Python Process Watcher

Occasionally an application may crash unexpectedly. Instead of reinventing the wheel I found a simple unix/linux daemon in Python for the daemon functionality and just added the run section logic. Using the bits below I can monitor or potentially restart the failed application. The run section forks a daemon which checks for the existence of a processes using pgrep every 5 seconds in a loop. It reads from a file named observe.list for any number of named processes. Each line in observe.list should contain a unique process name like puppetmasterd and on the next line httpd or whatever you'd like to watch. I tried using logger with SysLogHandler but I'm not sure it was available with python 2.4.3 which ships with RHEL 5 or CentOS 5.

#!/usr/bin/env python

import sys, time, subprocess, syslog
from daemon import Daemon

# file which contains the list of process to observe
process_file = open('observe.list', 'r')
process_list = []
for line in process_file:
    process_list.append(line.rstrip('\n'))

def isRunning ( process_name ):
    ps = subprocess.call("pgrep "+process_name, shell=True, stdout=subprocess.PIPE)
    if ps is 1:
        return False
    else:
        return True

class Observe(Daemon):
    def run(self):
        while True:
            for process in process_list:
                if isRunning(process) == False:
                    syslog.syslog(process + " not running!")
                    time.sleep(5)
                else:
                    syslog.syslog(process + ' is running!')
                    time.sleep(5)

if __name__ == "__main__":
    daemon = Observe('/tmp/observe.pid')
    if len(sys.argv) == 2:
        if 'start' == sys.argv[1]:
            daemon.start()
        elif 'stop' == sys.argv[1]:
            daemon.stop()
        elif 'restart' == sys.argv[1]:
            daemon.restart()
        else:
            print "Unknown command"
            sys.exit(2)
        sys.exit(0)
    else:
        print "usage: %s start|stop|restart" % sys.argv[0]
        sys.exit(2)