Difference between revisions of "Mod wsgi"

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(Use mod_wsgi and Python 3.1)
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* Navigate to <code>http://localhost/wsgi_app</code> and discover the ugly <code>environ</code> dictionary..
 
* Navigate to <code>http://localhost/wsgi_app</code> and discover the ugly <code>environ</code> dictionary..
  
{{Box BLUE|Example:|mod_python allow you to execute arbitrary Python script that end with .py. mod_wsgi behave another way : it only serve application. So mod_wsgi isn't an .py file handler as mod_wsgi.}}
+
{{Note|While [[mod_python]] will execute any Python script that ends with .py, mod_wsgi only executes python ''applications''.}}
  
 
===Customization===
 
===Customization===

Revision as of 22:25, 1 February 2011


Introduction

According to the project's site :

The aim of mod_wsgi is to implement a simple to use Apache module which can host any Python application which supports the Python WSGI interface. The module would be suitable for use in hosting high performance production web sites, as well as your average self managed personal sites running on web hosting services.

mod_wsgi is an Apache module that embeds a Python application within the server and allow them to communicate through the Python WSGI interface as defined in the Python PEP 333. WSGI is one of the Python ways to produce high quality and high performance web applications.

WSGI provide a standard way to interface different web-apps without hassle. Several well-know python applications or frameworks provide wsgi for easy deployment and embedding. It means that you can embed your Django-powered blog and your project's Trac into a single Pylons application that wraps around them to deals with, say, authentication without modifying the formers.

Example:

mod_wsgi 3.x supports those Python versions: 2.3, 2.4, 2.5, 2.6, 3.1 (3.0 is NOT supported as Python's developers have dropped support for Python 3.0).

Installation

Apache Module : mod_wsgi for Python 2.6

This document describes how to set up and test the Apache module mod_wsgi compiled against Python 2.6 on an Arch Linux system.

Install Package

The mod_wsgi package live in extra, install it with pacman (or whatever you want) :

   # pacman -S mod_wsgi

Configure Apache

  • As requested by the installer, add the following line to /etc/httpd/conf/httpd.conf:
LoadModule wsgi_module modules/mod_wsgi.so
  • Restart Apache
   # /etc/rc.d/httpd restart
  • Check to make sure that Apache loaded correctly

Test mod_wsgi

  • Add this block to /etc/httpd/conf/httpd.conf:
WSGIScriptAlias /wsgi_app /home/www/wsgi-scripts/wsgi_app.py

<Directory /home/www/wsgi-scripts>
    Order allow,deny
    Allow from all
</Directory>
  • Create a file in /home/www/wsgi-scripts called wsgi_app.py with this code :
#-*- coding: utf-8 -*-
import pprint
def wsgi_app(environ, start_response):
    """ Display the contents of the environ dictionary."""
    # produce some content
    output =  pprint.pformat(environ)

    # send first header and status
    status = '200 OK'
    headers = [('Content-type', 'text/plain'),
		('Content-Length', str(len(output)))]
    start_response(status, headers)

    # wsgi apps should return and iterable, the following is acceptable too :
    # return [output]
    yield output

# mod_wsgi need the *application* variable to serve our small app
application = wsgi_app
  • Restart Apache
   # /etc/rc.d/httpd  restart
  • Check to make sure that Apache loaded correctly
Note: While mod_python will execute any Python script that ends with .py, mod_wsgi only executes python applications.

Customization

Use mod_wsgi and Python 3.1

This document explain how run mod_wsgi along Python 3.1 t instead of Python 2.6 that the Arch Linux binary package from repository offer. It will be assumed you have already installed the necessary packages (as described in ABS plus Python 3.1 : pacman -S python3).

Compilation using ABS

  • Update your ABS to ensure you have the very last PKGBUILD version.
  • Prepare the mod_wsgi folder into your home:
   $ mkdir -p ~/abs
   $ cp -r /var/abs/extra/mod_wsgi ~/abs
  • Edit the PKGBUILD: replace the --with-python flag with the correct Python's version:
    --with-python=/usr/bin/python || return 1

by

--with-python=/usr/bin/python3.1 || return 1
  • Build the package (run this command inside the PKGBULD folder):
   $ makepkg -s
  • Install it (as a root):
   # pacman -U mod_wsgi-3.0-1-$ARCH.pkg.tar.gz
  • Restart Apache :
  # /etc/rc.d/httpd restart
  • Test your set-up with this small app :
#-*- coding: utf-8 -*-
def wsgi_app(environ, start_response):
    import sys
    output = str(sys.version)
    status = '200 OK'
    headers = [('Content-type', 'text/plain'),
               ('Content-Length', str(len(output)))]
    start_response(status, headers)
    yield output

application = wsgi_app

When browsing to the url you bound your app on you should see :

   3.1.1 (r311:74480, Aug 27 2009, 04:56:37) 
   [GCC 4.4.1]

If you read :

   2.6.4 (r264:75706, Oct 27 2009, 06:25:13) 
   [GCC 4.4.1]

You have failed to compile and install mod_wsgi against Python3.1. Retry and double check all the previous steps.

See Also

This article is partially adapted from mod_python. Many thanks to the authors.