
index 1219c444c7..1c0d3336ea 100644
--- a/src/core/httpcli/httpcli.c
+++ b/src/core/http/httpcli.c
@@ -31,7 +31,7 @@
  *
  */
 
-#include "src/core/httpcli/httpcli.h"
+#include "src/core/http/httpcli.h"
 #include "src/core/iomgr/sockaddr.h"
 
 #include <string.h>
@@ -40,8 +40,8 @@
 #include <grpc/support/log.h>
 #include <grpc/support/string_util.h>
 
-#include "src/core/httpcli/format_request.h"
-#include "src/core/httpcli/parser.h"
+#include "src/core/http/format_request.h"
+#include "src/core/http/parser.h"
 #include "src/core/iomgr/endpoint.h"
 #include "src/core/iomgr/iomgr_internal.h"
 #include "src/core/iomgr/resolve_address.h"
@@ -50,7 +50,7 @@
 
 typedef struct {
   gpr_slice request_text;
-  grpc_httpcli_parser parser;
+  grpc_http_parser parser;
   grpc_resolved_addresses *addresses;
   size_t next_address;
   grpc_endpoint *ep;
@@ -99,8 +99,9 @@ static void finish(grpc_exec_ctx *exec_ctx, internal_request *req,
                    int success) {
   grpc_pollset_set_del_pollset(exec_ctx, req->context->pollset_set,
                                req->pollset);
-  req->on_response(exec_ctx, req->user_data, success ? &req->parser.r : NULL);
-  grpc_httpcli_parser_destroy(&req->parser);
+  req->on_response(exec_ctx, req->user_data,
+                   success ? &req->parser.http.response : NULL);
+  grpc_http_parser_destroy(&req->parser);
   if (req->addresses != NULL) {
     grpc_resolved_addresses_destroy(req->addresses);
   }
@@ -129,7 +130,7 @@ static void on_read(grpc_exec_ctx *exec_ctx, void *user_data, bool success) {
   for (i = 0; i < req->incoming.count; i++) {
     if (GPR_SLICE_LENGTH(req->incoming.slices[i])) {
       req->have_read_byte = 1;
-      if (!grpc_httpcli_parser_parse(&req->parser, req->incoming.slices[i])) {
+      if (!grpc_http_parser_parse(&req->parser, req->incoming.slices[i])) {
         finish(exec_ctx, req, 0);
         return;
       }
@@ -141,7 +142,11 @@ static void on_read(grpc_exec_ctx *exec_ctx, void *user_data, bool success) {
   } else if (!req->have_read_byte) {
     next_address(exec_ctx, req);
   } else {
-    finish(exec_ctx, req, grpc_httpcli_parser_eof(&req->parser));
+    int parse_success = grpc_http_parser_eof(&req->parser);
+    if (parse_success && (req->parser.type != GRPC_HTTP_RESPONSE)) {
+      parse_success = 0;
+    }
+    finish(exec_ctx, req, parse_success);
   }
 }
 
@@ -223,7 +228,7 @@ static void internal_request_begin(
   internal_request *req = gpr_malloc(sizeof(internal_request));
   memset(req, 0, sizeof(*req));
   req->request_text = request_text;
-  grpc_httpcli_parser_init(&req->parser);
+  grpc_http_parser_init(&req->parser);
   req->on_response = on_response;
   req->user_data = user_data;
   req->deadline = deadline;
@@ -255,7 +260,7 @@ void grpc_httpcli_get(grpc_exec_ctx *exec_ctx, grpc_httpcli_context *context,
       g_get_override(exec_ctx, request, deadline, on_response, user_data)) {
     return;
   }
-  gpr_asprintf(&name, "HTTP:GET:%s:%s", request->host, request->path);
+  gpr_asprintf(&name, "HTTP:GET:%s:%s", request->host, request->http.path);
   internal_request_begin(exec_ctx, context, pollset, request, deadline,
                          on_response, user_data, name,
                          grpc_httpcli_format_get_request(request));
@@ -274,7 +279,7 @@ void grpc_httpcli_post(grpc_exec_ctx *exec_ctx, grpc_httpcli_context *context,
                       on_response, user_data)) {
     return;
   }
-  gpr_asprintf(&name, "HTTP:POST:%s:%s", request->host, request->path);
+  gpr_asprintf(&name, "HTTP:POST:%s:%s", request->host, request->http.path);
   internal_request_begin(
       exec_ctx, context, pollset, request, deadline, on_response, user_data,
       name, grpc_httpcli_format_post_request(request, body_bytes, body_size));
diff --git a/src/core/httpcli/httpcli.h b/src/core/http/httpcli.h
index 1fe5782657..0bf4f2f445 100644
--- a/src/core/httpcli/httpcli.h
+++ b/src/core/http/httpcli.h
@@ -31,27 +31,20 @@
  *
  */
 
-#ifndef GRPC_CORE_HTTPCLI_HTTPCLI_H
-#define GRPC_CORE_HTTPCLI_HTTPCLI_H
+#ifndef GRPC_CORE_HTTP_HTTPCLI_H
+#define GRPC_CORE_HTTP_HTTPCLI_H
 
 #include <stddef.h>
 
 #include <grpc/support/time.h>
 
+#include "src/core/http/parser.h"
 #include "src/core/iomgr/endpoint.h"
 #include "src/core/iomgr/iomgr_internal.h"
 #include "src/core/iomgr/pollset_set.h"
 
 /* User agent this library reports */
 #define GRPC_HTTPCLI_USER_AGENT "grpc-httpcli/0.0"
-/* Maximum length of a header string of the form 'Key: Value\r\n' */
-#define GRPC_HTTPCLI_MAX_HEADER_LENGTH 4096
-
-/* A single header to be passed in a request */
-typedef struct grpc_httpcli_header {
-  char *key;
-  char *value;
-} grpc_httpcli_header;
 
 /* Tracks in-progress http requests
    TODO(ctiller): allow caching and capturing multiple requests for the
@@ -77,33 +70,21 @@ typedef struct grpc_httpcli_request {
   char *host;
   /* The host to verify in the SSL handshake (or NULL) */
   char *ssl_host_override;
-  /* The path of the resource to fetch */
-  char *path;
-  /* Additional headers: count and key/values; the following are supplied
-     automatically and MUST NOT be set here:
+  /* The main part of the request
+     The following headers are supplied automatically and MUST NOT be set here:
      Host, Connection, User-Agent */
-  size_t hdr_count;
-  grpc_httpcli_header *hdrs;
+  grpc_http_request http;
   /* handshaker to use ssl for the request */
   const grpc_httpcli_handshaker *handshaker;
 } grpc_httpcli_request;
 
-/* A response */
-typedef struct grpc_httpcli_response {
-  /* HTTP status code */
-  int status;
-  /* Headers: count and key/values */
-  size_t hdr_count;
-  grpc_httpcli_header *hdrs;
-  /* Body: length and contents; contents are NOT null-terminated */
-  size_t body_length;
-  char *body;
-} grpc_httpcli_response;
+/* Expose the parser response type as a httpcli response too */
+typedef struct grpc_http_response grpc_httpcli_response;
 
 /* Callback for grpc_httpcli_get and grpc_httpcli_post. */
 typedef void (*grpc_httpcli_response_cb)(grpc_exec_ctx *exec_ctx,
                                          void *user_data,
-                                         const grpc_httpcli_response *response);
+                                         const grpc_http_response *response);
 
 void grpc_httpcli_context_init(grpc_httpcli_context *context);
 void grpc_httpcli_context_destroy(grpc_httpcli_context *context);
@@ -160,4 +141,4 @@ typedef int (*grpc_httpcli_post_override)(
 void grpc_httpcli_set_override(grpc_httpcli_get_override get,
                                grpc_httpcli_post_override post);
 
-#endif /* GRPC_CORE_HTTPCLI_HTTPCLI_H */
+#endif /* GRPC_CORE_HTTP_HTTPCLI_H */
diff --git a/src/core/httpcli/httpcli_security_connector.c b/src/core/http/httpcli_security_connector.c
index 156961a377..ce82701089 100644
--- a/src/core/httpcli/httpcli_security_connector.c
+++ b/src/core/http/httpcli_security_connector.c
@@ -31,7 +31,7 @@
  *
  */
 
-#include "src/core/httpcli/httpcli.h"
+#include "src/core/http/httpcli.h"
 
 #include <string.h>
 
diff --git a/src/core/http/parser.c b/src/core/http/parser.c
new file mode 100644
index 0000000000..ebec8a5157
--- /dev/null
+++ b/src/core/http/parser.c
@@ -0,0 +1,313 @@
+/*
+ *
+ * Copyright 2015-2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#include "src/core/http/parser.h"
+
+#include <string.h>
+
+#include <grpc/support/alloc.h>
+#include <grpc/support/log.h>
+#include <grpc/support/useful.h>
+
+static char *buf2str(void *buffer, size_t length) {
+  char *out = gpr_malloc(length + 1);
+  memcpy(out, buffer, length);
+  out[length] = 0;
+  return out;
+}
+
+static int handle_response_line(grpc_http_parser *parser) {
+  uint8_t *beg = parser->cur_line;
+  uint8_t *cur = beg;
+  uint8_t *end = beg + parser->cur_line_length;
+
+  if (cur == end || *cur++ != 'H') goto error;
+  if (cur == end || *cur++ != 'T') goto error;
+  if (cur == end || *cur++ != 'T') goto error;
+  if (cur == end || *cur++ != 'P') goto error;
+  if (cur == end || *cur++ != '/') goto error;
+  if (cur == end || *cur++ != '1') goto error;
+  if (cur == end || *cur++ != '.') goto error;
+  if (cur == end || *cur < '0' || *cur++ > '1') goto error;
+  if (cur == end || *cur++ != ' ') goto error;
+  if (cur == end || *cur < '1' || *cur++ > '9') goto error;
+  if (cur == end || *cur < '0' || *cur++ > '9') goto error;
+  if (cur == end || *cur < '0' || *cur++ > '9') goto error;
+  parser->http.response.status =
+      (cur[-3] - '0') * 100 + (cur[-2] - '0') * 10 + (cur[-1] - '0');
+  if (cur == end || *cur++ != ' ') goto error;
+
+  /* we don't really care about the status code message */
+
+  return 1;
+
+error:
+  gpr_log(GPR_ERROR, "Failed parsing response line");
+  return 0;
+}
+
+static int handle_request_line(grpc_http_parser *parser) {
+  uint8_t *beg = parser->cur_line;
+  uint8_t *cur = beg;
+  uint8_t *end = beg + parser->cur_line_length;
+  uint8_t vers_major = 0;
+  uint8_t vers_minor = 0;
+
+  while (cur != end && *cur++ != ' ')
+    ;
+  if (cur == end) goto error;
+  parser->http.request.method = buf2str(beg, (size_t)(cur - beg - 1));
+
+  beg = cur;
+  while (cur != end && *cur++ != ' ')
+    ;
+  if (cur == end) goto error;
+  parser->http.request.path = buf2str(beg, (size_t)(cur - beg - 1));
+
+  if (cur == end || *cur++ != 'H') goto error;
+  if (cur == end || *cur++ != 'T') goto error;
+  if (cur == end || *cur++ != 'T') goto error;
+  if (cur == end || *cur++ != 'P') goto error;
+  if (cur == end || *cur++ != '/') goto error;
+  vers_major = (uint8_t)(*cur++ - '1' + 1);
+  ++cur;
+  if (cur == end) goto error;
+  vers_minor = (uint8_t)(*cur++ - '1' + 1);
+
+  if (vers_major == 1) {
+    if (vers_minor == 0) {
+      parser->http.request.version = GRPC_HTTP_HTTP10;
+    } else if (vers_minor == 1) {
+      parser->http.request.version = GRPC_HTTP_HTTP11;
+    } else {
+      goto error;
+    }
+  } else if (vers_major == 2) {
+    if (vers_minor == 0) {
+      parser->http.request.version = GRPC_HTTP_HTTP20;
+    } else {
+      goto error;
+    }
+  } else {
+    goto error;
+  }
+
+  return 1;
+
+error:
+  gpr_log(GPR_ERROR, "Failed parsing request line");
+  return 0;
+}
+
+static int handle_first_line(grpc_http_parser *parser) {
+  if (parser->cur_line[0] == 'H') {
+    parser->type = GRPC_HTTP_RESPONSE;
+    return handle_response_line(parser);
+  } else {
+    parser->type = GRPC_HTTP_REQUEST;
+    return handle_request_line(parser);
+  }
+}
+
+static int add_header(grpc_http_parser *parser) {
+  uint8_t *beg = parser->cur_line;
+  uint8_t *cur = beg;
+  uint8_t *end = beg + parser->cur_line_length;
+  size_t *hdr_count = NULL;
+  grpc_http_header **hdrs = NULL;
+  grpc_http_header hdr = {NULL, NULL};
+
+  GPR_ASSERT(cur != end);
+
+  if (*cur == ' ' || *cur == '\t') {
+    gpr_log(GPR_ERROR, "Continued header lines not supported yet");
+    goto error;
+  }
+
+  while (cur != end && *cur != ':') {
+    cur++;
+  }
+  if (cur == end) {
+    gpr_log(GPR_ERROR, "Didn't find ':' in header string");
+    goto error;
+  }
+  GPR_ASSERT(cur >= beg);
+  hdr.key = buf2str(beg, (size_t)(cur - beg));
+  cur++; /* skip : */
+
+  while (cur != end && (*cur == ' ' || *cur == '\t')) {
+    cur++;
+  }
+  GPR_ASSERT(end - cur >= 2);
+  hdr.value = buf2str(cur, (size_t)(end - cur) - 2);
+
+  if (parser->type == GRPC_HTTP_RESPONSE) {
+    hdr_count = &parser->http.response.hdr_count;
+    hdrs = &parser->http.response.hdrs;
+  } else if (parser->type == GRPC_HTTP_REQUEST) {
+    hdr_count = &parser->http.request.hdr_count;
+    hdrs = &parser->http.request.hdrs;
+  } else {
+    return 0;
+  }
+
+  if (*hdr_count == parser->hdr_capacity) {
+    parser->hdr_capacity =
+        GPR_MAX(parser->hdr_capacity + 1, parser->hdr_capacity * 3 / 2);
+    *hdrs = gpr_realloc(*hdrs, parser->hdr_capacity * sizeof(**hdrs));
+  }
+  (*hdrs)[(*hdr_count)++] = hdr;
+  return 1;
+
+error:
+  gpr_free(hdr.key);
+  gpr_free(hdr.value);
+  return 0;
+}
+
+static int finish_line(grpc_http_parser *parser) {
+  switch (parser->state) {
+    case GRPC_HTTP_FIRST_LINE:
+      if (!handle_first_line(parser)) {
+        return 0;
+      }
+      parser->state = GRPC_HTTP_HEADERS;
+      break;
+    case GRPC_HTTP_HEADERS:
+      if (parser->cur_line_length == 2) {
+        parser->state = GRPC_HTTP_BODY;
+        break;
+      }
+      if (!add_header(parser)) {
+        return 0;
+      }
+      break;
+    case GRPC_HTTP_BODY:
+      GPR_UNREACHABLE_CODE(return 0);
+  }
+
+  parser->cur_line_length = 0;
+  return 1;
+}
+
+static int addbyte_body(grpc_http_parser *parser, uint8_t byte) {
+  size_t *body_length = NULL;
+  char **body = NULL;
+
+  if (parser->type == GRPC_HTTP_RESPONSE) {
+    body_length = &parser->http.response.body_length;
+    body = &parser->http.response.body;
+  } else if (parser->type == GRPC_HTTP_REQUEST) {
+    body_length = &parser->http.request.body_length;
+    body = &parser->http.request.body;
+  } else {
+    return 0;
+  }
+
+  if (*body_length == parser->body_capacity) {
+    parser->body_capacity = GPR_MAX(8, parser->body_capacity * 3 / 2);
+    *body = gpr_realloc((void *)*body, parser->body_capacity);
+  }
+  (*body)[*body_length] = (char)byte;
+  (*body_length)++;
+
+  return 1;
+}
+
+static int addbyte(grpc_http_parser *parser, uint8_t byte) {
+  switch (parser->state) {
+    case GRPC_HTTP_FIRST_LINE:
+    case GRPC_HTTP_HEADERS:
+      if (parser->cur_line_length >= GRPC_HTTP_PARSER_MAX_HEADER_LENGTH) {
+        gpr_log(GPR_ERROR, "HTTP client max line length (%d) exceeded",
+                GRPC_HTTP_PARSER_MAX_HEADER_LENGTH);
+        return 0;
+      }
+      parser->cur_line[parser->cur_line_length] = byte;
+      parser->cur_line_length++;
+      if (parser->cur_line_length >= 2 &&
+          parser->cur_line[parser->cur_line_length - 2] == '\r' &&
+          parser->cur_line[parser->cur_line_length - 1] == '\n') {
+        return finish_line(parser);
+      } else {
+        return 1;
+      }
+      GPR_UNREACHABLE_CODE(return 0);
+    case GRPC_HTTP_BODY:
+      return addbyte_body(parser, byte);
+  }
+  GPR_UNREACHABLE_CODE(return 0);
+}
+
+void grpc_http_parser_init(grpc_http_parser *parser) {
+  memset(parser, 0, sizeof(*parser));
+  parser->state = GRPC_HTTP_FIRST_LINE;
+  parser->type = GRPC_HTTP_UNKNOWN;
+}
+
+void grpc_http_parser_destroy(grpc_http_parser *parser) {
+  size_t i;
+  if (parser->type == GRPC_HTTP_RESPONSE) {
+    gpr_free(parser->http.response.body);
+    for (i = 0; i < parser->http.response.hdr_count; i++) {
+      gpr_free(parser->http.response.hdrs[i].key);
+      gpr_free(parser->http.response.hdrs[i].value);
+    }
+    gpr_free(parser->http.response.hdrs);
+  } else if (parser->type == GRPC_HTTP_REQUEST) {
+    gpr_free(parser->http.request.body);
+    for (i = 0; i < parser->http.request.hdr_count; i++) {
+      gpr_free(parser->http.request.hdrs[i].key);
+      gpr_free(parser->http.request.hdrs[i].value);
+    }
+    gpr_free(parser->http.request.hdrs);
+    gpr_free(parser->http.request.method);
+    gpr_free(parser->http.request.path);
+  }
+}
+
+int grpc_http_parser_parse(grpc_http_parser *parser, gpr_slice slice) {
+  size_t i;
+
+  for (i = 0; i < GPR_SLICE_LENGTH(slice); i++) {
+    if (!addbyte(parser, GPR_SLICE_START_PTR(slice)[i])) {
+      return 0;
+    }
+  }
+
+  return 1;
+}
+
+int grpc_http_parser_eof(grpc_http_parser *parser) {
+  return parser->state == GRPC_HTTP_BODY;
+}
diff --git a/src/core/http/parser.h b/src/core/http/parser.h
new file mode 100644
index 0000000000..39517e485a
--- /dev/null
+++ b/src/core/http/parser.h
@@ -0,0 +1,116 @@
+/*
+ *
+ * Copyright 2015-2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#ifndef GRPC_CORE_HTTP_PARSER_H
+#define GRPC_CORE_HTTP_PARSER_H
+
+#include <grpc/support/port_platform.h>
+#include <grpc/support/slice.h>
+
+/* Maximum length of a header string of the form 'Key: Value\r\n' */
+#define GRPC_HTTP_PARSER_MAX_HEADER_LENGTH 4096
+
+/* A single header to be passed in a request */
+typedef struct grpc_http_header {
+  char *key;
+  char *value;
+} grpc_http_header;
+
+typedef enum {
+  GRPC_HTTP_FIRST_LINE,
+  GRPC_HTTP_HEADERS,
+  GRPC_HTTP_BODY
+} grpc_http_parser_state;
+
+typedef enum {
+  GRPC_HTTP_HTTP10,
+  GRPC_HTTP_HTTP11,
+  GRPC_HTTP_HTTP20,
+} grpc_http_version;
+
+typedef enum {
+  GRPC_HTTP_RESPONSE,
+  GRPC_HTTP_REQUEST,
+  GRPC_HTTP_UNKNOWN
+} grpc_http_type;
+
+/* A request */
+typedef struct grpc_http_request {
+  /* Method of the request (e.g. GET, POST) */
+  char *method;
+  /* The path of the resource to fetch */
+  char *path;
+  /* HTTP version to use */
+  grpc_http_version version;
+  /* Headers attached to the request */
+  size_t hdr_count;
+  grpc_http_header *hdrs;
+  /* Body: length and contents; contents are NOT null-terminated */
+  size_t body_length;
+  char *body;
+} grpc_http_request;
+
+/* A response */
+typedef struct grpc_http_response {
+  /* HTTP status code */
+  int status;
+  /* Headers: count and key/values */
+  size_t hdr_count;
+  grpc_http_header *hdrs;
+  /* Body: length and contents; contents are NOT null-terminated */
+  size_t body_length;
+  char *body;
+} grpc_http_response;
+
+typedef struct {
+  grpc_http_parser_state state;
+  grpc_http_type type;
+
+  union {
+    grpc_http_response response;
+    grpc_http_request request;
+  } http;
+  size_t body_capacity;
+  size_t hdr_capacity;
+
+  uint8_t cur_line[GRPC_HTTP_PARSER_MAX_HEADER_LENGTH];
+  size_t cur_line_length;
+} grpc_http_parser;
+
+void grpc_http_parser_init(grpc_http_parser *parser);
+void grpc_http_parser_destroy(grpc_http_parser *parser);
+
+int grpc_http_parser_parse(grpc_http_parser *parser, gpr_slice slice);
+int grpc_http_parser_eof(grpc_http_parser *parser);
+
+#endif /* GRPC_CORE_HTTP_PARSER_H */
diff --git a/src/core/httpcli/parser.c b/src/core/httpcli/parser.c
deleted file mode 100644
index eb059e7804..0000000000
--- a/src/core/httpcli/parser.c
+++ /dev/null
@@ -1,219 +0,0 @@
-/*
- *
- * Copyright 2015, Google Inc.
- * All rights reserved.
- *
- * Redistribution and use in source and binary forms, with or without
- * modification, are permitted provided that the following conditions are
- * met:
- *
- *     * Redistributions of source code must retain the above copyright
- * notice, this list of conditions and the following disclaimer.
- *     * Redistributions in binary form must reproduce the above
- * copyright notice, this list of conditions and the following disclaimer
- * in the documentation and/or other materials provided with the
- * distribution.
- *     * Neither the name of Google Inc. nor the names of its
- * contributors may be used to endorse or promote products derived from
- * this software without specific prior written permission.
- *
- * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
- * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
- * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
- * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
- * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
- * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
- * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
- * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
- * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
- * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
- * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
- *
- */
-
-#include "src/core/httpcli/parser.h"
-
-#include <string.h>
-
-#include <grpc/support/alloc.h>
-#include <grpc/support/log.h>
-#include <grpc/support/useful.h>
-
-extern int grpc_http_trace;
-
-static int handle_response_line(grpc_httpcli_parser *parser) {
-  uint8_t *beg = parser->cur_line;
-  uint8_t *cur = beg;
-  uint8_t *end = beg + parser->cur_line_length;
-
-  if (cur == end || *cur++ != 'H') goto error;
-  if (cur == end || *cur++ != 'T') goto error;
-  if (cur == end || *cur++ != 'T') goto error;
-  if (cur == end || *cur++ != 'P') goto error;
-  if (cur == end || *cur++ != '/') goto error;
-  if (cur == end || *cur++ != '1') goto error;
-  if (cur == end || *cur++ != '.') goto error;
-  if (cur == end || *cur < '0' || *cur++ > '1') goto error;
-  if (cur == end || *cur++ != ' ') goto error;
-  if (cur == end || *cur < '1' || *cur++ > '9') goto error;
-  if (cur == end || *cur < '0' || *cur++ > '9') goto error;
-  if (cur == end || *cur < '0' || *cur++ > '9') goto error;
-  parser->r.status =
-      (cur[-3] - '0') * 100 + (cur[-2] - '0') * 10 + (cur[-1] - '0');
-  if (cur == end || *cur++ != ' ') goto error;
-
-  /* we don't really care about the status code message */
-
-  return 1;
-
-error:
-  if (grpc_http_trace) {
-    gpr_log(GPR_ERROR, "Failed parsing response line");
-  }
-  return 0;
-}
-
-static char *buf2str(void *buffer, size_t length) {
-  char *out = gpr_malloc(length + 1);
-  memcpy(out, buffer, length);
-  out[length] = 0;
-  return out;
-}
-
-static int add_header(grpc_httpcli_parser *parser) {
-  uint8_t *beg = parser->cur_line;
-  uint8_t *cur = beg;
-  uint8_t *end = beg + parser->cur_line_length;
-  grpc_httpcli_header hdr = {NULL, NULL};
-
-  GPR_ASSERT(cur != end);
-
-  if (*cur == ' ' || *cur == '\t') {
-    if (grpc_http_trace) {
-      gpr_log(GPR_ERROR, "Continued header lines not supported yet");
-    }
-    goto error;
-  }
-
-  while (cur != end && *cur != ':') {
-    cur++;
-  }
-  if (cur == end) {
-    if (grpc_http_trace) {
-      gpr_log(GPR_ERROR, "Didn't find ':' in header string");
-    }
-    goto error;
-  }
-  GPR_ASSERT(cur >= beg);
-  hdr.key = buf2str(beg, (size_t)(cur - beg));
-  cur++; /* skip : */
-
-  while (cur != end && (*cur == ' ' || *cur == '\t')) {
-    cur++;
-  }
-  GPR_ASSERT(end - cur >= 2);
-  hdr.value = buf2str(cur, (size_t)(end - cur) - 2);
-
-  if (parser->r.hdr_count == parser->hdr_capacity) {
-    parser->hdr_capacity =
-        GPR_MAX(parser->hdr_capacity + 1, parser->hdr_capacity * 3 / 2);
-    parser->r.hdrs = gpr_realloc(
-        parser->r.hdrs, parser->hdr_capacity * sizeof(*parser->r.hdrs));
-  }
-  parser->r.hdrs[parser->r.hdr_count++] = hdr;
-  return 1;
-
-error:
-  gpr_free(hdr.key);
-  gpr_free(hdr.value);
-  return 0;
-}
-
-static int finish_line(grpc_httpcli_parser *parser) {
-  switch (parser->state) {
-    case GRPC_HTTPCLI_INITIAL_RESPONSE:
-      if (!handle_response_line(parser)) {
-        return 0;
-      }
-      parser->state = GRPC_HTTPCLI_HEADERS;
-      break;
-    case GRPC_HTTPCLI_HEADERS:
-      if (parser->cur_line_length == 2) {
-        parser->state = GRPC_HTTPCLI_BODY;
-        break;
-      }
-      if (!add_header(parser)) {
-        return 0;
-      }
-      break;
-    case GRPC_HTTPCLI_BODY:
-      GPR_UNREACHABLE_CODE(return 0);
-  }
-
-  parser->cur_line_length = 0;
-  return 1;
-}
-
-static int addbyte(grpc_httpcli_parser *parser, uint8_t byte) {
-  switch (parser->state) {
-    case GRPC_HTTPCLI_INITIAL_RESPONSE:
-    case GRPC_HTTPCLI_HEADERS:
-      if (parser->cur_line_length >= GRPC_HTTPCLI_MAX_HEADER_LENGTH) {
-        gpr_log(GPR_ERROR, "HTTP client max line length (%d) exceeded",
-                GRPC_HTTPCLI_MAX_HEADER_LENGTH);
-        return 0;
-      }
-      parser->cur_line[parser->cur_line_length] = byte;
-      parser->cur_line_length++;
-      if (parser->cur_line_length >= 2 &&
-          parser->cur_line[parser->cur_line_length - 2] == '\r' &&
-          parser->cur_line[parser->cur_line_length - 1] == '\n') {
-        return finish_line(parser);
-      } else {
-        return 1;
-      }
-      GPR_UNREACHABLE_CODE(return 0);
-    case GRPC_HTTPCLI_BODY:
-      if (parser->r.body_length == parser->body_capacity) {
-        parser->body_capacity = GPR_MAX(8, parser->body_capacity * 3 / 2);
-        parser->r.body =
-            gpr_realloc((void *)parser->r.body, parser->body_capacity);
-      }
-      parser->r.body[parser->r.body_length] = (char)byte;
-      parser->r.body_length++;
-      return 1;
-  }
-  GPR_UNREACHABLE_CODE(return 0);
-}
-
-void grpc_httpcli_parser_init(grpc_httpcli_parser *parser) {
-  memset(parser, 0, sizeof(*parser));
-  parser->state = GRPC_HTTPCLI_INITIAL_RESPONSE;
-  parser->r.status = 500;
-}
-
-void grpc_httpcli_parser_destroy(grpc_httpcli_parser *parser) {
-  size_t i;
-  gpr_free(parser->r.body);
-  for (i = 0; i < parser->r.hdr_count; i++) {
-    gpr_free(parser->r.hdrs[i].key);
-    gpr_free(parser->r.hdrs[i].value);
-  }
-  gpr_free(parser->r.hdrs);
-}
-
-int grpc_httpcli_parser_parse(grpc_httpcli_parser *parser, gpr_slice slice) {
-  size_t i;
-
-  for (i = 0; i < GPR_SLICE_LENGTH(slice); i++) {
-    if (!addbyte(parser, GPR_SLICE_START_PTR(slice)[i])) {
-      return 0;
-    }
-  }
-
-  return 1;
-}
-
-int grpc_httpcli_parser_eof(grpc_httpcli_parser *parser) {
-  return parser->state == GRPC_HTTPCLI_BODY;
-}
diff --git a/src/core/iomgr/endpoint_pair_posix.c b/src/core/iomgr/endpoint_pair_posix.c
index 56f6f146fd..f84b8441df 100644
--- a/src/core/iomgr/endpoint_pair_posix.c
+++ b/src/core/iomgr/endpoint_pair_posix.c
@@ -1,6 +1,6 @@
 /*
  *
- * Copyright 2015, Google Inc.
+ * Copyright 2016, Google Inc.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -37,6 +37,7 @@
 
