Package org.apache.sling.event.impl.jobs.config

Class TopologyHandler

java.lang.Object

org.apache.sling.event.impl.jobs.config.TopologyHandler

All Implemented Interfaces:

Runnable, TopologyEventListener

public class TopologyHandler
extends Object
implements TopologyEventListener, Runnable

This topology handler is handling the topology change events asynchronously and processes them by queuing them.

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static final class	TopologyHandler.QueueItem	We need a holder class to be able to put something into the queue to stop it.

Constructor Summary

Constructors

Constructor	Description
TopologyHandler()

Method Summary

Modifier and Type	Method	Description
protected void	activate()
protected void	deactivate()
void	handleTopologyEvent(TopologyEvent event)	Inform the service about an event in the topology - or in the discovery of the topology.
void	run()

Methods inherited from class java.lang.Object

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

Constructor Details

TopologyHandler

public TopologyHandler()

Method Details

activate

protected void activate()

deactivate

protected void deactivate()

handleTopologyEvent

public void handleTopologyEvent(TopologyEvent event)

Description copied from interface: TopologyEventListener

Inform the service about an event in the topology - or in the discovery of the topology.

Implementors of this method must ensure that this method returns quickly and that no locks are being acquired that could cause deadlocks (ie the framework might call this method holding locks).

The TopologyEvent contains details about what changed. The supported event types are:

• TOPOLOGY_INIT sent when the TopologyEventListener was first bound to the discovery service - represents the initial state of the topology at that time.
• TOPOLOGY_CHANGING sent when the discovery service discovered a change in the topology and has started to settle the change. This event is sent before TOPOLOGY_CHANGED but is optional
• TOPOLOGY_CHANGED sent when the discovery service discovered a change in the topology and has settled it.
• PROPERTIES_CHANGED sent when the one or many properties have changed in an instance in the current topology

A note on instance restarts: it is currently not a requirement on the discovery service to send a TopologyEvent should an instance restart occur rapidly (ie within the change detection timeout). A TopologyEvent is only sent if the number of instances or any property changes. Should there be a requirement to detect a restart in a guaranteed fashion, it is always possible to set a particular property (using the PropertyProvider) to the instance start time and have others detect a change in that property.

Specified by:

handleTopologyEvent in interface TopologyEventListener

Parameters:

event - The topology event

run

public void run()

Specified by:

run in interface Runnable