org.apache.ambari.server.events.publishers

Class JPAEventPublisher

java.lang.Object

org.apache.ambari.server.events.publishers.JPAEventPublisher

public class JPAEventPublisher
extends Object

The JPAEventPublisher is used to publish events pertaining to EclipseLink and the persistence layer. This class uses a synchronized bus and will therefore run on the current thread. This is desirable since JPA events are time-senstive and cannot be executed in an asynchronous manner most of the time.

This publisher was created specifically for AMBARI-17970. The headless server thread which monitors the database for things to do (known as the action scheduler) polls every second. However, it takes EclipseLink up to 1000ms to update L1 persistence context cache references in other threads. Therefore, it's possible that the action scheduler can pickup a ClusterEntity with stale data, including stale configurations. Those stale configurations can then be sent in commands down to agents.

Constructor Summary

Constructors

Constructor and Description
JPAEventPublisher()

Method Summary

Modifier and Type	Method and Description
void	publish(JPAEvent event) Publishes the specified event to all registered listeners that Subscribe to any of the JPAEventPublisher instances.
void	register(Object object) Register a listener to receive events.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

JPAEventPublisher

public JPAEventPublisher()

Method Detail

publish

public void publish(JPAEvent event)

Publishes the specified event to all registered listeners that Subscribe to any of the JPAEventPublisher instances.

Parameters:

event - the event

register

public void register(Object object)

Register a listener to receive events. The listener should use the Subscribe annotation.

Parameters:

object - the listener to receive events.