forever.py

#!/usr/bin/env python

# Ensure that system-wide daemons are running.
# If <service> is not running, do "service <service> restart".
# We do NOT just do "service <service> start" since that does
# not work (it's just an observerable fact).
#
# Put this in a crontab, e.g.,
#
#    * * * * * /home/salvus/forever.py rethinkdb   >> /home/salvus/.forever_rethinkdb.log  2>> /home/salvus/.forever_rethinkdb.err
#

import os, sys, time

SERVICES = sys.argv[1:]
if len(SERVICES) == 0 or len([x for x in SERVICES if x.startswith('-')]):
    sys.stderr.write("usage: %s <service> <service> ...\n"%sys.argv[0])
    sys.exit(1)

def is_running(service):
    return bool(os.popen("pidof %s"%service).read())

def test(service):
    if not is_running(service):
        print("%s: %s not running so restarting"%(service, time.asctime()))
        os.system("sudo service %s restart"%service)

for service in SERVICES:
    test(service)