Transport issue with grpc

while gRPC server serving stream of response, it they are responding concurrently, looks likes it will then will fall into

INFO: Transport failed
java.lang.IllegalStateException: Stream 3 sent too many headers EOS: false
	at io.grpc.netty.shaded.io.netty.handler.codec.http2.DefaultHttp2ConnectionEncoder.validateHeadersSentState(DefaultHttp2ConnectionEncoder.java:157)
	at io.grpc.netty.shaded.io.netty.handler.codec.http2.DefaultHttp2ConnectionEncoder.writeHeaders0(DefaultHttp2ConnectionEncoder.java:230)
	at io.grpc.netty.shaded.io.netty.handler.codec.http2.DefaultHttp2ConnectionEncoder.writeHeaders(DefaultHttp2ConnectionEncoder.java:150)
	at io.grpc.netty.shaded.io.netty.handler.codec.http2.DecoratingHttp2FrameWriter.writeHeaders(DecoratingHttp2FrameWriter.java:45)
	at io.grpc.netty.shaded.io.grpc.netty.NettyServerHandler.sendResponseHeaders(NettyServerHandler.java:707)
	at io.grpc.netty.shaded.io.grpc.netty.NettyServerHandler.write(NettyServerHandler.java:626)

The solution is to stream in serial instead:

..
//.parallel()  //disable the parrallel stream
.mapToObj(value -> ...newBuilder().setMessage(value)....build())
.forEach(reply -> responseObserver.onNext(reply));