Ensure streams are sent in-order

src/core/transport/chttp2/internal.h

@@ -403,6 +403,8 @@ typedef struct {
   grpc_stream_op_buffer sopb;
   /** how strongly should we indicate closure with the next write */
   grpc_chttp2_send_closed send_closed;
+  /** how much window should we announce? */
+  gpr_uint32 announce_window;
 } grpc_chttp2_stream_writing;
 
 struct grpc_chttp2_stream_parsing {
@@ -513,7 +515,9 @@ void grpc_chttp2_list_add_writable_window_update_stream(
     grpc_chttp2_stream_global *stream_global);
 int grpc_chttp2_list_pop_writable_window_update_stream(
     grpc_chttp2_transport_global *transport_global,
-    grpc_chttp2_stream_global **stream_global);
+    grpc_chttp2_transport_writing *transport_writing,
+    grpc_chttp2_stream_global **stream_global,
+    grpc_chttp2_stream_writing **stream_writing);
 void grpc_chttp2_list_remove_writable_window_update_stream(
     grpc_chttp2_transport_global *transport_global,
     grpc_chttp2_stream_global *stream_global);

src/core/transport/chttp2/stream_lists.c

@@ -139,6 +139,7 @@ static void stream_list_add(grpc_chttp2_transport *t, grpc_chttp2_stream *s,
 void grpc_chttp2_list_add_writable_stream(
     grpc_chttp2_transport_global *transport_global,
     grpc_chttp2_stream_global *stream_global) {
+  GPR_ASSERT(stream_global->id != 0);
   stream_list_add(TRANSPORT_FROM_GLOBAL(transport_global),
                   STREAM_FROM_GLOBAL(stream_global), GRPC_CHTTP2_LIST_WRITABLE);
 }
@@ -204,6 +205,7 @@ int grpc_chttp2_list_pop_written_stream(
 void grpc_chttp2_list_add_writable_window_update_stream(
     grpc_chttp2_transport_global *transport_global,
     grpc_chttp2_stream_global *stream_global) {
+  GPR_ASSERT(stream_global->id != 0);
   stream_list_add(TRANSPORT_FROM_GLOBAL(transport_global),
                   STREAM_FROM_GLOBAL(stream_global),
                   GRPC_CHTTP2_LIST_WRITABLE_WINDOW_UPDATE);
@@ -211,11 +213,14 @@ void grpc_chttp2_list_add_writable_window_update_stream(
 
 int grpc_chttp2_list_pop_writable_window_update_stream(
     grpc_chttp2_transport_global *transport_global,
-    grpc_chttp2_stream_global **stream_global) {
+    grpc_chttp2_transport_writing *transport_writing,
+    grpc_chttp2_stream_global **stream_global,
+    grpc_chttp2_stream_writing **stream_writing) {
   grpc_chttp2_stream *stream;
   int r = stream_list_pop(TRANSPORT_FROM_GLOBAL(transport_global), &stream,
                           GRPC_CHTTP2_LIST_WRITABLE_WINDOW_UPDATE);
   *stream_global = &stream->global;
+  *stream_writing = &stream->writing;
   return r;
 }
 

src/core/transport/chttp2/writing.c

@@ -66,11 +66,9 @@ int grpc_chttp2_unlocking_check_writes(
   /* for each grpc_chttp2_stream that's become writable, frame it's data
      (according to
      available window sizes) and add to the output buffer */
-  while (transport_global->outgoing_window &&
-         grpc_chttp2_list_pop_writable_stream(transport_global,
+  while (grpc_chttp2_list_pop_writable_stream(transport_global,
                                               transport_writing, &stream_global,
-                                              &stream_writing) &&
-         stream_global->outgoing_window > 0) {
+                                              &stream_writing)) {
     stream_writing->id = stream_global->id;
     window_delta = grpc_chttp2_preencode(
         stream_global->outgoing_sopb->ops, &stream_global->outgoing_sopb->nops,
@@ -106,12 +104,11 @@ int grpc_chttp2_unlocking_check_writes(
   /* for each grpc_chttp2_stream that wants to update its window, add that
    * window here */
   while (grpc_chttp2_list_pop_writable_window_update_stream(transport_global,
-                                                            &stream_global)) {
+                                                            transport_writing,
+                                                            &stream_global,
+                                                            &stream_writing)) {
     if (!stream_global->read_closed && stream_global->unannounced_incoming_window > 0) {
-      gpr_slice_buffer_add(
-          &transport_writing->outbuf,
-          grpc_chttp2_window_update_create(
-              stream_global->id, stream_global->unannounced_incoming_window));
+      stream_writing->announce_window = stream_global->unannounced_incoming_window;
       GRPC_CHTTP2_FLOWCTL_TRACE_STREAM("write", transport_global, stream_global,
                                        incoming_window, stream_global->unannounced_incoming_window);
       GRPC_CHTTP2_FLOWCTL_TRACE_STREAM("write", transport_global, stream_global,
@@ -120,6 +117,7 @@ int grpc_chttp2_unlocking_check_writes(
       stream_global->unannounced_incoming_window = 0;
       grpc_chttp2_list_add_incoming_window_updated(transport_global,
                                                    stream_global);
+      grpc_chttp2_list_add_writing_stream(transport_writing, stream_writing);
     }
   }
 
@@ -169,10 +167,19 @@ static void finalize_outbuf(grpc_chttp2_transport_writing *transport_writing) {
 
   while (
       grpc_chttp2_list_pop_writing_stream(transport_writing, &stream_writing)) {
-    grpc_chttp2_encode(stream_writing->sopb.ops, stream_writing->sopb.nops,
-                       stream_writing->send_closed != GRPC_DONT_SEND_CLOSED,
-                       stream_writing->id, &transport_writing->hpack_compressor,
-                       &transport_writing->outbuf);
+    if (stream_writing->sopb.nops > 0 || stream_writing->send_closed != GRPC_DONT_SEND_CLOSED) {
+      grpc_chttp2_encode(stream_writing->sopb.ops, stream_writing->sopb.nops,
+                         stream_writing->send_closed != GRPC_DONT_SEND_CLOSED,
+                         stream_writing->id, &transport_writing->hpack_compressor,
+                         &transport_writing->outbuf);
+    }
+    if (stream_writing->announce_window > 0) {
+      gpr_slice_buffer_add(
+          &transport_writing->outbuf,
+          grpc_chttp2_window_update_create(
+              stream_writing->id, stream_writing->announce_window));
+      stream_writing->announce_window = 0;
+    }
     stream_writing->sopb.nops = 0;
     if (stream_writing->send_closed == GRPC_SEND_CLOSED_WITH_RST_STREAM) {
       gpr_slice_buffer_add(&transport_writing->outbuf,