Running a Pyramid Application under mod_wsgi

mod_wsgi is an Apache module developed by Graham Dumpleton. It allows WSGI programs to be served using the Apache web server.

This guide will outline broad steps that can be used to get a Pyramid application running under Apache via mod_wsgi. This particular tutorial was developed under Apple’s Mac OS X platform (Snow Leopard, on a 32-bit Mac), but the instructions should be largely the same for all systems, delta specific path information for commands and files.

Note

Unfortunately these instructions almost certainly won’t work for deploying a Pyramid application on a Windows system using mod_wsgi. If you have experience with Pyramid and mod_wsgi on Windows systems, please help us document this experience by submitting documentation to the Pylons-devel maillist.

1. The tutorial assumes you have Apache already installed on your system. If you do not, install Apache 2.X for your platform in whatever manner makes sense.

2. Once you have Apache installed, install mod_wsgi. Use the (excellent) installation instructions for your platform into your system’s Apache installation.

3. Install virtualenv into the Python which mod_wsgi will run using the easy_install program.

   $ sudo /usr/bin/easy_install-2.6 virtualenv
   

   This command may need to be performed as the root user.

4. Create a virtualenv which we’ll use to install our application.

   $ cd ~
   $ mkdir modwsgi
   $ cd modwsgi
   $ /usr/local/bin/virtualenv --no-site-packages env
   

5. Install Pyramid into the newly created virtualenv:

   $ cd ~/modwsgi/env
   $ bin/easy_install pyramid
   

6. Create and install your Pyramid application. For the purposes of this tutorial, we’ll just be using the pyramid_starter application as a baseline application. Substitute your existing Pyramid application as necessary if you already have one.

   $ cd ~/modwsgi/env
   $ bin/paster create -t pyramid_starter myapp
   $ cd myapp
   $ ../bin/python setup.py install
   

7. Within the virtualenv directory (~/modwsgi/env), create a script named pyramid.wsgi. Give it these contents:

   from pyramid.paster import get_app
   application = get_app(
     '/Users/chrism/modwsgi/env/myapp/production.ini', 'main')
   

   The first argument to get_app is the project Paste configuration file name. It’s best to use the production.ini file provided by your scaffold, as it contains settings appropriate for production. The second is the name of the section within the .ini file that should be loaded by mod_wsgi. The assignment to the name application is important: mod_wsgi requires finding such an assignment when it opens the file.

8. Make the pyramid.wsgi script executable.

   $ cd ~/modwsgi/env
   $ chmod 755 pyramid.wsgi
   

9. Edit your Apache configuration and add some stuff. I happened to create a file named /etc/apache2/other/modwsgi.conf on my own system while installing Apache, so this stuff went in there.

   # Use only 1 Python sub-interpreter.  Multiple sub-interpreters
   # play badly with C extensions.
   WSGIApplicationGroup %{GLOBAL}
   WSGIPassAuthorization On
   WSGIDaemonProcess pyramid user=chrism group=staff threads=4 \
      python-path=/Users/chrism/modwsgi/env/lib/python2.6/site-packages
   WSGIScriptAlias /myapp /Users/chrism/modwsgi/env/pyramid.wsgi
   
   <Directory /Users/chrism/modwsgi/env>
     WSGIProcessGroup pyramid
     Order allow,deny
     Allow from all
   </Directory>
   

10. Restart Apache

    $ sudo /usr/sbin/apachectl restart
    

11. Visit http://localhost/myapp in a browser. You should see the sample application rendered in your browser.

mod_wsgi has many knobs and a great variety of deployment modes. This is just one representation of how you might use it to serve up a Pyramid application. See the mod_wsgi configuration documentation for more in-depth configuration information.