Apache and mod_wsgi on Ubuntu 12.10

TheWSGI specification provides a standard and efficient method fordynamic web applications to communicate with web servers. mod_wsgiprovides a method for simply deploying WSGI applications with Apache.WSGI is used to deploy applications written with frameworks and toolslike Django,Bottle,Web.py,Werkzug, Chery.py, TurboGears, and Flask. These guides outline thisinstallation and configuration process for deploying WSGIapplications.

Contents

• Setthe Hostname

• InstallDependencies

• ConfigureWSGI Handler

  • BasicHello World WSGI Configuration

  • Web.pyWSGI Configuration

  • BottleWSGI Configuration

  • DjangoWSGI Configuration

• ConfigureApache

Setthe Hostname

sudo vi /etc/hosts

Addseveral items, for example:

127.0.1.1     wsgiserver
127.0.0.1    webpyserver
127.0.0.1    bottleserver
127.0.0.1    djangoserver

Beforeyou begin installing and configuring the components described inthis guide, please make sure you've followed our instructions forsettingyour hostname.Issue the following commands to make sure it is set properly:

hostname
hostname -f

Thefirst command should show your short hostname, and the second shouldshow your fully qualified domain name (FQDN).

InstallDependencies

Issuethe following commands to ensure that your system's packagerepositories and installed programs are up to date and that allrequired software is installed:

apt-get update
apt-get upgrade
apt-get install apache2 python-setuptools libapache2-mod-wsgi

Yourapplication may require additional dependencies. Install theseeither using the Ubuntu package tools or by using the easy_installcommand included in python-setuptoolsbefore proceeding.

ConfigureWSGI Handler

Inorder formod_wsgito be able to provide access to your application, you will need tocreate a application.wsgifile inside of your application directory. The application directoryshould be locatedoutsideof yourDocumentRoot.The following three sections each present a differentapplication.wsgiexample file to illustrate the basic structure of this file:

BasicHello World WSGI Configuration

Inthis example, the application is stored in/var/www/testwsgi/directory. Modify this example and all following examples toconform to the actual files and locations used in your deployment.

File:/var/www/testwsgi/main.wsgi

import os
import sys

sys.path.append('/var/www/testwsgi')
os.environ['PYTHON_EGG_CACHE'] = '/var/www/testwsgi/.python-egg'


def application(environ, start_response):
    status = '200 OK'
    output = 'Hello World!'

    response_headers = [('Content-type', 'text/plain'),
                        ('Content-Length', str(len(output)))]
    start_response(status, response_headers)

    return [output]

Youmust append the path of your application to the system path asabove. The declaration of the PYTHON_EGG_CACHEvariable is optional but may be required for some applications whenWSGI scripts are executed with the permissions of the web server.The WSGI application must be callable as "application",regardless of how the application code is structured.

Createa new apache site

sudo vi /etc/apache2/sites-available/testwsgi

Andadd the content

	ServerAdmin [email protected]
	ServerName	wsgiserver
	# ServName is configured in /etc/hosts

	# DocumentRoot /var/www/testwsgi

	
		Options FollowSymLinks
		AllowOverride None
	

	
		Options Indexes FollowSymLinks MultiViews
		AllowOverride None
		Order allow,deny
		allow from all
	



#	ScriptAlias /cgi-bin/ /usr/lib/cgi-bin/
	WSGIScriptAlias /wsgitest /var/www/testwsgi/main.py
	
		AllowOverride None
		Options +ExecCGI -MultiViews +SymLinksIfOwnerMatch
		Order allow,deny
		Allow from all
	



	ErrorLog ${APACHE_LOG_DIR}/error.log

	# Possible values include: debug, info, notice, warn, error, crit,
	# alert, emerg.
	LogLevel warn
	CustomLog ${APACHE_LOG_DIR}/access.log combined

Andactivate the site

sudo a2ensite testwsgi
sudo /etc/init.d/apache2 reload

Thenopen your web browser and browse to

http://wsgiserver/wsgitest

Youshould see a ‘Hello World!’ message

Web.pyWSGI Configuration

Considerthe following example Web.pyapplicationwhich is embeded in a application.wsgifile. The Web.pyFrameworkmust be installed in order for the following application to runsuccessfully.

Fileexcerpt:/srv/www/ducklington.org/application/application.wsgi

import web

urls = (
    '/(.*)', 'hello'
)

class hello:
    def GET(self, name):
        if not name:
            name = 'World'
        return 'Hello, ' + name + '!'

if __name__ == "__main__":
    app.run()

app = web.application(urls, globals(), autoreload=False)
application = app.wsgifunc()

Configureapache is similar to WSGI configuration above.

Bottle WSGI Configuration

Considerthe following exampleapp.wsgifile for Django applications:

Fileexcerpt:/home/songguo/bottle2/app.wsgi

import os, sys, bottle

# must be
sys.path = ['/home/songguo/bottle2/'] + sys.path
os.chdir(os.path.dirname(__file__))

# This loads your application
import file_download, hello

application = bottle.default_app()

Fileexcerpt:/home/songguo/bottle2/file_download.py

from bottle import route, static_file, run, template

@route('/download/')
def download(filename):
    return static_file(filename, root='/home/songguo/Downloads', download = filename)
@route('/images/')
def send_image(filename):
    return static_file(filename, root = '/home/songguo/Pictures/pngs',
                                 mimetype = 'image/png')

@route('/')
@route('/hello')
def hello():
    return "Hello World!"
    # return template('hello')
# run(host = 'localhost', port = 8000)

Whenyou run your application via mod_wsgi, it is imperative to removethe run()statement from your code, otherwise it won’t work here.

