[jira] [Commented] (FLINK-19515) Async RequestReply handler concurrency bug

["Igal Shilman (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/FLINK-19515?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17209119#comment-17209119 ] 

Igal Shilman commented on FLINK-19515:
--------------------------------------

Hi,
I think that you are correct, and it does seems like a bug.

The InvocationContext should be created in __call__ instead of the constructor. This also has to happen in the regular RequestRelplyHander.

Would you like to create a PR with the fix?


> 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
>            Priority: Minor
>
> 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 (-w 1).  
>  
>  
>  
> {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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