Fix writelast bug

3 files changed, 20 insertions, 7 deletions

diff --git a/include/grpc++/impl/codegen/method_handler_impl.h b/include/grpc++/impl/codegen/method_handler_impl.h
index 64c91bee22..5afa4e9f7e 100644
--- a/include/grpc++/impl/codegen/method_handler_impl.h
+++ b/include/grpc++/impl/codegen/method_handler_impl.h
@@ -141,6 +141,9 @@ class ServerStreamingHandler : public MethodHandler {
     }
     ops.ServerSendStatus(param.server_context->trailing_metadata_, status);
     param.call->PerformOps(&ops);
+    if (param.server_context->has_hanging_ops_) {
+      param.call->cq()->Pluck(&param.server_context->hanging_ops_);
+    }
     param.call->cq()->Pluck(&ops);
   }
 
diff --git a/include/grpc++/impl/codegen/server_context.h b/include/grpc++/impl/codegen/server_context.h
index 96fe645a15..d7bd7323f2 100644
--- a/include/grpc++/impl/codegen/server_context.h
+++ b/include/grpc++/impl/codegen/server_context.h
@@ -25,6 +25,7 @@
 
 #include <grpc/impl/codegen/compression_types.h>
 
+#include <grpc++/impl/codegen/call.h>
 #include <grpc++/impl/codegen/completion_queue_tag.h>
 #include <grpc++/impl/codegen/config.h>
 #include <grpc++/impl/codegen/create_auth_context.h>
@@ -272,6 +273,8 @@ class ServerContext {
 
   uint32_t initial_metadata_flags() const { return 0; }
 
+  CallOpSet<CallOpSendInitialMetadata, CallOpSendMessage> hanging_ops_;
+  bool has_hanging_ops_;
   CompletionOp* completion_op_;
   bool has_notify_when_done_tag_;
   void* async_notify_when_done_tag_;
diff --git a/include/grpc++/impl/codegen/sync_stream.h b/include/grpc++/impl/codegen/sync_stream.h
index 09836f340b..b7d81b3382 100644
--- a/include/grpc++/impl/codegen/sync_stream.h
+++ b/include/grpc++/impl/codegen/sync_stream.h
@@ -589,20 +589,27 @@ class ServerWriter final : public ServerWriterInterface<W> {
     if (options.is_last_message()) {
       options.set_buffer_hint();
     }
-    CallOpSet<CallOpSendInitialMetadata, CallOpSendMessage> ops;
-    if (!ops.SendMessage(msg, options).ok()) {
+    if (!ctx_->hanging_ops_.SendMessage(msg, options).ok()) {
       return false;
     }
     if (!ctx_->sent_initial_metadata_) {
-      ops.SendInitialMetadata(ctx_->initial_metadata_,
-                              ctx_->initial_metadata_flags());
+      ctx_->hanging_ops_.SendInitialMetadata(ctx_->initial_metadata_,
+                                             ctx_->initial_metadata_flags());
       if (ctx_->compression_level_set()) {
-        ops.set_compression_level(ctx_->compression_level());
+        ctx_->hanging_ops_.set_compression_level(ctx_->compression_level());
       }
       ctx_->sent_initial_metadata_ = true;
     }
-    call_->PerformOps(&ops);
-    return call_->cq()->Pluck(&ops);
+    call_->PerformOps(&ctx_->hanging_ops_);
+    // if this is the last message we defer the pluck until AFTER we start
+    // the trailing md op. This prevents hangs. See
+    // https://github.com/grpc/grpc/issues/11546
+    if (options.is_last_message()) {
+      ctx_->has_hanging_ops_ = true;
+      return true;
+    }
+    ctx_->has_hanging_ops_ = false;
+    return call_->cq()->Pluck(&ctx_->hanging_ops_);
   }
 
  private: