Efficiently distributing cron jobs

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 the jobs all 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 manifests/nodes.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:

   ubuntu@cookbook:~/puppet$ papply
   Notice: /Stage[main]//Node[cookbook]/Cron[run-backup]/ensure: created
   Notice: Finished catalog...