Merge github.com:grpc/grpc into optionalize_census

23 files changed, 328 insertions, 130 deletions

diff --git a/src/core/ext/transport/chttp2/transport/chttp2_transport.c b/src/core/ext/transport/chttp2/transport/chttp2_transport.c
index 0a307a73a6..b835e74c56 100644
--- a/src/core/ext/transport/chttp2/transport/chttp2_transport.c
+++ b/src/core/ext/transport/chttp2/transport/chttp2_transport.c
@@ -758,23 +758,35 @@ static void maybe_start_some_streams(
   }
 }
 
+#define CLOSURE_BARRIER_STATS_BIT (1 << 0)
+#define CLOSURE_BARRIER_FAILURE_BIT (1 << 1)
+#define CLOSURE_BARRIER_FIRST_REF_BIT (1 << 16)
+
 static grpc_closure *add_closure_barrier(grpc_closure *closure) {
-  closure->final_data += 2;
+  closure->final_data += CLOSURE_BARRIER_FIRST_REF_BIT;
   return closure;
 }
 
 void grpc_chttp2_complete_closure_step(grpc_exec_ctx *exec_ctx,
+                                       grpc_chttp2_stream_global *stream_global,
                                        grpc_closure **pclosure, int success) {
   grpc_closure *closure = *pclosure;
   if (closure == NULL) {
     return;
   }
-  closure->final_data -= 2;
+  closure->final_data -= CLOSURE_BARRIER_FIRST_REF_BIT;
   if (!success) {
-    closure->final_data |= 1;
+    closure->final_data |= CLOSURE_BARRIER_FAILURE_BIT;
   }
-  if (closure->final_data < 2) {
-    grpc_exec_ctx_enqueue(exec_ctx, closure, closure->final_data == 0, NULL);
+  if (closure->final_data < CLOSURE_BARRIER_FIRST_REF_BIT) {
+    if (closure->final_data & CLOSURE_BARRIER_STATS_BIT) {
+      grpc_transport_move_stats(&stream_global->stats,
+                                stream_global->collecting_stats);
+      stream_global->collecting_stats = NULL;
+    }
+    grpc_exec_ctx_enqueue(
+        exec_ctx, closure,
+        (closure->final_data & CLOSURE_BARRIER_FAILURE_BIT) == 0, NULL);
   }
   *pclosure = NULL;
 }
@@ -807,7 +819,13 @@ static void perform_stream_op_locked(
   }
   /* use final_data as a barrier until enqueue time; the inital counter is
      dropped at the end of this function */
-  on_complete->final_data = 2;
+  on_complete->final_data = CLOSURE_BARRIER_FIRST_REF_BIT;
+
+  if (op->collect_stats != NULL) {
+    GPR_ASSERT(stream_global->collecting_stats == NULL);
+    stream_global->collecting_stats = op->collect_stats;
+    on_complete->final_data |= CLOSURE_BARRIER_STATS_BIT;
+  }
 
   if (op->cancel_with_status != GRPC_STATUS_OK) {
     cancel_from_api(exec_ctx, transport_global, stream_global,
@@ -840,7 +858,8 @@ static void perform_stream_op_locked(
       }
     } else {
       grpc_chttp2_complete_closure_step(
-          exec_ctx, &stream_global->send_initial_metadata_finished, 0);
+          exec_ctx, stream_global,
+          &stream_global->send_initial_metadata_finished, 0);
     }
   }
 
@@ -850,7 +869,7 @@ static void perform_stream_op_locked(
     stream_global->send_message_finished = add_closure_barrier(on_complete);
     if (stream_global->write_closed) {
       grpc_chttp2_complete_closure_step(
-          exec_ctx, &stream_global->send_message_finished, 0);
+          exec_ctx, stream_global, &stream_global->send_message_finished, 0);
     } else {
       stream_global->send_message = op->send_message;
       if (stream_global->id != 0) {
@@ -870,7 +889,8 @@ static void perform_stream_op_locked(
     }
     if (stream_global->write_closed) {
       grpc_chttp2_complete_closure_step(
-          exec_ctx, &stream_global->send_trailing_metadata_finished,
+          exec_ctx, stream_global,
+          &stream_global->send_trailing_metadata_finished,
           grpc_metadata_batch_is_empty(op->send_trailing_metadata));
     } else if (stream_global->id != 0) {
       /* TODO(ctiller): check if there's flow control for any outstanding
@@ -909,7 +929,7 @@ static void perform_stream_op_locked(
     grpc_chttp2_list_add_check_read_ops(transport_global, stream_global);
   }
 
-  grpc_chttp2_complete_closure_step(exec_ctx, &on_complete, 1);
+  grpc_chttp2_complete_closure_step(exec_ctx, stream_global, &on_complete, 1);
 
   GPR_TIMER_END("perform_stream_op_locked", 0);
 }
@@ -1080,7 +1100,8 @@ static void check_read_ops(grpc_exec_ctx *exec_ctx,
             &stream_global->received_trailing_metadata,
             stream_global->recv_trailing_metadata);
         grpc_chttp2_complete_closure_step(
-            exec_ctx, &stream_global->recv_trailing_metadata_finished, 1);
+            exec_ctx, stream_global,
+            &stream_global->recv_trailing_metadata_finished, 1);
       }
     }
   }
@@ -1131,7 +1152,8 @@ static void cancel_from_api(grpc_exec_ctx *exec_ctx,
         &transport_global->qbuf,
         grpc_chttp2_rst_stream_create(
             stream_global->id,
-            (uint32_t)grpc_chttp2_grpc_status_to_http2_error(status)));
+            (uint32_t)grpc_chttp2_grpc_status_to_http2_error(status),
+            &stream_global->stats.outgoing));
   }
   grpc_chttp2_fake_status(exec_ctx, transport_global, stream_global, status,
                           NULL);
@@ -1179,10 +1201,12 @@ void grpc_chttp2_fake_status(grpc_exec_ctx *exec_ctx,
 static void fail_pending_writes(grpc_exec_ctx *exec_ctx,
                                 grpc_chttp2_stream_global *stream_global) {
   grpc_chttp2_complete_closure_step(
-      exec_ctx, &stream_global->send_initial_metadata_finished, 0);
+      exec_ctx, stream_global, &stream_global->send_initial_metadata_finished,
+      0);
   grpc_chttp2_complete_closure_step(
-      exec_ctx, &stream_global->send_trailing_metadata_finished, 0);
-  grpc_chttp2_complete_closure_step(exec_ctx,
+      exec_ctx, stream_global, &stream_global->send_trailing_metadata_finished,
+      0);
+  grpc_chttp2_complete_closure_step(exec_ctx, stream_global,
                                     &stream_global->send_message_finished, 0);
 }
 
@@ -1319,7 +1343,8 @@ static void close_from_api(grpc_exec_ctx *exec_ctx,
 
   gpr_slice_buffer_add(
       &transport_global->qbuf,
-      grpc_chttp2_rst_stream_create(stream_global->id, GRPC_CHTTP2_NO_ERROR));
+      grpc_chttp2_rst_stream_create(stream_global->id, GRPC_CHTTP2_NO_ERROR,
+                                    &stream_global->stats.outgoing));
 
   if (optional_message) {
     gpr_slice_ref(*optional_message);
diff --git a/src/core/ext/transport/chttp2/transport/frame_data.c b/src/core/ext/transport/chttp2/transport/frame_data.c
index cdd624647c..baa66e0008 100644
--- a/src/core/ext/transport/chttp2/transport/frame_data.c
+++ b/src/core/ext/transport/chttp2/transport/frame_data.c
@@ -113,11 +113,13 @@ grpc_byte_stream *grpc_chttp2_incoming_frame_queue_pop(
 
 void grpc_chttp2_encode_data(uint32_t id, gpr_slice_buffer *inbuf,
                              uint32_t write_bytes, int is_eof,
+                             grpc_transport_one_way_stats *stats,
                              gpr_slice_buffer *outbuf) {
   gpr_slice hdr;
   uint8_t *p;
+  static const size_t header_size = 9;
 
