How to handle Broken pipe errors with Flask/gunicorn?

Question

I have a Flask API that is being run by gunicorn. To my knowledge and this SO link gunicorn should be handling any Broken pipe errors automatically for me which is why this error is confusing to me. Whenever the user hits the API endpoint a call to a MySQL database is made with SQLAlchemy. I suspect that the SQLAlchemy connection is remaining open after a query but I had trouble verifying that information. I have found the following error signals in the logs for the application but have had difficulty reproducing the behaviour myself.

[INFO] Handling signal: term 
[17] [INFO] Worker exiting (pid: 17) 
[16] [INFO] Worker exiting (pid: 16) 
[24] [INFO] Worker exiting (pid: 24) 
[18] [INFO] Worker exiting (pid: 18) 
[19] [INFO] Worker exiting (pid: 19) 
[22] [INFO] Worker exiting (pid: 22) 
[23] [INFO] Worker exiting (pid: 23) 
[20] [INFO] Worker exiting (pid: 20) 
[21] [INFO] Worker exiting (pid: 21) 
[1] [INFO] Shutting down: Master 
ERROR:sqlalchemy.pool.impl.QueuePool:Exception during reset or similar
BrokenPipeError: [Errno 32] Broken pipe

Why might this behaviour not be handled when a user disconnects prematurely and how would I verify what connections remain open on the program terminating?

score 0 · Answer 1 · answered Mar 06 '20 at 16:39

0

The log says your Gunicorn is receiving the termination signal. There's nothing to really handle as things are dying.

Gunicorn will handle a broken pipe if it happens during a regular request.

answered Mar 06 '20 at 16:39

AKX

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Why is the broken pipe error happening in that case? Shouldn't everything be shut down if gunicorn receives a term signal? – Josh Zwiebel Mar 06 '20 at 16:40
That's probably the Sqlalchemy pool to your database getting shut down, not the client connection Gunicorn manages. – AKX Mar 06 '20 at 17:07
How would I verify/fix that? – Josh Zwiebel Mar 06 '20 at 17:10
Is this a connection or session issue – Josh Zwiebel Mar 06 '20 at 19:17
There is no issue if anything doesn't seem broken. – AKX Mar 07 '20 at 11:33

How to handle Broken pipe errors with Flask/gunicorn?

1 Answers1