treibsand.com - Django and FastCGI

Django and FastCGI

Tags: Django, Python

Sometimes it's not possible to use Django's prefered setup (Apache & mod_python) for production servers. Either mod_python is not available, or you need some stuff which is not possible with it, so do I. I needed to access some environment variables, but mod_python removes most.

So why not use FastCGI? FastCGI is a language independent open extension to CGI that provides high performance.
So what do I need?

Flup Package
mod_fastcgi for Apache

FastCGI needs a local server, which is accessible by Apache, either using TCP/IP or Unix Sockets. There is a small script, which can start and stop the server.

#!/usr/bin/env python2.4

import os
import sys

if os.name == 'posix':

def become_daemon(ourHomeDir='.',outLog='/dev/null',errLog='/dev/null'):
                """
                Robustly turn us into a UNIX daemon, running in ourHomeDir.
                Modelled after the original code of this module and some
                sample code from the net.
                """

# first fork
                try:
                        if os.fork() > 0:
                                sys.exit(0)     # kill off parent
                except OSError, e:
                        sys.stderr.write("fork #1 failed: (%d) %s\n" % (e.errno, e.strerror))
                        sys.exit(1)
                os.setsid()
                os.chdir(ourHomeDir)
                os.umask(0)
                # second fork
                try:
                        if os.fork() > 0:
                                sys.exit(0)
                except OSError, e:
                        sys.stderr.write("fork #2 failed: (%d) %s\n" % (e.errno, e.strerror))
                        sys.exit(1)

si = open('/dev/null', 'r')
                so = open(outLog, 'a+', 0)
                se = open(errLog, 'a+', 0)
                os.dup2(si.fileno(), sys.stdin.fileno())
                os.dup2(so.fileno(), sys.stdout.fileno())
                os.dup2(se.fileno(), sys.stderr.fileno())

else:

def become_daemon(ourHomeDir='.',outLog=None,errLog=None):
                """
                If we are not running under a POSIX system, just simulate
                the daemon mode by doing redirections and directory changeing
                """

os.chdir(ourHomeDir)
                os.umask(0)
                sys.stdin.close()
                sys.stdout.close()
                sys.stderr.close()
                if errLog and outLog:
                            sys.stderr=open (errLog, 'a', 0)
                            sys.stdout=open (outLog, 'a', 0)
                elif errLog:
                            sys.stderr=open (errLog, 'a', 0)
                            sys.stdout=NullDevice ()
                elif outLog:
                            sys.stdout=open (outLog, 'a', 0)
                            sys.stderr=NullDevice ()
                else:
                            sys.stdout = NullDevice()
                            sys.stderr = NullDevice()

class NullDevice:
                """
                A substitute for stdout and stderr that writes to nowhere.
                This is a substitute for /dev/null
                """
        
                def write(self, s):
                        pass

def main():
        from flup.server.fcgi_fork import WSGIServer
        from django.core.handlers.wsgi import WSGIHandler

import getopt

(opts, args) = getopt.getopt(sys.argv[1:], 'f:s:h:p:',
                ['settings=','socket=','host=','port=',
                 'minspare=', 'maxspare=', 'maxchildren=',
                 'daemon', 'etclog=', 'errorlog=', 'workdir='])
        
        socket = None
        host = None
        port = None

minspare = 1
        maxspare = 5
        maxchildren = 50

daemon = None
        workdir = '.'
        etclog = '/dev/null'
        errorlog = '/dev/null'

for (o, v) in opts:
                if o in ('-s', '--socket'):
                        socket = v
                elif o in ('-h', '--host'):
                        host = v
                elif o in ('-p', '--port'):
                        port = int(v)
                elif o in ('-f', '--settings'):
                        os.environ['DJANGO_SETTINGS_MODULE'] = v
                elif o in ('--minspare',):
                        minspare = int(v)
                elif o in ('--maxspare',):
                        maxspare = int(v)
                elif o in ('--maxchildren',):
                        maxchildren = int(v)
                elif o in ('--daemon',):
                        daemon = 1
                elif o in ('--errorlog',):
                        errorlog = v
                elif o in ('--etclog',):
                        etclog = v
                elif o in ('--workdir',):
                        workdir = v

# if we should run as a daemon, use the above function to turn us
        # into one reliably. This should correctly detach from the tty.
        if daemon:
                become_daemon(ourHomeDir=workdir,
                        outLog=etclog, errLog=errorlog)

if socket and not host and not port:
                WSGIServer(WSGIHandler(), minSpare=minspare, maxSpare=maxspare, maxChildren=maxchildren, bindAddress=socket).run()
        elif not socket and host and port:
                WSGIServer(WSGIHandler(), minSpare=minspare, maxSpare=maxspare, maxChildren=maxchildren, bindAddress=(host, port)).run()
        else:
                print "usage: django-fcgi.py [--settings=<settingsmodule>] --socket=<socketname>"
                print "   or: django-fcgi.py [--settings=<settingsmodule>] --host==<hostname> --port=<portnumber>"
                print
                print "   additional options are:"
                print "      --minspare=<minimum number of spare processes, default 1>"
                print "      --maxspare=<maximum number of spare processes, default 5>"
                print "      --maxchildren=<maximum number of child processes, default 50>"
                print
                print "      --daemon"
                print "      --etclog=<path for stdout log, default /dev/null>"
                print "      --errorlog=<path for stderr log, default /dev/null>"
                print "      --workdir=<path for working directory, default .>"

if __name__ == '__main__':

import socket
        if not hasattr(socket, 'socketpair'):
                import eunuchs.socketpair

def socketpair():
                        (p,c) = eunuchs.socketpair.socketpair()
                        return (socket.fromfd(p,1,1), socket.fromfd(c,1,1))

socket.socketpair = socketpair

main()

Use following commands to start and stop the fcgi Server.

start:	django-fcgi.py --settings=myproject.settings --host 127.0.0.1 --port 8882 --daemon

stop:	kill `ps auxww | grep [d]jango-fcgi | awk '{print $2}'`

Now you need to configure Apache.

FastCgiExternalServer /var/www/localhost/htdocs/django.fcgi -host 127.0.0.1:8882 # in httpd.conf

# and in virt host config..
RewriteEngine On
RewriteRule ^(/myapp.*)$ /django.fcgi$1 [L]

Finally give Apache a restart and your done! :-)

15. Juni, 2006

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