-  hdr = gpr_slice_malloc(9);
+  hdr = gpr_slice_malloc(header_size);
   p = GPR_SLICE_START_PTR(hdr);
   GPR_ASSERT(write_bytes < (1 << 24));
   *p++ = (uint8_t)(write_bytes >> 16);
@@ -132,6 +134,9 @@ void grpc_chttp2_encode_data(uint32_t id, gpr_slice_buffer *inbuf,
   gpr_slice_buffer_add(outbuf, hdr);
 
   gpr_slice_buffer_move_first(inbuf, write_bytes, outbuf);
+
+  stats->framing_bytes += header_size;
+  stats->data_bytes += write_bytes;
 }
 
 grpc_chttp2_parse_error grpc_chttp2_data_parser_parse(
@@ -156,6 +161,7 @@ grpc_chttp2_parse_error grpc_chttp2_data_parser_parse(
   switch (p->state) {
   fh_0:
     case GRPC_CHTTP2_DATA_FH_0:
+      stream_parsing->stats.incoming.framing_bytes++;
       p->frame_type = *cur;
       switch (p->frame_type) {
         case 0:
@@ -174,6 +180,7 @@ grpc_chttp2_parse_error grpc_chttp2_data_parser_parse(
       }
     /* fallthrough */
     case GRPC_CHTTP2_DATA_FH_1:
+      stream_parsing->stats.incoming.framing_bytes++;
       p->frame_size = ((uint32_t)*cur) << 24;
       if (++cur == end) {
         p->state = GRPC_CHTTP2_DATA_FH_2;
@@ -181,6 +188,7 @@ grpc_chttp2_parse_error grpc_chttp2_data_parser_parse(
       }
     /* fallthrough */
     case GRPC_CHTTP2_DATA_FH_2:
+      stream_parsing->stats.incoming.framing_bytes++;
       p->frame_size |= ((uint32_t)*cur) << 16;
       if (++cur == end) {
         p->state = GRPC_CHTTP2_DATA_FH_3;
@@ -188,6 +196,7 @@ grpc_chttp2_parse_error grpc_chttp2_data_parser_parse(
       }
     /* fallthrough */
     case GRPC_CHTTP2_DATA_FH_3:
+      stream_parsing->stats.incoming.framing_bytes++;
       p->frame_size |= ((uint32_t)*cur) << 8;
       if (++cur == end) {
         p->state = GRPC_CHTTP2_DATA_FH_4;
@@ -195,6 +204,7 @@ grpc_chttp2_parse_error grpc_chttp2_data_parser_parse(
       }
     /* fallthrough */
     case GRPC_CHTTP2_DATA_FH_4:
+      stream_parsing->stats.incoming.framing_bytes++;
       p->frame_size |= ((uint32_t)*cur);
       p->state = GRPC_CHTTP2_DATA_FRAME;
       ++cur;
@@ -215,7 +225,9 @@ grpc_chttp2_parse_error grpc_chttp2_data_parser_parse(
       }
       grpc_chttp2_list_add_parsing_seen_stream(transport_parsing,
                                                stream_parsing);
-      if ((uint32_t)(end - cur) == p->frame_size) {
+      uint32_t remaining = (uint32_t)(end - cur);
+      if (remaining == p->frame_size) {
+        stream_parsing->stats.incoming.data_bytes += p->frame_size;
         grpc_chttp2_incoming_byte_stream_push(
             exec_ctx, p->parsing_frame,
             gpr_slice_sub(slice, (size_t)(cur - beg), (size_t)(end - beg)));
@@ -224,7 +236,8 @@ grpc_chttp2_parse_error grpc_chttp2_data_parser_parse(
         p->parsing_frame = NULL;
         p->state = GRPC_CHTTP2_DATA_FH_0;
         return GRPC_CHTTP2_PARSE_OK;
-      } else if ((uint32_t)(end - cur) > p->frame_size) {
+      } else if (remaining > p->frame_size) {
+        stream_parsing->stats.incoming.data_bytes += p->frame_size;
         grpc_chttp2_incoming_byte_stream_push(
             exec_ctx, p->parsing_frame,
             gpr_slice_sub(slice, (size_t)(cur - beg),
@@ -235,11 +248,12 @@ grpc_chttp2_parse_error grpc_chttp2_data_parser_parse(
         cur += p->frame_size;
         goto fh_0; /* loop */
       } else {
+        GPR_ASSERT(remaining <= p->frame_size);
         grpc_chttp2_incoming_byte_stream_push(
             exec_ctx, p->parsing_frame,
             gpr_slice_sub(slice, (size_t)(cur - beg), (size_t)(end - beg)));
-        GPR_ASSERT((size_t)(end - cur) <= p->frame_size);
-        p->frame_size -= (uint32_t)(end - cur);
+        p->frame_size -= remaining;
+        stream_parsing->stats.incoming.data_bytes += remaining;
         return GRPC_CHTTP2_PARSE_OK;
       }
   }
diff --git a/src/core/ext/transport/chttp2/transport/frame_data.h b/src/core/ext/transport/chttp2/transport/frame_data.h
index f2762ed9de..8a073a9c11 100644
--- a/src/core/ext/transport/chttp2/transport/frame_data.h
+++ b/src/core/ext/transport/chttp2/transport/frame_data.h
@@ -41,6 +41,7 @@
 #include "src/core/ext/transport/chttp2/transport/frame.h"
 #include "src/core/lib/iomgr/exec_ctx.h"
 #include "src/core/lib/transport/byte_stream.h"
+#include "src/core/lib/transport/transport.h"
 
 typedef enum {
   GRPC_CHTTP2_DATA_FH_0,
@@ -96,6 +97,7 @@ grpc_chttp2_parse_error grpc_chttp2_data_parser_parse(
 
 void grpc_chttp2_encode_data(uint32_t id, gpr_slice_buffer *inbuf,
                              uint32_t write_bytes, int is_eof,
+                             grpc_transport_one_way_stats *stats,
                              gpr_slice_buffer *outbuf);
 
 #endif /* GRPC_CORE_EXT_TRANSPORT_CHTTP2_TRANSPORT_FRAME_DATA_H */
diff --git a/src/core/ext/transport/chttp2/transport/frame_rst_stream.c b/src/core/ext/transport/chttp2/transport/frame_rst_stream.c
index acfc3627e8..d9a04bbf3c 100644
--- a/src/core/ext/transport/chttp2/transport/frame_rst_stream.c
+++ b/src/core/ext/transport/chttp2/transport/frame_rst_stream.c
@@ -38,8 +38,11 @@
 
 #include "src/core/ext/transport/chttp2/transport/frame.h"
 
-gpr_slice grpc_chttp2_rst_stream_create(uint32_t id, uint32_t code) {
-  gpr_slice slice = gpr_slice_malloc(13);
+gpr_slice grpc_chttp2_rst_stream_create(uint32_t id, uint32_t code,
+                                        grpc_transport_one_way_stats *stats) {
+  static const size_t frame_size = 13;
+  gpr_slice slice = gpr_slice_malloc(frame_size);
+  stats->framing_bytes += frame_size;
   uint8_t *p = GPR_SLICE_START_PTR(slice);
 
   *p++ = 0;
@@ -84,6 +87,7 @@ grpc_chttp2_parse_error grpc_chttp2_rst_stream_parser_parse(
     cur++;
     p->byte++;
   }
+  stream_parsing->stats.incoming.framing_bytes += (uint64_t)(end - cur);
 
   if (p->byte == 4) {
     GPR_ASSERT(is_last);
diff --git a/src/core/ext/transport/chttp2/transport/frame_rst_stream.h b/src/core/ext/transport/chttp2/transport/frame_rst_stream.h
index 134f1368a0..729274e9a2 100644
--- a/src/core/ext/transport/chttp2/transport/frame_rst_stream.h
+++ b/src/core/ext/transport/chttp2/transport/frame_rst_stream.h
@@ -37,13 +37,15 @@
 #include <grpc/support/slice.h>
 #include "src/core/ext/transport/chttp2/transport/frame.h"
 #include "src/core/lib/iomgr/exec_ctx.h"
+#include "src/core/lib/transport/transport.h"
 
 typedef struct {
   uint8_t byte;
   uint8_t reason_bytes[4];
 } grpc_chttp2_rst_stream_parser;
 
-gpr_slice grpc_chttp2_rst_stream_create(uint32_t stream_id, uint32_t code);
+gpr_slice grpc_chttp2_rst_stream_create(uint32_t stream_id, uint32_t code,
+                                        grpc_transport_one_way_stats *stats);
 
 grpc_chttp2_parse_error grpc_chttp2_rst_stream_parser_begin_frame(
     grpc_chttp2_rst_stream_parser *parser, uint32_t length, uint8_t flags);
diff --git a/src/core/ext/transport/chttp2/transport/frame_window_update.c b/src/core/ext/transport/chttp2/transport/frame_window_update.c
index 1a561cebaf..0baf6d2fdd 100644
--- a/src/core/ext/transport/chttp2/transport/frame_window_update.c
+++ b/src/core/ext/transport/chttp2/transport/frame_window_update.c
@@ -36,9 +36,11 @@
 
 #include <grpc/support/log.h>
 
-gpr_slice grpc_chttp2_window_update_create(uint32_t id,
-                                           uint32_t window_update) {
-  gpr_slice slice = gpr_slice_malloc(13);
+gpr_slice grpc_chttp2_window_update_create(
+    uint32_t id, uint32_t window_update, grpc_transport_one_way_stats *stats) {
+  static const size_t frame_size = 13;
+  gpr_slice slice = gpr_slice_malloc(frame_size);
+  stats->header_bytes += frame_size;
   uint8_t *p = GPR_SLICE_START_PTR(slice);
 
   GPR_ASSERT(window_update);
@@ -87,6 +89,10 @@ grpc_chttp2_parse_error grpc_chttp2_window_update_parser_parse(
     p->byte++;
   }
 
+  if (stream_parsing != NULL) {
+    stream_parsing->stats.incoming.framing_bytes += (uint32_t)(end - cur);
+  }
+
   if (p->byte == 4) {
     uint32_t received_update = p->amount;
     if (received_update == 0 || (received_update & 0x80000000u)) {
diff --git a/src/core/ext/transport/chttp2/transport/frame_window_update.h b/src/core/ext/transport/chttp2/transport/frame_window_update.h
index f9f670b6f1..a1093a6041 100644
--- a/src/core/ext/transport/chttp2/transport/frame_window_update.h
+++ b/src/core/ext/transport/chttp2/transport/frame_window_update.h
@@ -37,6 +37,7 @@
 #include <grpc/support/slice.h>
 #include "src/core/ext/transport/chttp2/transport/frame.h"
 #include "src/core/lib/iomgr/exec_ctx.h"
+#include "src/core/lib/transport/transport.h"
 
 typedef struct {
   uint8_t byte;
@@ -44,7 +45,8 @@ typedef struct {
   uint32_t amount;
 } grpc_chttp2_window_update_parser;
 
