Event Handlers are a feature within Opsview that moves your monitoring solution away from a 'detect and alert' system to a more proactive monitoring tool. For example, if Opsview detects that a web service is not running on a host it can not only alert you, but it can also automatically restart that web service.
Learn More About Event Handlers
How Event Handlers Work
An Opsview Collector runs an Event Handler when a service changes to a non-OK state. The Collector is likely monitoring the server at a one-minute interval (if the default value is unmodified). This means that once the Event Handler has been run, the Opsview server should detect that the service is now back 'up' and running, and thus the service check should return to 'OK' .
How to Create an Event Handler
An Event Handler can be applied to a service check (and all hosts that use that service check). Or, you can create an Event Handler for an individual host to have more granular control.