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Host monitoring with Jaiku

A few weeks back, we were having trouble with dogma, our shared server where is hosted, which would occasionally be unavailable for unknown reasons. We needed to monitor its availability so that it could be fixed when it crashed again, and we’d be able to investigate quickly. Since it was happening mostly out of working hours, SMS notification was essential.

Normally, that kind of monitoring is pretty basic stuff, and there’s plenty of services out there, from to the more complex self-hosted apps like monit and Nagios which can do that. But looking around, I found that none of them offered SMS notification for free, and since this was our personal-use server, I wasn’t willing to sign up for a $10-per-month paid account to support it, or buy any hardware to act as a private SMS gateway.

Instead, I thought of Jaiku — the Finnish company which offers a microblogging/presence platform similar to Twitter. Jaiku had a couple of cool features:

  • SMS notifications
  • it’s possible to broadcast messages to a “channel”, which others could subscribe to, IRC-style
  • it has an open API

This would allow me to notify any interested party of dogma’s downtime, allowing subscribers to subscribe and unsubscribe using whatever notification systems Jaiku support.

With a little perl and LWP, I rigged up a quick monitoring script to check via HTTP, and report if it was unavailable over the course of 5 retries in 50 seconds. If it was broken, the script sends a JSON-formatted POST request to Jaiku’s “presence.send” method, informing the target channel of the issue. (Perl source here.)

You can see the ‘#dogmastatus’ channel here — as you can see, we fixed the problem with dogma just over 2 weeks ago ;)

It’s worth noting that I had to set up an additional user, “downtimebot”, on Jaiku to send the messages — otherwise I’d never see them on my configured mobile phone! Jaiku uses the optimisation that, if I sent the message, there’s no need to cc me with a copy of what I just sent; logical enough.

Anyway, if you’re interested in dogma’s availability (there might be one or two readers who are), feel free to add yourself to the #dogmastatus channel and receive any updates.

Update: Fergal noted that it’s pretty simple to use Cape Clear’s assembly framework to perform a HTTP ping test with output to Jabber/XMPP. nifty!