Server writes a response with HTTP/2 even after receiving a RST_STREAM frame

[jrhee17]

Problem statement

When client-side requests time out, a RST_STREAM is sent and the HTTP/2 stream is closed.
However, server-side may not close the response immediately, which may cause responses to still be written.
This is a violation of the HTTP/2 specification.

The RST_STREAM frame fully terminates the referenced stream and causes it to enter the "closed" state. After receiving a RST_STREAM on a stream, the receiver MUST NOT send additional frames for that stream, with the exception of PRIORITY

https://httpwg.org/specs/rfc7540.html#RST_STREAM

As a result the following logs are printed in client-side.

io.netty.handler.codec.http2.Http2Exception$StreamException: Received HEADERS frame for an unknown stream 3
io.netty.handler.codec.http2.Http2Exception$StreamException: Received DATA frame for an unknown stream 3

Analysis

Running the following test reproduces the issue:

armeria/grpc/src/test/java/com/linecorp/armeria/client/grpc/GrpcClientTimeoutTest.java

Line 89 in 76c50fe

void clientTimeout() throws InterruptedException {

1. A client-side responseTimeout closes the stream and sends a RST_STREAM

armeria/core/src/main/java/com/linecorp/armeria/client/HttpResponseDecoder.java

Line 429 in 76c50fe

delegate.close(cause);

Afterwards, the stream is closed and the response is removed

armeria/core/src/main/java/com/linecorp/armeria/client/Http2ResponseDecoder.java

Line 137 in 76c50fe

final HttpResponseWrapper res = removeResponse(streamIdToId(stream.id()));

2. Server-side receives a RST_STREAM

armeria/core/src/main/java/com/linecorp/armeria/server/Http2RequestDecoder.java

Line 356 in 76c50fe

req.abortResponse(cause, /* cancel */ true);

and calls close on the ctx and response sequentially.

armeria/core/src/main/java/com/linecorp/armeria/server/AggregatingDecodedHttpRequest.java

Lines 175 to 185 in 76c50fe

	isResponseAborted = true;
	// Make sure to invoke the ServiceRequestContext.whenRequestCancelling() and whenRequestCancelled()
	// by cancelling a request
	if (cancel && ctx != null) {
	ctx.cancel(cause);
	}
	if (response != null && !response.isComplete()) {
	response.abort(cause);
	}

However, FramedGrpcService registers callbacks on ctx.close

armeria/grpc/src/main/java/com/linecorp/armeria/server/grpc/FramedGrpcService.java

Lines 313 to 320 in 76c50fe

	ctx.whenRequestCancelling().handle((cancellationCause, unused) -> {
	Status status = Status.CANCELLED.withCause(cancellationCause);
	if (cancellationCause instanceof RequestTimeoutException) {
	status = status.withDescription("Request timed out");
	}
	call.close(status, new Metadata());
	return null;
	});

and writes a response before ctx.close is invoked

armeria/grpc/src/main/java/com/linecorp/armeria/server/grpc/AbstractServerCall.java

Line 297 in 76c50fe

res.abort(statusException);

[jrhee17]

I believe this was handled by @trustin in #4789 🙇