 #include "src/core/iomgr/endpoint_pair.h"
 #include "src/core/iomgr/socket_utils_posix.h"
+#include "src/core/iomgr/unix_sockets_posix.h"
 
 #include <errno.h>
 #include <fcntl.h>
@@ -52,7 +53,7 @@
 
 static void create_sockets(int sv[2]) {
   int flags;
-  GPR_ASSERT(socketpair(AF_UNIX, SOCK_STREAM, 0, sv) == 0);
+  grpc_create_socketpair_if_unix(sv);
   flags = fcntl(sv[0], F_GETFL, 0);
   GPR_ASSERT(fcntl(sv[0], F_SETFL, flags | O_NONBLOCK) == 0);
   flags = fcntl(sv[1], F_GETFL, 0);
diff --git a/src/core/iomgr/fd_posix.c b/src/core/iomgr/fd_posix.c
index 3edafa0b07..b4d038a3a1 100644
--- a/src/core/iomgr/fd_posix.c
+++ b/src/core/iomgr/fd_posix.c
@@ -72,9 +72,6 @@ static grpc_fd *fd_freelist = NULL;
 static gpr_mu fd_freelist_mu;
 
 static void freelist_fd(grpc_fd *fd) {
-  // Note that this function must be called after a release store (or
-  // full-barrier operation) on refst so that prior actions on the fd are
-  // ordered before the fd becomes visible to the freelist
   gpr_mu_lock(&fd_freelist_mu);
   fd->freelist_next = fd_freelist;
   fd_freelist = fd;
@@ -95,6 +92,7 @@ static grpc_fd *alloc_fd(int fd) {
     gpr_mu_init(&r->mu);
   }
 
+  gpr_mu_lock(&r->mu);
   r->shutdown = 0;
   r->read_closure = CLOSURE_NOT_READY;
   r->write_closure = CLOSURE_NOT_READY;
@@ -106,11 +104,9 @@ static grpc_fd *alloc_fd(int fd) {
   r->on_done_closure = NULL;
   r->closed = 0;
   r->released = 0;
-  // The last operation on r before returning it should be a release-store
-  // so that all the above fields are globally visible before the value of
-  // r could escape to another thread. Our refcount itself needs a release-store
-  // so use this
   gpr_atm_rel_store(&r->refst, 1);
+  gpr_mu_unlock(&r->mu);
+
   return r;
 }
 
diff --git a/src/core/iomgr/resolve_address_posix.c b/src/core/iomgr/resolve_address_posix.c
index a6c9893f23..26b3aa8189 100644
--- a/src/core/iomgr/resolve_address_posix.c
+++ b/src/core/iomgr/resolve_address_posix.c
@@ -39,7 +39,6 @@
 
 #include <string.h>
 #include <sys/types.h>
-#include <sys/un.h>
 
 #include <grpc/support/alloc.h>
 #include <grpc/support/host_port.h>
@@ -51,6 +50,7 @@
 #include "src/core/iomgr/executor.h"
 #include "src/core/iomgr/iomgr_internal.h"
 #include "src/core/iomgr/sockaddr_utils.h"
+#include "src/core/iomgr/unix_sockets_posix.h"
 #include "src/core/support/block_annotate.h"
 #include "src/core/support/string.h"
 
@@ -71,18 +71,10 @@ static grpc_resolved_addresses *blocking_resolve_address_impl(
   int s;
   size_t i;
   grpc_resolved_addresses *addrs = NULL;
-  struct sockaddr_un *un;
 
   if (name[0] == 'u' && name[1] == 'n' && name[2] == 'i' && name[3] == 'x' &&
       name[4] == ':' && name[5] != 0) {
-    addrs = gpr_malloc(sizeof(grpc_resolved_addresses));
-    addrs->naddrs = 1;
-    addrs->addrs = gpr_malloc(sizeof(grpc_resolved_address));
-    un = (struct sockaddr_un *)addrs->addrs->addr;
-    un->sun_family = AF_UNIX;
-    strcpy(un->sun_path, name + 5);
-    addrs->addrs->len = strlen(un->sun_path) + sizeof(un->sun_family) + 1;
-    return addrs;
+    return grpc_resolve_unix_domain_address(name + 5);
   }
 
   /* parse name, splitting it into host and port parts */
diff --git a/src/core/iomgr/sockaddr_utils.c b/src/core/iomgr/sockaddr_utils.c
index 61006d7a7a..a3c3a874c1 100644
--- a/src/core/iomgr/sockaddr_utils.c
+++ b/src/core/iomgr/sockaddr_utils.c
@@ -1,6 +1,6 @@
 /*
  *
- * Copyright 2015, Google Inc.
+ * Copyright 2016, Google Inc.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -36,16 +36,13 @@
 #include <errno.h>
 #include <string.h>
 
-#ifdef GPR_POSIX_SOCKET
-#include <sys/un.h>
-#endif
-
 #include <grpc/support/alloc.h>
 #include <grpc/support/host_port.h>
 #include <grpc/support/log.h>
 #include <grpc/support/port_platform.h>
 #include <grpc/support/string_util.h>
 
+#include "src/core/iomgr/unix_sockets_posix.h"
 #include "src/core/support/string.h"
 
 static const uint8_t kV4MappedPrefix[] = {0, 0, 0, 0, 0,    0,
@@ -191,14 +188,9 @@ char *grpc_sockaddr_to_uri(const struct sockaddr *addr) {
       gpr_asprintf(&result, "ipv6:%s", temp);
       gpr_free(temp);
       return result;
-#ifdef GPR_POSIX_SOCKET
-    case AF_UNIX:
-      gpr_asprintf(&result, "unix:%s", ((struct sockaddr_un *)addr)->sun_path);
-      return result;
-#endif
+    default:
+      return grpc_sockaddr_to_uri_unix_if_possible(addr);
   }
-
-  return NULL;
 }
 
 int grpc_sockaddr_get_port(const struct sockaddr *addr) {
@@ -207,9 +199,10 @@ int grpc_sockaddr_get_port(const struct sockaddr *addr) {
       return ntohs(((struct sockaddr_in *)addr)->sin_port);
     case AF_INET6:
       return ntohs(((struct sockaddr_in6 *)addr)->sin6_port);
-    case AF_UNIX:
-      return 1;
     default:
+      if (grpc_is_unix_socket(addr)) {
+        return 1;
+      }
       gpr_log(GPR_ERROR, "Unknown socket family %d in grpc_sockaddr_get_port",
               addr->sa_family);
       return 0;
diff --git a/src/core/iomgr/tcp_client_posix.c b/src/core/iomgr/tcp_client_posix.c
index 15727856ab..1d3f9b6555 100644
--- a/src/core/iomgr/tcp_client_posix.c
+++ b/src/core/iomgr/tcp_client_posix.c
@@ -54,6 +54,7 @@
 #include "src/core/iomgr/socket_utils_posix.h"
 #include "src/core/iomgr/tcp_posix.h"
 #include "src/core/iomgr/timer.h"
+#include "src/core/iomgr/unix_sockets_posix.h"
 #include "src/core/support/string.h"
 
 extern int grpc_tcp_trace;
@@ -77,13 +78,12 @@ static int prepare_socket(const struct sockaddr *addr, int fd) {
   }
 
   if (!grpc_set_socket_nonblocking(fd, 1) || !grpc_set_socket_cloexec(fd, 1) ||
-      (addr->sa_family != AF_UNIX && !grpc_set_socket_low_latency(fd, 1)) ||
+      (!grpc_is_unix_socket(addr) && !grpc_set_socket_low_latency(fd, 1)) ||
       !grpc_set_socket_no_sigpipe_if_possible(fd)) {
     gpr_log(GPR_ERROR, "Unable to configure socket %d: %s", fd,
             strerror(errno));
     goto error;
   }
-
   return 1;
 
 error:
diff --git a/src/core/iomgr/tcp_server_posix.c b/src/core/iomgr/tcp_server_posix.c
index 5e07f8261c..03dfddd925 100644
--- a/src/core/iomgr/tcp_server_posix.c
+++ b/src/core/iomgr/tcp_server_posix.c
@@ -52,7 +52,6 @@
 #include <sys/socket.h>
 #include <sys/stat.h>
 #include <sys/types.h>
-#include <sys/un.h>
 #include <unistd.h>
 
 #include "src/core/iomgr/pollset_posix.h"
@@ -60,6 +59,7 @@
 #include "src/core/iomgr/sockaddr_utils.h"
 #include "src/core/iomgr/socket_utils_posix.h"
 #include "src/core/iomgr/tcp_posix.h"
+#include "src/core/iomgr/unix_sockets_posix.h"
 #include "src/core/support/string.h"
 #include <grpc/support/alloc.h>
 #include <grpc/support/log.h>
@@ -81,7 +81,6 @@ struct grpc_tcp_listener {
   union {
     uint8_t untyped[GRPC_MAX_SOCKADDR_SIZE];
     struct sockaddr sockaddr;
-    struct sockaddr_un un;
   } addr;
   size_t addr_len;
   int port;
@@ -98,14 +97,6 @@ struct grpc_tcp_listener {
   int is_sibling;
 };
 
-static void unlink_if_unix_domain_socket(const struct sockaddr_un *un) {
-  struct stat st;
-
-  if (stat(un->sun_path, &st) == 0 && (st.st_mode & S_IFMT) == S_IFSOCK) {
-    unlink(un->sun_path);
-  }
-}
-
 /* the overall server */
 struct grpc_tcp_server {
   gpr_refcount refs;
@@ -203,9 +194,7 @@ static void deactivated_all_ports(grpc_exec_ctx *exec_ctx, grpc_tcp_server *s) {
   if (s->head) {
     grpc_tcp_listener *sp;
     for (sp = s->head; sp; sp = sp->next) {
-      if (sp->addr.sockaddr.sa_family == AF_UNIX) {
-        unlink_if_unix_domain_socket(&sp->addr.un);
-      }
+      grpc_unlink_if_unix_domain_socket(&sp->addr.sockaddr);
       sp->destroyed_closure.cb = destroyed_port;
       sp->destroyed_closure.cb_arg = s;
       grpc_fd_orphan(exec_ctx, sp->emfd, &sp->destroyed_closure, NULL,
@@ -281,7 +270,7 @@ static int prepare_socket(int fd, const struct sockaddr *addr,
   }
 
   if (!grpc_set_socket_nonblocking(fd, 1) || !grpc_set_socket_cloexec(fd, 1) ||
-      (addr->sa_family != AF_UNIX && (!grpc_set_socket_low_latency(fd, 1) ||
+      (!grpc_is_unix_socket(addr) && (!grpc_set_socket_low_latency(fd, 1) ||
                                       !grpc_set_socket_reuse_addr(fd, 1))) ||
       !grpc_set_socket_no_sigpipe_if_possible(fd)) {
     gpr_log(GPR_ERROR, "Unable to configure socket %d: %s", fd,
@@ -451,9 +440,7 @@ int grpc_tcp_server_add_port(grpc_tcp_server *s, const void *addr,
   if (s->tail != NULL) {
     port_index = s->tail->port_index + 1;
   }
-  if (((struct sockaddr *)addr)->sa_family == AF_UNIX) {
-    unlink_if_unix_domain_socket(addr);
-  }
+  grpc_unlink_if_unix_domain_socket((struct sockaddr *)addr);
 
