Django app hangs when attempting to connect to dat

Question

I am having difficulty troubleshooting this issue. I have a Django app running on an Ubuntu 14.04 server (with Apache 2.4 and mod_wsgi for Python 3.4). It connects to SQL Server via pymssql.

In development, the app works fine. I query the database, and the database returns the expected results.

In production (under the Apache user), however, the script hangs at the exact point that a database query is made. My browser (Chrome or Firefox) shows a spinning wheel that continues to spin as long as the browser window is open.

I have the following in my apache2.conf file:

ServerName localhost
# WSGIDaemonProcess application
WSGIPythonPath /home/production_code/python3env/lib/python3.4/site-packages:/home/production_code/school
# WSGIProcessGroup application
WSGIScriptAlias / /home/production_code/school/school/wsgi.py
# Python virtualenv home
WSGIPythonHome /home/production_code/python3env
# Include the virtual host configurations:
IncludeOptional sites-enabled/*.conf

And the following in my sites-enabled/000-default.conf file:

<VirtualHost *:80>    
        ServerAdmin *****@school.edu
        ServerName  localhost
        DocumentRoot /var/www/html

        ErrorLog ${APACHE_LOG_DIR}/error.log
        CustomLog ${APACHE_LOG_DIR}/access.log combined

        Alias /static/ /home/production_code/school/static/

        <Directory /home/production_code/school/>
            Require all granted
        </Directory>
        <Directory /home/production_code/school/>
            <Files wsgi.py>
                Require all granted
            </Files>
        </Directory>
        <Directory /home/production_code/school/static>
            Require all granted
        </Directory>
</VirtualHost>

Does anyone have any idea what might be causing this or how I might troubleshoot this? The Apache error logs and access logs are not particularly helpful in this situation, since a response to the request is never rendered. Similarly, Django debugging is also not useful here.

Answer 1

Instead of:

# WSGIDaemonProcess application
WSGIPythonPath /home/production_code/python3env/lib/python3.4/site-packages:/home/production_code/school
# WSGIProcessGroup application

use:

WSGIDaemonProcess application python-path=/home/production_code/python3env/lib/python3.4/site-packages:/home/production_code/school
WSGIProcessGroup application
WSGIApplicationGroup %{GLOBAL}

A key part of this is the WSGIApplicationGroup directive, with it being set to %{GLOBAL}.

This is to get around faulty third party extension modules for Python that don't work in sub interpreters and which can fail with a dead lock or crash.

See:

• https://code.google.com/p/modwsgi/wiki/ApplicationIssues#Python_Simplified_GIL_State_API

It is also recommend you go back to using daemon mode. It is generally not a good idea to use embedded mode.

• http://blog.dscpl.com.au/2012/10/why-are-you-using-embedded-mode-of.html