How to debug hanging app?

[Fabrice Triboix]

Hi everyone,

I tried to find some articles online to help me, but I can't find anything about my specific problem, except for a couple of unanswered questions on SO...

So my Flask-based app runs fine on its own, but when I try to run it in Elastic Beanstalk, it hangs.

I located the line of code which hangs, which is: `from profanity_check import predict_prob`

Because it hangs only when I run it in EB, I need to be enable some kind of debugging at WSGI level. I found many resources about how to deal with crashes and stack traces, but what I need is be able to trace where exactly the app is hanging, as I can't instrument a library such as profanity_check. I was thinking of using the `trace` module to print out every single line of code that is executed, but I don't know how to do that through WSGI....

Any help would be greatly appreciated!

  Fabrice

[Graham Dumpleton]

An app that hangs is most often because a third party Python package is used which has a C extension which hasn’t been implemented properly so it works with sub interpreters. You need to ensure your application runs in the main Python sub interpreter. See:

https://modwsgi.readthedocs.io/en/develop/user-guides/application-issues.html#python-simplified-gil-state-api

If you don’t have direct access to change the Apache config with EB, you will need to work out what the equivalent is for setting:

    WSGIApplicationGroup %{GLOBAL}

Graham

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[Fabrice Triboix]

Hi Graham,

Thanks a lot for your input. Apologies for the late response. We decided to remove the offending import and the code depending on it for now.

When we put it back, and if the problem still occurs, I will try to suggestion.

Thanks a lot!

  Fabrice

Graham

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