   /* Check if this is a wildcard port, and if so, try to keep the port the same
      as some previously created listener. */
diff --git a/src/core/iomgr/udp_server.c b/src/core/iomgr/udp_server.c
index ef548cfe4d..efedd9f32e 100644
--- a/src/core/iomgr/udp_server.c
+++ b/src/core/iomgr/udp_server.c
@@ -52,7 +52,6 @@
 #include <sys/socket.h>
 #include <sys/stat.h>
 #include <sys/types.h>
-#include <sys/un.h>
 #include <unistd.h>
 
 #include "src/core/iomgr/fd_posix.h"
@@ -60,6 +59,7 @@
 #include "src/core/iomgr/resolve_address.h"
 #include "src/core/iomgr/sockaddr_utils.h"
 #include "src/core/iomgr/socket_utils_posix.h"
+#include "src/core/iomgr/unix_sockets_posix.h"
 #include "src/core/support/string.h"
 #include <grpc/support/alloc.h>
 #include <grpc/support/log.h>
@@ -77,7 +77,6 @@ typedef struct {
   union {
     uint8_t untyped[GRPC_MAX_SOCKADDR_SIZE];
     struct sockaddr sockaddr;
-    struct sockaddr_un un;
   } addr;
   size_t addr_len;
   grpc_closure read_closure;
@@ -85,14 +84,6 @@ typedef struct {
   grpc_udp_server_read_cb read_cb;
 } server_port;
 
-static void unlink_if_unix_domain_socket(const struct sockaddr_un *un) {
-  struct stat st;
-
-  if (stat(un->sun_path, &st) == 0 && (st.st_mode & S_IFMT) == S_IFSOCK) {
-    unlink(un->sun_path);
-  }
-}
-
 /* the overall server */
 struct grpc_udp_server {
   gpr_mu mu;
@@ -176,9 +167,7 @@ static void deactivated_all_ports(grpc_exec_ctx *exec_ctx, grpc_udp_server *s) {
   if (s->nports) {
     for (i = 0; i < s->nports; i++) {
       server_port *sp = &s->ports[i];
-      if (sp->addr.sockaddr.sa_family == AF_UNIX) {
-        unlink_if_unix_domain_socket(&sp->addr.un);
-      }
+      grpc_unlink_if_unix_domain_socket(&sp->addr.sockaddr);
       sp->destroyed_closure.cb = destroyed_port;
       sp->destroyed_closure.cb_arg = s;
       grpc_fd_orphan(exec_ctx, sp->emfd, &sp->destroyed_closure, NULL,
@@ -336,9 +325,7 @@ int grpc_udp_server_add_port(grpc_udp_server *s, const void *addr,
   socklen_t sockname_len;
   int port;
 
-  if (((struct sockaddr *)addr)->sa_family == AF_UNIX) {
-    unlink_if_unix_domain_socket(addr);
-  }
+  grpc_unlink_if_unix_domain_socket((struct sockaddr *)addr);
 
   /* Check if this is a wildcard port, and if so, try to keep the port the same
      as some previously created listener. */
diff --git a/src/core/iomgr/udp_server.h b/src/core/iomgr/udp_server.h
index 1e59a92392..148c04fa9b 100644
--- a/src/core/iomgr/udp_server.h
+++ b/src/core/iomgr/udp_server.h
@@ -37,15 +37,16 @@
 #include "src/core/iomgr/endpoint.h"
 #include "src/core/iomgr/fd_posix.h"
 
-/* Forward decl of grpc_server */
-typedef struct grpc_server grpc_server;
+/* Forward decl of struct grpc_server */
+/* This is not typedef'ed to avoid a typedef-redefinition error */
+struct grpc_server;
 
 /* Forward decl of grpc_udp_server */
 typedef struct grpc_udp_server grpc_udp_server;
 
 /* Called when data is available to read from the socket. */
 typedef void (*grpc_udp_server_read_cb)(grpc_exec_ctx *exec_ctx, grpc_fd *emfd,
-                                        grpc_server *server);
+                                        struct grpc_server *server);
 
 /* Create a server, initially not bound to any ports */
 grpc_udp_server *grpc_udp_server_create(void);
@@ -53,7 +54,7 @@ grpc_udp_server *grpc_udp_server_create(void);
 /* Start listening to bound ports */
 void grpc_udp_server_start(grpc_exec_ctx *exec_ctx, grpc_udp_server *udp_server,
                            grpc_pollset **pollsets, size_t pollset_count,
-                           grpc_server *server);
+                           struct grpc_server *server);
 
 int grpc_udp_server_get_fd(grpc_udp_server *s, unsigned index);
 
diff --git a/src/core/iomgr/unix_sockets_posix.c b/src/core/iomgr/unix_sockets_posix.c
new file mode 100644
index 0000000000..480ff613f6
--- /dev/null
+++ b/src/core/iomgr/unix_sockets_posix.c
@@ -0,0 +1,103 @@
+/*
+ *
+ * Copyright 2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#include "src/core/iomgr/unix_sockets_posix.h"
+
+#ifdef GPR_HAVE_UNIX_SOCKET
+
+#include <string.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <sys/un.h>
+
+#include <grpc/support/alloc.h>
+
+void grpc_create_socketpair_if_unix(int sv[2]) {
+  GPR_ASSERT(socketpair(AF_UNIX, SOCK_STREAM, 0, sv) == 0);
+}
+
+grpc_resolved_addresses *grpc_resolve_unix_domain_address(const char *name) {
+  struct sockaddr_un *un;
+
+  grpc_resolved_addresses *addrs = gpr_malloc(sizeof(grpc_resolved_addresses));
+  addrs->naddrs = 1;
+  addrs->addrs = gpr_malloc(sizeof(grpc_resolved_address));
+  un = (struct sockaddr_un *)addrs->addrs->addr;
+  un->sun_family = AF_UNIX;
+  strcpy(un->sun_path, name);
+  addrs->addrs->len = strlen(un->sun_path) + sizeof(un->sun_family) + 1;
+  return addrs;
+}
+
+int grpc_is_unix_socket(const struct sockaddr *addr) {
+  return addr->sa_family == AF_UNIX;
+}
+
+void grpc_unlink_if_unix_domain_socket(const struct sockaddr *addr) {
+  if (addr->sa_family != AF_UNIX) {
+    return;
+  }
+  struct sockaddr_un *un = (struct sockaddr_un *)addr;
+  struct stat st;
+
+  if (stat(un->sun_path, &st) == 0 && (st.st_mode & S_IFMT) == S_IFSOCK) {
+    unlink(un->sun_path);
+  }
+}
+
+int grpc_parse_unix(grpc_uri *uri, struct sockaddr_storage *addr, size_t *len) {
+  struct sockaddr_un *un = (struct sockaddr_un *)addr;
+
+  un->sun_family = AF_UNIX;
+  strcpy(un->sun_path, uri->path);
+  *len = strlen(un->sun_path) + sizeof(un->sun_family) + 1;
+
+  return 1;
+}
+
+char *grpc_unix_get_default_authority(grpc_resolver_factory *factory,
+                                      grpc_uri *uri) {
+  return gpr_strdup("localhost");
+}
+
+char *grpc_sockaddr_to_uri_unix_if_possible(const struct sockaddr *addr) {
+  if (addr->sa_family != AF_UNIX) {
+    return NULL;
+  }
+
+  char *result;
+  gpr_asprintf(&result, "unix:%s", ((struct sockaddr_un *)addr)->sun_path);
+  return result;
+}
+
+#endif
diff --git a/src/core/channel/client_uchannel.h b/src/core/iomgr/unix_sockets_posix.h
index 8bb288e7d4..e842ba3770 100644
--- a/src/core/channel/client_uchannel.h
+++ b/src/core/iomgr/unix_sockets_posix.h
@@ -1,6 +1,6 @@
 /*
  *
- * Copyright 2015-2016, Google Inc.
+ * Copyright 2016, Google Inc.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -31,30 +31,31 @@
  *
  */
 
-#ifndef GRPC_CORE_CHANNEL_CLIENT_UCHANNEL_H
-#define GRPC_CORE_CHANNEL_CLIENT_UCHANNEL_H
+#ifndef GRPC_CORE_IOMGR_UNIX_SOCKETS_POSIX_H
+#define GRPC_CORE_IOMGR_UNIX_SOCKETS_POSIX_H
 
-#include "src/core/channel/channel_stack.h"
-#include "src/core/client_config/resolver.h"
+#include <grpc/support/port_platform.h>
 
-#define GRPC_MICROCHANNEL_SUBCHANNEL_ARG "grpc.microchannel_subchannel_key"
+#include <grpc/support/string_util.h>
 
-/* A client microchannel (aka uchannel) is a channel wrapping a subchannel, for
- * the purposes of lightweight RPC communications from within the core.*/
+#include "src/core/client_config/resolver_factory.h"
+#include "src/core/client_config/uri_parser.h"
+#include "src/core/iomgr/resolve_address.h"
+#include "src/core/iomgr/sockaddr.h"
 
-extern const grpc_channel_filter grpc_client_uchannel_filter;
+void grpc_create_socketpair_if_unix(int sv[2]);
 
-grpc_connectivity_state grpc_client_uchannel_check_connectivity_state(
-    grpc_exec_ctx *exec_ctx, grpc_channel_element *elem, int try_to_connect);
+grpc_resolved_addresses *grpc_resolve_unix_domain_address(const char *name);
 
-void grpc_client_uchannel_watch_connectivity_state(
-    grpc_exec_ctx *exec_ctx, grpc_channel_element *elem, grpc_pollset *pollset,
-    grpc_connectivity_state *state, grpc_closure *on_complete);
+int grpc_is_unix_socket(const struct sockaddr *addr);
 
-grpc_channel *grpc_client_uchannel_create(grpc_subchannel *subchannel,
-                                          grpc_channel_args *args);
+void grpc_unlink_if_unix_domain_socket(const struct sockaddr *addr);
 
-void grpc_client_uchannel_set_connected_subchannel(
-    grpc_channel *uchannel, grpc_connected_subchannel *connected_subchannel);
+int grpc_parse_unix(grpc_uri *uri, struct sockaddr_storage *addr, size_t *len);
 
-#endif /* GRPC_CORE_CHANNEL_CLIENT_UCHANNEL_H */
+char *grpc_unix_get_default_authority(grpc_resolver_factory *factory,
+                                      grpc_uri *uri);
+
+char *grpc_sockaddr_to_uri_unix_if_possible(const struct sockaddr *addr);
+
+#endif /* GRPC_CORE_IOMGR_UNIX_SOCKETS_POSIX_H */
diff --git a/src/core/httpcli/parser.h b/src/core/iomgr/unix_sockets_posix_noop.c
index cd4a737245..045467bea4 100644
--- a/src/core/httpcli/parser.h
+++ b/src/core/iomgr/unix_sockets_posix_noop.c
@@ -1,6 +1,6 @@
 /*
  *
- * Copyright 2015-2016, Google Inc.
+ * Copyright 2016, Google Inc.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -31,34 +31,31 @@
  *
  */
 
-#ifndef GRPC_CORE_HTTPCLI_PARSER_H
-#define GRPC_CORE_HTTPCLI_PARSER_H
+#include "src/core/iomgr/unix_sockets_posix.h"
 
-#include "src/core/httpcli/httpcli.h"
-#include <grpc/support/port_platform.h>
-#include <grpc/support/slice.h>
+#ifndef GPR_HAVE_UNIX_SOCKET
 
-typedef enum {
-  GRPC_HTTPCLI_INITIAL_RESPONSE,
-  GRPC_HTTPCLI_HEADERS,
-  GRPC_HTTPCLI_BODY
-} grpc_httpcli_parser_state;
+void grpc_create_socketpair_if_unix(int sv[2]) {}
 
-typedef struct {
-  grpc_httpcli_parser_state state;
+grpc_resolved_addresses *grpc_resolve_unix_domain_address(const char *name) {
+  return NULL;
+}
 
-  grpc_httpcli_response r;
-  size_t body_capacity;
-  size_t hdr_capacity;
+int grpc_is_unix_socket(const struct sockaddr *addr) { return false; }
 
-  uint8_t cur_line[GRPC_HTTPCLI_MAX_HEADER_LENGTH];
-  size_t cur_line_length;
-} grpc_httpcli_parser;
+void grpc_unlink_if_unix_domain_socket(const struct sockaddr *addr) {}
 
-void grpc_httpcli_parser_init(grpc_httpcli_parser* parser);
-void grpc_httpcli_parser_destroy(grpc_httpcli_parser* parser);
+int grpc_parse_unix(grpc_uri *uri, struct sockaddr_storage *addr, size_t *len) {
+  return 0;
+}
 
-int grpc_httpcli_parser_parse(grpc_httpcli_parser* parser, gpr_slice slice);
-int grpc_httpcli_parser_eof(grpc_httpcli_parser* parser);
+char *grpc_unix_get_default_authority(grpc_resolver_factory *factory,
+                                      grpc_uri *uri) {
+  return NULL;
+}
 
-#endif /* GRPC_CORE_HTTPCLI_PARSER_H */
+char *grpc_sockaddr_to_uri_unix_if_possible(const struct sockaddr *addr) {
+  return NULL;
+}
+
+#endif
diff --git a/src/core/iomgr/wakeup_fd_pipe.c b/src/core/iomgr/wakeup_fd_pipe.c
index 80de181d9d..dd2fd1f057 100644
--- a/src/core/iomgr/wakeup_fd_pipe.c
+++ b/src/core/iomgr/wakeup_fd_pipe.c
@@ -1,6 +1,6 @@
 /*
  *
- * Copyright 2015, Google Inc.
+ * Copyright 2015-2016, Google Inc.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -41,13 +41,18 @@
 #include <string.h>
 #include <unistd.h>
 
-#include "src/core/iomgr/socket_utils_posix.h"
 #include <grpc/support/log.h>
 
+#include "src/core/iomgr/socket_utils_posix.h"
+
 static void pipe_init(grpc_wakeup_fd* fd_info) {
   int pipefd[2];
   /* TODO(klempner): Make this nonfatal */
-  GPR_ASSERT(0 == pipe(pipefd));
+  int r = pipe(pipefd);
+  if (0 != r) {
+    gpr_log(GPR_ERROR, "pipe creation failed (%d): %s", errno, strerror(errno));
+    abort();
+  }
   GPR_ASSERT(grpc_set_socket_nonblocking(pipefd[0], 1));
   GPR_ASSERT(grpc_set_socket_nonblocking(pipefd[1], 1));
   fd_info->read_fd = pipefd[0];
diff --git a/src/core/security/credentials.c b/src/core/security/credentials.c
index b4fa616fa7..0ba6d5dd84 100644
--- a/src/core/security/credentials.c
+++ b/src/core/security/credentials.c
@@ -38,7 +38,8 @@
 
 #include "src/core/channel/channel_args.h"
 #include "src/core/channel/http_client_filter.h"
-#include "src/core/httpcli/httpcli.h"
+#include "src/core/http/parser.h"
+#include "src/core/http/httpcli.h"
 #include "src/core/iomgr/executor.h"
 #include "src/core/json/json.h"
 #include "src/core/support/string.h"
@@ -539,7 +540,7 @@ static void oauth2_token_fetcher_destruct(grpc_call_credentials *creds) {
 
 grpc_credentials_status
 grpc_oauth2_token_fetcher_credentials_parse_server_response(
-    const grpc_httpcli_response *response, grpc_credentials_md_store **token_md,
+    const grpc_http_response *response, grpc_credentials_md_store **token_md,
     gpr_timespec *token_lifetime) {
   char *null_terminated_body = NULL;
   char *new_access_token = NULL;
@@ -629,7 +630,7 @@ end:
 
 static void on_oauth2_token_fetcher_http_response(
     grpc_exec_ctx *exec_ctx, void *user_data,
-    const grpc_httpcli_response *response) {
+    const grpc_http_response *response) {
   grpc_credentials_metadata_request *r =
       (grpc_credentials_metadata_request *)user_data;
   grpc_oauth2_token_fetcher_credentials *c =
@@ -706,13 +707,13 @@ static void compute_engine_fetch_oauth2(
     grpc_exec_ctx *exec_ctx, grpc_credentials_metadata_request *metadata_req,
     grpc_httpcli_context *httpcli_context, grpc_pollset *pollset,
     grpc_httpcli_response_cb response_cb, gpr_timespec deadline) {
-  grpc_httpcli_header header = {"Metadata-Flavor", "Google"};
+  grpc_http_header header = {"Metadata-Flavor", "Google"};
   grpc_httpcli_request request;
   memset(&request, 0, sizeof(grpc_httpcli_request));
   request.host = GRPC_COMPUTE_ENGINE_METADATA_HOST;
-  request.path = GRPC_COMPUTE_ENGINE_METADATA_TOKEN_PATH;
-  request.hdr_count = 1;
-  request.hdrs = &header;
+  request.http.path = GRPC_COMPUTE_ENGINE_METADATA_TOKEN_PATH;
+  request.http.hdr_count = 1;
+  request.http.hdrs = &header;
   grpc_httpcli_get(exec_ctx, httpcli_context, pollset, &request, deadline,
                    response_cb, metadata_req);
 }
@@ -747,8 +748,8 @@ static void refresh_token_fetch_oauth2(
     grpc_httpcli_response_cb response_cb, gpr_timespec deadline) {
   grpc_google_refresh_token_credentials *c =
       (grpc_google_refresh_token_credentials *)metadata_req->creds;
-  grpc_httpcli_header header = {"Content-Type",
-                                "application/x-www-form-urlencoded"};
+  grpc_http_header header = {"Content-Type",
+                             "application/x-www-form-urlencoded"};
   grpc_httpcli_request request;
   char *body = NULL;
   gpr_asprintf(&body, GRPC_REFRESH_TOKEN_POST_BODY_FORMAT_STRING,
@@ -756,9 +757,9 @@ static void refresh_token_fetch_oauth2(
                c->refresh_token.refresh_token);
   memset(&request, 0, sizeof(grpc_httpcli_request));
   request.host = GRPC_GOOGLE_OAUTH2_SERVICE_HOST;
-  request.path = GRPC_GOOGLE_OAUTH2_SERVICE_TOKEN_PATH;
-  request.hdr_count = 1;
-  request.hdrs = &header;
+  request.http.path = GRPC_GOOGLE_OAUTH2_SERVICE_TOKEN_PATH;
+  request.http.hdr_count = 1;
+  request.http.hdrs = &header;
   request.handshaker = &grpc_httpcli_ssl;
   grpc_httpcli_post(exec_ctx, httpcli_context, pollset, &request, body,
                     strlen(body), deadline, response_cb, metadata_req);
diff --git a/src/core/security/credentials.h b/src/core/security/credentials.h
index 133aa9d8d9..afac7a5bf2 100644
--- a/src/core/security/credentials.h
+++ b/src/core/security/credentials.h
@@ -39,11 +39,12 @@
 #include <grpc/grpc_security.h>
 #include <grpc/support/sync.h>
 
-#include "src/core/httpcli/httpcli.h"
+#include "src/core/http/httpcli.h"
+#include "src/core/http/parser.h"
 #include "src/core/security/json_token.h"
 #include "src/core/security/security_connector.h"
 
-struct grpc_httpcli_response;
+struct grpc_http_response;
 
 /* --- Constants. --- */
 
@@ -207,7 +208,7 @@ grpc_call_credentials *grpc_credentials_contains_type(
 /* Exposed for testing only. */
 grpc_credentials_status
 grpc_oauth2_token_fetcher_credentials_parse_server_response(
-    const struct grpc_httpcli_response *response,
+    const struct grpc_http_response *response,
     grpc_credentials_md_store **token_md, gpr_timespec *token_lifetime);
 
 void grpc_flush_cached_google_default_credentials(void);
diff --git a/src/core/security/google_default_credentials.c b/src/core/security/google_default_credentials.c
index 1f4f3e4aa5..3872e86993 100644
--- a/src/core/security/google_default_credentials.c
+++ b/src/core/security/google_default_credentials.c
@@ -39,7 +39,8 @@
 #include <grpc/support/log.h>
 #include <grpc/support/sync.h>
 
