fix StreamBufferingEncoder

netty/src/main/java/io/grpc/netty/StreamBufferingEncoder.java

@@ -42,9 +42,29 @@
 import java.util.TreeMap;
 
 /**
- * This is a temporary copy of {@link io.netty.handler.codec.http2.DecoratingHttp2ConnectionEncoder}
- * with a bug fix that is not available yet in the latest netty release.
+ * Implementation of a {@link Http2ConnectionEncoder} that dispatches all method call to another
+ * {@link Http2ConnectionEncoder}, until {@code SETTINGS_MAX_CONCURRENT_STREAMS} is reached.
+ * <p/>
+ * <p>When this limit is hit, instead of rejecting any new streams this implementation buffers newly
+ * created streams and their corresponding frames. Once an active stream gets closed or the maximum
+ * number of concurrent streams is increased, this encoder will automatically try to empty its
+ * buffer and create as many new streams as possible.
+ * <p/>
+ * <p>
+ * If a {@code GOAWAY} frame is received from the remote endpoint, all buffered writes for streams
+ * with an ID less than the specified {@code lastStreamId} will immediately fail with a
+ * {@link io.netty.handler.codec.http2.StreamBufferingEncoder.Http2GoAwayException}.
+ * <p/>
+ * <p>
+ * If the channel/encoder gets closed, all new and buffered writes will immediately fail with a
+ * {@link io.netty.handler.codec.http2.StreamBufferingEncoder.Http2ChannelClosedException}.
+ * </p>
+ * <p>This implementation makes the buffering mostly transparent and is expected to be used as a
+ * drop-in decorator of {@link io.netty.handler.codec.http2.DefaultHttp2ConnectionEncoder}.
+ * </p>
  */
+// This is a temporary copy of {@link io.netty.handler.codec.http2.DecoratingHttp2ConnectionEncoder}
+// with a bug fix that is not available yet in the latest netty release.
 class StreamBufferingEncoder extends DecoratingHttp2ConnectionEncoder {
 
   /**
@@ -138,11 +158,7 @@ public ChannelFuture writeHeaders(ChannelHandlerContext ctx, int streamId, Http2
     if (closed) {
       return promise.setFailure(new Http2ChannelClosedException());
     }
-    if (isExistingStream(streamId) || connection().goAwayReceived()) {
-      return super.writeHeaders(ctx, streamId, headers, streamDependency, weight,
-          exclusive, padding, endOfStream, promise);
-    }
-    if (canCreateStream()) {
+    if (isExistingStream(streamId) || canCreateStream()) {
       return super.writeHeaders(ctx, streamId, headers, streamDependency, weight,
           exclusive, padding, endOfStream, promise);
     }