-gpr_slice grpc_chttp2_window_update_create(uint32_t id, uint32_t window_delta);
+gpr_slice grpc_chttp2_window_update_create(uint32_t id, uint32_t window_delta,
+                                           grpc_transport_one_way_stats *stats);
 
 grpc_chttp2_parse_error grpc_chttp2_window_update_parser_begin_frame(
     grpc_chttp2_window_update_parser *parser, uint32_t length, uint8_t flags);
diff --git a/src/core/ext/transport/chttp2/transport/hpack_encoder.c b/src/core/ext/transport/chttp2/transport/hpack_encoder.c
index 819addd9e3..880305afdd 100644
--- a/src/core/ext/transport/chttp2/transport/hpack_encoder.c
+++ b/src/core/ext/transport/chttp2/transport/hpack_encoder.c
@@ -74,6 +74,7 @@ typedef struct {
   /* output stream id */
   uint32_t stream_id;
   gpr_slice_buffer *output;
+  grpc_transport_one_way_stats *stats;
 } framer_state;
 
 /* fills p (which is expected to be 9 bytes long) with a data frame header */
@@ -102,6 +103,7 @@ static void finish_frame(framer_state *st, int is_header_boundary,
       st->stream_id, st->output->length - st->output_length_at_start_of_frame,
       (uint8_t)((is_last_in_stream ? GRPC_CHTTP2_DATA_FLAG_END_STREAM : 0) |
                 (is_header_boundary ? GRPC_CHTTP2_DATA_FLAG_END_HEADERS : 0)));
+  st->stats->framing_bytes += 9;
   st->is_first_frame = 0;
 }
 
@@ -147,8 +149,10 @@ static void add_header_data(framer_state *st, gpr_slice slice) {
   remaining = GRPC_CHTTP2_MAX_PAYLOAD_LENGTH +
               st->output_length_at_start_of_frame - st->output->length;
   if (len <= remaining) {
+    st->stats->header_bytes += len;
     gpr_slice_buffer_add(st->output, slice);
   } else {
+    st->stats->header_bytes += remaining;
     gpr_slice_buffer_add(st->output, gpr_slice_split_head(&slice, remaining));
     finish_frame(st, 0, 0);
     begin_frame(st);
@@ -535,6 +539,7 @@ void grpc_chttp2_hpack_compressor_set_max_table_size(
 void grpc_chttp2_encode_header(grpc_chttp2_hpack_compressor *c,
                                uint32_t stream_id,
                                grpc_metadata_batch *metadata, int is_eof,
+                               grpc_transport_one_way_stats *stats,
                                gpr_slice_buffer *outbuf) {
   framer_state st;
   grpc_linked_mdelem *l;
@@ -546,6 +551,7 @@ void grpc_chttp2_encode_header(grpc_chttp2_hpack_compressor *c,
   st.stream_id = stream_id;
   st.output = outbuf;
   st.is_first_frame = 1;
+  st.stats = stats;
 
   /* Encode a metadata batch; store the returned values, representing
      a metadata element that needs to be unreffed back into the metadata
diff --git a/src/core/ext/transport/chttp2/transport/hpack_encoder.h b/src/core/ext/transport/chttp2/transport/hpack_encoder.h
index d79de35979..91c368fbe2 100644
--- a/src/core/ext/transport/chttp2/transport/hpack_encoder.h
+++ b/src/core/ext/transport/chttp2/transport/hpack_encoder.h
@@ -40,6 +40,7 @@
 #include "src/core/ext/transport/chttp2/transport/frame.h"
 #include "src/core/lib/transport/metadata.h"
 #include "src/core/lib/transport/metadata_batch.h"
+#include "src/core/lib/transport/transport.h"
 
 #define GRPC_CHTTP2_HPACKC_NUM_FILTERS 256
 #define GRPC_CHTTP2_HPACKC_NUM_VALUES 256
@@ -90,6 +91,7 @@ void grpc_chttp2_hpack_compressor_set_max_usable_size(
 
 void grpc_chttp2_encode_header(grpc_chttp2_hpack_compressor *c, uint32_t id,
                                grpc_metadata_batch *metadata, int is_eof,
+                               grpc_transport_one_way_stats *stats,
                                gpr_slice_buffer *outbuf);
 
 #endif /* GRPC_CORE_EXT_TRANSPORT_CHTTP2_TRANSPORT_HPACK_ENCODER_H */
diff --git a/src/core/ext/transport/chttp2/transport/hpack_parser.c b/src/core/ext/transport/chttp2/transport/hpack_parser.c
index ec3387efb8..259452fa42 100644
--- a/src/core/ext/transport/chttp2/transport/hpack_parser.c
+++ b/src/core/ext/transport/chttp2/transport/hpack_parser.c
@@ -1426,6 +1426,9 @@ grpc_chttp2_parse_error grpc_chttp2_header_parser_parse(
     grpc_chttp2_stream_parsing *stream_parsing, gpr_slice slice, int is_last) {
   grpc_chttp2_hpack_parser *parser = hpack_parser;
   GPR_TIMER_BEGIN("grpc_chttp2_hpack_parser_parse", 0);
+  if (stream_parsing != NULL) {
+    stream_parsing->stats.incoming.header_bytes += GPR_SLICE_LENGTH(slice);
+  }
   if (!grpc_chttp2_hpack_parser_parse(parser, GPR_SLICE_START_PTR(slice),
                                       GPR_SLICE_END_PTR(slice))) {
     GPR_TIMER_END("grpc_chttp2_hpack_parser_parse", 0);
diff --git a/src/core/ext/transport/chttp2/transport/internal.h b/src/core/ext/transport/chttp2/transport/internal.h
index 2fae653623..2c3c7a3820 100644
--- a/src/core/ext/transport/chttp2/transport/internal.h
+++ b/src/core/ext/transport/chttp2/transport/internal.h
@@ -394,6 +394,9 @@ typedef struct {
   grpc_metadata_batch *recv_trailing_metadata;
   grpc_closure *recv_trailing_metadata_finished;
 
+  grpc_transport_stream_stats *collecting_stats;
+  grpc_transport_stream_stats stats;
+
   /** when the application requests writes be closed, the write_closed is
       'queued'; when the close is flow controlled into the send path, we are
       'sending' it; when the write has been performed it is 'sent' */
@@ -435,6 +438,8 @@ typedef struct {
   gpr_slice fetching_slice;
   size_t stream_fetched;
   grpc_closure finished_fetch;
+  /** stats gathered during the write */
+  grpc_transport_one_way_stats stats;
 } grpc_chttp2_stream_writing;
 
 struct grpc_chttp2_stream_parsing {
@@ -460,6 +465,8 @@ struct grpc_chttp2_stream_parsing {
   int64_t outgoing_window;
   /** number of bytes received - reset at end of parse thread execution */
   int64_t received_bytes;
+  /** stats gathered during the parse */
+  grpc_transport_stream_stats stats;
 
   /** incoming metadata */
   grpc_chttp2_incoming_metadata_buffer metadata_buffer[2];
@@ -635,6 +642,7 @@ void grpc_chttp2_parsing_become_skip_parser(
     grpc_exec_ctx *exec_ctx, grpc_chttp2_transport_parsing *transport_parsing);
 
 void grpc_chttp2_complete_closure_step(grpc_exec_ctx *exec_ctx,
+                                       grpc_chttp2_stream_global *stream_global,
                                        grpc_closure **pclosure, int success);
 
 #define GRPC_CHTTP2_CLIENT_CONNECT_STRING "PRI * HTTP/2.0\r\n\r\nSM\r\n\r\n"
diff --git a/src/core/ext/transport/chttp2/transport/parsing.c b/src/core/ext/transport/chttp2/transport/parsing.c
index a9f043cee3..1e815e096b 100644
--- a/src/core/ext/transport/chttp2/transport/parsing.c
+++ b/src/core/ext/transport/chttp2/transport/parsing.c
@@ -171,6 +171,9 @@ void grpc_chttp2_publish_reads(
       grpc_chttp2_list_add_check_read_ops(transport_global, stream_global);
     }
 