-#include "src/core/httpcli/httpcli.h"
+#include "src/core/http/httpcli.h"
+#include "src/core/http/parser.h"
 #include "src/core/support/env.h"
 #include "src/core/support/load_file.h"
 #include "src/core/surface/api_trace.h"
@@ -66,14 +67,14 @@ typedef struct {
 
 static void on_compute_engine_detection_http_response(
     grpc_exec_ctx *exec_ctx, void *user_data,
-    const grpc_httpcli_response *response) {
+    const grpc_http_response *response) {
   compute_engine_detector *detector = (compute_engine_detector *)user_data;
   if (response != NULL && response->status == 200 && response->hdr_count > 0) {
     /* Internet providers can return a generic response to all requests, so
        it is necessary to check that metadata header is present also. */
     size_t i;
     for (i = 0; i < response->hdr_count; i++) {
-      grpc_httpcli_header *header = &response->hdrs[i];
+      grpc_http_header *header = &response->hdrs[i];
       if (strcmp(header->key, "Metadata-Flavor") == 0 &&
           strcmp(header->value, "Google") == 0) {
         detector->success = 1;
@@ -109,7 +110,7 @@ static int is_stack_running_on_compute_engine(void) {
 
   memset(&request, 0, sizeof(grpc_httpcli_request));
   request.host = GRPC_COMPUTE_ENGINE_DETECTION_HOST;
-  request.path = "/";
+  request.http.path = "/";
 
   grpc_httpcli_context_init(&context);
 
diff --git a/src/core/security/jwt_verifier.c b/src/core/security/jwt_verifier.c
index 928c6c148d..0bb8e05306 100644
--- a/src/core/security/jwt_verifier.c
+++ b/src/core/security/jwt_verifier.c
@@ -36,7 +36,7 @@
 #include <limits.h>
 #include <string.h>
 
-#include "src/core/httpcli/httpcli.h"
+#include "src/core/http/httpcli.h"
 #include "src/core/security/b64.h"
 #include "src/core/tsi/ssl_types.h"
 
@@ -635,11 +635,11 @@ static void on_openid_config_retrieved(grpc_exec_ctx *exec_ctx, void *user_data,
   jwks_uri += 8;
   req.handshaker = &grpc_httpcli_ssl;
   req.host = gpr_strdup(jwks_uri);
-  req.path = strchr(jwks_uri, '/');
-  if (req.path == NULL) {
-    req.path = "";
+  req.http.path = strchr(jwks_uri, '/');
+  if (req.http.path == NULL) {
+    req.http.path = "";
   } else {
-    *(req.host + (req.path - jwks_uri)) = '\0';
+    *(req.host + (req.http.path - jwks_uri)) = '\0';
   }
   grpc_httpcli_get(
       exec_ctx, &ctx->verifier->http_ctx, ctx->pollset, &req,
@@ -725,20 +725,20 @@ static void retrieve_key_and_verify(grpc_exec_ctx *exec_ctx,
     req.host = gpr_strdup(mapping->key_url_prefix);
     path_prefix = strchr(req.host, '/');
     if (path_prefix == NULL) {
-      gpr_asprintf(&req.path, "/%s", iss);
+      gpr_asprintf(&req.http.path, "/%s", iss);
     } else {
       *(path_prefix++) = '\0';
-      gpr_asprintf(&req.path, "/%s/%s", path_prefix, iss);
+      gpr_asprintf(&req.http.path, "/%s/%s", path_prefix, iss);
     }
     http_cb = on_keys_retrieved;
   } else {
     req.host = gpr_strdup(strstr(iss, "https://") == iss ? iss + 8 : iss);
     path_prefix = strchr(req.host, '/');
     if (path_prefix == NULL) {
-      req.path = gpr_strdup(GRPC_OPENID_CONFIG_URL_SUFFIX);
+      req.http.path = gpr_strdup(GRPC_OPENID_CONFIG_URL_SUFFIX);
     } else {
       *(path_prefix++) = 0;
-      gpr_asprintf(&req.path, "/%s%s", path_prefix,
+      gpr_asprintf(&req.http.path, "/%s%s", path_prefix,
                    GRPC_OPENID_CONFIG_URL_SUFFIX);
     }
     http_cb = on_openid_config_retrieved;
@@ -749,7 +749,7 @@ static void retrieve_key_and_verify(grpc_exec_ctx *exec_ctx,
       gpr_time_add(gpr_now(GPR_CLOCK_REALTIME), grpc_jwt_verifier_max_delay),
       http_cb, ctx);
   gpr_free(req.host);
-  gpr_free(req.path);
+  gpr_free(req.http.path);
   return;
 
 error:
diff --git a/src/core/support/backoff.c b/src/core/support/backoff.c
index 7458219645..4ccfb774ed 100644
--- a/src/core/support/backoff.c
+++ b/src/core/support/backoff.c
@@ -69,3 +69,8 @@ gpr_timespec gpr_backoff_step(gpr_backoff *backoff, gpr_timespec now) {
   return gpr_time_add(
       now, gpr_time_from_millis(backoff->current_timeout_millis, GPR_TIMESPAN));
 }
+
+void gpr_backoff_reset(gpr_backoff *backoff) {
+  // forces step() to return a timeout of min_timeout_millis
+  backoff->current_timeout_millis = 0;
+}
diff --git a/src/core/support/backoff.h b/src/core/support/backoff.h
index f7730fde2a..0f933c3149 100644
--- a/src/core/support/backoff.h
+++ b/src/core/support/backoff.h
@@ -61,5 +61,8 @@ void gpr_backoff_init(gpr_backoff *backoff, double multiplier, double jitter,
 gpr_timespec gpr_backoff_begin(gpr_backoff *backoff, gpr_timespec now);
 /// Step a retry loop: returns a timespec for the NEXT retry
 gpr_timespec gpr_backoff_step(gpr_backoff *backoff, gpr_timespec now);
+/// Reset the backoff, so the next gpr_backoff_step will be a gpr_backoff_begin
+/// instead
+void gpr_backoff_reset(gpr_backoff *backoff);
 
 #endif /* GRPC_CORE_SUPPORT_BACKOFF_H */
diff --git a/src/core/surface/channel_connectivity.c b/src/core/surface/channel_connectivity.c
index 2dd4fce26b..18267939ed 100644
--- a/src/core/surface/channel_connectivity.c
+++ b/src/core/surface/channel_connectivity.c
@@ -37,7 +37,6 @@
 #include <grpc/support/log.h>
 
 #include "src/core/channel/client_channel.h"
-#include "src/core/channel/client_uchannel.h"
 #include "src/core/iomgr/timer.h"
 #include "src/core/surface/api_trace.h"
 #include "src/core/surface/completion_queue.h"
@@ -58,12 +57,6 @@ grpc_connectivity_state grpc_channel_check_connectivity_state(
     grpc_exec_ctx_finish(&exec_ctx);
     return state;
   }
-  if (client_channel_elem->filter == &grpc_client_uchannel_filter) {
-    state = grpc_client_uchannel_check_connectivity_state(
-        &exec_ctx, client_channel_elem, try_to_connect);
-    grpc_exec_ctx_finish(&exec_ctx);
-    return state;
-  }
   gpr_log(GPR_ERROR,
           "grpc_channel_check_connectivity_state called on something that is "
           "not a (u)client channel, but '%s'",
@@ -98,9 +91,6 @@ static void delete_state_watcher(grpc_exec_ctx *exec_ctx, state_watcher *w) {
   if (client_channel_elem->filter == &grpc_client_channel_filter) {
     GRPC_CHANNEL_INTERNAL_UNREF(exec_ctx, w->channel,
                                 "watch_channel_connectivity");
-  } else if (client_channel_elem->filter == &grpc_client_uchannel_filter) {
-    GRPC_CHANNEL_INTERNAL_UNREF(exec_ctx, w->channel,
-                                "watch_uchannel_connectivity");
   } else {
     abort();
   }
@@ -209,11 +199,8 @@ void grpc_channel_watch_connectivity_state(
     grpc_client_channel_watch_connectivity_state(&exec_ctx, client_channel_elem,
                                                  grpc_cq_pollset(cq), &w->state,
                                                  &w->on_complete);
-  } else if (client_channel_elem->filter == &grpc_client_uchannel_filter) {
-    GRPC_CHANNEL_INTERNAL_REF(channel, "watch_uchannel_connectivity");
-    grpc_client_uchannel_watch_connectivity_state(
-        &exec_ctx, client_channel_elem, grpc_cq_pollset(cq), &w->state,
-        &w->on_complete);
+  } else {
+    abort();
   }
 
   grpc_exec_ctx_finish(&exec_ctx);
diff --git a/src/core/surface/channel_init.c b/src/core/surface/channel_init.c
index 538be84696..ac962f3972 100644
--- a/src/core/surface/channel_init.c
+++ b/src/core/surface/channel_init.c
@@ -112,8 +112,6 @@ static const char *name_for_type(grpc_channel_stack_type type) {
       return "CLIENT_SUBCHANNEL";
     case GRPC_SERVER_CHANNEL:
       return "SERVER_CHANNEL";
-    case GRPC_CLIENT_UCHANNEL:
-      return "CLIENT_UCHANNEL";
     case GRPC_CLIENT_LAME_CHANNEL:
       return "CLIENT_LAME_CHANNEL";
     case GRPC_CLIENT_DIRECT_CHANNEL:
diff --git a/src/core/surface/channel_stack_type.c b/src/core/surface/channel_stack_type.c
index 6fd33d411d..29bb7704f8 100644
--- a/src/core/surface/channel_stack_type.c
+++ b/src/core/surface/channel_stack_type.c
@@ -39,8 +39,6 @@ bool grpc_channel_stack_type_is_client(grpc_channel_stack_type type) {
   switch (type) {
     case GRPC_CLIENT_CHANNEL:
       return true;
-    case GRPC_CLIENT_UCHANNEL:
-      return true;
     case GRPC_CLIENT_SUBCHANNEL:
       return true;
     case GRPC_CLIENT_LAME_CHANNEL:
diff --git a/src/core/surface/channel_stack_type.h b/src/core/surface/channel_stack_type.h
index 846391a68a..75a1b9c072 100644
--- a/src/core/surface/channel_stack_type.h
+++ b/src/core/surface/channel_stack_type.h
@@ -39,9 +39,6 @@
 typedef enum {
   // normal top-half client channel with load-balancing, connection management
   GRPC_CLIENT_CHANNEL,
-  // abbreviated top-half client channel bound to one subchannel - for internal
-  // load balancing implementation
-  GRPC_CLIENT_UCHANNEL,
   // bottom-half of a client channel: everything that happens post-load
   // balancing (bound to a specific transport)
   GRPC_CLIENT_SUBCHANNEL,
diff --git a/src/core/surface/init.c b/src/core/surface/init.c
index b50770959f..2ce50a0d82 100644
--- a/src/core/surface/init.c
+++ b/src/core/surface/init.c
@@ -45,7 +45,6 @@
 #include "src/core/channel/compress_filter.h"
 #include "src/core/channel/connected_channel.h"
 #include "src/core/channel/client_channel.h"
-#include "src/core/channel/client_uchannel.h"
 #include "src/core/channel/http_client_filter.h"
 #include "src/core/channel/http_server_filter.h"
 #include "src/core/client_config/lb_policy_registry.h"
@@ -112,9 +111,6 @@ static void register_builtin_channel_init() {
   grpc_channel_init_register_stage(GRPC_CLIENT_DIRECT_CHANNEL, INT_MAX,
                                    prepend_filter,
                                    (void *)&grpc_compress_filter);
-  grpc_channel_init_register_stage(GRPC_CLIENT_UCHANNEL, INT_MAX,
-                                   prepend_filter,
-                                   (void *)&grpc_compress_filter);
   grpc_channel_init_register_stage(GRPC_SERVER_CHANNEL, INT_MAX, prepend_filter,
                                    (void *)&grpc_compress_filter);
   grpc_channel_init_register_stage(GRPC_CLIENT_SUBCHANNEL, INT_MAX,
@@ -134,8 +130,6 @@ static void register_builtin_channel_init() {
                                    grpc_add_connected_filter, NULL);
   grpc_channel_init_register_stage(GRPC_CLIENT_CHANNEL, INT_MAX, append_filter,
                                    (void *)&grpc_client_channel_filter);
-  grpc_channel_init_register_stage(GRPC_CLIENT_UCHANNEL, INT_MAX, append_filter,
-                                   (void *)&grpc_client_uchannel_filter);
   grpc_channel_init_register_stage(GRPC_CLIENT_LAME_CHANNEL, INT_MAX,
                                    append_filter, (void *)&grpc_lame_filter);
   grpc_channel_init_register_stage(GRPC_SERVER_CHANNEL, INT_MAX, prepend_filter,
diff --git a/src/core/transport/chttp2/timeout_encoding.c b/src/core/transport/chttp2/timeout_encoding.c
index a6f7081d21..c4802e050e 100644
--- a/src/core/transport/chttp2/timeout_encoding.c
+++ b/src/core/transport/chttp2/timeout_encoding.c
@@ -150,7 +150,7 @@ int grpc_chttp2_decode_timeout(const char *buffer, gpr_timespec *timeout) {
     /* spec allows max. 8 digits, but we allow values up to 1,000,000,000 */
     if (x >= (100 * 1000 * 1000)) {
       if (x != (100 * 1000 * 1000) || digit != 0) {
-        *timeout = gpr_inf_future(GPR_CLOCK_REALTIME);
+        *timeout = gpr_inf_future(GPR_TIMESPAN);
         return 1;
       }
     }
diff --git a/src/core/transport/static_metadata.c b/src/core/transport/static_metadata.c
index eeedae0619..84abb59e99 100644
--- a/src/core/transport/static_metadata.c
+++ b/src/core/transport/static_metadata.c
@@ -50,7 +50,7 @@ grpc_mdstr grpc_static_mdstr_table[GRPC_STATIC_MDSTR_COUNT];
 grpc_mdelem grpc_static_mdelem_table[GRPC_STATIC_MDELEM_COUNT];
 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, 3, 7, 5, 2, 4, 8, 6, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 4, 8, 6, 2, 4, 8, 6, 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};
 
diff --git a/src/node/ext/call_credentials.cc b/src/node/ext/call_credentials.cc
index 98696db232..bd2d146bbc 100644
--- a/src/node/ext/call_credentials.cc
+++ b/src/node/ext/call_credentials.cc
@@ -35,6 +35,8 @@
 #include <nan.h>
 #include <uv.h>
 
+#include <list>
+
 #include "grpc/grpc.h"
 #include "grpc/grpc_security.h"
 #include "grpc/support/log.h"
@@ -161,6 +163,15 @@ NAN_METHOD(CallCredentials::CreateFromPlugin) {
   grpc_metadata_credentials_plugin plugin;
   plugin_state *state = new plugin_state;
   state->callback = new Nan::Callback(info[0].As<Function>());
+  state->pending_callbacks = new std::list<plugin_callback_data*>();
+  uv_mutex_init(&state->plugin_mutex);
+  uv_async_init(uv_default_loop(),
+                &state->plugin_async,
+                SendPluginCallback);
+  uv_unref((uv_handle_t*)&state->plugin_async);
+
+  state->plugin_async.data = state;
+
   plugin.get_metadata = plugin_get_metadata;
   plugin.destroy = plugin_destroy_state;
   plugin.state = reinterpret_cast<void*>(state);
@@ -208,48 +219,60 @@ NAN_METHOD(PluginCallback) {
 
 NAUV_WORK_CB(SendPluginCallback) {
   Nan::HandleScope scope;
-  plugin_callback_data *data = reinterpret_cast<plugin_callback_data*>(
-      async->data);
-  // Attach cb and user_data to plugin_callback so that it can access them later
-  v8::Local<v8::Function> plugin_callback = Nan::GetFunction(
-      Nan::New<v8::FunctionTemplate>(PluginCallback)).ToLocalChecked();
-  Nan::Set(plugin_callback, Nan::New("cb").ToLocalChecked(),
-           Nan::New<v8::External>(reinterpret_cast<void*>(data->cb)));
-  Nan::Set(plugin_callback, Nan::New("user_data").ToLocalChecked(),
-           Nan::New<v8::External>(data->user_data));
-  const int argc = 2;
-  v8::Local<v8::Value> argv[argc] = {
-    Nan::New(data->service_url).ToLocalChecked(),
-    plugin_callback
-  };
-  Nan::Callback *callback = data->state->callback;
-  callback->Call(argc, argv);
-  delete data;
-  uv_unref((uv_handle_t *)async);
-  uv_close((uv_handle_t *)async, (uv_close_cb)free);
+  plugin_state *state = reinterpret_cast<plugin_state*>(async->data);
+  std::list<plugin_callback_data*> callbacks;
+  uv_mutex_lock(&state->plugin_mutex);
+  callbacks.splice(callbacks.begin(), *state->pending_callbacks);
+  uv_mutex_unlock(&state->plugin_mutex);
+  while (!callbacks.empty()) {
+    plugin_callback_data *data = callbacks.front();
+    callbacks.pop_front();
+    // Attach cb and user_data to plugin_callback so that it can access them later
+    v8::Local<v8::Function> plugin_callback = Nan::GetFunction(
+        Nan::New<v8::FunctionTemplate>(PluginCallback)).ToLocalChecked();
+    Nan::Set(plugin_callback, Nan::New("cb").ToLocalChecked(),
+             Nan::New<v8::External>(reinterpret_cast<void*>(data->cb)));
+    Nan::Set(plugin_callback, Nan::New("user_data").ToLocalChecked(),
+             Nan::New<v8::External>(data->user_data));
+    const int argc = 2;
+    v8::Local<v8::Value> argv[argc] = {
+      Nan::New(data->service_url).ToLocalChecked(),
+      plugin_callback
+    };
+    Nan::Callback *callback = state->callback;
+    callback->Call(argc, argv);
+    delete data;
+  }
 }
 
 void plugin_get_metadata(void *state, grpc_auth_metadata_context context,
                          grpc_credentials_plugin_metadata_cb cb,
                          void *user_data) {
-  uv_async_t *async = static_cast<uv_async_t*>(malloc(sizeof(uv_async_t)));
-  uv_async_init(uv_default_loop(),
-                async,
-                SendPluginCallback);
+  plugin_state *p_state = reinterpret_cast<plugin_state*>(state);
   plugin_callback_data *data = new plugin_callback_data;
-  data->state = reinterpret_cast<plugin_state*>(state);
   data->service_url = context.service_url;
   data->cb = cb;
   data->user_data = user_data;
-  async->data = data;
-  /* libuv says that it will coalesce calls to uv_async_send. If there is ever a
-   * problem with a callback not getting called, that is probably the reason */
-  uv_async_send(async);
+
+  uv_mutex_lock(&p_state->plugin_mutex);
+  p_state->pending_callbacks->push_back(data);
+  uv_mutex_unlock(&p_state->plugin_mutex);
+
+  uv_async_send(&p_state->plugin_async);
+}
+
+void plugin_uv_close_cb(uv_handle_t *handle) {
+  uv_async_t *async = reinterpret_cast<uv_async_t*>(handle);
+  plugin_state *state = reinterpret_cast<plugin_state *>(async->data);
+  uv_mutex_destroy(&state->plugin_mutex);
+  delete state->pending_callbacks;
+  delete state->callback;
+  delete state;
 }
 
 void plugin_destroy_state(void *ptr) {
   plugin_state *state = reinterpret_cast<plugin_state *>(ptr);
-  delete state->callback;
+  uv_close((uv_handle_t*)&state->plugin_async, plugin_uv_close_cb);
 }
 
 }  // namespace node
diff --git a/src/node/ext/call_credentials.h b/src/node/ext/call_credentials.h
index a9bfe30f94..1f35595f3d 100644
--- a/src/node/ext/call_credentials.h
+++ b/src/node/ext/call_credentials.h
@@ -1,6 +1,6 @@
 /*
  *
- * Copyright 2015, Google Inc.
+ * Copyright 2015-2016, Google Inc.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -34,8 +34,11 @@
 #ifndef GRPC_NODE_CALL_CREDENTIALS_H_
 #define GRPC_NODE_CALL_CREDENTIALS_H_
 
+#include <list>
+
 #include <node.h>
 #include <nan.h>
+#include <uv.h>
 #include "grpc/grpc_security.h"
 
 namespace grpc {
@@ -73,17 +76,20 @@ class CallCredentials : public Nan::ObjectWrap {
 
