Dec 182012
 

For a project that I started working on with a friend back in November, we needed to use a project management system for bugs and progress tracking, and we decided to try Trac an open project management system with svn integration written in python.

I run nginx to do all of my web serving needs, so I followed the instructions given for nginx configuration for Trac, and I was a little disappointed to find that the FastCGI script given didn’t do any normal server things, like fork a child process to run in the background. I also wanted to integrate the FastCGI server with the service management tools available in CentOS, so I set to work.

First, I modified the nginx-specific FastCGI script to accept a number of command line arguments, allowing me to use the same script to run multiple track servers for multiple different projects. In total, it accepts a project path, a user, a unix socket to listen for fcgi connections, and a location to store the server process pid. Then, I added the child fork to allow me to run it as a service. Here is the version that I use now:

#!/usr/bin/env python
from optparse import OptionParser
import os
import pwd

parser = OptionParser()
parser.add_option("-s", "--sock", dest="sockaddr", help="Use a specific unix socket", default="/var/trac/run/instance.sock")
parser.add_option("-u", "--user", dest="user", help="Run FCGI process as a specific user", default="nginx")
parser.add_option("-t", "--trac", dest="trac_env", help="Trac environment path to use", default="/var/trac/project")
parser.add_option("-p", "--pid", dest="pidfile", help="Location to store pid file", default="/var/run/trac.fcgi.pid")
(options, args) = parser.parse_args()

os.environ['TRAC_ENV'] = options.trac_env

try:
     from trac.web.main import dispatch_request
     import trac.web._fcgi

     pid = os.fork()
     if pid == 0:
          os.setuid(pwd.getpwnam(options.user)[2])
          fcgiserv = trac.web._fcgi.WSGIServer(dispatch_request, bindAddress = options.sockaddr, umask = 7)
          fcgiserv.run()
     else:
          os.system("echo " + str(pid) + " > " + options.pidfile)

except OSError, oe:
    raise
except SystemExit:
    raise
except Exception, e:
    print 'Content-Type: text/plain\r\n\r\n',
    print 'Oops...'
    print
    print 'Trac detected an internal error:'
    print
    print e
    print
    import traceback
    import StringIO
    tb = StringIO.StringIO()
    traceback.print_exc(file=tb)
    print tb.getvalue()

With a service-capable FastCGI script, now I needed to create an /etc/init.d script to control the process. Because I am running CentOS, I also wanted the script to be compatible with chkconfig so that it can be used with the service utility. This was pretty simple, as I just copied an existing init script and ripped out most of its guts, replacing with a minimal set of controls: start, stop, and restart. Here’s the full init script, which I saved as /etc/init.d/trac-fcgi :

#!/bin/sh
#
# chkconfig:   - 85 15
# description:  Runs trac's fcgi script as a daemon
# processname:  trac.fcgi
# pidfile:     /var/run/trac.fcgi.pid

# Source function library.
. /etc/rc.d/init.d/functions

# Source networking configuration.
. /etc/sysconfig/network

# Check that networking is up.
[ "$NETWORKING" = "no" ] && exit 0

tracfcgi="/var/trac/trac.fcgi"
prog=$(basename $tracfcgi)
pidfile="/var/run/${prog}.pid"

start() {
    echo -n $"Starting $prog: "
    daemon $tracfcgi
    retval=$?
    echo
    return $retval
}

stop() {
    echo -n $"Stopping $prog: "
    killproc -p $pidfile $prog
    retval=$?
    echo
    return $retval
}

restart() {
	stop
	start
}

rh_status() {
	status $prog
}

rh_status_q() {
    rh_status >/dev/null 2>&1
}

case "$1" in
    start)
        rh_status_q && exit 0
        $1
        ;;
    stop)
        rh_status_q || exit 0
        $1
        ;;
    restart)
        $1
        ;;
    status|status_q)
        rh_$1
        ;;
    condrestart|try-restart)
        rh_status_q || exit 7
        restart
	    ;;
    *)
        echo $"Usage: $0 {start|stop|status|restart}"
        exit 2
esac

Finally, the new init script is added with a simple call to chkconfig:

# chkconfig --add trac-fcgi

If you want to run multiple trac servers with different configurations, you will need to create a copy of the init.d script per configuration and add them using command line arguments on the line that reads daemon $tracfcgi after the $tracfcgi variable. Then, add each configuration’s script to chkconfig using the same method as before.