+    /* flush stats to global stream state */
+    grpc_transport_move_stats(&stream_parsing->stats, &stream_global->stats);
+
     /* update outgoing flow control window */
     was_zero = stream_global->outgoing_window <= 0;
     GRPC_CHTTP2_FLOW_MOVE_STREAM("parsed", transport_global, stream_global,
@@ -544,8 +547,13 @@ static int init_data_frame_parser(
       grpc_chttp2_parsing_lookup_stream(transport_parsing,
                                         transport_parsing->incoming_stream_id);
   grpc_chttp2_parse_error err = GRPC_CHTTP2_PARSE_OK;
-  if (!stream_parsing || stream_parsing->received_close)
+  if (stream_parsing == NULL) {
+    return init_skip_frame_parser(exec_ctx, transport_parsing, 0);
+  }
+  stream_parsing->stats.incoming.framing_bytes += 9;
+  if (stream_parsing->received_close) {
     return init_skip_frame_parser(exec_ctx, transport_parsing, 0);
+  }
   if (err == GRPC_CHTTP2_PARSE_OK) {
     err = update_incoming_window(exec_ctx, transport_parsing, stream_parsing);
   }
@@ -566,7 +574,8 @@ static int init_data_frame_parser(
       gpr_slice_buffer_add(
           &transport_parsing->qbuf,
           grpc_chttp2_rst_stream_create(transport_parsing->incoming_stream_id,
-                                        GRPC_CHTTP2_PROTOCOL_ERROR));
+                                        GRPC_CHTTP2_PROTOCOL_ERROR,
+                                        &stream_parsing->stats.outgoing));
       return init_skip_frame_parser(exec_ctx, transport_parsing, 0);
     case GRPC_CHTTP2_CONNECTION_ERROR:
       return 0;
@@ -717,6 +726,7 @@ static int init_header_frame_parser(
     transport_parsing->incoming_stream = stream_parsing;
   }
   GPR_ASSERT(stream_parsing != NULL && (via_accept == 0 || via_accept == 1));
+  stream_parsing->stats.incoming.framing_bytes += 9;
   if (stream_parsing->received_close) {
     gpr_log(GPR_ERROR, "skipping already closed grpc_chttp2_stream header");
     transport_parsing->incoming_stream = NULL;
@@ -752,9 +762,14 @@ static int init_window_update_frame_parser(
                                        &transport_parsing->simple.window_update,
                                        transport_parsing->incoming_frame_size,
                                        transport_parsing->incoming_frame_flags);
-  if (transport_parsing->incoming_stream_id) {
-    transport_parsing->incoming_stream = grpc_chttp2_parsing_lookup_stream(
-        transport_parsing, transport_parsing->incoming_stream_id);
+  if (transport_parsing->incoming_stream_id != 0) {
+    grpc_chttp2_stream_parsing *stream_parsing =
+        transport_parsing->incoming_stream = grpc_chttp2_parsing_lookup_stream(
+            transport_parsing, transport_parsing->incoming_stream_id);
+    if (stream_parsing == NULL) {
+      return init_skip_frame_parser(exec_ctx, transport_parsing, 0);
+    }
+    stream_parsing->stats.incoming.framing_bytes += 9;
   }
   transport_parsing->parser = grpc_chttp2_window_update_parser_parse;
   transport_parsing->parser_data = &transport_parsing->simple.window_update;
@@ -778,11 +793,13 @@ static int init_rst_stream_parser(
                                        &transport_parsing->simple.rst_stream,
                                        transport_parsing->incoming_frame_size,
                                        transport_parsing->incoming_frame_flags);
-  transport_parsing->incoming_stream = grpc_chttp2_parsing_lookup_stream(
-      transport_parsing, transport_parsing->incoming_stream_id);
+  grpc_chttp2_stream_parsing *stream_parsing =
+      transport_parsing->incoming_stream = grpc_chttp2_parsing_lookup_stream(
+          transport_parsing, transport_parsing->incoming_stream_id);
   if (!transport_parsing->incoming_stream) {
     return init_skip_frame_parser(exec_ctx, transport_parsing, 0);
   }
+  stream_parsing->stats.incoming.framing_bytes += 9;
   transport_parsing->parser = grpc_chttp2_rst_stream_parser_parse;
   transport_parsing->parser_data = &transport_parsing->simple.rst_stream;
   return ok;
@@ -856,7 +873,8 @@ static int parse_frame_slice(grpc_exec_ctx *exec_ctx,
         gpr_slice_buffer_add(
             &transport_parsing->qbuf,
             grpc_chttp2_rst_stream_create(transport_parsing->incoming_stream_id,
-                                          GRPC_CHTTP2_PROTOCOL_ERROR));
+                                          GRPC_CHTTP2_PROTOCOL_ERROR,
+                                          &stream_parsing->stats.outgoing));
       }
       return 1;
     case GRPC_CHTTP2_CONNECTION_ERROR:
diff --git a/src/core/ext/transport/chttp2/transport/writing.c b/src/core/ext/transport/chttp2/transport/writing.c
index 8d5886f225..6bb188f1da 100644
--- a/src/core/ext/transport/chttp2/transport/writing.c
+++ b/src/core/ext/transport/chttp2/transport/writing.c
@@ -161,8 +161,10 @@ int grpc_chttp2_unlocking_check_writes(
         transport_global->announce_incoming_window, UINT32_MAX);
     GRPC_CHTTP2_FLOW_DEBIT_TRANSPORT("write", transport_global,
                                      announce_incoming_window, announced);
-    gpr_slice_buffer_add(&transport_writing->outbuf,
-                         grpc_chttp2_window_update_create(0, announced));
+    grpc_transport_one_way_stats throwaway_stats;
+    gpr_slice_buffer_add(
+        &transport_writing->outbuf,
+        grpc_chttp2_window_update_create(0, announced, &throwaway_stats));
   }
 
   GPR_TIMER_END("grpc_chttp2_unlocking_check_writes", 0);
@@ -205,7 +207,8 @@ static void finalize_outbuf(grpc_exec_ctx *exec_ctx,
     if (stream_writing->send_initial_metadata != NULL) {
       grpc_chttp2_encode_header(
           &transport_writing->hpack_compressor, stream_writing->id,
-          stream_writing->send_initial_metadata, 0, &transport_writing->outbuf);
+          stream_writing->send_initial_metadata, 0, &stream_writing->stats,
+          &transport_writing->outbuf);
       stream_writing->send_initial_metadata = NULL;
       stream_writing->sent_initial_metadata = 1;
     }
@@ -216,7 +219,8 @@ static void finalize_outbuf(grpc_exec_ctx *exec_ctx,
       gpr_slice_buffer_add(
           &transport_writing->outbuf,
           grpc_chttp2_window_update_create(stream_writing->id,
-                                           stream_writing->announce_window));
+                                           stream_writing->announce_window,
+                                           &stream_writing->stats));
       GRPC_CHTTP2_FLOW_DEBIT_STREAM("write", transport_writing, stream_writing,
                                     announce_window, announce);
       stream_writing->announce_window = 0;
@@ -255,7 +259,8 @@ static void finalize_outbuf(grpc_exec_ctx *exec_ctx,
                                 stream_writing->send_trailing_metadata);
         grpc_chttp2_encode_data(
             stream_writing->id, &stream_writing->flow_controlled_buffer,
-            send_bytes, is_last_frame, &transport_writing->outbuf);
+            send_bytes, is_last_frame, &stream_writing->stats,
+            &transport_writing->outbuf);
         GRPC_CHTTP2_FLOW_DEBIT_STREAM("write", transport_writing,
                                       stream_writing, outgoing_window,
                                       send_bytes);
@@ -281,19 +286,20 @@ static void finalize_outbuf(grpc_exec_ctx *exec_ctx,
         stream_writing->send_trailing_metadata != NULL) {
       if (grpc_metadata_batch_is_empty(
               stream_writing->send_trailing_metadata)) {
-        grpc_chttp2_encode_data(stream_writing->id,
-                                &stream_writing->flow_controlled_buffer, 0, 1,
-                                &transport_writing->outbuf);
+        grpc_chttp2_encode_data(
+            stream_writing->id, &stream_writing->flow_controlled_buffer, 0, 1,
+            &stream_writing->stats, &transport_writing->outbuf);
       } else {
-        grpc_chttp2_encode_header(&transport_writing->hpack_compressor,
-                                  stream_writing->id,
-                                  stream_writing->send_trailing_metadata, 1,
-                                  &transport_writing->outbuf);
+        grpc_chttp2_encode_header(
+            &transport_writing->hpack_compressor, stream_writing->id,
+            stream_writing->send_trailing_metadata, 1, &stream_writing->stats,
+            &transport_writing->outbuf);
       }
       if (!transport_writing->is_client && !stream_writing->read_closed) {
         gpr_slice_buffer_add(&transport_writing->outbuf,
                              grpc_chttp2_rst_stream_create(
-                                 stream_writing->id, GRPC_CHTTP2_NO_ERROR));
+                                 stream_writing->id, GRPC_CHTTP2_NO_ERROR,
+                                 &stream_writing->stats));
       }
       stream_writing->send_trailing_metadata = NULL;
       stream_writing->sent_trailing_metadata = 1;
@@ -328,17 +334,21 @@ void grpc_chttp2_cleanup_writing(
       transport_global, transport_writing, &stream_global, &stream_writing)) {
     if (stream_writing->sent_initial_metadata) {
       grpc_chttp2_complete_closure_step(
-          exec_ctx, &stream_global->send_initial_metadata_finished, 1);
+          exec_ctx, stream_global,
+          &stream_global->send_initial_metadata_finished, 1);
     }
+    grpc_transport_move_one_way_stats(&stream_writing->stats,
+                                      &stream_global->stats.outgoing);
     if (stream_writing->sent_message) {
       GPR_ASSERT(stream_writing->send_message == NULL);
       grpc_chttp2_complete_closure_step(
-          exec_ctx, &stream_global->send_message_finished, 1);
+          exec_ctx, stream_global, &stream_global->send_message_finished, 1);
       stream_writing->sent_message = 0;
     }
     if (stream_writing->sent_trailing_metadata) {
       grpc_chttp2_complete_closure_step(
-          exec_ctx, &stream_global->send_trailing_metadata_finished, 1);
+          exec_ctx, stream_global,
+          &stream_global->send_trailing_metadata_finished, 1);
     }
     if (stream_writing->sent_trailing_metadata) {
       grpc_chttp2_mark_stream_closed(exec_ctx, transport_global, stream_global,
diff --git a/src/core/lib/channel/http_client_filter.c b/src/core/lib/channel/http_client_filter.c
index 7dbac38414..b4e58b7f29 100644
--- a/src/core/lib/channel/http_client_filter.c
+++ b/src/core/lib/channel/http_client_filter.c
@@ -112,7 +112,9 @@ static void hc_mutate_op(grpc_call_element *elem,
     /* Send : prefixed headers, which have to be before any application
        layer headers. */
     grpc_metadata_batch_add_head(op->send_initial_metadata, &calld->method,
-                                 GRPC_MDELEM_METHOD_POST);
+                                 op->send_idempotent_request
+                                     ? GRPC_MDELEM_METHOD_PUT
+                                     : GRPC_MDELEM_METHOD_POST);
     grpc_metadata_batch_add_head(op->send_initial_metadata, &calld->scheme,
                                  channeld->static_scheme);
     grpc_metadata_batch_add_tail(op->send_initial_metadata, &calld->te_trailers,
diff --git a/src/core/lib/channel/http_server_filter.c b/src/core/lib/channel/http_server_filter.c
index df99b77ab3..db1a3d5010 100644
--- a/src/core/lib/channel/http_server_filter.c
+++ b/src/core/lib/channel/http_server_filter.c
@@ -41,7 +41,7 @@
 
