Semintelligent

Nagios Performance Tuning: Early Lessons Learned, Lessons Shared. Part 5 - Circular Dependency Checking · 6 August 2009, 12:36

NOTE – we are using Nagios 3.0.3, which does not have the very cool patch for the circular dependency checking algorithm recently introduced into the Nagios 3.1.x release tree.

Our startup times for our Nagios instances jumped dramatically today (more than 6x) due to some of our users adding large numbers of new services to their hosts that are associated with their hosts through the

service -> hostgroup -> host

relationship I have discussed often and that we make use of often. We always want our Nagios instance to start on a 5 minute interval as we push most of the performance data we get back from checks into a long-term trending data warehouse.

We also test every configuration release in an integration and test environment before doing a deployment.

With this in mind, we decided to try turning off circular dependency checking on startup for our production Nagios instances.

On one this reduced startup time from 763! seconds to 16 seconds; on the other startup times were reduced from 158 seconds to 6 seconds.

There you have it, a simple way to dramatically reduce startup times, but again, only do this if you test your configuration beforehand in an environment with circular dependency checking on.

— Max Schubert

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