Nagios XI - Service Dependencies

Overview

This guide on Best Practices briefly explains service dependencies in Nagios XI.

Service Dependencies

When a host goes down, the services still get executed and can result in services in an unknown or critical state. Nagios suppresses any notifications however they still appear as critical in the interface.

Sometimes a host can be up but the monitoring agent can be down. An example of this is an NRPE agent.

By using service dependencies, if the master service goes down, you prevent notifications being sent OR prevent checks from being executed. Either option simply pushes the next check or notification to the next interval.

This is very similar to this KB article "Intervals - Host vs Service", make sure your master service goes down HARD before the dependent services, use different check intervals or retries.

Master service e.g. - Ping or NRPE Version.

Disable Service Checks

A new feature of Nagios Core 4.1.0 (included in XI 5 onwards) is a configuration directive called host_down_disable_service_checks.

It’s best described as automatic service dependencies on their own hosts.
System wide setting, this applies across the board, it is not granular.Can reduce the load on the XI host as plugins will not be executed if this host is down.
- Define in /usr/local/nagios/etc/nagios.cfg
  - ```
  host_down_disable_service_checks=1
```
- Can also be defined via CCM > Advanced > Nagios Core Main Config
- Restart nagios monitoring engine or Apply Configuration for setting to take effect
Keep in mind that if the host is down then any defined service dependencies will be ignored.

Final Thoughts

For any support related questions please visit the Nagios Support Forums at:

http://support.nagios.com/forum/