 typedef struct call_data {
   uint8_t seen_path;
-  uint8_t seen_post;
+  uint8_t seen_method;
   uint8_t sent_status;
   uint8_t seen_scheme;
   uint8_t seen_te_trailers;
@@ -50,6 +50,7 @@ typedef struct call_data {
   grpc_linked_mdelem content_type;
 
   grpc_metadata_batch *recv_initial_metadata;
+  bool *recv_idempotent_request;
   /** Closure to call when finished with the hs_on_recv hook */
   grpc_closure *on_done_recv;
   /** Receive closures are chained: we inject this closure as the on_done_recv
@@ -72,11 +73,16 @@ static grpc_mdelem *server_filter(void *user_data, grpc_mdelem *md) {
 
   /* Check if it is one of the headers we care about. */
   if (md == GRPC_MDELEM_TE_TRAILERS || md == GRPC_MDELEM_METHOD_POST ||
-      md == GRPC_MDELEM_SCHEME_HTTP || md == GRPC_MDELEM_SCHEME_HTTPS ||
+      md == GRPC_MDELEM_METHOD_PUT || md == GRPC_MDELEM_SCHEME_HTTP ||
+      md == GRPC_MDELEM_SCHEME_HTTPS ||
       md == GRPC_MDELEM_CONTENT_TYPE_APPLICATION_SLASH_GRPC) {
     /* swallow it */
     if (md == GRPC_MDELEM_METHOD_POST) {
-      calld->seen_post = 1;
+      calld->seen_method = 1;
+      *calld->recv_idempotent_request = false;
+    } else if (md == GRPC_MDELEM_METHOD_PUT) {
+      calld->seen_method = 1;
+      *calld->recv_idempotent_request = true;
     } else if (md->key == GRPC_MDSTR_SCHEME) {
       calld->seen_scheme = 1;
     } else if (md == GRPC_MDELEM_TE_TRAILERS) {
@@ -142,7 +148,7 @@ static void hs_on_recv(grpc_exec_ctx *exec_ctx, void *user_data, bool success) {
     /* Have we seen the required http2 transport headers?
        (:method, :scheme, content-type, with :path and :authority covered
        at the channel level right now) */
-    if (calld->seen_post && calld->seen_scheme && calld->seen_te_trailers &&
+    if (calld->seen_method && calld->seen_scheme && calld->seen_te_trailers &&
         calld->seen_path && calld->seen_authority) {
       /* do nothing */
     } else {
@@ -152,7 +158,7 @@ static void hs_on_recv(grpc_exec_ctx *exec_ctx, void *user_data, bool success) {
       if (!calld->seen_authority) {
         gpr_log(GPR_ERROR, "Missing :authority header");
       }
-      if (!calld->seen_post) {
+      if (!calld->seen_method) {
         gpr_log(GPR_ERROR, "Missing :method header");
       }
       if (!calld->seen_scheme) {
@@ -185,7 +191,9 @@ static void hs_mutate_op(grpc_call_element *elem,
 
   if (op->recv_initial_metadata) {
     /* substitute our callback for the higher callback */
+    GPR_ASSERT(op->recv_idempotent_request != NULL);
     calld->recv_initial_metadata = op->recv_initial_metadata;
+    calld->recv_idempotent_request = op->recv_idempotent_request;
     calld->on_done_recv = op->recv_initial_metadata_ready;
     op->recv_initial_metadata_ready = &calld->hs_on_recv;
   }
diff --git a/src/core/lib/iomgr/unix_sockets_posix_noop.c b/src/core/lib/iomgr/unix_sockets_posix_noop.c
index 06f6ee05e7..43e006e15e 100644
--- a/src/core/lib/iomgr/unix_sockets_posix_noop.c
+++ b/src/core/lib/iomgr/unix_sockets_posix_noop.c
@@ -35,7 +35,12 @@
 
 #ifndef GPR_HAVE_UNIX_SOCKET
 
-void grpc_create_socketpair_if_unix(int sv[2]) {}
+void grpc_create_socketpair_if_unix(int sv[2]) {
+  // TODO: Either implement this for the non-Unix socket case or make
+  // sure that it is never called in any such case. Until then, leave an
+  // assertion to notify if this gets called inadvertently
+  GPR_ASSERT(0);
+}
 
 grpc_resolved_addresses *grpc_resolve_unix_domain_address(const char *name) {
   return NULL;
diff --git a/src/core/lib/surface/call.c b/src/core/lib/surface/call.c
index d63a4a7401..77ad410b50 100644
--- a/src/core/lib/surface/call.c
+++ b/src/core/lib/surface/call.c
@@ -174,6 +174,9 @@ struct grpc_call {
   /* Received call statuses from various sources */
   received_status status[STATUS_SOURCE_COUNT];
 
+  /* Call stats: only valid after trailing metadata received */
+  grpc_transport_stream_stats stats;
+
   /* Compression algorithm for the call */
   grpc_compression_algorithm compression_algorithm;
   /* Supported encodings (compression algorithms), a bitset */
@@ -909,7 +912,7 @@ static void set_cancelled_value(grpc_status_code status, void *dest) {
   *(int *)dest = (status != GRPC_STATUS_OK);
 }
 
-static int are_write_flags_valid(uint32_t flags) {
+static bool are_write_flags_valid(uint32_t flags) {
   /* check that only bits in GRPC_WRITE_(INTERNAL?)_USED_MASK are set */
   const uint32_t allowed_write_positions =
       (GRPC_WRITE_USED_MASK | GRPC_WRITE_INTERNAL_USED_MASK);
@@ -917,6 +920,15 @@ static int are_write_flags_valid(uint32_t flags) {
   return !(flags & invalid_positions);
 }
 
