We value our customers a lot and so we use all the tools and services to make our client’s application highly available in production. Monit is one of the tools we use in production to ensure that all essential services and applications are up and running.

This post explains how to configure Monit for commonly used tools and services with a rails application.

Installing Monit on Linux is super easy. Checkout the steps mentioned in previous post for more details.

Once the Monit is installed, you can add applications and tools you want to monitor in /etc/monit/monitrc configuration file like as below. Here are configurations of some of the most common applications used with Rails:

Nginx

check process nginx with pidfile /var/run/nginx.pid
  start program = "/etc/init.d/nginx start"
  stop program = "/etc/init.d/nginx stop"

MySQL

check process mysqld with pidfile /var/run/mysqld/mysqld.pid
  start program = "/etc/init.d/mysql start"
  stop program = "/etc/init.d/mysql stop"

Apache

check process apache
  with pidfile "/var/run/httpd.pid"
  start program = "/etc/init.d/httpd start"
  stop program = "/etc/init.d/httpd stop"

Mongo

check process mongodb
  with pidfile /var/run/mongodb.pid
  start program = "/etc/init.d/mongodb start"
  stop program = "/etc/init.d/mongodb stop"

Redis

check process redis
  with pidfile /var/run/redis.pid
  start program = "/etc/init.d/redis start"
  stop program = "/etc/init.d/redis stop"

Unicorn

check process unicorn with pidfile 
/home/USER_NAME/APP_NAME/shared/pids/unicorn.pid
  start program = "/etc/init.d/unicorn start"
  stop program = "/etc/init.d/unicorn stop"

Delayed Jobs

Monit does not have Rails and RVM environment variables so that cannot start delayed_job directly like as other services defined above.

Solution :

  • Create /home/USER_NAME/APP_NAME/shared/delayed_job.monitrc
  • Add the code for start and stop services in /home/USER_NAME/APP_NAME/shared/delayed_job.monitrc file. Do not add this code in /etc/monit/monitrc.

  • Create new bash file /etc/init.d/delayed_job init script for monit to start the delayled_job.
  • Change its access mode to 755, edit /etc/init.d/delayed_job bash file and add following script.

Finish Up

Once you have configured all of the programs, reload the Monit.

$ sudo monit reload

and start running all of the monitored programs by following command:

$ sudo monit start all

You can check the logs for all running process into /var/log/monit.log file.

Here you can find many more examples of how to configure other services like cron, File, FTP, mail etc.

Happy Monitoring!!

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