org.apache.flink.runtime.highavailability.nonha.leaderelection

Class SingleLeaderElectionService

java.lang.Object

org.apache.flink.runtime.highavailability.nonha.leaderelection.SingleLeaderElectionService

All Implemented Interfaces:

LeaderElectionService

public class SingleLeaderElectionService
extends Object
implements LeaderElectionService

An implementation of the LeaderElectionService interface that handles a single leader contender. When started, this service immediately grants the contender the leadership.

The implementation accepts a single static leader session ID and is hence compatible with pre-configured single leader (no leader failover) setups.

This implementation supports a series of leader listeners that receive notifications about the leader contender.

Constructor Summary

Constructors

Constructor and Description
SingleLeaderElectionService(Executor notificationsDispatcher, UUID leaderId) Creates a new leader election service.

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.
LeaderRetrievalService	createLeaderRetrievalService()
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.
boolean	isShutdown()
void	shutdown()
void	start(LeaderContender contender) Starts the leader election service.
void	stop() Stops the leader election service.

Methods inherited from class java.lang.Object

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

Constructor Detail

SingleLeaderElectionService

public SingleLeaderElectionService(Executor notificationsDispatcher,
                                   UUID leaderId)

Creates a new leader election service. The service assigns the given leader ID to the leader contender.

Parameters:

leaderId - The constant leader ID assigned to the leader.

Method Detail

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()

Description copied from interface: LeaderElectionService

Stops the leader election service.

Specified by:

stop in interface LeaderElectionService

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(@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

isShutdown

public boolean isShutdown()

shutdown

public void shutdown()

createLeaderRetrievalService

public LeaderRetrievalService createLeaderRetrievalService()