Fixing watermark preconditions (#1509)

This fixes a bug in my implementation of #150 where we were passing connection-level flow control blockage to new client side streams but not new server side streams.

source/common/http/http2/codec_impl.cc

@@ -802,6 +802,9 @@ int ServerConnectionImpl::onBeginHeaders(const nghttp2_frame* frame) {
   }
 
   StreamImplPtr stream(new ServerStreamImpl(*this, per_stream_buffer_limit_));
+  if (connection_.aboveHighWatermark()) {
+    stream->runHighWatermarkCallbacks();
+  }
   stream->decoder_ = &callbacks_.newStream(*stream);
   stream->stream_id_ = frame->hd.stream_id;
   stream->moveIntoList(std::move(stream), active_streams_);

test/common/http/http2/codec_impl_test.cc

@@ -399,6 +399,10 @@ TEST_P(Http2CodecImplFlowControlTest, TestFlowControlInPendingSendData) {
   StreamEncoder* response_encoder2;
   MockStreamCallbacks server_stream_callbacks2;
   MockStreamDecoder request_decoder2;
+  // When the server stream is created it should check the status of the
+  // underlying connection.  Pretend it is overrun.
+  EXPECT_CALL(server_connection_, aboveHighWatermark()).WillOnce(Return(true));
+  EXPECT_CALL(server_stream_callbacks2, onAboveWriteBufferHighWatermark());
   EXPECT_CALL(server_callbacks_, newStream(_))
       .WillOnce(Invoke([&](StreamEncoder& encoder) -> StreamDecoder& {
         response_encoder2 = &encoder;
@@ -411,7 +415,7 @@ TEST_P(Http2CodecImplFlowControlTest, TestFlowControlInPendingSendData) {
   // been noticed that the connection was backed up.  Any new subscriber to
   // stream callbacks should get a callback when they addCallbacks.
   MockStreamCallbacks callbacks2;
-  EXPECT_CALL(callbacks2, onAboveWriteBufferHighWatermark()).Times(1);
+  EXPECT_CALL(callbacks2, onAboveWriteBufferHighWatermark());
   request_encoder_->getStream().addCallbacks(callbacks2);
 
   // Now unblock the server's stream.  This will cause the bytes to be consumed, flow control
@@ -504,8 +508,8 @@ TEST_P(Http2CodecImplTest, WatermarkUnderEndStream) {
   // ends.
   EXPECT_CALL(callbacks, onAboveWriteBufferHighWatermark()).Times(0);
   EXPECT_CALL(callbacks, onBelowWriteBufferLowWatermark()).Times(0);
-  EXPECT_CALL(server_stream_callbacks_, onAboveWriteBufferHighWatermark()).Times(1);
-  EXPECT_CALL(server_stream_callbacks_, onBelowWriteBufferLowWatermark()).Times(1);
+  EXPECT_CALL(server_stream_callbacks_, onAboveWriteBufferHighWatermark());
+  EXPECT_CALL(server_stream_callbacks_, onBelowWriteBufferLowWatermark());
   EXPECT_CALL(request_decoder_, decodeData(_, true)).WillOnce(InvokeWithoutArgs([&]() -> void {
     client_.onUnderlyingConnectionAboveWriteBufferHighWatermark();
     client_.onUnderlyingConnectionBelowWriteBufferLowWatermark();