## <a id="event-handlers"></a> Event Handlers

Event handlers are defined as `EventCommand` objects in Icinga 2.

Unlike notifications event commands are called on every host/service state change
if defined. Therefore the `EventCommand` object should define a command line
evaluating the current service state and other service runtime attributes
available through runtime macros. Runtime macros such as `$SERVICESTATETYPE$`
and `$SERVICESTATE$` will be processed by Icinga 2 helping on fine-granular
events being triggered.

Common use case scenarios are a failing HTTP check requiring an immediate
restart via event command, or if an application is locked and requires
a restart upon detection.