Debugging monit

Solution 1:

I've had the same problem. Using monit's verbose command-line option helps a bit, but I found the best way was to create an environment as similar as possible to the monit environment and run the start/stop program from there.

# monit runs as superuser
$ sudo su

# the -i option ignores the inherited environment
# this PATH is what monit supplies by default
$ env -i PATH=/bin:/usr/bin:/sbin:/usr/sbin /bin/sh

# try running start/stop program here
$

I've found the most common problems are environment variable related (especially PATH) or permission-related. You should remember that monit usually runs as root.

Also if you use as uid myusername in your monit config, then you should change to user myusername before carrying out the test.

I hope that helps.

Solution 2:

Be sure to always double check your conf and monitor your processes by hand before letting monit handle everything. systat(1), top(1) and ps(1) are your friends to figure out resource usage and limits. Knowing the process you monitor is essential too.

Regarding the start and stop scripts i use a wrapper script to redirect output and inspect environment and other variables. Something like this :

$ cat monit-wrapper.sh

#!/bin/sh
{
  echo "MONIT-WRAPPER date"
  date
  echo "MONIT-WRAPPER env"
  env
  echo "MONIT-WRAPPER $@"
  $@
  R=$?
  echo "MONIT-WRAPPER exit code $R"
} >/tmp/monit.log 2>&1

Then in monit :

start program = "/home/billitch/bin/monit-wrapper.sh my-real-start-script and args"
stop program = "/home/billitch/bin/monit-wrapper.sh my-real-stop-script and args"

You still have to figure out what infos you want in the wrapper, like process infos, id, system resources limits, etc.