 /* Auth metadata plugin functionality */
 
-typedef struct plugin_state {
-  Nan::Callback *callback;
-} plugin_state;
-
 typedef struct plugin_callback_data {
-  plugin_state *state;
   const char *service_url;
   grpc_credentials_plugin_metadata_cb cb;
   void *user_data;
 } plugin_callback_data;
 
+typedef struct plugin_state {
+  Nan::Callback *callback;
+  std::list<plugin_callback_data*> *pending_callbacks;
+  uv_mutex_t plugin_mutex;
+  // async.data == this
+  uv_async_t plugin_async;
+} plugin_state;
+
 void plugin_get_metadata(void *state, grpc_auth_metadata_context context,
                          grpc_credentials_plugin_metadata_cb cb,
                          void *user_data);
diff --git a/src/node/src/credentials.js b/src/node/src/credentials.js
index 1d73723cc0..97c4bd73ac 100644
--- a/src/node/src/credentials.js
+++ b/src/node/src/credentials.js
@@ -118,7 +118,6 @@ exports.createFromMetadataGenerator = function(metadata_generator) {
 exports.createFromGoogleCredential = function(google_credential) {
   return exports.createFromMetadataGenerator(function(auth_context, callback) {
     var service_url = auth_context.service_url;
-    console.log('Service URL:', service_url);
     google_credential.getRequestMetadata(service_url, function(err, header) {
       if (err) {
         console.log('Auth error:', err);
@@ -127,7 +126,6 @@ exports.createFromGoogleCredential = function(google_credential) {
       }
       var metadata = new Metadata();
       metadata.add('authorization', header.Authorization);
-      console.log(header.Authorization);
       callback(null, metadata);
     });
   });
diff --git a/src/objective-c/GRPCClient/GRPCCall.m b/src/objective-c/GRPCClient/GRPCCall.m
index 2d45818b6e..51263b073c 100644
--- a/src/objective-c/GRPCClient/GRPCCall.m
+++ b/src/objective-c/GRPCClient/GRPCCall.m
@@ -1,6 +1,6 @@
 /*
  *
- * Copyright 2015, Google Inc.
+ * Copyright 2015-2016, Google Inc.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -308,37 +308,30 @@ NSString * const kGRPCTrailersKey = @"io.grpc.TrailersKey";
 }
 
 - (void)invokeCall {
-  __weak GRPCCall *weakSelf = self;
   [self invokeCallWithHeadersHandler:^(NSDictionary *headers) {
     // Response headers received.
-    GRPCCall *strongSelf = weakSelf;
-    if (strongSelf) {
-      strongSelf.responseHeaders = headers;
-      [strongSelf startNextRead];
-    }
+    self.responseHeaders = headers;
+    [self startNextRead];
   } completionHandler:^(NSError *error, NSDictionary *trailers) {
-    GRPCCall *strongSelf = weakSelf;
-    if (strongSelf) {
-      strongSelf.responseTrailers = trailers;
-
-      if (error) {
-        NSMutableDictionary *userInfo = [NSMutableDictionary dictionary];
-        if (error.userInfo) {
-          [userInfo addEntriesFromDictionary:error.userInfo];
-        }
-        userInfo[kGRPCTrailersKey] = strongSelf.responseTrailers;
-        // TODO(jcanizales): The C gRPC library doesn't guarantee that the headers block will be
-        // called before this one, so an error might end up with trailers but no headers. We
-        // shouldn't call finishWithError until ater both blocks are called. It is also when this is
-        // done that we can provide a merged view of response headers and trailers in a thread-safe
-        // way.
-        if (strongSelf.responseHeaders) {
-          userInfo[kGRPCHeadersKey] = strongSelf.responseHeaders;
-        }
-        error = [NSError errorWithDomain:error.domain code:error.code userInfo:userInfo];
+    self.responseTrailers = trailers;
+
+    if (error) {
+      NSMutableDictionary *userInfo = [NSMutableDictionary dictionary];
+      if (error.userInfo) {
+        [userInfo addEntriesFromDictionary:error.userInfo];
+      }
+      userInfo[kGRPCTrailersKey] = self.responseTrailers;
+      // TODO(jcanizales): The C gRPC library doesn't guarantee that the headers block will be
+      // called before this one, so an error might end up with trailers but no headers. We
+      // shouldn't call finishWithError until ater both blocks are called. It is also when this is
+      // done that we can provide a merged view of response headers and trailers in a thread-safe
+      // way.
+      if (self.responseHeaders) {
+        userInfo[kGRPCHeadersKey] = self.responseHeaders;
       }
-      [strongSelf finishWithError:error];
+      error = [NSError errorWithDomain:error.domain code:error.code userInfo:userInfo];
     }
+    [self finishWithError:error];
   }];
   // Now that the RPC has been initiated, request writes can start.
   @synchronized(_requestWriter) {
@@ -377,7 +370,6 @@ NSString * const kGRPCTrailersKey = @"io.grpc.TrailersKey";
       [strongSelf finishWithError:[NSError errorWithDomain:kGRPCErrorDomain
                                                       code:GRPCErrorCodeUnavailable
                                                   userInfo:@{NSLocalizedDescriptionKey: @"Connectivity lost."}]];
-      [[GRPCHost hostWithAddress:strongSelf->_host] disconnect];
     }
   }];
 }
diff --git a/src/objective-c/GRPCClient/private/GRPCWrappedCall.m b/src/objective-c/GRPCClient/private/GRPCWrappedCall.m
index fe3d51da53..f6527e283c 100644
--- a/src/objective-c/GRPCClient/private/GRPCWrappedCall.m
+++ b/src/objective-c/GRPCClient/private/GRPCWrappedCall.m
@@ -1,6 +1,6 @@
 /*
  *
- * Copyright 2015, Google Inc.
+ * Copyright 2015-2016, Google Inc.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -54,7 +54,9 @@
 
 - (void)finish {
   if (_handler) {
-    _handler();
+    void(^handler)() = _handler;
+    _handler = nil;
+    handler();
   }
 }
 @end
diff --git a/src/proto/grpc/testing/metrics.proto b/src/proto/grpc/testing/metrics.proto
index 4485d3a53b..0cc4b60239 100644
--- a/src/proto/grpc/testing/metrics.proto
+++ b/src/proto/grpc/testing/metrics.proto
@@ -1,4 +1,3 @@
-
 // Copyright 2015, Google Inc.
 // All rights reserved.
 //
@@ -28,12 +27,17 @@
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
-// An integration test service that covers all the method signature permutations
-// of unary/streaming requests/responses.
+// Contains the definitions for a metrics service and the type of metrics
+// exposed by the service.
+//
+// Currently, 'Gauge' (i.e a metric that represents the measured value of
+// something at an instant of time) is the only metric type supported by the
+// service.
 syntax = "proto3";
 
 package grpc.testing;
 
+// Reponse message containing the gauge name and value
 message GaugeResponse {
   string name = 1;
   oneof value {
@@ -43,11 +47,18 @@ message GaugeResponse {
   }
 }
 
-message GaugeRequest { string name = 1; }
+// Request message containing the gauge name
+message GaugeRequest {
+  string name = 1;
+}
 
 message EmptyMessage {}
 
 service MetricsService {
+  // Returns the values of all the gauges that are currently being maintained by
+  // the service
   rpc GetAllGauges(EmptyMessage) returns (stream GaugeResponse);
+
+  // Returns the value of one gauge
   rpc GetGauge(GaugeRequest) returns (GaugeResponse);
 }
diff --git a/src/python/grpcio/grpc/_cython/_cygrpc/records.pyx.pxi b/src/python/grpcio/grpc/_cython/_cygrpc/records.pyx.pxi
index 851389a261..6ecdcf7222 100644
--- a/src/python/grpcio/grpc/_cython/_cygrpc/records.pyx.pxi
+++ b/src/python/grpcio/grpc/_cython/_cygrpc/records.pyx.pxi
@@ -254,7 +254,7 @@ cdef class ByteBuffer:
     if self.c_byte_buffer != NULL:
       with nogil:
         grpc_byte_buffer_reader_init(&reader, self.c_byte_buffer)
-      result = b""
+      result = bytearray()
       with nogil:
         while grpc_byte_buffer_reader_next(&reader, &data_slice):
           data_slice_pointer = gpr_slice_start_ptr(data_slice)
@@ -263,7 +263,7 @@ cdef class ByteBuffer:
             result += (<char *>data_slice_pointer)[:data_slice_length]
       with nogil:
         grpc_byte_buffer_reader_destroy(&reader)
-      return result
+      return bytes(result)
     else:
       return None
 
diff --git a/src/python/grpcio/grpc/framework/alpha/_face_utilities.py b/src/python/grpcio/grpc/framework/alpha/_face_utilities.py
index c97307df16..b5e4133cad 100644
--- a/src/python/grpcio/grpc/framework/alpha/_face_utilities.py
+++ b/src/python/grpcio/grpc/framework/alpha/_face_utilities.py
@@ -111,7 +111,7 @@ def break_down_invocation(service_name, method_descriptions):
   face_cardinalities = {}
   request_serializers = {}
   response_deserializers = {}
-  for name, method_description in method_descriptions.iteritems():
+  for name, method_description in six.iteritems(method_descriptions):
     qualified_name = _qualified_name(service_name, name)
     method_cardinality = method_description.cardinality()
     cardinalities[name] = method_description.cardinality()
@@ -139,7 +139,7 @@ def break_down_service(service_name, method_descriptions):
   implementations = {}
   request_deserializers = {}
   response_serializers = {}
-  for name, method_description in method_descriptions.iteritems():
+  for name, method_description in six.iteritems(method_descriptions):
     qualified_name = _qualified_name(service_name, name)
     method_cardinality = method_description.cardinality()
     if method_cardinality is interfaces.Cardinality.UNARY_UNARY:
diff --git a/src/python/grpcio/grpc/framework/alpha/_reexport.py b/src/python/grpcio/grpc/framework/alpha/_reexport.py
index 198cb95ad5..4ea0e94d80 100644
--- a/src/python/grpcio/grpc/framework/alpha/_reexport.py
+++ b/src/python/grpcio/grpc/framework/alpha/_reexport.py
@@ -1,4 +1,4 @@
-# Copyright 2015, Google Inc.
+# Copyright 2015-2016, Google Inc.
 # All rights reserved.
 #
 # Redistribution and use in source and binary forms, with or without
@@ -27,6 +27,8 @@
 # (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 # OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
+import six
+
 from grpc.framework.common import cardinality
 from grpc.framework.face import exceptions as face_exceptions
 from grpc.framework.face import interfaces as face_interfaces
@@ -181,7 +183,7 @@ def common_cardinality(early_adopter_cardinality):
 
 def common_cardinalities(early_adopter_cardinalities):
   common_cardinalities = {}
-  for name, early_adopter_cardinality in early_adopter_cardinalities.iteritems():
+  for name, early_adopter_cardinality in six.iteritems(early_adopter_cardinalities):
     common_cardinalities[name] = _EARLY_ADOPTER_CARDINALITY_TO_COMMON_CARDINALITY[
         early_adopter_cardinality]
   return common_cardinalities
diff --git a/src/python/grpcio/grpc/framework/crust/implementations.py b/src/python/grpcio/grpc/framework/crust/implementations.py
index 4ebc4e9ae8..d0ecafcaf6 100644
--- a/src/python/grpcio/grpc/framework/crust/implementations.py
+++ b/src/python/grpcio/grpc/framework/crust/implementations.py
@@ -1,4 +1,4 @@
-# Copyright 2015, Google Inc.
+# Copyright 2015-2016, Google Inc.
 # All rights reserved.
 #
 # Redistribution and use in source and binary forms, with or without
@@ -29,6 +29,8 @@
 
 """Entry points into the Crust layer of RPC Framework."""
 
+import six
+
 from grpc.framework.common import cardinality
 from grpc.framework.common import style
 from grpc.framework.crust import _calls
@@ -271,7 +273,7 @@ class _DynamicStub(face.DynamicStub):
 
 def _adapt_method_implementations(method_implementations, pool):
   adapted_implementations = {}
-  for name, method_implementation in method_implementations.iteritems():
+  for name, method_implementation in six.iteritems(method_implementations):
     if method_implementation.style is style.Service.INLINE:
       if method_implementation.cardinality is cardinality.Cardinality.UNARY_UNARY:
         adapted_implementations[name] = _service.adapt_inline_unary_unary(
diff --git a/src/python/grpcio/grpc/framework/face/implementations.py b/src/python/grpcio/grpc/framework/face/implementations.py
index 4a6de52974..9c75a5faf4 100644
--- a/src/python/grpcio/grpc/framework/face/implementations.py
+++ b/src/python/grpcio/grpc/framework/face/implementations.py
@@ -1,4 +1,4 @@
-# Copyright 2015, Google Inc.
+# Copyright 2015-2016, Google Inc.
 # All rights reserved.
 #
 # Redistribution and use in source and binary forms, with or without
@@ -29,6 +29,8 @@
 
 """Entry points into the Face layer of RPC Framework."""
 
+import six
+
 from grpc.framework.common import cardinality
 from grpc.framework.common import style
 from grpc.framework.base import exceptions as _base_exceptions
@@ -228,7 +230,7 @@ class _DynamicStub(interfaces.DynamicStub):
 
 def _adapt_method_implementations(method_implementations, pool):
   adapted_implementations = {}
-  for name, method_implementation in method_implementations.iteritems():
+  for name, method_implementation in six.iteritems(method_implementations):
     if method_implementation.style is style.Service.INLINE:
       if method_implementation.cardinality is cardinality.Cardinality.UNARY_UNARY:
         adapted_implementations[name] = _service.adapt_inline_value_in_value_out(
diff --git a/src/python/grpcio/grpc_core_dependencies.py b/src/python/grpcio/grpc_core_dependencies.py
index b9e7d8c898..27cd8d60bc 100644
--- a/src/python/grpcio/grpc_core_dependencies.py
+++ b/src/python/grpcio/grpc_core_dependencies.py
@@ -81,7 +81,6 @@ CORE_SOURCE_FILES = [
   'src/core/channel/channel_stack.c',
   'src/core/channel/channel_stack_builder.c',
   'src/core/channel/client_channel.c',
-  'src/core/channel/client_uchannel.c',
   'src/core/channel/compress_filter.c',
   'src/core/channel/connected_channel.c',
   'src/core/channel/http_client_filter.c',
@@ -109,9 +108,9 @@ CORE_SOURCE_FILES = [
   'src/core/compression/compression_algorithm.c',
   'src/core/compression/message_compress.c',
   'src/core/debug/trace.c',
-  'src/core/httpcli/format_request.c',
-  'src/core/httpcli/httpcli.c',
-  'src/core/httpcli/parser.c',
+  'src/core/http/format_request.c',
+  'src/core/http/httpcli.c',
+  'src/core/http/parser.c',
   'src/core/iomgr/closure.c',
   'src/core/iomgr/endpoint.c',
   'src/core/iomgr/endpoint_pair_posix.c',
@@ -146,6 +145,8 @@ CORE_SOURCE_FILES = [
   'src/core/iomgr/timer.c',
   'src/core/iomgr/timer_heap.c',
   'src/core/iomgr/udp_server.c',
+  'src/core/iomgr/unix_sockets_posix.c',
+  'src/core/iomgr/unix_sockets_posix_noop.c',
   'src/core/iomgr/wakeup_fd_eventfd.c',
   'src/core/iomgr/wakeup_fd_nospecial.c',
   'src/core/iomgr/wakeup_fd_pipe.c',
@@ -207,7 +208,7 @@ CORE_SOURCE_FILES = [
   'src/core/transport/static_metadata.c',
   'src/core/transport/transport.c',
   'src/core/transport/transport_op_string.c',
-  'src/core/httpcli/httpcli_security_connector.c',
+  'src/core/http/httpcli_security_connector.c',
   'src/core/security/b64.c',
   'src/core/security/client_auth_filter.c',
   'src/core/security/credentials.c',
diff --git a/src/python/grpcio/tests/__init__.py b/src/python/grpcio/tests/__init__.py
index b76b3985a1..c3b80d766d 100644
--- a/src/python/grpcio/tests/__init__.py
+++ b/src/python/grpcio/tests/__init__.py
@@ -1,4 +1,4 @@
-# Copyright 2015, Google Inc.
+# Copyright 2015-2016, Google Inc.
 # All rights reserved.
 #
 # Redistribution and use in source and binary forms, with or without
@@ -27,6 +27,8 @@
 # (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 # OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
+from __future__ import absolute_import
+
 from tests import _loader
 from tests import _runner
 
diff --git a/src/python/grpcio/tests/_loader.py b/src/python/grpcio/tests/_loader.py
index 6992029b5e..2f9e5c660e 100644
--- a/src/python/grpcio/tests/_loader.py
+++ b/src/python/grpcio/tests/_loader.py
@@ -1,4 +1,4 @@
-# Copyright 2015, Google Inc.
+# Copyright 2015-2016, Google Inc.
 # All rights reserved.
 #
 # Redistribution and use in source and binary forms, with or without
@@ -27,6 +27,8 @@
 # (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 # OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
+from __future__ import absolute_import
+
 import importlib
 import pkgutil
 import re
diff --git a/src/python/grpcio/tests/_result.py b/src/python/grpcio/tests/_result.py
index 0670be921f..065153f0c3 100644
--- a/src/python/grpcio/tests/_result.py
+++ b/src/python/grpcio/tests/_result.py
@@ -1,4 +1,4 @@
-# Copyright 2015, Google Inc.
+# Copyright 2015-2016, Google Inc.
 # All rights reserved.
 #
 # Redistribution and use in source and binary forms, with or without
@@ -27,7 +27,8 @@
 # (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 # OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
-import cStringIO as StringIO
+from __future__ import absolute_import
+
 import collections
 import itertools
 import traceback
@@ -35,6 +36,7 @@ import unittest
 from xml.etree import ElementTree
 
 import coverage
+from six import moves
 
 from tests import _loader
 
@@ -356,7 +358,7 @@ def _traceback_string(type, value, trace):
   Returns:
     str: Formatted exception descriptive string.
   """
-  buffer = StringIO.StringIO()
+  buffer = moves.cStringIO()
   traceback.print_exception(type, value, trace, file=buffer)
   return buffer.getvalue()
 
diff --git a/src/python/grpcio/tests/_runner.py b/src/python/grpcio/tests/_runner.py
index 3b5ca03dd9..e899154b0b 100644
--- a/src/python/grpcio/tests/_runner.py
+++ b/src/python/grpcio/tests/_runner.py
@@ -27,7 +27,8 @@
 # (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 # OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
-import cStringIO as StringIO
+from __future__ import absolute_import
+
 import collections
 import fcntl
 import multiprocessing
@@ -41,6 +42,8 @@ import time
 import unittest
 import uuid
 
+from six import moves
+
 from tests import _loader
 from tests import _result
 
@@ -143,7 +146,7 @@ class Runner(object):
                        for case in filtered_cases]
     case_id_by_case = dict((augmented_case.case, augmented_case.id)
                            for augmented_case in augmented_cases)
-    result_out = StringIO.StringIO()
+    result_out = moves.cStringIO()
     result = _result.TerminalResult(
         result_out, id_map=lambda case: case_id_by_case[case])
     stdout_pipe = CaptureFile(sys.stdout.fileno())
diff --git a/src/python/grpcio/tests/unit/_core_over_links_base_interface_test.py b/src/python/grpcio/tests/unit/_core_over_links_base_interface_test.py
index efc990421a..881633754c 100644
--- a/src/python/grpcio/tests/unit/_core_over_links_base_interface_test.py
+++ b/src/python/grpcio/tests/unit/_core_over_links_base_interface_test.py
@@ -1,4 +1,4 @@
-# Copyright 2015, Google Inc.
+# Copyright 2015-2016, Google Inc.
 # All rights reserved.
 #
 # Redistribution and use in source and binary forms, with or without
@@ -35,6 +35,8 @@ import random
 import time
 import unittest
 
+import six
+
 from grpc._adapter import _intermediary_low
 from grpc._links import invocation
 from grpc._links import service
@@ -68,7 +70,7 @@ def _serialization_behaviors_from_serializations(serializations):
   request_deserializers = {}
   response_serializers = {}
   response_deserializers = {}
-  for (group, method), serialization in serializations.iteritems():
+  for (group, method), serialization in six.iteritems(serializations):
     request_serializers[group, method] = serialization.serialize_request
     request_deserializers[group, method] = serialization.deserialize_request
     response_serializers[group, method] = serialization.serialize_response
diff --git a/src/python/grpcio/tests/unit/_crust_over_core_over_links_face_interface_test.py b/src/python/grpcio/tests/unit/_crust_over_core_over_links_face_interface_test.py
index 4faaaadc2b..3be3b051fb 100644
--- a/src/python/grpcio/tests/unit/_crust_over_core_over_links_face_interface_test.py
+++ b/src/python/grpcio/tests/unit/_crust_over_core_over_links_face_interface_test.py
@@ -1,4 +1,4 @@
-# Copyright 2015, Google Inc.
+# Copyright 2015-2016, Google Inc.
 # All rights reserved.
 #
 # Redistribution and use in source and binary forms, with or without
@@ -32,6 +32,8 @@
 import collections
 import unittest
 