+static bool are_initial_metadata_flags_valid(uint32_t flags, bool is_client) {
+  /* check that only bits in GRPC_WRITE_(INTERNAL?)_USED_MASK are set */
+  uint32_t invalid_positions = ~GRPC_INITIAL_METADATA_USED_MASK;
+  if (!is_client) {
+    invalid_positions |= GRPC_INITIAL_METADATA_IDEMPOTENT_REQUEST;
+  }
+  return !(flags & invalid_positions);
+}
+
 static batch_control *allocate_batch_control(grpc_call *call) {
   size_t i;
   for (i = 0; i < MAX_CONCURRENT_BATCHES; i++) {
@@ -1196,7 +1208,7 @@ static grpc_call_error call_start_batch(grpc_exec_ctx *exec_ctx,
     switch (op->op) {
       case GRPC_OP_SEND_INITIAL_METADATA:
         /* Flag validation: currently allow no flags */
-        if (op->flags != 0) {
+        if (!are_initial_metadata_flags_valid(op->flags, call->is_client)) {
           error = GRPC_CALL_ERROR_INVALID_FLAGS;
           goto done_with_error;
         }
@@ -1220,6 +1232,8 @@ static grpc_call_error call_start_batch(grpc_exec_ctx *exec_ctx,
         call->metadata_batch[0][0].deadline = call->send_deadline;
         stream_op.send_initial_metadata =
             &call->metadata_batch[0 /* is_receiving */][0 /* is_trailing */];
+        stream_op.send_idempotent_request =
+            (op->flags & GRPC_INITIAL_METADATA_IDEMPOTENT_REQUEST) != 0;
         break;
       case GRPC_OP_SEND_MESSAGE:
         if (!are_write_flags_valid(op->flags)) {
@@ -1371,6 +1385,7 @@ static grpc_call_error call_start_batch(grpc_exec_ctx *exec_ctx,
         bctl->recv_final_op = 1;
         stream_op.recv_trailing_metadata =
             &call->metadata_batch[1 /* is_receiving */][1 /* is_trailing */];
+        stream_op.collect_stats = &call->stats;
         break;
       case GRPC_OP_RECV_CLOSE_ON_SERVER:
         /* Flag validation: currently allow no flags */
@@ -1392,6 +1407,7 @@ static grpc_call_error call_start_batch(grpc_exec_ctx *exec_ctx,
         bctl->recv_final_op = 1;
         stream_op.recv_trailing_metadata =
             &call->metadata_batch[1 /* is_receiving */][1 /* is_trailing */];
+        stream_op.collect_stats = &call->stats;
         break;
     }
   }
diff --git a/src/core/lib/surface/init.c b/src/core/lib/surface/init.c
index 432c7590b2..786bf1d5da 100644
--- a/src/core/lib/surface/init.c
+++ b/src/core/lib/surface/init.c
@@ -168,7 +168,7 @@ void grpc_init(void) {
     grpc_register_resolver_type(grpc_dns_resolver_factory_create());
     grpc_register_resolver_type(grpc_ipv4_resolver_factory_create());
     grpc_register_resolver_type(grpc_ipv6_resolver_factory_create());
-#ifdef GPR_POSIX_SOCKET
+#ifdef GPR_HAVE_UNIX_SOCKET
     grpc_register_resolver_type(grpc_unix_resolver_factory_create());
 #endif
     grpc_register_tracer("api", &grpc_api_trace);
diff --git a/src/core/lib/surface/server.c b/src/core/lib/surface/server.c
index 080734e9d5..55e5e49e11 100644
--- a/src/core/lib/surface/server.c
+++ b/src/core/lib/surface/server.c
@@ -100,6 +100,7 @@ typedef struct requested_call {
 
 typedef struct channel_registered_method {
   registered_method *server_registered_method;
+  uint32_t flags;
   grpc_mdstr *method;
   grpc_mdstr *host;
 } channel_registered_method;
@@ -152,6 +153,7 @@ struct call_data {
   grpc_completion_queue *cq_new;
 
   grpc_metadata_batch *recv_initial_metadata;
+  bool recv_idempotent_request;
   grpc_metadata_array initial_metadata;
 
   grpc_closure got_initial_metadata;
@@ -171,6 +173,7 @@ struct request_matcher {
 struct registered_method {
   char *method;
   char *host;
+  uint32_t flags;
   request_matcher request_matcher;
   registered_method *next;
 };
@@ -468,6 +471,9 @@ static void start_new_rpc(grpc_exec_ctx *exec_ctx, grpc_call_element *elem) {
       if (!rm) break;
       if (rm->host != calld->host) continue;
       if (rm->method != calld->path) continue;
+      if ((rm->flags & GRPC_INITIAL_METADATA_IDEMPOTENT_REQUEST) &&
+          !calld->recv_idempotent_request)
+        continue;
       finish_start_new_rpc(exec_ctx, server, elem,
                            &rm->server_registered_method->request_matcher);
       return;
@@ -480,6 +486,9 @@ static void start_new_rpc(grpc_exec_ctx *exec_ctx, grpc_call_element *elem) {
       if (!rm) break;
       if (rm->host != NULL) continue;
       if (rm->method != calld->path) continue;
+      if ((rm->flags & GRPC_INITIAL_METADATA_IDEMPOTENT_REQUEST) &&
+          !calld->recv_idempotent_request)
+        continue;
       finish_start_new_rpc(exec_ctx, server, elem,
                            &rm->server_registered_method->request_matcher);
       return;
@@ -598,9 +607,11 @@ static void server_mutate_op(grpc_call_element *elem,
   call_data *calld = elem->call_data;
 
   if (op->recv_initial_metadata != NULL) {
+    GPR_ASSERT(op->recv_idempotent_request == NULL);
     calld->recv_initial_metadata = op->recv_initial_metadata;
     calld->on_done_recv_initial_metadata = op->recv_initial_metadata_ready;
     op->recv_initial_metadata_ready = &calld->server_on_recv_initial_metadata;
+    op->recv_idempotent_request = &calld->recv_idempotent_request;
   }
 }
 
@@ -830,10 +841,12 @@ static int streq(const char *a, const char *b) {
 }
 
 void *grpc_server_register_method(grpc_server *server, const char *method,
-                                  const char *host) {
+                                  const char *host, uint32_t flags) {
   registered_method *m;
-  GRPC_API_TRACE("grpc_server_register_method(server=%p, method=%s, host=%s)",
-                 3, (server, method, host));
+  GRPC_API_TRACE(
+      "grpc_server_register_method(server=%p, method=%s, host=%s, "
+      "flags=0x%08x)",
+      4, (server, method, host, flags));
   if (!method) {
     gpr_log(GPR_ERROR,
             "grpc_server_register_method method string cannot be NULL");
@@ -846,12 +859,18 @@ void *grpc_server_register_method(grpc_server *server, const char *method,
       return NULL;
     }
   }
+  if ((flags & ~GRPC_INITIAL_METADATA_USED_MASK) != 0) {
+    gpr_log(GPR_ERROR, "grpc_server_register_method invalid flags 0x%08x",
+            flags);
+    return NULL;
+  }
   m = gpr_malloc(sizeof(registered_method));
   memset(m, 0, sizeof(*m));
   request_matcher_init(&m->request_matcher, server->max_requested_calls);
   m->method = gpr_strdup(method);
   m->host = gpr_strdup(host);
   m->next = server->registered_methods;
+  m->flags = flags;
   server->registered_methods = m;
   return m;
 }
@@ -930,6 +949,7 @@ void grpc_server_setup_transport(grpc_exec_ctx *exec_ctx, grpc_server *s,
       if (probes > max_probes) max_probes = probes;
       crm = &chand->registered_methods[(hash + probes) % slots];
       crm->server_registered_method = rm;
+      crm->flags = rm->flags;
       crm->host = host;
       crm->method = method;
     }
@@ -1247,6 +1267,10 @@ static void begin_call(grpc_exec_ctx *exec_ctx, grpc_server *server,
       cpstr(&rc->data.batch.details->method,
             &rc->data.batch.details->method_capacity, calld->path);
       rc->data.batch.details->deadline = calld->deadline;
+      rc->data.batch.details->flags =
+          0 | (calld->recv_idempotent_request
+                   ? GRPC_INITIAL_METADATA_IDEMPOTENT_REQUEST
+                   : 0);
       break;
     case REGISTERED_CALL:
       *rc->data.registered.deadline = calld->deadline;
diff --git a/src/core/lib/transport/static_metadata.c b/src/core/lib/transport/static_metadata.c
index eda277b3dc..bde1fafc88 100644
--- a/src/core/lib/transport/static_metadata.c
+++ b/src/core/lib/transport/static_metadata.c
@@ -1,5 +1,4 @@
 /*
- *
  * Copyright 2015-2016, Google Inc.
  * All rights reserved.
  *
@@ -28,19 +27,16 @@
  * 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.
- *
  */
 
 /*
  * WARNING: Auto-generated code.
  *
  * To make changes to this file, change
- * tools/codegen/core/gen_static_metadata.py,
- * and then re-run it.
+ * tools/codegen/core/gen_static_metadata.py, and then re-run it.
  *
  * See metadata.h for an explanation of the interface here, and metadata.c for
- * an
- * explanation of what's going on.
+ * an explanation of what's going on.
  */
 
 #include "src/core/lib/transport/static_metadata.h"
@@ -52,7 +48,7 @@ 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, 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};
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0};
 
 const uint8_t grpc_static_metadata_elem_indices[GRPC_STATIC_MDELEM_COUNT * 2] =
     {11, 35, 10, 35, 12, 35, 12, 49, 13, 35, 14, 35, 15, 35, 16, 35, 17, 35,
@@ -60,10 +56,10 @@ const uint8_t grpc_static_metadata_elem_indices[GRPC_STATIC_MDELEM_COUNT * 2] =
      30, 18, 30, 35, 31, 35, 32, 35, 36, 35, 37, 35, 38, 35, 39, 35, 42, 33,
      42, 34, 42, 48, 42, 53, 42, 54, 42, 55, 42, 56, 43, 33, 43, 48, 43, 53,
      46, 0,  46, 1,  46, 2,  50, 35, 57, 35, 58, 35, 59, 35, 60, 35, 61, 35,
-     62, 35, 63, 35, 64, 35, 65, 35, 66, 40, 66, 68, 67, 78, 67, 79, 69, 35,
-     70, 35, 71, 35, 72, 35, 73, 35, 74, 35, 75, 41, 75, 51, 75, 52, 76, 35,
-     77, 35, 80, 3,  80, 4,  80, 5,  80, 6,  80, 7,  80, 8,  80, 9,  81, 35,
-     82, 83, 84, 35, 85, 35, 86, 35, 87, 35, 88, 35};
+     62, 35, 63, 35, 64, 35, 65, 35, 66, 40, 66, 68, 66, 71, 67, 79, 67, 80,
+     69, 35, 70, 35, 72, 35, 73, 35, 74, 35, 75, 35, 76, 41, 76, 51, 76, 52,
+     77, 35, 78, 35, 81, 3,  81, 4,  81, 5,  81, 6,  81, 7,  81, 8,  81, 9,
+     82, 35, 83, 84, 85, 35, 86, 35, 87, 35, 88, 35, 89, 35};
 
 const char *const grpc_static_metadata_strings[GRPC_STATIC_MDSTR_COUNT] = {
     "0",
@@ -137,6 +133,7 @@ const char *const grpc_static_metadata_strings[GRPC_STATIC_MDSTR_COUNT] = {
     "POST",
     "proxy-authenticate",
     "proxy-authorization",
+    "PUT",
     "range",
     "referer",
     "refresh",
diff --git a/src/core/lib/transport/static_metadata.h b/src/core/lib/transport/static_metadata.h
index aff136a6d2..a05553a870 100644
--- a/src/core/lib/transport/static_metadata.h
+++ b/src/core/lib/transport/static_metadata.h
@@ -1,5 +1,4 @@
 /*
- *
  * Copyright 2015-2016, Google Inc.
  * All rights reserved.
  *
@@ -28,19 +27,16 @@
  * 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.
- *
  */
 
