504 gateway timeout flask socketio

Question

I am working on a flask-socketio server which is getting stuck in a state where only 504s (gateway timeout) are returned. We are using AWS ELB in front of the server. I was wondering if anyone wouldn't mind giving some tips as to how to debug this issue.

Other symptoms:

• This problem does not occur consistently, but once it begins happening, only 504s are received from requests. Restarting the process seems to fix the issue.
• When I run netstat -nt on the server, I see many entries with rec-q's of over 100 stuck in the CLOSE_WAIT state
• When I run strace on the process, I only see select and clock_gettime
• When I run tcpdump on the server, I can see the valid requests coming into the server
• AWS health checks are coming back succesfully

EDIT: I should also add two things:

• flask-socketio's server is used for production (not gunicorn or uWSGI)
• Python's daemonize function is used for daemonizing the app

Answer 1

It seemed that switching to gunicorn as the wsgi server fixed the problem. This legitimately might be an issue with the flask-socketio wsgi server.