mod_python

mod_python is an Apache HTTP Server module that integrates the Python programming language into the Apache server. It is intended to replace Common Gateway Interface (CGI) as a method of executing Python scripts on a web server. The promised benefits are faster execution speed and maintaining data over multiple sessions.

Benefits

Ordinary CGI execution starts a new process every time a connection is made to a script on the server. This works well in low to medium traffic sites, but does not scale well when used on a high traffic site. There are methods of enhancing the performance of CGI, such as FastCGI, but it is often easier to use a specialized module to embed the desired language into the web server itself. This is exactly what mod_python is designed to do. Since the process is not terminated after the script execution like CGI, persistent data can be stored, such as database connections. This may reduce script execution overhead.

Since mod_python modules are integrated with the web server, they can do almost anything an Apache module written in C can do: implement protocols besides HTTP, filter the request and response, determine a document's content type, etc.

Another advantage to mod_python is that it can talk directly to Apache's core system, and interface as well as actually control the heart of Apache. This is done by handlers that the programmer specificies in the Apache configuration file, and every client request directed at that specific directory will not be processed by Apache, rather by mod_python and a "Main" function that handles all requests.

Using mod_python also has the advantage of Python Server Pages (PSP), a way to embed Python code into HTML pages, similar to ASP, PHP, and JavaServer Pages (JSP).

Problems

Embedding the Python interpreter (and different Python applications) directly into the Apache process is not without problems, especially when looking at shared Python web application hosting:

• all hosted applications run under the same uid/gid (bad for security and separation of different users' web applications)
• restarting Apache (usually needs root user privileges) might be necessary:
  • if some Python code malfunctions
  • in case of memory leaks
  • after a user upgraded his Python code

Additionally to the problematic embedded mode offered by Mod_python, mod wsgi (another alternative Apache module for running Python web applications) also offers a daemon mode that is more secure and easier handled for a non-root webhosting user.

History

The initial implementation of mod_python was originally written by Aaron Watters and distributed on the CD for the book "Internet Programming with Python". The First version of mod_python as modified by Gregory Trubetskoy was released in 2000. In September 2002 mod_python was donated to the Apache Software Foundation and became part of the Apache HTTP Server project.

See also

• Apache HTTP Server
• Python
• mod_wsgi
• mod_jk
• mod_perl
• mod_parrot
• Spyce

External links

• Official mod_python website
• mod_python Tutorial
• mod_python manual