# mod_wsgi (Apache)

If you are using the Apache webserver you should consider using mod_wsgi.

Watch Out

Please make sure in advance that your app.run() call you might have in your application file, is inside an if __name__ == '__main__': or moved to a separate file. Just make sure it's not called because this will always start a local WSGI server which we do not want if we deploy that application to mod_wsgi.

## Installing mod_wsgi

If you don't have mod_wsgi installed yet you have to either install it using a package manager or compile it yourself.

The mod_wsgi installation instructions cover source installations on UNIX systems.

If you are using Ubuntu/Debian you can apt-get it and activate it as follows:

# apt-get install libapache2-mod-wsgi


On FreeBSD install mod_wsgi by compiling the www/mod_wsgi port or by using pkg_add:

# pkg_add -r mod_wsgi


If you are using pkgsrc you can install mod_wsgi by compiling the www/ap2-wsgi package.

If you encounter segfaulting child processes after the first apache reload you can safely ignore them. Just restart the server.

## Creating a .wsgi file

To run your application you need a yourapplication.wsgi file. This file contains the code mod_wsgi is executing on startup to get the application object. The object called application in that file is then used as application.

For most applications the following file should be sufficient:

from yourapplication import app as application


If you don't have a factory function for application creation but a singleton instance you can directly import that one as application.

Store that file somewhere that you will find it again (e.g.: /var/www/yourapplication) and make sure that yourapplication and all the libraries that are in use are on the python load path. If you don't want to install it system wide consider using a virtual python instance.

## Configuring Apache

The last thing you have to do is to create an Apache configuration file for your application. In this example we are telling mod_wsgi to execute the application under a different user for security reasons:

<VirtualHost *>
ServerName example.com

WSGIScriptAlias / /var/www/yourapplication/yourapplication.wsgi

<Directory /var/www/yourapplication>
WSGIProcessGroup yourapplication
WSGIApplicationGroup %{GLOBAL}
Order deny,allow
Allow from all
</Directory>
</VirtualHost>


## Troubleshooting

Problem: application does not run, errorlog shows SystemExit ignored
You have a app.run() call in your application file that is not guarded by an if __name__ == '__main__': condition. Either remove that :meth:~flask.Flask.run call from the file and move it into a separate run.py file or put it into such an if block.
Problem: application gives permission errors
Probably caused by your application running as the wrong user. Make sure the folders the application needs access to have the proper privileges set and the application runs as the correct user (user and group parameter to the WSGIDaemonProcess directive)
Problem: application dies with an error on print

Keep in mind that mod_wsgi disallows doing anything with :data:sys.stdout and :data:sys.stderr. You can disable this protection from the config by setting the WSGIRestrictStdout to off:

WSGIRestrictStdout Off


Alternatively you can also replace the standard out in the .wsgi file with a different stream:

import sys
sys.stdout = sys.stderr

Problem: accessing resources gives IO errors

Your application probably is a single .py file you symlinked into the site-packages folder. Please be aware that this does not work, instead you either have to put the folder into the pythonpath the file is stored in, or convert your application into a package.

The reason for this is that for non-installed packages, the module filename is used to locate the resources and for symlinks the wrong filename is picked up.

To help deployment tools you can activate support for automatic reloading. Whenever something changes the .wsgi file, mod_wsgi will reload all the daemon processes for us.

WSGIScriptReloading On


## Working with Virtual Environments

Virtual environments have the advantage that they never install the required dependencies system wide so you have a better control over what is used where. If you want to use a virtual environment with mod_wsgi you have to modify your .wsgi file slightly.

activate_this = '/path/to/env/bin/activate_this.py'