Event Listener
openLooKeng supports custom event listeners that are invoked for the following events:
- Query creation
- Query completion (success or failure)
- Split completion (success or failure)
This functionality enables development of custom logging, debugging and performance analysis plugins. In a openLooKeng cluster, only a single event listener plugin can be active at a time .
Implementation
EventListenerFactory is responsible for creating an EventListener instance. It also defines an EventListener name which is used by the administrator in a openLooKeng configuration. Implementations of
EventListener implement methods for the event types they are interested in handling.
The implementation of EventListener and EventListenerFactory must be wrapped as a plugin and installed on the openLooKeng cluster.
Configuration
After a plugin that implements EventListener and EventListenerFactory has been installed on the coordinator, it is configured using an etc/event-listener.properties file. All of the
properties other than event-listener.name are specific to the EventListener implementation.
The event-listener.name property is used by openLooKeng to find a registered EventListenerFactory based on the name returned by EventListenerFactory.getName(). The remaining properties are passed as
a map to EventListenerFactory.create().
Example configuration file:
event-listener.name=custom-event-listener
custom-property1=custom-value1
custom-property2=custom-value2