Introduction

In a previous article, I showed to how to install Supervisor and Superlance on CentOS. While Superlance is great for telling you when one of your child threads goes down, what about when Supervisor itself goes down? That is where Monit¹ comes in.

In this tutorial, we will install Monit from the EPEL² repository, and then configure it to send us an email alert if Supervisor goes offline. It will also automatically restart Supervisor for you if it crashes.

Installing Monit

I got 5.1 from EPEL (5.8 is the latest):

$ yum install monit

Enable Monit email alerts

Edit /etc/monit.conf, add:

set mailserver localhost
set alert you@yourmail.com

You should set mailserver to point to your SMTP, and alert to point to your email address that will receive Monit alerts.

Configure Monit to monitor Supervisor

Create the file /etc/monit.d/supervisor with the following content:

check process cron with pidfile /var/run/supervisord.pid
   group supervisor
   start program = "/etc/init.d/supervisord start"
   stop  program = "/etc/init.d/supervisord stop"
   if 5 restarts within 5 cycles then timeout

The configuration will monitor the Supervisord PID file (/var/run/supervisord.pid), alerting when that file disappears due to a crash or changes due to a restart. There is a lot more your can do with Supervisor service monitoring, but this is the most basic config to get you up-and-running monitoring Supervisor.

Starting the service

$ service monit start

Now just for fun, try this and see what happens:

$ service supervisord stop

References