Thursday, August 21, 2008

Cron entry mistakes

This mistake came at the expense of one of my old co-workers, who decided to share this with me over Instant Messenger. I got a good laugh at his misfortune. He wanted to set up a cron job that would restart a poorly performing service every 6 hours. This is the cron entry he added.

* */6 * * *

The lead developer, whose app depends on that service, came up to him wondering why his app was having outages. What my colleague should have configured was

0 */6 * * *

His cron entry was restarting the service every 6 hours, and then restarting it every minute for an hour during that sixth hour. Brilliant! Although I guess I shouldn't throw stones in glass houses.