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