Using AMQP to do cron-like scheduling
This page is a mirrored copy of an article originally posted on the (now sadly defunct) LShift blog; see the archive index here.
Fri, 8 February 2008
Barry Pederson’s excellent py-amqplib Python AMQP client comes with a very cute little demo, demonstrating how easy it is to do sophisticated cron-like things with AMQP and RabbitMQ.
As Barry writes in the example, the trick is to “[fire] off simple messages at one-minute intervals to a topic exchange named ‘clock’, with the topic of the message being the local time as ‘year.month.date.dow.hour.minute‘, for example: ‘2007.11.26.1.12.33′, where the dow (day of week) is 0 for Sunday, 1 for Monday, and so on (similar to Unix crontab). A consumer could then bind a queue to the routing key ‘#.0′ for example to get a message at the beginning of each hour.”
Lovely!
Interesting!
You could even build an extension to the rabbit server to produce the timer event that would be published to the exchange - so that the cron daemon is self contained within the rabbit server.