cluster monitoring toolkit - scalable Nagios integration

 ganglia-nagios-bridge brings Ganglia and Nagios together, taking the
 metrics from Ganglia agents, applying thresholds, deciding when they are
 in a bad state and mapping them to service definitions in Nagios.
 Nagios can then display the network state, highlight hotspots and raise
 notifications in the usual manner.
 .
 Using regular expressions in the ganglia-nagios-bridge config and the
 nagios config files it is possible to enable alerting for thousands of
 hosts very quickly, with less than 50 lines of config in total.