Who will monitor the monitors?

21 Aug

This is the second time that an error in a monitoring/testing tool that we use has caused me to waste a good deal of time trying to solve a non-problem.

The first was when we were using a tool to test the scaling performance of a new feature. According to this tool the performance was absolutely abysmal with only 50 virtual clients, and I spent a couple of days writing alternative algorithms and trying to test them with this tool. The scalability was horrible no matter what I did, so I added some logging to see if something was going on that wasn’t supposed to be. It was. The testing tool was sending completely wrong information, creating completely unrealistic scenarios. The testing implementation was done by another developer who was sure that he had set it up right, and I was not familiar with the tool so I assumed that it was a problem with my code. Having another developer write the tests was supposed to save me time.

The latest monitoring snag was caused by a monitoring tool that, for our convenience, tails the php error log and sends the last couple hundred lines to us whenever there is an error. We kept getting the same error periodically and could not track down the source; everything seemed to be working perfectly, but we still got the error. Usage of the site every day is breaking new records so we assumed that it had something to do with the unprecedented load on servers, but could never pinpoint the source of the errors. Today I looked a bit more closely at the error log only to discover that the log was from 3 days ago!

So the question is, when your testing or monitoring tools report an error, how do you ensure that the error is real and not just in the tool itself?

  1. Travis

    August 21, 2008 at 7:05 pm

    A real computer scientist won’t be satisfied until his programs put his programs out of a job.

  2. Skyler

    August 23, 2008 at 3:52 pm

    Who will monitor the monitors? Why, Zabbix, of course :).