 /*
  * WARNING: Auto-generated code.
  *
  * To make changes to this file, change
- * tools/codegen/core/gen_static_metadata.py,
- * and then re-run it.
+ * tools/codegen/core/gen_static_metadata.py, and then re-run it.
  *
  * See metadata.h for an explanation of the interface here, and metadata.c for
- * an
- * explanation of what's going on.
+ * an explanation of what's going on.
  */
 
 #ifndef GRPC_CORE_LIB_TRANSPORT_STATIC_METADATA_H
@@ -48,7 +44,7 @@
 
 #include "src/core/lib/transport/metadata.h"
 
-#define GRPC_STATIC_MDSTR_COUNT 89
+#define GRPC_STATIC_MDSTR_COUNT 90
 extern grpc_mdstr grpc_static_mdstr_table[GRPC_STATIC_MDSTR_COUNT];
 /* "0" */
 #define GRPC_MDSTR_0 (&grpc_static_mdstr_table[0])
@@ -193,44 +189,46 @@ extern grpc_mdstr grpc_static_mdstr_table[GRPC_STATIC_MDSTR_COUNT];
 #define GRPC_MDSTR_PROXY_AUTHENTICATE (&grpc_static_mdstr_table[69])
 /* "proxy-authorization" */
 #define GRPC_MDSTR_PROXY_AUTHORIZATION (&grpc_static_mdstr_table[70])
+/* "PUT" */
+#define GRPC_MDSTR_PUT (&grpc_static_mdstr_table[71])
 /* "range" */
-#define GRPC_MDSTR_RANGE (&grpc_static_mdstr_table[71])
+#define GRPC_MDSTR_RANGE (&grpc_static_mdstr_table[72])
 /* "referer" */
-#define GRPC_MDSTR_REFERER (&grpc_static_mdstr_table[72])
+#define GRPC_MDSTR_REFERER (&grpc_static_mdstr_table[73])
 /* "refresh" */
-#define GRPC_MDSTR_REFRESH (&grpc_static_mdstr_table[73])
+#define GRPC_MDSTR_REFRESH (&grpc_static_mdstr_table[74])
 /* "retry-after" */
-#define GRPC_MDSTR_RETRY_AFTER (&grpc_static_mdstr_table[74])
+#define GRPC_MDSTR_RETRY_AFTER (&grpc_static_mdstr_table[75])
 /* ":scheme" */
-#define GRPC_MDSTR_SCHEME (&grpc_static_mdstr_table[75])
+#define GRPC_MDSTR_SCHEME (&grpc_static_mdstr_table[76])
 /* "server" */
-#define GRPC_MDSTR_SERVER (&grpc_static_mdstr_table[76])
+#define GRPC_MDSTR_SERVER (&grpc_static_mdstr_table[77])
 /* "set-cookie" */
-#define GRPC_MDSTR_SET_COOKIE (&grpc_static_mdstr_table[77])
+#define GRPC_MDSTR_SET_COOKIE (&grpc_static_mdstr_table[78])
 /* "/" */
-#define GRPC_MDSTR_SLASH (&grpc_static_mdstr_table[78])
+#define GRPC_MDSTR_SLASH (&grpc_static_mdstr_table[79])
 /* "/index.html" */
-#define GRPC_MDSTR_SLASH_INDEX_DOT_HTML (&grpc_static_mdstr_table[79])
+#define GRPC_MDSTR_SLASH_INDEX_DOT_HTML (&grpc_static_mdstr_table[80])
 /* ":status" */
-#define GRPC_MDSTR_STATUS (&grpc_static_mdstr_table[80])
+#define GRPC_MDSTR_STATUS (&grpc_static_mdstr_table[81])
 /* "strict-transport-security" */
-#define GRPC_MDSTR_STRICT_TRANSPORT_SECURITY (&grpc_static_mdstr_table[81])
+#define GRPC_MDSTR_STRICT_TRANSPORT_SECURITY (&grpc_static_mdstr_table[82])
 /* "te" */
-#define GRPC_MDSTR_TE (&grpc_static_mdstr_table[82])
+#define GRPC_MDSTR_TE (&grpc_static_mdstr_table[83])
 /* "trailers" */
-#define GRPC_MDSTR_TRAILERS (&grpc_static_mdstr_table[83])
+#define GRPC_MDSTR_TRAILERS (&grpc_static_mdstr_table[84])
 /* "transfer-encoding" */
-#define GRPC_MDSTR_TRANSFER_ENCODING (&grpc_static_mdstr_table[84])
+#define GRPC_MDSTR_TRANSFER_ENCODING (&grpc_static_mdstr_table[85])
 /* "user-agent" */
-#define GRPC_MDSTR_USER_AGENT (&grpc_static_mdstr_table[85])
+#define GRPC_MDSTR_USER_AGENT (&grpc_static_mdstr_table[86])
 /* "vary" */
-#define GRPC_MDSTR_VARY (&grpc_static_mdstr_table[86])
+#define GRPC_MDSTR_VARY (&grpc_static_mdstr_table[87])
 /* "via" */
-#define GRPC_MDSTR_VIA (&grpc_static_mdstr_table[87])
+#define GRPC_MDSTR_VIA (&grpc_static_mdstr_table[88])
 /* "www-authenticate" */
-#define GRPC_MDSTR_WWW_AUTHENTICATE (&grpc_static_mdstr_table[88])
+#define GRPC_MDSTR_WWW_AUTHENTICATE (&grpc_static_mdstr_table[89])
 
