mod_wsgi

mod_wsgi is a WSGI server integrated with the Apache httpd server. The modern mod_wsgi-express command makes it easy to configure and start the server without needing to write Apache httpd configuration.

  • Tightly integrated with Apache httpd.

  • Supports Windows directly.

  • Requires a compiler and the Apache development headers to install.

  • Does not require a reverse proxy setup.

This page outlines the basics of running mod_wsgi-express, not the more complex installation and configuration with httpd. Be sure to read the mod_wsgi-express, mod_wsgi, and Apache httpd documentation to understand what features are available.

Installing

Installing mod_wsgi requires a compiler and the Apache server and development headers installed. You will get an error if they are not. How to install them depends on the OS and package manager that you use.

Create a virtualenv, install your application, then install mod_wsgi.

  1. $ cd hello-app
  2. $ python -m venv .venv
  3. $ . .venv/bin/activate
  4. $ pip install .  # install your application
  5. $ pip install mod_wsgi

Running

The only argument to mod_wsgi-express specifies a script containing your Flask application, which must be called application. You can write a small script to import your app with this name, or to create it if using the app factory pattern.

wsgi.py

  1. from hello import app
  3. application = app

wsgi.py

  1. from hello import create_app
  3. application = create_app()

Now run the mod_wsgi-express start-server command.

  1. $ mod_wsgi-express start-server wsgi.py --processes 4

The --processes option specifies the number of worker processes to run; a starting value could be CPU * 2.

Logs for each request aren’t show in the terminal. If an error occurs, its information is written to the error log file shown when starting the server.

Binding Externally

Unlike the other WSGI servers in these docs, mod_wsgi can be run as root to bind to privileged ports like 80 and 443. However, it must be configured to drop permissions to a different user and group for the worker processes.

For example, if you created a hello user and group, you should install your virtualenv and application as that user, then tell mod_wsgi to drop to that user after starting.

  1. $ sudo /home/hello/.venv/bin/mod_wsgi-express start-server \
  2.     /home/hello/wsgi.py \
  3.     --user hello --group hello --port 80 --processes 4