+import six
+
 from grpc._adapter import _intermediary_low
 from grpc._links import invocation
 from grpc._links import service
@@ -59,7 +61,7 @@ def _serialization_behaviors_from_test_methods(test_methods):
   request_deserializers = {}
   response_serializers = {}
   response_deserializers = {}
-  for (group, method), test_method in test_methods.iteritems():
+  for (group, method), test_method in six.iteritems(test_methods):
     request_serializers[group, method] = test_method.serialize_request
     request_deserializers[group, method] = test_method.deserialize_request
     response_serializers[group, method] = test_method.serialize_response
@@ -108,7 +110,7 @@ class _Implementation(test_interfaces.Implementation):
     # _digest.TestServiceDigest.
     cardinalities = {
         method: method_object.cardinality()
-        for (group, method), method_object in methods.iteritems()}
+        for (group, method), method_object in six.iteritems(methods)}
     dynamic_stub = crust_implementations.dynamic_stub(
         invocation_end_link, group, cardinalities, pool)
 
diff --git a/src/python/grpcio/tests/unit/beta/_face_interface_test.py b/src/python/grpcio/tests/unit/beta/_face_interface_test.py
index 1c21dfd03d..cb302bbf68 100644
--- a/src/python/grpcio/tests/unit/beta/_face_interface_test.py
+++ b/src/python/grpcio/tests/unit/beta/_face_interface_test.py
@@ -1,4 +1,4 @@
-# Copyright 2015, Google Inc.
+# Copyright 2015-2016, Google Inc.
 # All rights reserved.
 #
 # Redistribution and use in source and binary forms, with or without
@@ -32,6 +32,8 @@
 import collections
 import unittest
 
+import six
+
 from grpc.beta import implementations
 from grpc.beta import interfaces
 from tests.unit import resources
@@ -57,7 +59,7 @@ def _serialization_behaviors_from_test_methods(test_methods):
   request_deserializers = {}
   response_serializers = {}
   response_deserializers = {}
-  for (group, method), test_method in test_methods.iteritems():
+  for (group, method), test_method in six.iteritems(test_methods):
     request_serializers[group, method] = test_method.serialize_request
     request_deserializers[group, method] = test_method.deserialize_request
     response_serializers[group, method] = test_method.serialize_response
@@ -79,7 +81,7 @@ class _Implementation(test_interfaces.Implementation):
     # _digest.TestServiceDigest.
     cardinalities = {
         method: method_object.cardinality()
-        for (group, method), method_object in methods.iteritems()}
+        for (group, method), method_object in six.iteritems(methods)}
 
     server_options = implementations.server_options(
         request_deserializers=serialization_behaviors.request_deserializers,
diff --git a/src/python/grpcio/tests/unit/framework/_crust_over_core_face_interface_test.py b/src/python/grpcio/tests/unit/framework/_crust_over_core_face_interface_test.py
index 360ecc95d5..fd2d4298f9 100644
--- a/src/python/grpcio/tests/unit/framework/_crust_over_core_face_interface_test.py
+++ b/src/python/grpcio/tests/unit/framework/_crust_over_core_face_interface_test.py
@@ -1,4 +1,4 @@
-# Copyright 2015, Google Inc.
+# Copyright 2015-2016, Google Inc.
 # All rights reserved.
 #
 # Redistribution and use in source and binary forms, with or without
@@ -32,6 +32,8 @@
 import collections
 import unittest
 
+import six
+
 from grpc.framework.core import implementations as core_implementations
 from grpc.framework.crust import implementations as crust_implementations
 from grpc.framework.foundation import logging_pool
@@ -66,7 +68,7 @@ class _Implementation(test_interfaces.Implementation):
     # _digest.TestServiceDigest.
     cardinalities = {
         method: method_object.cardinality()
-        for (group, method), method_object in methods.iteritems()}
+        for (group, method), method_object in six.iteritems(methods)}
     dynamic_stub = crust_implementations.dynamic_stub(
         invocation_end_link, group, cardinalities, pool)
 
diff --git a/src/python/grpcio/tests/unit/framework/face/testing/blocking_invocation_inline_service_test_case.py b/src/python/grpcio/tests/unit/framework/face/testing/blocking_invocation_inline_service_test_case.py
index 2fc67f6292..b0b00bfa81 100644
--- a/src/python/grpcio/tests/unit/framework/face/testing/blocking_invocation_inline_service_test_case.py
+++ b/src/python/grpcio/tests/unit/framework/face/testing/blocking_invocation_inline_service_test_case.py
@@ -74,7 +74,7 @@ class BlockingInvocationInlineServiceTestCase(
 
   def testSuccessfulUnaryRequestUnaryResponse(self):
     for name, test_messages_sequence in (
-        self.digest.unary_unary_messages_sequences.iteritems()):
+        six.iteritems(self.digest.unary_unary_messages_sequences)):
       for test_messages in test_messages_sequence:
         request = test_messages.request()
 
@@ -85,7 +85,7 @@ class BlockingInvocationInlineServiceTestCase(
 
   def testSuccessfulUnaryRequestStreamResponse(self):
     for name, test_messages_sequence in (
-        self.digest.unary_stream_messages_sequences.iteritems()):
+        six.iteritems(self.digest.unary_stream_messages_sequences)):
       for test_messages in test_messages_sequence:
         request = test_messages.request()
 
@@ -97,7 +97,7 @@ class BlockingInvocationInlineServiceTestCase(
 
   def testSuccessfulStreamRequestUnaryResponse(self):
     for name, test_messages_sequence in (
-        self.digest.stream_unary_messages_sequences.iteritems()):
+        six.iteritems(self.digest.stream_unary_messages_sequences)):
       for test_messages in test_messages_sequence:
         requests = test_messages.requests()
 
@@ -108,7 +108,7 @@ class BlockingInvocationInlineServiceTestCase(
 
   def testSuccessfulStreamRequestStreamResponse(self):
     for name, test_messages_sequence in (
-        self.digest.stream_stream_messages_sequences.iteritems()):
+        six.iteritems(self.digest.stream_stream_messages_sequences)):
       for test_messages in test_messages_sequence:
         requests = test_messages.requests()
 
@@ -120,7 +120,7 @@ class BlockingInvocationInlineServiceTestCase(
 
   def testSequentialInvocations(self):
     for name, test_messages_sequence in (
-        self.digest.unary_unary_messages_sequences.iteritems()):
+        six.iteritems(self.digest.unary_unary_messages_sequences)):
       for test_messages in test_messages_sequence:
         first_request = test_messages.request()
         second_request = test_messages.request()
@@ -137,7 +137,7 @@ class BlockingInvocationInlineServiceTestCase(
 
   def testExpiredUnaryRequestUnaryResponse(self):
     for name, test_messages_sequence in (
-        self.digest.unary_unary_messages_sequences.iteritems()):
+        six.iteritems(self.digest.unary_unary_messages_sequences)):
       for test_messages in test_messages_sequence:
         request = test_messages.request()
 
@@ -148,7 +148,7 @@ class BlockingInvocationInlineServiceTestCase(
 
   def testExpiredUnaryRequestStreamResponse(self):
     for name, test_messages_sequence in (
-        self.digest.unary_stream_messages_sequences.iteritems()):
+        six.iteritems(self.digest.unary_stream_messages_sequences)):
       for test_messages in test_messages_sequence:
         request = test_messages.request()
 
@@ -160,7 +160,7 @@ class BlockingInvocationInlineServiceTestCase(
 
   def testExpiredStreamRequestUnaryResponse(self):
     for name, test_messages_sequence in (
-        self.digest.stream_unary_messages_sequences.iteritems()):
+        six.iteritems(self.digest.stream_unary_messages_sequences)):
       for test_messages in test_messages_sequence:
         requests = test_messages.requests()
 
@@ -171,7 +171,7 @@ class BlockingInvocationInlineServiceTestCase(
 
   def testExpiredStreamRequestStreamResponse(self):
     for name, test_messages_sequence in (
-        self.digest.stream_stream_messages_sequences.iteritems()):
+        six.iteritems(self.digest.stream_stream_messages_sequences)):
       for test_messages in test_messages_sequence:
         requests = test_messages.requests()
 
@@ -183,7 +183,7 @@ class BlockingInvocationInlineServiceTestCase(
 
   def testFailedUnaryRequestUnaryResponse(self):
     for name, test_messages_sequence in (
-        self.digest.unary_unary_messages_sequences.iteritems()):
+        six.iteritems(self.digest.unary_unary_messages_sequences)):
       for test_messages in test_messages_sequence:
         request = test_messages.request()
 
@@ -193,7 +193,7 @@ class BlockingInvocationInlineServiceTestCase(
 
   def testFailedUnaryRequestStreamResponse(self):
     for name, test_messages_sequence in (
-        self.digest.unary_stream_messages_sequences.iteritems()):
+        six.iteritems(self.digest.unary_stream_messages_sequences)):
       for test_messages in test_messages_sequence:
         request = test_messages.request()
 
@@ -204,7 +204,7 @@ class BlockingInvocationInlineServiceTestCase(
 
   def testFailedStreamRequestUnaryResponse(self):
     for name, test_messages_sequence in (
-        self.digest.stream_unary_messages_sequences.iteritems()):
+        six.iteritems(self.digest.stream_unary_messages_sequences)):
       for test_messages in test_messages_sequence:
         requests = test_messages.requests()
 
@@ -214,7 +214,7 @@ class BlockingInvocationInlineServiceTestCase(
 
   def testFailedStreamRequestStreamResponse(self):
     for name, test_messages_sequence in (
-        self.digest.stream_stream_messages_sequences.iteritems()):
+        six.iteritems(self.digest.stream_stream_messages_sequences)):
       for test_messages in test_messages_sequence:
         requests = test_messages.requests()
 
diff --git a/src/python/grpcio/tests/unit/framework/face/testing/digest.py b/src/python/grpcio/tests/unit/framework/face/testing/digest.py
index 39f28b9657..100067cc83 100644
--- a/src/python/grpcio/tests/unit/framework/face/testing/digest.py
+++ b/src/python/grpcio/tests/unit/framework/face/testing/digest.py
@@ -1,4 +1,4 @@
-# Copyright 2015, Google Inc.
+# Copyright 2015-2016, Google Inc.
 # All rights reserved.
 #
 # Redistribution and use in source and binary forms, with or without
@@ -32,6 +32,8 @@
 import collections
 import threading
 
+import six
+
 # testing_control, interfaces, and testing_service are referenced from
 # specification in this module.
 from grpc.framework.common import cardinality
@@ -368,7 +370,7 @@ def _assemble(
   events = {}
   adaptations = {}
   messages = {}
-  for name, scenario in scenarios.iteritems():
+  for name, scenario in six.iteritems(scenarios):
     if name in names:
       raise ValueError('Repeated name "%s"!' % name)
 
diff --git a/src/python/grpcio/tests/unit/framework/face/testing/event_invocation_synchronous_event_service_test_case.py b/src/python/grpcio/tests/unit/framework/face/testing/event_invocation_synchronous_event_service_test_case.py
index b707dcdf6c..db901cfe4e 100644
--- a/src/python/grpcio/tests/unit/framework/face/testing/event_invocation_synchronous_event_service_test_case.py
+++ b/src/python/grpcio/tests/unit/framework/face/testing/event_invocation_synchronous_event_service_test_case.py
@@ -74,7 +74,7 @@ class EventInvocationSynchronousEventServiceTestCase(
 
   def testSuccessfulUnaryRequestUnaryResponse(self):
     for name, test_messages_sequence in (
-        self.digest.unary_unary_messages_sequences.iteritems()):
+        six.iteritems(self.digest.unary_unary_messages_sequences)):
       for test_messages in test_messages_sequence:
         request = test_messages.request()
         callback = testing_callback.Callback()
@@ -89,7 +89,7 @@ class EventInvocationSynchronousEventServiceTestCase(
 
   def testSuccessfulUnaryRequestStreamResponse(self):
     for name, test_messages_sequence in (
-        self.digest.unary_stream_messages_sequences.iteritems()):
+        six.iteritems(self.digest.unary_stream_messages_sequences)):
       for test_messages in test_messages_sequence:
         request = test_messages.request()
         callback = testing_callback.Callback()
@@ -104,7 +104,7 @@ class EventInvocationSynchronousEventServiceTestCase(
 
   def testSuccessfulStreamRequestUnaryResponse(self):
     for name, test_messages_sequence in (
-        self.digest.stream_unary_messages_sequences.iteritems()):
+        six.iteritems(self.digest.stream_unary_messages_sequences)):
       for test_messages in test_messages_sequence:
         requests = test_messages.requests()
         callback = testing_callback.Callback()
@@ -122,7 +122,7 @@ class EventInvocationSynchronousEventServiceTestCase(
 
   def testSuccessfulStreamRequestStreamResponse(self):
     for name, test_messages_sequence in (
-        self.digest.stream_stream_messages_sequences.iteritems()):
+        six.iteritems(self.digest.stream_stream_messages_sequences)):
       for test_messages in test_messages_sequence:
         requests = test_messages.requests()
         callback = testing_callback.Callback()
@@ -140,7 +140,7 @@ class EventInvocationSynchronousEventServiceTestCase(
   def testSequentialInvocations(self):
     # pylint: disable=cell-var-from-loop
     for name, test_messages_sequence in (
-        self.digest.unary_unary_messages_sequences.iteritems()):
+        six.iteritems(self.digest.unary_unary_messages_sequences)):
       for test_messages in test_messages_sequence:
         first_request = test_messages.request()
         second_request = test_messages.request()
@@ -165,7 +165,7 @@ class EventInvocationSynchronousEventServiceTestCase(
 
   def testExpiredUnaryRequestUnaryResponse(self):
     for name, test_messages_sequence in (
-        self.digest.unary_unary_messages_sequences.iteritems()):
+        six.iteritems(self.digest.unary_unary_messages_sequences)):
       for test_messages in test_messages_sequence:
         request = test_messages.request()
         callback = testing_callback.Callback()
@@ -180,7 +180,7 @@ class EventInvocationSynchronousEventServiceTestCase(
 
   def testExpiredUnaryRequestStreamResponse(self):
     for name, test_messages_sequence in (
-        self.digest.unary_stream_messages_sequences.iteritems()):
+        six.iteritems(self.digest.unary_stream_messages_sequences)):
       for test_messages in test_messages_sequence:
         request = test_messages.request()
         callback = testing_callback.Callback()
@@ -195,7 +195,7 @@ class EventInvocationSynchronousEventServiceTestCase(
 
   def testExpiredStreamRequestUnaryResponse(self):
     for name, test_messages_sequence in (
-        self.digest.stream_unary_messages_sequences.iteritems()):
+        six.iteritems(self.digest.stream_unary_messages_sequences)):
       for unused_test_messages in test_messages_sequence:
         callback = testing_callback.Callback()
 
@@ -208,7 +208,7 @@ class EventInvocationSynchronousEventServiceTestCase(
 
   def testExpiredStreamRequestStreamResponse(self):
     for name, test_messages_sequence in (
-        self.digest.stream_stream_messages_sequences.iteritems()):
+        six.iteritems(self.digest.stream_stream_messages_sequences)):
       for test_messages in test_messages_sequence:
         requests = test_messages.requests()
         callback = testing_callback.Callback()
@@ -223,7 +223,7 @@ class EventInvocationSynchronousEventServiceTestCase(
 
   def testFailedUnaryRequestUnaryResponse(self):
     for name, test_messages_sequence in (
-        self.digest.unary_unary_messages_sequences.iteritems()):
+        six.iteritems(self.digest.unary_unary_messages_sequences)):
       for test_messages in test_messages_sequence:
         request = test_messages.request()
         callback = testing_callback.Callback()
@@ -239,7 +239,7 @@ class EventInvocationSynchronousEventServiceTestCase(
 
   def testFailedUnaryRequestStreamResponse(self):
     for name, test_messages_sequence in (
-        self.digest.unary_stream_messages_sequences.iteritems()):
+        six.iteritems(self.digest.unary_stream_messages_sequences)):
       for test_messages in test_messages_sequence:
         request = test_messages.request()
         callback = testing_callback.Callback()
@@ -255,7 +255,7 @@ class EventInvocationSynchronousEventServiceTestCase(
 
   def testFailedStreamRequestUnaryResponse(self):
     for name, test_messages_sequence in (
-        self.digest.stream_unary_messages_sequences.iteritems()):
+        six.iteritems(self.digest.stream_unary_messages_sequences)):
       for test_messages in test_messages_sequence:
         requests = test_messages.requests()
         callback = testing_callback.Callback()
@@ -274,7 +274,7 @@ class EventInvocationSynchronousEventServiceTestCase(
 
   def testFailedStreamRequestStreamResponse(self):
     for name, test_messages_sequence in (
-        self.digest.stream_stream_messages_sequences.iteritems()):
+        six.iteritems(self.digest.stream_stream_messages_sequences)):
       for test_messages in test_messages_sequence:
         requests = test_messages.requests()
         callback = testing_callback.Callback()
@@ -291,7 +291,7 @@ class EventInvocationSynchronousEventServiceTestCase(
 
   def testParallelInvocations(self):
     for name, test_messages_sequence in (
-        self.digest.unary_unary_messages_sequences.iteritems()):
+        six.iteritems(self.digest.unary_unary_messages_sequences)):
       for test_messages in test_messages_sequence:
         first_request = test_messages.request()
         first_callback = testing_callback.Callback()
@@ -318,7 +318,7 @@ class EventInvocationSynchronousEventServiceTestCase(
 
   def testCancelledUnaryRequestUnaryResponse(self):
     for name, test_messages_sequence in (
-        self.digest.unary_unary_messages_sequences.iteritems()):
+        six.iteritems(self.digest.unary_unary_messages_sequences)):
       for test_messages in test_messages_sequence:
         request = test_messages.request()
         callback = testing_callback.Callback()
@@ -334,7 +334,7 @@ class EventInvocationSynchronousEventServiceTestCase(
 
   def testCancelledUnaryRequestStreamResponse(self):
     for name, test_messages_sequence in (
-        self.digest.unary_stream_messages_sequences.iteritems()):
+        six.iteritems(self.digest.unary_stream_messages_sequences)):
       for test_messages in test_messages_sequence:
         request = test_messages.request()
         callback = testing_callback.Callback()
@@ -349,7 +349,7 @@ class EventInvocationSynchronousEventServiceTestCase(
 
   def testCancelledStreamRequestUnaryResponse(self):
     for name, test_messages_sequence in (
-        self.digest.stream_unary_messages_sequences.iteritems()):
+        six.iteritems(self.digest.stream_unary_messages_sequences)):
       for test_messages in test_messages_sequence:
         requests = test_messages.requests()
         callback = testing_callback.Callback()
@@ -366,7 +366,7 @@ class EventInvocationSynchronousEventServiceTestCase(
 
   def testCancelledStreamRequestStreamResponse(self):
     for name, test_messages_sequence in (
-        self.digest.stream_stream_messages_sequences.iteritems()):
+        six.iteritems(self.digest.stream_stream_messages_sequences)):
       for unused_test_messages in test_messages_sequence:
         callback = testing_callback.Callback()
 
diff --git a/src/python/grpcio/tests/unit/framework/face/testing/future_invocation_asynchronous_event_service_test_case.py b/src/python/grpcio/tests/unit/framework/face/testing/future_invocation_asynchronous_event_service_test_case.py
index 8adfc613c6..d8706aa39e 100644
--- a/src/python/grpcio/tests/unit/framework/face/testing/future_invocation_asynchronous_event_service_test_case.py
+++ b/src/python/grpcio/tests/unit/framework/face/testing/future_invocation_asynchronous_event_service_test_case.py
@@ -110,7 +110,7 @@ class FutureInvocationAsynchronousEventServiceTestCase(
 
   def testSuccessfulUnaryRequestUnaryResponse(self):
     for name, test_messages_sequence in (
-        self.digest.unary_unary_messages_sequences.iteritems()):
+        six.iteritems(self.digest.unary_unary_messages_sequences)):
       for test_messages in test_messages_sequence:
         request = test_messages.request()
 
