Distributing cron jobs efficiently

When you have many servers executing the same cron job, it's usually a good idea not to run them all at the same time. If all the jobs access a common server (for example, when running backups), it may put too much load on that server, and even if they don't, all the servers will be busy at the same time, which may affect their capacity to provide other services.

As usual, Puppet can help; this time, using the inline_template function to calculate a unique time for each job.

How to do it...

Here's how to have Puppet schedule the same job at a different time for each machine:

1. Modify your site.pp file as follows:

   node 'cookbook' {
     cron { 'run-backup':
       ensure  => present,
       command => '/usr/local/bin/backup',
       hour    => inline_template('<%= @hostname.sum % 24 %>'),
       minute  => '00',
     }
   }

2. Run Puppet:

   [root@cookbook ~]# puppet agent -t
   Info: Caching catalog for cookbook.example.com
   Info: Applying configuration version '1413730771...