org.apache.flink.runtime.leaderelection

Class ZooKeeperLeaderElectionService

java.lang.Object

org.apache.flink.runtime.leaderelection.ZooKeeperLeaderElectionService

All Implemented Interfaces:

org.apache.curator.framework.api.UnhandledErrorListener, 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, org.apache.curator.framework.api.UnhandledErrorListener

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	confirmLeadership(UUID leaderSessionID, String leaderAddress) Confirms that the LeaderContender has accepted the leadership identified by the given leader session id.
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(UUID leaderSessionId) Returns true if the LeaderContender with which the service has been started owns currently the leadership under the given leader session id.
void	isLeader()
void	nodeChanged()
void	notLeader()
void	start(LeaderContender contender) Starts the leader election service.
void	stop() Stops the leader election service.
String	toString()
void	unhandledError(String message, Throwable e)
protected void	writeLeaderInformation() 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, 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

confirmLeadership

public void confirmLeadership(UUID leaderSessionID,
                              String leaderAddress)

Description copied from interface: LeaderElectionService

Confirms that the LeaderContender has accepted the leadership identified by the given leader session id. It also publishes the leader address under which the leader is reachable.

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 as well as the leader address to the leader retrieval services.

Specified by:

confirmLeadership in interface LeaderElectionService

Parameters:

leaderSessionID - The new leader session ID

leaderAddress - The address of the new leader

hasLeadership

public boolean hasLeadership(@Nonnull
                             UUID leaderSessionId)

Description copied from interface: LeaderElectionService

Returns true if the LeaderContender with which the service has been started owns currently the leadership under the given leader session id.

Specified by:

hasLeadership in interface LeaderElectionService

Parameters:

leaderSessionId - identifying the current leader

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()

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

handleStateChange

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

unhandledError

public void unhandledError(String message,
                           Throwable e)

Specified by:

unhandledError in interface org.apache.curator.framework.api.UnhandledErrorListener

toString

public String toString()

Overrides:

toString in class Object