Django/WSGI/Apache – How to Debug Errors

djangomod-wsgi

I have a Django 1.11.17 application deployed on Apache 2 and WSGI, Python 2.7.

Apache shows an error "Truncated or oversized response headers received from daemon process"

I have checked the solution given in
WSGI : Truncated or oversized response headers received from daemon process

and WSGIApplicationGroup %{GLOBAL} is in the virtual host file. However the error persists.

Django shell works. Django check returns no errors. Django runserver works. Django log shows no errors.

How can I see the exact error that is making WSGI not working?

Best Answer

There is a debugging mode that you can use provided by mod_wsgi. You can find the documentation here:
https://modwsgi.readthedocs.io/en/develop/user-guides/debugging-techniques.html

However, we found that we were using third-party packages such as numpy or psycopg2-binary that were causing issues. In our case, we were using psycopg2-binary which is a big no no for production apps. We removed it and followed their documentation on pip installation and everything worked. We also added WSGIApplicationGroup %{GLOBAL} to our apache2 server settings.

You may find the psycopg documentation at http://initd.org/psycopg/docs/install.html#prerequisites

Hope this helps.

Related Solutions

File upload issue with Django app running under Apache/mod_wsgi when daemonized

At a guess, you are not running latest mod_wsgi 2.X version and are using Opera browser.

There is a known issue with Opera and its use of HTTP 100-continue when using mod_wsgi daemon mode. This issue was fixed in mod_wsgi 2.4.

Since though you don't say what version of mod_wsgi you are using, nor which browser you are using, this is only a guess.

HTTP 500 error from POST reuqest to django vai WSGI and apache

Ok, so once again we come down to user error. At some point the problem changed because I changed some of the code above, so that

def post_authentication_api(request):

became

def post_authentication_api(self, request):

this doesnt work because as Graham said at the django mailing list

"If you ... have a 'self' first argument for a function which isn't a method of a class, it is obvious you are going to get:"

Exception Type: TypeError at /auth/post_authentication_api 
  Exception Value: post_authentication_api() takes exactly 2 arguments 
(1 given)

So after I fixed that up I came to the root of the problem (as far as I can tell) which was that wsgi was blocking sys.stdout. which I think seems fair to me, and I had some print statements in my code and this is why it wasnt running. A very simple problem that for some reason became very complicated.

Anyway, Great thanks to Graham who has helped me out for the last week on this. He has been tireless and very accommodating to someone who is quite embarrassed about the final outcome. Some votes will be coming his way for the comments and my many thanks as well.

Thanks again

Mark

Best Answer

Related Solutions

File upload issue with Django app running under Apache/mod_wsgi when daemonized

HTTP 500 error from POST reuqest to django vai WSGI and apache

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