org.apache.flink.runtime.leaderelection

Class ZooKeeperLeaderElectionService

java.lang.Object

org.apache.flink.runtime.leaderelection.ZooKeeperLeaderElectionService

All Implemented Interfaces:

org.apache.curator.framework.recipes.cache.NodeCacheListener, org.apache.curator.framework.recipes.leader.LeaderLatchListener, LeaderElectionService

public class ZooKeeperLeaderElectionService
extends Object
implements LeaderElectionService, org.apache.curator.framework.recipes.leader.LeaderLatchListener, org.apache.curator.framework.recipes.cache.NodeCacheListener

Leader election service for multiple JobManager. The leading JobManager is elected using ZooKeeper. The current leader's address as well as its leader session ID is published via ZooKeeper as well.

Constructor Summary

Constructors

Constructor and Description
ZooKeeperLeaderElectionService(org.apache.curator.framework.CuratorFramework client, String latchPath, String leaderPath) Creates a ZooKeeperLeaderElectionService object.

Method Summary

Modifier and Type	Method and Description
void	confirmLeaderSessionID(UUID leaderSessionID) Confirms that the new leader session ID has been successfully received by the new leader.
UUID	getLeaderSessionID() Returns the current leader session ID or null, if the contender is not the leader.
protected void	handleStateChange(org.apache.curator.framework.state.ConnectionState newState)
boolean	hasLeadership() Returns true if the LeaderContender with which the service has been started owns currently the leadership.
void	isLeader()
void	nodeChanged()
void	notLeader()
void	start(LeaderContender contender) Starts the leader election service.
void	stop() Stops the leader election service.
protected void	writeLeaderInformation(UUID leaderSessionID) Writes the current leader's address as well the given leader session ID to ZooKeeper.

Methods inherited from class java.lang.Object

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

Constructor Detail

ZooKeeperLeaderElectionService

public ZooKeeperLeaderElectionService(org.apache.curator.framework.CuratorFramework client,
                                      String latchPath,
                                      String leaderPath)

Creates a ZooKeeperLeaderElectionService object.

Parameters:

client - Client which is connected to the ZooKeeper quorum

latchPath - ZooKeeper node path for the leader election latch

leaderPath - ZooKeeper node path for the node which stores the current leader information

Method Detail

getLeaderSessionID

public UUID getLeaderSessionID()

Returns the current leader session ID or null, if the contender is not the leader.

Returns:

The last leader session ID or null, if the contender is not the leader

start

public void start(LeaderContender contender)
           throws Exception

Description copied from interface: LeaderElectionService

Starts the leader election service. This method can only be called once.

Specified by:

start in interface LeaderElectionService

Parameters:

contender - LeaderContender which applies for the leadership

Throws:

Exception

stop

public void stop()
          throws Exception

Description copied from interface: LeaderElectionService

Stops the leader election service.

Specified by:

stop in interface LeaderElectionService

Throws:

Exception

confirmLeaderSessionID

public void confirmLeaderSessionID(UUID leaderSessionID)

Description copied from interface: LeaderElectionService

Confirms that the new leader session ID has been successfully received by the new leader. This method is usually called by the newly appointed LeaderContender. The rational behind this method is to establish an order between setting the new leader session ID in the LeaderContender and publishing the new leader session ID to the leader retrieval services.

Specified by:

confirmLeaderSessionID in interface LeaderElectionService

Parameters:

leaderSessionID - The new leader session ID

hasLeadership

public boolean hasLeadership()

Description copied from interface: LeaderElectionService

Returns true if the LeaderContender with which the service has been started owns currently the leadership.

Specified by:

hasLeadership in interface LeaderElectionService

Returns:

true if the associated LeaderContender is the leader, otherwise false

isLeader

public void isLeader()

Specified by:

isLeader in interface org.apache.curator.framework.recipes.leader.LeaderLatchListener

notLeader

public void notLeader()

Specified by:

notLeader in interface org.apache.curator.framework.recipes.leader.LeaderLatchListener

nodeChanged

public void nodeChanged()
                 throws Exception

Specified by:

nodeChanged in interface org.apache.curator.framework.recipes.cache.NodeCacheListener

Throws:

Exception

writeLeaderInformation

protected void writeLeaderInformation(UUID leaderSessionID)

Writes the current leader's address as well the given leader session ID to ZooKeeper.

Parameters:

leaderSessionID - Leader session ID which is written to ZooKeeper

handleStateChange

protected void handleStateChange(org.apache.curator.framework.state.ConnectionState newState)