A short time after I installed Monit, I tried to monitor a background running process that does not support daemon mode.
It is an exceptionally rare situation, but very interesting one, so after a while a came with a quite simple solution using additional shell script.
This is a shell script used to start/stop service. It will execute
/opt/service/service command in the background and manage PID file.
$ cat /usr/sbin/service.sh
#!/bin/sh # start/stop service and create pid file for a non-daemon app # service command service_cmd="/opt/service/service" # pid file location service_pid="/var/run/service.pid" if [ $# -eq 1 -a "$1" = "start" ]; then if [ -f "$service_pid" ]; then kill -0 $(cat $service_pid) 2>/dev/null # check pid if [ $? -eq 0 ]; then exit 2; # process is running, exit else unlink $service_pid # process is not running # remove stale pid file fi fi # start service in background and store process pid $service_cmd >/dev/null & echo $! > $service_pid elif [ $# -eq 1 -a "$1" = "stop" -a -f "$service_pid" ]; then kill -0 $(cat $service_pid) 2>/dev/null # check pid if [ $? -eq 0 ]; then kill $(cat $service_pid) # kill process if it is running fi unlink $service_pid fi
This shell script is quite simple, but there are several commands that are worth your attention. I described them in two earlier blog posts: How to get PID of the background process, How to check whether the process ID still exists.
Use defined PID file and code listed in the previous section to manage service using Monit.
# cat /etc/monit/conf.d/service.conf
check process service with pidfile /var/run/service.pid start program = "/usr/sbin/service.sh start" stop program = "/usr/sbin/service.sh stop" depend on service_bin check file service_bin with path /usr/sbin/service.sh if failed checksum then unmonitor if failed permission 755 then unmonitor if failed uid root then unmonitor if failed gid root then unmonitor
Sample summary information.
$ sudo monit summary The Monit daemon 5.4 uptime: 16h 22m Process 'service' Running File 'service_bin' Accessible
Sample status information.
$ sudo monit status The Monit daemon 5.4 uptime: 16h 22m Process 'service' status Running monitoring status Monitored pid 1883 parent pid 1 uptime 16h 19m children 0 memory kilobytes 1900 memory kilobytes total 1900 memory percent 0.1% memory percent total 0.1% cpu percent 0.0% cpu percent total 0.0% data collected Tue, 30 Sep 2014 18:35:40 File 'service_bin' status Accessible monitoring status Monitored permission 755 uid 0 gid 0 timestamp Tue, 30 Sep 2014 18:35:40 size 1306006 B checksum bc9b654871c608bee03bf8a781c14818 (MD5) data collected Tue, 30 Sep 2014 18:35:40