@@ -122,7 +122,7 @@ class FutureInvocationAsynchronousEventServiceTestCase(
 
   def testSuccessfulUnaryRequestStreamResponse(self):
     for name, test_messages_sequence in (
-        self.digest.unary_stream_messages_sequences.iteritems()):
+        six.iteritems(self.digest.unary_stream_messages_sequences)):
       for test_messages in test_messages_sequence:
         request = test_messages.request()
 
@@ -134,7 +134,7 @@ class FutureInvocationAsynchronousEventServiceTestCase(
 
   def testSuccessfulStreamRequestUnaryResponse(self):
     for name, test_messages_sequence in (
-        self.digest.stream_unary_messages_sequences.iteritems()):
+        six.iteritems(self.digest.stream_unary_messages_sequences)):
       for test_messages in test_messages_sequence:
         requests = test_messages.requests()
         request_iterator = _PauseableIterator(iter(requests))
@@ -150,7 +150,7 @@ class FutureInvocationAsynchronousEventServiceTestCase(
 
   def testSuccessfulStreamRequestStreamResponse(self):
     for name, test_messages_sequence in (
-        self.digest.stream_stream_messages_sequences.iteritems()):
+        six.iteritems(self.digest.stream_stream_messages_sequences)):
       for test_messages in test_messages_sequence:
         requests = test_messages.requests()
         request_iterator = _PauseableIterator(iter(requests))
@@ -166,7 +166,7 @@ class FutureInvocationAsynchronousEventServiceTestCase(
 
   def testSequentialInvocations(self):
     for name, test_messages_sequence in (
-        self.digest.unary_unary_messages_sequences.iteritems()):
+        six.iteritems(self.digest.unary_unary_messages_sequences)):
       for test_messages in test_messages_sequence:
         first_request = test_messages.request()
         second_request = test_messages.request()
@@ -185,7 +185,7 @@ class FutureInvocationAsynchronousEventServiceTestCase(
 
   def testExpiredUnaryRequestUnaryResponse(self):
     for name, test_messages_sequence in (
-        self.digest.unary_unary_messages_sequences.iteritems()):
+        six.iteritems(self.digest.unary_unary_messages_sequences)):
       for test_messages in test_messages_sequence:
         request = test_messages.request()
 
@@ -200,7 +200,7 @@ class FutureInvocationAsynchronousEventServiceTestCase(
 
   def testExpiredUnaryRequestStreamResponse(self):
     for name, test_messages_sequence in (
-        self.digest.unary_stream_messages_sequences.iteritems()):
+        six.iteritems(self.digest.unary_stream_messages_sequences)):
       for test_messages in test_messages_sequence:
         request = test_messages.request()
 
@@ -212,7 +212,7 @@ class FutureInvocationAsynchronousEventServiceTestCase(
 
   def testExpiredStreamRequestUnaryResponse(self):
     for name, test_messages_sequence in (
-        self.digest.stream_unary_messages_sequences.iteritems()):
+        six.iteritems(self.digest.stream_unary_messages_sequences)):
       for test_messages in test_messages_sequence:
         requests = test_messages.requests()
 
@@ -227,7 +227,7 @@ class FutureInvocationAsynchronousEventServiceTestCase(
 
   def testExpiredStreamRequestStreamResponse(self):
     for name, test_messages_sequence in (
-        self.digest.stream_stream_messages_sequences.iteritems()):
+        six.iteritems(self.digest.stream_stream_messages_sequences)):
       for test_messages in test_messages_sequence:
         requests = test_messages.requests()
 
@@ -239,7 +239,7 @@ class FutureInvocationAsynchronousEventServiceTestCase(
 
   def testFailedUnaryRequestUnaryResponse(self):
     for name, test_messages_sequence in (
-        self.digest.unary_unary_messages_sequences.iteritems()):
+        six.iteritems(self.digest.unary_unary_messages_sequences)):
       for test_messages in test_messages_sequence:
         request = test_messages.request()
 
@@ -258,7 +258,7 @@ class FutureInvocationAsynchronousEventServiceTestCase(
 
   def testFailedUnaryRequestStreamResponse(self):
     for name, test_messages_sequence in (
-        self.digest.unary_stream_messages_sequences.iteritems()):
+        six.iteritems(self.digest.unary_stream_messages_sequences)):
       for test_messages in test_messages_sequence:
         request = test_messages.request()
 
@@ -273,7 +273,7 @@ class FutureInvocationAsynchronousEventServiceTestCase(
 
   def testFailedStreamRequestUnaryResponse(self):
     for name, test_messages_sequence in (
-        self.digest.stream_unary_messages_sequences.iteritems()):
+        six.iteritems(self.digest.stream_unary_messages_sequences)):
       for test_messages in test_messages_sequence:
         requests = test_messages.requests()
 
@@ -292,7 +292,7 @@ class FutureInvocationAsynchronousEventServiceTestCase(
 
   def testFailedStreamRequestStreamResponse(self):
     for name, test_messages_sequence in (
-        self.digest.stream_stream_messages_sequences.iteritems()):
+        six.iteritems(self.digest.stream_stream_messages_sequences)):
       for test_messages in test_messages_sequence:
         requests = test_messages.requests()
 
@@ -307,7 +307,7 @@ class FutureInvocationAsynchronousEventServiceTestCase(
 
   def testParallelInvocations(self):
     for name, test_messages_sequence in (
-        self.digest.unary_unary_messages_sequences.iteritems()):
+        six.iteritems(self.digest.unary_unary_messages_sequences)):
       for test_messages in test_messages_sequence:
         first_request = test_messages.request()
         second_request = test_messages.request()
@@ -329,7 +329,7 @@ class FutureInvocationAsynchronousEventServiceTestCase(
 
   def testCancelledUnaryRequestUnaryResponse(self):
     for name, test_messages_sequence in (
-        self.digest.unary_unary_messages_sequences.iteritems()):
+        six.iteritems(self.digest.unary_unary_messages_sequences)):
       for test_messages in test_messages_sequence:
         request = test_messages.request()
 
@@ -343,7 +343,7 @@ class FutureInvocationAsynchronousEventServiceTestCase(
 
   def testCancelledUnaryRequestStreamResponse(self):
     for name, test_messages_sequence in (
-        self.digest.unary_stream_messages_sequences.iteritems()):
+        six.iteritems(self.digest.unary_stream_messages_sequences)):
       for test_messages in test_messages_sequence:
         request = test_messages.request()
 
@@ -357,7 +357,7 @@ class FutureInvocationAsynchronousEventServiceTestCase(
 
   def testCancelledStreamRequestUnaryResponse(self):
     for name, test_messages_sequence in (
-        self.digest.stream_unary_messages_sequences.iteritems()):
+        six.iteritems(self.digest.stream_unary_messages_sequences)):
       for test_messages in test_messages_sequence:
         requests = test_messages.requests()
 
@@ -371,7 +371,7 @@ class FutureInvocationAsynchronousEventServiceTestCase(
 
   def testCancelledStreamRequestStreamResponse(self):
     for name, test_messages_sequence in (
-        self.digest.stream_stream_messages_sequences.iteritems()):
+        six.iteritems(self.digest.stream_stream_messages_sequences)):
       for test_messages in test_messages_sequence:
         requests = test_messages.requests()
 
diff --git a/src/python/grpcio/tests/unit/framework/interfaces/face/_blocking_invocation_inline_service.py b/src/python/grpcio/tests/unit/framework/interfaces/face/_blocking_invocation_inline_service.py
index a47fcd3681..530ba4ff0f 100644
--- a/src/python/grpcio/tests/unit/framework/interfaces/face/_blocking_invocation_inline_service.py
+++ b/src/python/grpcio/tests/unit/framework/interfaces/face/_blocking_invocation_inline_service.py
@@ -82,7 +82,7 @@ class TestCase(six.with_metaclass(abc.ABCMeta, test_coverage.Coverage, unittest.
 
   def testSuccessfulUnaryRequestUnaryResponse(self):
     for (group, method), test_messages_sequence in (
-        self._digest.unary_unary_messages_sequences.iteritems()):
+        six.iteritems(self._digest.unary_unary_messages_sequences)):
       for test_messages in test_messages_sequence:
         request = test_messages.request()
 
@@ -93,7 +93,7 @@ class TestCase(six.with_metaclass(abc.ABCMeta, test_coverage.Coverage, unittest.
 
   def testSuccessfulUnaryRequestStreamResponse(self):
     for (group, method), test_messages_sequence in (
-        self._digest.unary_stream_messages_sequences.iteritems()):
+        six.iteritems(self._digest.unary_stream_messages_sequences)):
       for test_messages in test_messages_sequence:
         request = test_messages.request()
 
@@ -105,7 +105,7 @@ class TestCase(six.with_metaclass(abc.ABCMeta, test_coverage.Coverage, unittest.
 
   def testSuccessfulStreamRequestUnaryResponse(self):
     for (group, method), test_messages_sequence in (
-        self._digest.stream_unary_messages_sequences.iteritems()):
+        six.iteritems(self._digest.stream_unary_messages_sequences)):
       for test_messages in test_messages_sequence:
         requests = test_messages.requests()
 
@@ -116,7 +116,7 @@ class TestCase(six.with_metaclass(abc.ABCMeta, test_coverage.Coverage, unittest.
 
   def testSuccessfulStreamRequestStreamResponse(self):
     for (group, method), test_messages_sequence in (
-        self._digest.stream_stream_messages_sequences.iteritems()):
+        six.iteritems(self._digest.stream_stream_messages_sequences)):
       for test_messages in test_messages_sequence:
         requests = test_messages.requests()
 
@@ -128,7 +128,7 @@ class TestCase(six.with_metaclass(abc.ABCMeta, test_coverage.Coverage, unittest.
 
   def testSequentialInvocations(self):
     for (group, method), test_messages_sequence in (
-        self._digest.unary_unary_messages_sequences.iteritems()):
+        six.iteritems(self._digest.unary_unary_messages_sequences)):
       for test_messages in test_messages_sequence:
         first_request = test_messages.request()
         second_request = test_messages.request()
@@ -146,7 +146,7 @@ class TestCase(six.with_metaclass(abc.ABCMeta, test_coverage.Coverage, unittest.
   def testParallelInvocations(self):
     pool = logging_pool.pool(test_constants.PARALLELISM)
     for (group, method), test_messages_sequence in (
-        self._digest.unary_unary_messages_sequences.iteritems()):
+        six.iteritems(self._digest.unary_unary_messages_sequences)):
       for test_messages in test_messages_sequence:
         requests = []
         response_futures = []
@@ -168,7 +168,7 @@ class TestCase(six.with_metaclass(abc.ABCMeta, test_coverage.Coverage, unittest.
   def testWaitingForSomeButNotAllParallelInvocations(self):
     pool = logging_pool.pool(test_constants.PARALLELISM)
     for (group, method), test_messages_sequence in (
-        self._digest.unary_unary_messages_sequences.iteritems()):
+        six.iteritems(self._digest.unary_unary_messages_sequences)):
       for test_messages in test_messages_sequence:
         requests = []
         response_futures_to_indices = {}
@@ -206,7 +206,7 @@ class TestCase(six.with_metaclass(abc.ABCMeta, test_coverage.Coverage, unittest.
 
   def testExpiredUnaryRequestUnaryResponse(self):
     for (group, method), test_messages_sequence in (
-        self._digest.unary_unary_messages_sequences.iteritems()):
+        six.iteritems(self._digest.unary_unary_messages_sequences)):
       for test_messages in test_messages_sequence:
         request = test_messages.request()
 
@@ -217,7 +217,7 @@ class TestCase(six.with_metaclass(abc.ABCMeta, test_coverage.Coverage, unittest.
 
   def testExpiredUnaryRequestStreamResponse(self):
     for (group, method), test_messages_sequence in (
-        self._digest.unary_stream_messages_sequences.iteritems()):
+        six.iteritems(self._digest.unary_stream_messages_sequences)):
       for test_messages in test_messages_sequence:
         request = test_messages.request()
 
@@ -229,7 +229,7 @@ class TestCase(six.with_metaclass(abc.ABCMeta, test_coverage.Coverage, unittest.
 
   def testExpiredStreamRequestUnaryResponse(self):
     for (group, method), test_messages_sequence in (
-        self._digest.stream_unary_messages_sequences.iteritems()):
+        six.iteritems(self._digest.stream_unary_messages_sequences)):
       for test_messages in test_messages_sequence:
         requests = test_messages.requests()
 
@@ -240,7 +240,7 @@ class TestCase(six.with_metaclass(abc.ABCMeta, test_coverage.Coverage, unittest.
 
   def testExpiredStreamRequestStreamResponse(self):
     for (group, method), test_messages_sequence in (
-        self._digest.stream_stream_messages_sequences.iteritems()):
+        six.iteritems(self._digest.stream_stream_messages_sequences)):
       for test_messages in test_messages_sequence:
         requests = test_messages.requests()
 
@@ -252,7 +252,7 @@ class TestCase(six.with_metaclass(abc.ABCMeta, test_coverage.Coverage, unittest.
 
   def testFailedUnaryRequestUnaryResponse(self):
     for (group, method), test_messages_sequence in (
-        self._digest.unary_unary_messages_sequences.iteritems()):
+        six.iteritems(self._digest.unary_unary_messages_sequences)):
       for test_messages in test_messages_sequence:
         request = test_messages.request()
 
@@ -262,7 +262,7 @@ class TestCase(six.with_metaclass(abc.ABCMeta, test_coverage.Coverage, unittest.
 
   def testFailedUnaryRequestStreamResponse(self):
     for (group, method), test_messages_sequence in (
-        self._digest.unary_stream_messages_sequences.iteritems()):
+        six.iteritems(self._digest.unary_stream_messages_sequences)):
       for test_messages in test_messages_sequence:
         request = test_messages.request()
 
@@ -273,7 +273,7 @@ class TestCase(six.with_metaclass(abc.ABCMeta, test_coverage.Coverage, unittest.
 
   def testFailedStreamRequestUnaryResponse(self):
     for (group, method), test_messages_sequence in (
-        self._digest.stream_unary_messages_sequences.iteritems()):
+        six.iteritems(self._digest.stream_unary_messages_sequences)):
       for test_messages in test_messages_sequence:
         requests = test_messages.requests()
 
@@ -283,7 +283,7 @@ class TestCase(six.with_metaclass(abc.ABCMeta, test_coverage.Coverage, unittest.
 
   def testFailedStreamRequestStreamResponse(self):
     for (group, method), test_messages_sequence in (
-        self._digest.stream_stream_messages_sequences.iteritems()):
+        six.iteritems(self._digest.stream_stream_messages_sequences)):
       for test_messages in test_messages_sequence:
         requests = test_messages.requests()
 
diff --git a/src/python/grpcio/tests/unit/framework/interfaces/face/_digest.py b/src/python/grpcio/tests/unit/framework/interfaces/face/_digest.py
index 9304b6b1db..40c03f9e71 100644
--- a/src/python/grpcio/tests/unit/framework/interfaces/face/_digest.py
+++ b/src/python/grpcio/tests/unit/framework/interfaces/face/_digest.py
@@ -1,4 +1,4 @@
-# Copyright 2015, Google Inc.
+# Copyright 2015-2016, Google Inc.
 # All rights reserved.
 #
 # Redistribution and use in source and binary forms, with or without
@@ -32,6 +32,8 @@
 import collections
 import threading
 
+import six
+
 # test_control, _service, and test_interfaces are referenced from specification
 # in this module.
 from grpc.framework.common import cardinality
@@ -363,7 +365,7 @@ def _assemble(
   events = {}
   adaptations = {}
   messages = {}
-  for identifier, scenario in scenarios.iteritems():
+  for identifier, scenario in six.iteritems(scenarios):
     if identifier in identifiers:
       raise ValueError('Repeated identifier "(%s, %s)"!' % identifier)
 
diff --git a/src/python/grpcio/tests/unit/framework/interfaces/face/_future_invocation_asynchronous_event_service.py b/src/python/grpcio/tests/unit/framework/interfaces/face/_future_invocation_asynchronous_event_service.py
index c1081a7d99..89f344c289 100644
--- a/src/python/grpcio/tests/unit/framework/interfaces/face/_future_invocation_asynchronous_event_service.py
+++ b/src/python/grpcio/tests/unit/framework/interfaces/face/_future_invocation_asynchronous_event_service.py
@@ -145,7 +145,7 @@ class TestCase(six.with_metaclass(abc.ABCMeta, test_coverage.Coverage, unittest.
 
   def testSuccessfulUnaryRequestUnaryResponse(self):
     for (group, method), test_messages_sequence in (
-        self._digest.unary_unary_messages_sequences.iteritems()):
+        six.iteritems(self._digest.unary_unary_messages_sequences)):
       for test_messages in test_messages_sequence:
         request = test_messages.request()
         callback = _Callback()
@@ -160,7 +160,7 @@ class TestCase(six.with_metaclass(abc.ABCMeta, test_coverage.Coverage, unittest.
 
   def testSuccessfulUnaryRequestStreamResponse(self):
     for (group, method), test_messages_sequence in (
-        self._digest.unary_stream_messages_sequences.iteritems()):
+        six.iteritems(self._digest.unary_stream_messages_sequences)):
       for test_messages in test_messages_sequence:
         request = test_messages.request()
 
@@ -172,7 +172,7 @@ class TestCase(six.with_metaclass(abc.ABCMeta, test_coverage.Coverage, unittest.
 
   def testSuccessfulStreamRequestUnaryResponse(self):
     for (group, method), test_messages_sequence in (
-        self._digest.stream_unary_messages_sequences.iteritems()):
+        six.iteritems(self._digest.stream_unary_messages_sequences)):
       for test_messages in test_messages_sequence:
         requests = test_messages.requests()
         request_iterator = _PauseableIterator(iter(requests))
@@ -192,7 +192,7 @@ class TestCase(six.with_metaclass(abc.ABCMeta, test_coverage.Coverage, unittest.
 
   def testSuccessfulStreamRequestStreamResponse(self):
     for (group, method), test_messages_sequence in (
-        self._digest.stream_stream_messages_sequences.iteritems()):
+        six.iteritems(self._digest.stream_stream_messages_sequences)):
       for test_messages in test_messages_sequence:
         requests = test_messages.requests()
         request_iterator = _PauseableIterator(iter(requests))
@@ -208,7 +208,7 @@ class TestCase(six.with_metaclass(abc.ABCMeta, test_coverage.Coverage, unittest.
 
   def testSequentialInvocations(self):
     for (group, method), test_messages_sequence in (
-        self._digest.unary_unary_messages_sequences.iteritems()):
+        six.iteritems(self._digest.unary_unary_messages_sequences)):
       for test_messages in test_messages_sequence:
         first_request = test_messages.request()
         second_request = test_messages.request()
@@ -227,7 +227,7 @@ class TestCase(six.with_metaclass(abc.ABCMeta, test_coverage.Coverage, unittest.
 
   def testParallelInvocations(self):
     for (group, method), test_messages_sequence in (
-        self._digest.unary_unary_messages_sequences.iteritems()):
+        six.iteritems(self._digest.unary_unary_messages_sequences)):
       for test_messages in test_messages_sequence:
         first_request = test_messages.request()
         second_request = test_messages.request()
@@ -243,7 +243,7 @@ class TestCase(six.with_metaclass(abc.ABCMeta, test_coverage.Coverage, unittest.
         test_messages.verify(second_request, second_response, self)
 
     for (group, method), test_messages_sequence in (
-        self._digest.unary_unary_messages_sequences.iteritems()):
+        six.iteritems(self._digest.unary_unary_messages_sequences)):
       for test_messages in test_messages_sequence:
         requests = []
         response_futures = []
@@ -263,7 +263,7 @@ class TestCase(six.with_metaclass(abc.ABCMeta, test_coverage.Coverage, unittest.
   def testWaitingForSomeButNotAllParallelInvocations(self):
     pool = logging_pool.pool(test_constants.PARALLELISM)
     for (group, method), test_messages_sequence in (
-        self._digest.unary_unary_messages_sequences.iteritems()):
+        six.iteritems(self._digest.unary_unary_messages_sequences)):
       for test_messages in test_messages_sequence:
         requests = []
         response_futures_to_indices = {}
@@ -285,7 +285,7 @@ class TestCase(six.with_metaclass(abc.ABCMeta, test_coverage.Coverage, unittest.
 