-#define GRPC_STATIC_MDELEM_COUNT 78
+#define GRPC_STATIC_MDELEM_COUNT 79
 extern grpc_mdelem grpc_static_mdelem_table[GRPC_STATIC_MDELEM_COUNT];
 extern uintptr_t grpc_static_mdelem_user_data[GRPC_STATIC_MDELEM_COUNT];
 /* "accept-charset": "" */
@@ -343,61 +341,63 @@ extern uintptr_t grpc_static_mdelem_user_data[GRPC_STATIC_MDELEM_COUNT];
 #define GRPC_MDELEM_METHOD_GET (&grpc_static_mdelem_table[49])
 /* ":method": "POST" */
 #define GRPC_MDELEM_METHOD_POST (&grpc_static_mdelem_table[50])
+/* ":method": "PUT" */
+#define GRPC_MDELEM_METHOD_PUT (&grpc_static_mdelem_table[51])
 /* ":path": "/" */
-#define GRPC_MDELEM_PATH_SLASH (&grpc_static_mdelem_table[51])
+#define GRPC_MDELEM_PATH_SLASH (&grpc_static_mdelem_table[52])
 /* ":path": "/index.html" */
-#define GRPC_MDELEM_PATH_SLASH_INDEX_DOT_HTML (&grpc_static_mdelem_table[52])
+#define GRPC_MDELEM_PATH_SLASH_INDEX_DOT_HTML (&grpc_static_mdelem_table[53])
 /* "proxy-authenticate": "" */
-#define GRPC_MDELEM_PROXY_AUTHENTICATE_EMPTY (&grpc_static_mdelem_table[53])
+#define GRPC_MDELEM_PROXY_AUTHENTICATE_EMPTY (&grpc_static_mdelem_table[54])
 /* "proxy-authorization": "" */
-#define GRPC_MDELEM_PROXY_AUTHORIZATION_EMPTY (&grpc_static_mdelem_table[54])
+#define GRPC_MDELEM_PROXY_AUTHORIZATION_EMPTY (&grpc_static_mdelem_table[55])
 /* "range": "" */
-#define GRPC_MDELEM_RANGE_EMPTY (&grpc_static_mdelem_table[55])
+#define GRPC_MDELEM_RANGE_EMPTY (&grpc_static_mdelem_table[56])
 /* "referer": "" */
-#define GRPC_MDELEM_REFERER_EMPTY (&grpc_static_mdelem_table[56])
+#define GRPC_MDELEM_REFERER_EMPTY (&grpc_static_mdelem_table[57])
 /* "refresh": "" */
-#define GRPC_MDELEM_REFRESH_EMPTY (&grpc_static_mdelem_table[57])
+#define GRPC_MDELEM_REFRESH_EMPTY (&grpc_static_mdelem_table[58])
 /* "retry-after": "" */
-#define GRPC_MDELEM_RETRY_AFTER_EMPTY (&grpc_static_mdelem_table[58])
+#define GRPC_MDELEM_RETRY_AFTER_EMPTY (&grpc_static_mdelem_table[59])
 /* ":scheme": "grpc" */
-#define GRPC_MDELEM_SCHEME_GRPC (&grpc_static_mdelem_table[59])
+#define GRPC_MDELEM_SCHEME_GRPC (&grpc_static_mdelem_table[60])
 /* ":scheme": "http" */
-#define GRPC_MDELEM_SCHEME_HTTP (&grpc_static_mdelem_table[60])
+#define GRPC_MDELEM_SCHEME_HTTP (&grpc_static_mdelem_table[61])
 /* ":scheme": "https" */
-#define GRPC_MDELEM_SCHEME_HTTPS (&grpc_static_mdelem_table[61])
+#define GRPC_MDELEM_SCHEME_HTTPS (&grpc_static_mdelem_table[62])
 /* "server": "" */
-#define GRPC_MDELEM_SERVER_EMPTY (&grpc_static_mdelem_table[62])
+#define GRPC_MDELEM_SERVER_EMPTY (&grpc_static_mdelem_table[63])
 /* "set-cookie": "" */
-#define GRPC_MDELEM_SET_COOKIE_EMPTY (&grpc_static_mdelem_table[63])
+#define GRPC_MDELEM_SET_COOKIE_EMPTY (&grpc_static_mdelem_table[64])
 /* ":status": "200" */
-#define GRPC_MDELEM_STATUS_200 (&grpc_static_mdelem_table[64])
+#define GRPC_MDELEM_STATUS_200 (&grpc_static_mdelem_table[65])
 /* ":status": "204" */
-#define GRPC_MDELEM_STATUS_204 (&grpc_static_mdelem_table[65])
+#define GRPC_MDELEM_STATUS_204 (&grpc_static_mdelem_table[66])
 /* ":status": "206" */
-#define GRPC_MDELEM_STATUS_206 (&grpc_static_mdelem_table[66])
+#define GRPC_MDELEM_STATUS_206 (&grpc_static_mdelem_table[67])
 /* ":status": "304" */
-#define GRPC_MDELEM_STATUS_304 (&grpc_static_mdelem_table[67])
+#define GRPC_MDELEM_STATUS_304 (&grpc_static_mdelem_table[68])
 /* ":status": "400" */
-#define GRPC_MDELEM_STATUS_400 (&grpc_static_mdelem_table[68])
+#define GRPC_MDELEM_STATUS_400 (&grpc_static_mdelem_table[69])
 /* ":status": "404" */
-#define GRPC_MDELEM_STATUS_404 (&grpc_static_mdelem_table[69])
+#define GRPC_MDELEM_STATUS_404 (&grpc_static_mdelem_table[70])
 /* ":status": "500" */
-#define GRPC_MDELEM_STATUS_500 (&grpc_static_mdelem_table[70])
+#define GRPC_MDELEM_STATUS_500 (&grpc_static_mdelem_table[71])
 /* "strict-transport-security": "" */
 #define GRPC_MDELEM_STRICT_TRANSPORT_SECURITY_EMPTY \
-  (&grpc_static_mdelem_table[71])
+  (&grpc_static_mdelem_table[72])
 /* "te": "trailers" */
-#define GRPC_MDELEM_TE_TRAILERS (&grpc_static_mdelem_table[72])
+#define GRPC_MDELEM_TE_TRAILERS (&grpc_static_mdelem_table[73])
 /* "transfer-encoding": "" */
-#define GRPC_MDELEM_TRANSFER_ENCODING_EMPTY (&grpc_static_mdelem_table[73])
+#define GRPC_MDELEM_TRANSFER_ENCODING_EMPTY (&grpc_static_mdelem_table[74])
 /* "user-agent": "" */
-#define GRPC_MDELEM_USER_AGENT_EMPTY (&grpc_static_mdelem_table[74])
+#define GRPC_MDELEM_USER_AGENT_EMPTY (&grpc_static_mdelem_table[75])
 /* "vary": "" */
-#define GRPC_MDELEM_VARY_EMPTY (&grpc_static_mdelem_table[75])
+#define GRPC_MDELEM_VARY_EMPTY (&grpc_static_mdelem_table[76])
 /* "via": "" */
-#define GRPC_MDELEM_VIA_EMPTY (&grpc_static_mdelem_table[76])
+#define GRPC_MDELEM_VIA_EMPTY (&grpc_static_mdelem_table[77])
 /* "www-authenticate": "" */
-#define GRPC_MDELEM_WWW_AUTHENTICATE_EMPTY (&grpc_static_mdelem_table[77])
+#define GRPC_MDELEM_WWW_AUTHENTICATE_EMPTY (&grpc_static_mdelem_table[78])
 
 extern const uint8_t
     grpc_static_metadata_elem_indices[GRPC_STATIC_MDELEM_COUNT * 2];
diff --git a/src/core/lib/transport/transport.c b/src/core/lib/transport/transport.c
index 18256aae5e..411e4f140a 100644
--- a/src/core/lib/transport/transport.c
+++ b/src/core/lib/transport/transport.c
@@ -35,6 +35,7 @@
 #include <grpc/support/alloc.h>
 #include <grpc/support/atm.h>
 #include <grpc/support/log.h>
+#include <grpc/support/sync.h>
 #include "src/core/lib/transport/transport_impl.h"
 
 #ifdef GRPC_STREAM_REFCOUNT_DEBUG
@@ -76,6 +77,24 @@ void grpc_stream_ref_init(grpc_stream_refcount *refcount, int initial_refs,
   grpc_closure_init(&refcount->destroy, cb, cb_arg);
 }
 
+static void move64(uint64_t *from, uint64_t *to) {
+  *to += *from;
+  *from = 0;
+}
+
+void grpc_transport_move_one_way_stats(grpc_transport_one_way_stats *from,
+                                       grpc_transport_one_way_stats *to) {
+  move64(&from->framing_bytes, &to->framing_bytes);
+  move64(&from->data_bytes, &to->data_bytes);
+  move64(&from->header_bytes, &to->header_bytes);
+}
+
+void grpc_transport_move_stats(grpc_transport_stream_stats *from,
+                               grpc_transport_stream_stats *to) {
+  grpc_transport_move_one_way_stats(&from->incoming, &to->incoming);
+  grpc_transport_move_one_way_stats(&from->outgoing, &to->outgoing);
+}
+
 size_t grpc_transport_stream_size(grpc_transport *transport) {
   return transport->vtable->sizeof_stream;
 }
diff --git a/src/core/lib/transport/transport.h b/src/core/lib/transport/transport.h
index e98cfe9515..6dd782c19e 100644
--- a/src/core/lib/transport/transport.h
+++ b/src/core/lib/transport/transport.h
@@ -78,11 +78,32 @@ void grpc_stream_unref(grpc_exec_ctx *exec_ctx, grpc_stream_refcount *refcount);
   grpc_stream_ref_init(rc, ir, cb, cb_arg)
 #endif
 
+typedef struct {
+  uint64_t framing_bytes;
+  uint64_t data_bytes;
+  uint64_t header_bytes;
+} grpc_transport_one_way_stats;
+
+typedef struct grpc_transport_stream_stats {
+  grpc_transport_one_way_stats incoming;
+  grpc_transport_one_way_stats outgoing;
+} grpc_transport_stream_stats;
+
+void grpc_transport_move_one_way_stats(grpc_transport_one_way_stats *from,
+                                       grpc_transport_one_way_stats *to);
+
+void grpc_transport_move_stats(grpc_transport_stream_stats *from,
+                               grpc_transport_stream_stats *to);
+
 /* Transport stream op: a set of operations to perform on a transport
    against a single stream */
 typedef struct grpc_transport_stream_op {
-  /** Send initial metadata to the peer, from the provided metadata batch. */
+  /** Send initial metadata to the peer, from the provided metadata batch.
+      idempotent_request MUST be set if this is non-null */
   grpc_metadata_batch *send_initial_metadata;
+  /** Iff send_initial_metadata != NULL, flags if this is an idempotent request
+      or not */
+  bool send_idempotent_request;
 
   /** Send trailing metadata to the peer, from the provided metadata batch. */
   grpc_metadata_batch *send_trailing_metadata;
@@ -92,6 +113,7 @@ typedef struct grpc_transport_stream_op {
 
   /** Receive initial metadata from the stream, into provided metadata batch. */
   grpc_metadata_batch *recv_initial_metadata;
+  bool *recv_idempotent_request;
   /** Should be enqueued when initial metadata is ready to be processed. */
   grpc_closure *recv_initial_metadata_ready;
 
@@ -104,6 +126,9 @@ typedef struct grpc_transport_stream_op {
    */
   grpc_metadata_batch *recv_trailing_metadata;
 
+  /** Collect any stats into provided buffer, zero internal stat counters */
+  grpc_transport_stream_stats *collect_stats;
+
   /** Should be enqueued when all requested operations (excluding recv_message
       and recv_initial_metadata which have their own closures) in a given batch
       have been completed. */