Package com.linkedin.venice.helix

Class HelixLiveInstanceMonitor

java.lang.Object

com.linkedin.venice.helix.HelixLiveInstanceMonitor

All Implemented Interfaces:

LiveInstanceMonitor, VeniceResource, org.apache.helix.zookeeper.zkclient.IZkChildListener

public class HelixLiveInstanceMonitor
extends java.lang.Object
implements org.apache.helix.zookeeper.zkclient.IZkChildListener, VeniceResource, LiveInstanceMonitor

This class is used to monitor the current live instances(Helix participators). Here, it is not using HelixManager because HelixManager is using the same ZkClient being used for all the Helix related ZK Watches/data operations. When there are a lot of state transitions during node starts/stops, it will take a very long time to let HelixManager to report the instance list change since those state transition notifications could happen earlier than node stop/start event. Under this circumstance, HelixManager won't report node list change in time. Using a separate ZkClient will allow node list change notification happen in a separate channel, so that node list change can be captured in time. This way is a little hacky since this class is reading from Helix ZK directory directly.

Constructor Summary

Constructors

Constructor	Description
HelixLiveInstanceMonitor(org.apache.helix.zookeeper.impl.client.ZkClient zkClient, java.lang.String clusterName)

Method Summary

Modifier and Type	Method	Description
void	clear()
java.util.Set<Instance>	getAllLiveInstances()
void	handleChildChange(java.lang.String parentPath, java.util.List<java.lang.String> currentChildren)
boolean	isInstanceAlive(Instance instance)	Check whether current instance is alive or not.
void	refresh()	Must be run during service start else it wont subscribe to state changes.
void	registerLiveInstanceChangedListener(LiveInstanceChangedListener listener)

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.apache.helix.zookeeper.zkclient.IZkChildListener

handleChildChange

Constructor Detail

HelixLiveInstanceMonitor

public HelixLiveInstanceMonitor(org.apache.helix.zookeeper.impl.client.ZkClient zkClient,
                                java.lang.String clusterName)

Method Detail

refresh

public void refresh()

Must be run during service start else it wont subscribe to state changes.

Specified by:

refresh in interface VeniceResource

clear

public void clear()

Specified by:

clear in interface VeniceResource

handleChildChange

public void handleChildChange(java.lang.String parentPath,
                              java.util.List<java.lang.String> currentChildren)
                       throws java.lang.Exception

Specified by:

handleChildChange in interface org.apache.helix.zookeeper.zkclient.IZkChildListener

Throws:

java.lang.Exception

isInstanceAlive

public boolean isInstanceAlive(Instance instance)

Description copied from interface: LiveInstanceMonitor

Check whether current instance is alive or not.

Specified by:

isInstanceAlive in interface LiveInstanceMonitor

Returns:

getAllLiveInstances

public java.util.Set<Instance> getAllLiveInstances()

Specified by:

getAllLiveInstances in interface LiveInstanceMonitor

registerLiveInstanceChangedListener

public void registerLiveInstanceChangedListener(LiveInstanceChangedListener listener)

Specified by:

registerLiveInstanceChangedListener in interface LiveInstanceMonitor