   def testCancelledUnaryRequestUnaryResponse(self):
     for (group, method), test_messages_sequence in (
-        self._digest.unary_unary_messages_sequences.iteritems()):
+        six.iteritems(self._digest.unary_unary_messages_sequences)):
       for test_messages in test_messages_sequence:
         request = test_messages.request()
         callback = _Callback()
@@ -302,7 +302,7 @@ class TestCase(six.with_metaclass(abc.ABCMeta, test_coverage.Coverage, unittest.
 
   def testCancelledUnaryRequestStreamResponse(self):
     for (group, method), test_messages_sequence in (
-        self._digest.unary_stream_messages_sequences.iteritems()):
+        six.iteritems(self._digest.unary_stream_messages_sequences)):
       for test_messages in test_messages_sequence:
         request = test_messages.request()
 
@@ -316,7 +316,7 @@ class TestCase(six.with_metaclass(abc.ABCMeta, test_coverage.Coverage, unittest.
 
   def testCancelledStreamRequestUnaryResponse(self):
     for (group, method), test_messages_sequence in (
-        self._digest.stream_unary_messages_sequences.iteritems()):
+        six.iteritems(self._digest.stream_unary_messages_sequences)):
       for test_messages in test_messages_sequence:
         requests = test_messages.requests()
         callback = _Callback()
@@ -333,7 +333,7 @@ class TestCase(six.with_metaclass(abc.ABCMeta, test_coverage.Coverage, unittest.
 
   def testCancelledStreamRequestStreamResponse(self):
     for (group, method), test_messages_sequence in (
-        self._digest.stream_stream_messages_sequences.iteritems()):
+        six.iteritems(self._digest.stream_stream_messages_sequences)):
       for test_messages in test_messages_sequence:
         requests = test_messages.requests()
 
@@ -347,7 +347,7 @@ class TestCase(six.with_metaclass(abc.ABCMeta, test_coverage.Coverage, unittest.
 
   def testExpiredUnaryRequestUnaryResponse(self):
     for (group, method), test_messages_sequence in (
-        self._digest.unary_unary_messages_sequences.iteritems()):
+        six.iteritems(self._digest.unary_unary_messages_sequences)):
       for test_messages in test_messages_sequence:
         request = test_messages.request()
         callback = _Callback()
@@ -364,7 +364,7 @@ class TestCase(six.with_metaclass(abc.ABCMeta, test_coverage.Coverage, unittest.
 
   def testExpiredUnaryRequestStreamResponse(self):
     for (group, method), test_messages_sequence in (
-        self._digest.unary_stream_messages_sequences.iteritems()):
+        six.iteritems(self._digest.unary_stream_messages_sequences)):
       for test_messages in test_messages_sequence:
         request = test_messages.request()
 
@@ -376,7 +376,7 @@ class TestCase(six.with_metaclass(abc.ABCMeta, test_coverage.Coverage, unittest.
 
   def testExpiredStreamRequestUnaryResponse(self):
     for (group, method), test_messages_sequence in (
-        self._digest.stream_unary_messages_sequences.iteritems()):
+        six.iteritems(self._digest.stream_unary_messages_sequences)):
       for test_messages in test_messages_sequence:
         requests = test_messages.requests()
         callback = _Callback()
@@ -393,7 +393,7 @@ class TestCase(six.with_metaclass(abc.ABCMeta, test_coverage.Coverage, unittest.
 
   def testExpiredStreamRequestStreamResponse(self):
     for (group, method), test_messages_sequence in (
-        self._digest.stream_stream_messages_sequences.iteritems()):
+        six.iteritems(self._digest.stream_stream_messages_sequences)):
       for test_messages in test_messages_sequence:
         requests = test_messages.requests()
 
@@ -405,7 +405,7 @@ class TestCase(six.with_metaclass(abc.ABCMeta, test_coverage.Coverage, unittest.
 
   def testFailedUnaryRequestUnaryResponse(self):
     for (group, method), test_messages_sequence in (
-        self._digest.unary_unary_messages_sequences.iteritems()):
+        six.iteritems(self._digest.unary_unary_messages_sequences)):
       for test_messages in test_messages_sequence:
         request = test_messages.request()
         callback = _Callback()
@@ -427,7 +427,7 @@ class TestCase(six.with_metaclass(abc.ABCMeta, test_coverage.Coverage, unittest.
 
   def testFailedUnaryRequestStreamResponse(self):
     for (group, method), test_messages_sequence in (
-        self._digest.unary_stream_messages_sequences.iteritems()):
+        six.iteritems(self._digest.unary_stream_messages_sequences)):
       for test_messages in test_messages_sequence:
         request = test_messages.request()
 
@@ -442,7 +442,7 @@ class TestCase(six.with_metaclass(abc.ABCMeta, test_coverage.Coverage, unittest.
 
   def testFailedStreamRequestUnaryResponse(self):
     for (group, method), test_messages_sequence in (
-        self._digest.stream_unary_messages_sequences.iteritems()):
+        six.iteritems(self._digest.stream_unary_messages_sequences)):
       for test_messages in test_messages_sequence:
         requests = test_messages.requests()
         callback = _Callback()
@@ -464,7 +464,7 @@ class TestCase(six.with_metaclass(abc.ABCMeta, test_coverage.Coverage, unittest.
 
   def testFailedStreamRequestStreamResponse(self):
     for (group, method), test_messages_sequence in (
-        self._digest.stream_stream_messages_sequences.iteritems()):
+        six.iteritems(self._digest.stream_stream_messages_sequences)):
       for test_messages in test_messages_sequence:
         requests = test_messages.requests()
 
diff --git a/src/python/grpcio/tests/unit/test_common.py b/src/python/grpcio/tests/unit/test_common.py
index 29431bfb9d..824f1cbd16 100644
--- a/src/python/grpcio/tests/unit/test_common.py
+++ b/src/python/grpcio/tests/unit/test_common.py
@@ -1,4 +1,4 @@
-# Copyright 2015, Google Inc.
+# Copyright 2015-2016, Google Inc.
 # All rights reserved.
 #
 # Redistribution and use in source and binary forms, with or without
@@ -31,6 +31,8 @@
 
 import collections
 
+import six
+
 INVOCATION_INITIAL_METADATA = ((b'0', b'abc'), (b'1', b'def'), (b'2', b'ghi'),)
 SERVICE_INITIAL_METADATA = ((b'3', b'jkl'), (b'4', b'mno'), (b'5', b'pqr'),)
 SERVICE_TERMINAL_METADATA = ((b'6', b'stu'), (b'7', b'vwx'), (b'8', b'yza'),)
@@ -65,7 +67,7 @@ def metadata_transmitted(original_metadata, transmitted_metadata):
     key, value = tuple(key_value_pair)
     transmitted[key].append(value)
 
-  for key, values in original.iteritems():
+  for key, values in six.iteritems(original):
     transmitted_values = transmitted[key]
     transmitted_iterator = iter(transmitted_values)
     try:
diff --git a/src/ruby/ext/grpc/rb_call.c b/src/ruby/ext/grpc/rb_call.c
index af05ddf6e7..cd0aa6aaf2 100644
--- a/src/ruby/ext/grpc/rb_call.c
+++ b/src/ruby/ext/grpc/rb_call.c
@@ -72,6 +72,10 @@ static ID id_cq;
  * the flags used to create metadata from a Hash */
 static ID id_flags;
 
+/* id_credentials is the name of the hidden ivar that preserves the value
+ * of the credentials added to the call */
+static ID id_credentials;
+
 /* id_input_md is the name of the hidden ivar that preserves the hash used to
  * create metadata, so that references to the strings it contains last as long
  * as the call the metadata is added to. */
@@ -299,6 +303,7 @@ static VALUE grpc_rb_call_set_credentials(VALUE self, VALUE credentials) {
              "grpc_call_set_credentials failed with %s (code=%d)",
              grpc_call_error_detail_of(err), err);
   }
+  rb_ivar_set(self, id_credentials, credentials);
   return Qnil;
 }
 
@@ -859,6 +864,7 @@ void Init_grpc_call() {
   id_cq = rb_intern("__cq");
   id_flags = rb_intern("__flags");
   id_input_md = rb_intern("__input_md");
+  id_credentials = rb_intern("__credentials");
 
   /* Ids used in constructing the batch result. */
   sym_send_message = ID2SYM(rb_intern("send_message"));
diff --git a/src/ruby/ext/grpc/rb_call_credentials.c b/src/ruby/ext/grpc/rb_call_credentials.c
index 2426f106a9..2b978fcdd0 100644
--- a/src/ruby/ext/grpc/rb_call_credentials.c
+++ b/src/ruby/ext/grpc/rb_call_credentials.c
@@ -41,6 +41,7 @@
 #include <grpc/grpc.h>
 #include <grpc/grpc_security.h>
 #include <grpc/support/alloc.h>
+#include <grpc/support/log.h>
 
 #include "rb_call.h"
 #include "rb_event_thread.h"
@@ -50,9 +51,9 @@
  * grpc_call_credentials */
 static VALUE grpc_rb_cCallCredentials = Qnil;
 
-/* grpc_rb_call_credentials wraps a grpc_call_credentials. It provides a peer
- * ruby object, 'mark' to minimize copying when a credential is created from
- * ruby. */
+/* grpc_rb_call_credentials wraps a grpc_call_credentials. It provides a mark
+ * object that is used to hold references to any objects used to create the
+ * credentials. */
 typedef struct grpc_rb_call_credentials {
   /* Holder of ruby objects involved in contructing the credentials */
   VALUE mark;
@@ -81,14 +82,23 @@ static VALUE grpc_rb_call_credentials_callback(VALUE callback_args) {
 static VALUE grpc_rb_call_credentials_callback_rescue(VALUE args,
                                                       VALUE exception_object) {
   VALUE result = rb_hash_new();
+  VALUE backtrace = rb_funcall(
+      rb_funcall(exception_object, rb_intern("backtrace"), 0),
+      rb_intern("join"),
+      1, rb_str_new2("\n\tfrom "));
+  VALUE exception_info = rb_funcall(exception_object, rb_intern("to_s"), 0);
+  const char *exception_classname = rb_obj_classname(exception_object);
   (void)args;
+  gpr_log(GPR_INFO, "Call credentials callback failed: %s: %s\n%s",
+          exception_classname, StringValueCStr(exception_info),
+          StringValueCStr(backtrace));
   rb_hash_aset(result, rb_str_new2("metadata"), Qnil);
   /* Currently only gives the exception class name. It should be possible get
      more details */
   rb_hash_aset(result, rb_str_new2("status"),
                INT2NUM(GRPC_STATUS_PERMISSION_DENIED));
   rb_hash_aset(result, rb_str_new2("details"),
-               rb_str_new2(rb_obj_classname(exception_object)));
+               rb_str_new2(exception_classname));
   return result;
 }
 
@@ -146,13 +156,8 @@ static void grpc_rb_call_credentials_free(void *p) {
     return;
   }
   wrapper = (grpc_rb_call_credentials *)p;
-
-  /* Delete the wrapped object if the mark object is Qnil, which indicates that
-   * no other object is the actual owner. */
-  if (wrapper->wrapped != NULL && wrapper->mark == Qnil) {
-    grpc_call_credentials_release(wrapper->wrapped);
-    wrapper->wrapped = NULL;
-  }
+  grpc_call_credentials_release(wrapper->wrapped);
+  wrapper->wrapped = NULL;
 
   xfree(p);
 }
@@ -164,8 +169,6 @@ static void grpc_rb_call_credentials_mark(void *p) {
     return;
   }
   wrapper = (grpc_rb_call_credentials *)p;
-
-  /* If it's not already cleaned up, mark the mark object */
   if (wrapper->mark != Qnil) {
     rb_gc_mark(wrapper->mark);
   }
@@ -194,7 +197,7 @@ static VALUE grpc_rb_call_credentials_alloc(VALUE cls) {
 /* Creates a wrapping object for a given call credentials. This should only be
  * called with grpc_call_credentials objects that are not already associated
  * with any Ruby object */
-VALUE grpc_rb_wrap_call_credentials(grpc_call_credentials *c) {
+VALUE grpc_rb_wrap_call_credentials(grpc_call_credentials *c, VALUE mark) {
   VALUE rb_wrapper;
   grpc_rb_call_credentials *wrapper;
   if (c == NULL) {
@@ -204,6 +207,7 @@ VALUE grpc_rb_wrap_call_credentials(grpc_call_credentials *c) {
   TypedData_Get_Struct(rb_wrapper, grpc_rb_call_credentials,
                        &grpc_rb_call_credentials_data_type, wrapper);
   wrapper->wrapped = c;
+  wrapper->mark = mark;
   return rb_wrapper;
 }
 
@@ -267,6 +271,7 @@ static VALUE grpc_rb_call_credentials_init(VALUE self, VALUE proc) {
     return Qnil;
   }
 
+  wrapper->mark = proc;
   wrapper->wrapped = creds;
   rb_ivar_set(self, id_callback, proc);
 
@@ -277,15 +282,18 @@ static VALUE grpc_rb_call_credentials_compose(int argc, VALUE *argv,
                                               VALUE self) {
   grpc_call_credentials *creds;
   grpc_call_credentials *other;
+  VALUE mark;
   if (argc == 0) {
     return self;
   }
+  mark = rb_ary_new();
   creds = grpc_rb_get_wrapped_call_credentials(self);
   for (int i = 0; i < argc; i++) {
+    rb_ary_push(mark, argv[i]);
     other = grpc_rb_get_wrapped_call_credentials(argv[i]);
     creds = grpc_composite_call_credentials_create(creds, other, NULL);
   }
-  return grpc_rb_wrap_call_credentials(creds);
+  return grpc_rb_wrap_call_credentials(creds, mark);
 }
 
 void Init_grpc_call_credentials() {
diff --git a/src/ruby/ext/grpc/rb_channel.c b/src/ruby/ext/grpc/rb_channel.c
index 0e6badbdaf..e1aaa539db 100644
--- a/src/ruby/ext/grpc/rb_channel.c
+++ b/src/ruby/ext/grpc/rb_channel.c
@@ -70,11 +70,10 @@ static VALUE grpc_rb_cChannel = Qnil;
 /* Used during the conversion of a hash to channel args during channel setup */
 static VALUE grpc_rb_cChannelArgs;
 
-/* grpc_rb_channel wraps a grpc_channel.  It provides a peer ruby object,
- * 'mark' to minimize copying when a channel is created from ruby. */
+/* grpc_rb_channel wraps a grpc_channel. */
 typedef struct grpc_rb_channel {
-  /* Holder of ruby objects involved in constructing the channel */
-  VALUE mark;
+  VALUE credentials;
+
   /* The actual channel */
   grpc_channel *wrapped;
 } grpc_rb_channel;
@@ -87,13 +86,8 @@ static void grpc_rb_channel_free(void *p) {
   };
   ch = (grpc_rb_channel *)p;
 
-  /* Deletes the wrapped object if the mark object is Qnil, which indicates
-   * that no other object is the actual owner. */
-  if (ch->wrapped != NULL && ch->mark == Qnil) {
+  if (ch->wrapped != NULL) {
     grpc_channel_destroy(ch->wrapped);
-    rb_warning("channel gc: destroyed the c channel");
-  } else {
-    rb_warning("channel gc: did not destroy the c channel");
   }
 
   xfree(p);
@@ -106,8 +100,8 @@ static void grpc_rb_channel_mark(void *p) {
     return;
   }
   channel = (grpc_rb_channel *)p;
-  if (channel->mark != Qnil) {
-    rb_gc_mark(channel->mark);
+  if (channel->credentials != Qnil) {
+    rb_gc_mark(channel->credentials);
   }
 }
 
@@ -125,7 +119,7 @@ static rb_data_type_t grpc_channel_data_type = {
 static VALUE grpc_rb_channel_alloc(VALUE cls) {
   grpc_rb_channel *wrapper = ALLOC(grpc_rb_channel);
   wrapper->wrapped = NULL;
-  wrapper->mark = Qnil;
+  wrapper->credentials = Qnil;
   return TypedData_Wrap_Struct(cls, &grpc_channel_data_type, wrapper);
 }
 
@@ -162,6 +156,7 @@ static VALUE grpc_rb_channel_init(int argc, VALUE *argv, VALUE self) {
     }
     ch = grpc_insecure_channel_create(target_chars, &args, NULL);
   } else {
+    wrapper->credentials = credentials;
     creds = grpc_rb_get_wrapped_channel_credentials(credentials);
     ch = grpc_secure_channel_create(creds, target_chars, &args, NULL);
   }
@@ -330,7 +325,6 @@ static VALUE grpc_rb_channel_destroy(VALUE self) {
   if (ch != NULL) {
     grpc_channel_destroy(ch);
     wrapper->wrapped = NULL;
-    wrapper->mark = Qnil;
   }
 
   return Qnil;
diff --git a/src/ruby/ext/grpc/rb_channel_credentials.c b/src/ruby/ext/grpc/rb_channel_credentials.c
index 8c6fc3b7eb..f649084311 100644
--- a/src/ruby/ext/grpc/rb_channel_credentials.c
+++ b/src/ruby/ext/grpc/rb_channel_credentials.c
@@ -49,8 +49,8 @@
 static VALUE grpc_rb_cChannelCredentials = Qnil;
 
 /* grpc_rb_channel_credentials wraps a grpc_channel_credentials.  It provides a
- * peer ruby object, 'mark' to minimize copying when a credential is
- * created from ruby. */
+ * mark object that is used to hold references to any objects used to create
+ * the credentials. */
 typedef struct grpc_rb_channel_credentials {
   /* Holder of ruby objects involved in constructing the credentials */
   VALUE mark;
@@ -66,13 +66,8 @@ static void grpc_rb_channel_credentials_free(void *p) {
     return;
   };
   wrapper = (grpc_rb_channel_credentials *)p;
-
-  /* Delete the wrapped object if the mark object is Qnil, which indicates that
-   * no other object is the actual owner. */
-  if (wrapper->wrapped != NULL && wrapper->mark == Qnil) {
-    grpc_channel_credentials_release(wrapper->wrapped);
-    wrapper->wrapped = NULL;
-  }
+  grpc_channel_credentials_release(wrapper->wrapped);
+  wrapper->wrapped = NULL;
 
   xfree(p);
 }
@@ -85,7 +80,6 @@ static void grpc_rb_channel_credentials_mark(void *p) {
   }
   wrapper = (grpc_rb_channel_credentials *)p;
 
-  /* If it's not already cleaned up, mark the mark object */
   if (wrapper->mark != Qnil) {
     rb_gc_mark(wrapper->mark);
   }
@@ -114,7 +108,7 @@ static VALUE grpc_rb_channel_credentials_alloc(VALUE cls) {
 /* Creates a wrapping object for a given channel credentials. This should only
  * be called with grpc_channel_credentials objects that are not already
  * associated with any Ruby object. */
-VALUE grpc_rb_wrap_channel_credentials(grpc_channel_credentials *c) {
+VALUE grpc_rb_wrap_channel_credentials(grpc_channel_credentials *c, VALUE mark) {
   VALUE rb_wrapper;
   grpc_rb_channel_credentials *wrapper;
   if (c == NULL) {
@@ -124,6 +118,7 @@ VALUE grpc_rb_wrap_channel_credentials(grpc_channel_credentials *c) {
   TypedData_Get_Struct(rb_wrapper, grpc_rb_channel_credentials,
                        &grpc_rb_channel_credentials_data_type, wrapper);
   wrapper->wrapped = c;
+  wrapper->mark = mark;
   return rb_wrapper;
 }
 
@@ -222,11 +217,15 @@ static VALUE grpc_rb_channel_credentials_compose(int argc, VALUE *argv,
                                                  VALUE self) {
   grpc_channel_credentials *creds;
   grpc_call_credentials *other;
+  VALUE mark;
   if (argc == 0) {
     return self;
   }
+  mark = rb_ary_new();
+  rb_ary_push(mark, self);
   creds = grpc_rb_get_wrapped_channel_credentials(self);
   for (int i = 0; i < argc; i++) {
+    rb_ary_push(mark, argv[i]);
     other = grpc_rb_get_wrapped_call_credentials(argv[i]);
     creds = grpc_composite_channel_credentials_create(creds, other, NULL);
     if (creds == NULL) {
@@ -234,7 +233,7 @@ static VALUE grpc_rb_channel_credentials_compose(int argc, VALUE *argv,
                "Failed to compose channel and call credentials");
     }
   }
-  return grpc_rb_wrap_channel_credentials(creds);
+  return grpc_rb_wrap_channel_credentials(creds, mark);
 }
 
 void Init_grpc_channel_credentials() {