Frans King created FLINK-19515:
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Summary: Async RequestReply handler concurrency bug
Key: FLINK-19515
URL: https://issues.apache.org/jira/browse/FLINK-19515
Project: Flink
Issue Type: Bug
Affects Versions: statefun-2.2.0
Reporter: Frans King
Async RequestReply handler implemented in
https://issues.apache.org/jira/browse/FLINK-18518 has a concurrency problem.
Lines 151 to 152 of
[https://github.com/apache/flink-statefun/blob/master/statefun-python-sdk/statefun/request_reply.py]
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
In short:
{code:java}
ic.setup(request_bytes)
await self.handle_invocation(ic)
return ic.complete()
{code}
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.
{code:java}
response_data = await handler(request_data)
File "/home/pi/.local/lib/python3.7/site-packages/statefun/request_reply.py",
line 152, in __call__
return ic.complete()
File "/home/pi/.local/lib/python3.7/site-packages/statefun/request_reply.py",
line 57, in complete
self.add_mutations(context, invocation_result)
File "/home/pi/.local/lib/python3.7/site-packages/statefun/request_reply.py",
line 82, in add_mutations
for name, handle in context.states.items():
AttributeError: 'NoneType' object has no attribute 'states'
{code}
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