Async RequestReply handler implemented in https://issues.apache.org/jira/browse/FLINK-18518 has a concurrency problem.
The coro is awaiting and may yield. Another coro may continue that was yielding and call ic.complete() which sets the ic.context to None
Needs to happen atomically.
I worked around this by creating an AsyncRequestReplyHandler for each request.
It should be possible to re-produce this by putting an await asyncio.sleep(5) in the greeter example and then run in gunicorn with a single asyncio thread/event loop (-w 1).