Package org.apache.druid.curator.discovery

Class CuratorDruidLeaderSelector

java.lang.Object

org.apache.druid.curator.discovery.CuratorDruidLeaderSelector

All Implemented Interfaces:

DruidLeaderSelector

public class CuratorDruidLeaderSelector
extends Object
implements DruidLeaderSelector

Nested Class Summary

Nested classes/interfaces inherited from interface org.apache.druid.discovery.DruidLeaderSelector

DruidLeaderSelector.Listener

Constructor Summary

Constructors

Constructor	Description
CuratorDruidLeaderSelector(org.apache.curator.framework.CuratorFramework curator, DruidNode self, String latchPath)

Method Summary

Modifier and Type	Method	Description
String	getCurrentLeader()	Get ID of current Leader.
boolean	isLeader()	Returns true if this node is elected leader from underlying system's point of view.
int	localTerm()	Implementation would increment it everytime it becomes leader.
void	registerListener(DruidLeaderSelector.Listener listener)	Register the listener for watching leadership notifications.
void	unregisterListener()	Unregisters the listener.

Methods inherited from class java.lang.Object

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

Constructor Detail

CuratorDruidLeaderSelector

public CuratorDruidLeaderSelector(org.apache.curator.framework.CuratorFramework curator,
                                  DruidNode self,
                                  String latchPath)

Method Detail

getCurrentLeader

@Nullable
public String getCurrentLeader()

Description copied from interface: DruidLeaderSelector

Get ID of current Leader. Returns NULL if it can't find the leader. Note that it is possible for leadership to change right after this call returns, so caller would get wrong leader. This is expected to work even if a listener is not registered.

Specified by:

getCurrentLeader in interface DruidLeaderSelector

isLeader

public boolean isLeader()

Description copied from interface: DruidLeaderSelector

Returns true if this node is elected leader from underlying system's point of view. For example if curator is used to implement this then true would be returned when curator believes this node to be the leader. Note that it is possible for leadership to change right after this call returns, so caller would get wrong status.

Specified by:

isLeader in interface DruidLeaderSelector

localTerm

public int localTerm()

Description copied from interface: DruidLeaderSelector

Implementation would increment it everytime it becomes leader. This allows users to start a long running task when they become leader and be able to intermittently check that they are still leader from same term when they started. DruidCoordinator class uses it to do intermittent checks and stop the activity as needed.

Specified by:

localTerm in interface DruidLeaderSelector

registerListener

public void registerListener(DruidLeaderSelector.Listener listener)

Description copied from interface: DruidLeaderSelector

Register the listener for watching leadership notifications. It should only be called once.

Specified by:

registerListener in interface DruidLeaderSelector

unregisterListener

public void unregisterListener()

Description copied from interface: DruidLeaderSelector

Unregisters the listener.

Specified by:

unregisterListener in interface DruidLeaderSelector