Fileexcerpt:/home/songguo/bottle2/hello.pyomitted.

Createa new apache site

sudo vi /etc/apache2/sites-available/testbottle

Andadd the content

	ServerAdmin [email protected]
	ServerName	bottleserver
	# ServName is configured in /etc/hosts
	
		Options FollowSymLinks
		AllowOverride None
	
	
		Options Indexes FollowSymLinks MultiViews
		AllowOverride None
		Order allow,deny
		allow from all
	

#	ScriptAlias /cgi-bin/ /usr/lib/cgi-bin/
    WSGIDaemonProcess bottleserver processes=2 threads=15 display-name=%{GROUP}
    WSGIProcessGroup bottleserver
	WSGIScriptAlias / /home/songguo/bottle2/app.wsgi 

	
		AllowOverride None
		Options +ExecCGI -MultiViews +SymLinksIfOwnerMatch
		Order allow,deny
		Allow from all
	

	ErrorLog ${APACHE_LOG_DIR}/error.log
	# Possible values include: debug, info, notice, warn, error, crit,
	# alert, emerg.
        LogLevel warn
	CustomLog ${APACHE_LOG_DIR}/access.log combined

Andactivate the site

sudo a2ensite testbottle
sudo /etc/init.d/apache2 reload

DjangoWSGI Configuration

Considerthe following exampleapplication.wsgifile for Django applications:

Fileexcerpt:/home/songguo/django/songuo/apache/django.wsgi

import os
import sys

path = '/home/songguo/django/songuo'

if path not in sys.path:
    sys.path.insert(0, path)

os.environ['DJANGO_SETTINGS_MODULE'] = 'songuo.settings'

import django.core.handlers.wsgi
application = django.core.handlers.wsgi.WSGIHandler()

Djangoapplication directory structrue:

Djangomust be installed on your system and a working Django applicationbefore this example will function. The "DJANGO_SETTINGS_MODULE"points to the "settings.pyfile for your application, which would be located in the"/home/songguo/django/songuo/songuo/settings.pyin the case of this example.

Createa new apache site

sudo vi /etc/apache2/sites-available/testdjango

Andadd the content

	ServerAdmin [email protected]
	ServerName	djangoserver
	# ServName is configured in /etc/hosts
	DocumentRoot /home/songguo/django/songuo
	
		Options FollowSymLinks
		AllowOverride None
	
	
		Options Indexes FollowSymLinks MultiViews
		AllowOverride None
		Order allow,deny
		allow from all
	

#	ScriptAlias /cgi-bin/ /usr/lib/cgi-bin/
    WSGIDaemonProcess djangoserver processes=2 threads=15 display-name=%{GROUP}
    WSGIProcessGroup djangoserver
	WSGIScriptAlias / /home/songguo/django/songuo/apache/django.wsgi
    
    Alias /static /home/songguo/django/songuo/static

	
		AllowOverride None
		Options +ExecCGI -MultiViews +SymLinksIfOwnerMatch
		Order allow,deny
		Allow from all
	

	ErrorLog ${APACHE_LOG_DIR}/error.log

	# Possible values include: debug, info, notice, warn, error, crit,
	# alert, emerg.
	LogLevel warn

	CustomLog ${APACHE_LOG_DIR}/access.log combined

Andactivate the site

sudo a2ensite testdjango
sudo /etc/init.d/apache2 reload

ConfigureApache

Deploythe followingVirtualHostconfiguration and modify the paths and domains to reflect therequirements of your application:

Fileexcerpt:Apache``VirtualHost`` Configuration

/etc/apache2/sites-available/name

	ServerAdmin [[email protected]]
	# ServName is configured in /etc/hosts
	ServerName	[server name in /etc/hosts]
	
	# DocumentRoot /path/to/your/document/root
	
		Options FollowSymLinks
		AllowOverride None
	
	
		Options Indexes FollowSymLinks MultiViews
		AllowOverride None
		Order allow,deny
		allow from all
	

#	ScriptAlias /cgi-bin/ /usr/lib/cgi-bin/
    WSGIDaemonProcess [server name] processes=2 threads=15 display-name=%{GROUP}
    WSGIProcessGroup [server name]
	WSGIScriptAlias /[access prefix path] /path/to/your/app/name.wsgi
    
    # Alias /static /path/to/your/app/static

	
		AllowOverride None
		Options +ExecCGI -MultiViews +SymLinksIfOwnerMatch
		Order allow,deny
		Allow from all
	

	ErrorLog ${APACHE_LOG_DIR}/error.log

	# Possible values include: debug, info, notice, warn, error, crit,
	# alert, emerg.
	LogLevel warn
	CustomLog ${APACHE_LOG_DIR}/access.log combined

Inthis example, theWSGIScriptAliasdirective tells Apache that for this VirtualHost,all requests below /should be handled by the WSGI script specified. The series of fourAliasdirectives allow Apache to serve therobots.txtandfavicon.icofiles as well as all resources beneath the /imagesand/staticlocations, directly from the DocumentRootwithout engaging the WSGI application. You can add as manyAliasdirectivesas you require.

Whenyou have configured your ApacheVirtualHost,issue the following command to restart the web server:

/etc/init.d/apache2 restart

Youwill need to restart the web server every time theapplication.wsgifile changes. However, all other modifications to your applicationdo not require a web server restart. Congratulations! You have nowsuccessfully deployed a WSGI application usingmod_wsgi.