org.springframework.integration.support.leader

Class LockRegistryLeaderInitiator

java.lang.Object

org.springframework.integration.support.leader.LockRegistryLeaderInitiator

All Implemented Interfaces:

Aware, DisposableBean, ApplicationEventPublisherAware, Lifecycle, Phased, SmartLifecycle

public class LockRegistryLeaderInitiator
extends Object
implements SmartLifecycle, DisposableBean, ApplicationEventPublisherAware

Component that initiates leader election based on holding a lock. If the lock has the right properties (global with expiry), there will never be more than one leader, but there may occasionally be no leader for short periods. If the lock has stronger guarantees, and it interrupts the holder's thread when it expires or is stolen, then you can adjust the parameters to reduce the leaderless period to be limited only by latency to the lock provider. The election process ties up a thread perpetually while we hold and try to acquire the lock, so a native leader initiator (not based on a lock) is likely to be more efficient. If there is no native leader initiator available, but there is a lock registry (e.g. on a shared database), this implementation is likely to be useful.

Since:

4.3.1

Author:

Dave Syer, Artem Bilan, Vedran Pavic, Glenn Renfro, Kiel Boatman, Gary Russell

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
protected class	LockRegistryLeaderInitiator.LeaderSelector

Field Summary

Fields

Modifier and Type	Field and Description
static long	DEFAULT_BUSY_WAIT_TIME
static long	DEFAULT_HEART_BEAT_TIME

Fields inherited from interface org.springframework.context.SmartLifecycle

DEFAULT_PHASE

Constructor Summary

Constructors

Constructor and Description
LockRegistryLeaderInitiator(LockRegistry locks) Create a new leader initiator with the provided lock registry and a default candidate (which just logs the leadership events).
LockRegistryLeaderInitiator(LockRegistry locks, Candidate candidate) Create a new leader initiator.

Method Summary

Modifier and Type	Method and Description
void	destroy()
Context	getContext()
int	getPhase()
boolean	isAutoStartup()
boolean	isPublishFailedEvents()
boolean	isRunning()
void	setApplicationEventPublisher(ApplicationEventPublisher applicationEventPublisher)
void	setAutoStartup(boolean autoStartup)
void	setBusyWaitMillis(long busyWaitMillis)
void	setExecutorService(ExecutorService executorService) Set the ExecutorService, where is not provided then a default of single thread Executor will be used.
void	setHeartBeatMillis(long heartBeatMillis)
void	setLeaderEventPublisher(LeaderEventPublisher leaderEventPublisher) Set the LeaderEventPublisher.
void	setPhase(int phase)
void	setPublishFailedEvents(boolean publishFailedEvents) Enable or disable the publishing of failed events to the specified applicationEventPublisher.
void	start() Start the registration of the candidate for leader election.
void	stop() Stop the registration of the candidate for leader election.

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.springframework.context.SmartLifecycle

stop

Field Detail

DEFAULT_HEART_BEAT_TIME

public static final long DEFAULT_HEART_BEAT_TIME

See Also:

Constant Field Values

DEFAULT_BUSY_WAIT_TIME

public static final long DEFAULT_BUSY_WAIT_TIME

See Also:

Constant Field Values

Constructor Detail

LockRegistryLeaderInitiator

public LockRegistryLeaderInitiator(LockRegistry locks)

Create a new leader initiator with the provided lock registry and a default candidate (which just logs the leadership events).

Parameters:

locks - lock registry

LockRegistryLeaderInitiator

public LockRegistryLeaderInitiator(LockRegistry locks,
                                   Candidate candidate)

Create a new leader initiator. The candidate implementation is provided by the user to listen for leadership events and carry out business actions.

Parameters:

locks - lock registry

candidate - leadership election candidate

Method Detail

setExecutorService

public void setExecutorService(ExecutorService executorService)

Set the ExecutorService, where is not provided then a default of single thread Executor will be used.

Parameters:

executorService - the executor service

Since:

5.0.2

setHeartBeatMillis

public void setHeartBeatMillis(long heartBeatMillis)

setBusyWaitMillis

public void setBusyWaitMillis(long busyWaitMillis)

setLeaderEventPublisher

public void setLeaderEventPublisher(LeaderEventPublisher leaderEventPublisher)

Set the LeaderEventPublisher.

Parameters:

leaderEventPublisher - the event publisher

setApplicationEventPublisher

public void setApplicationEventPublisher(ApplicationEventPublisher applicationEventPublisher)

Specified by:

setApplicationEventPublisher in interface ApplicationEventPublisherAware

isRunning

public boolean isRunning()

Specified by:

isRunning in interface Lifecycle

Returns:

true if leadership election for this candidate is running.

getPhase

public int getPhase()

Specified by:

getPhase in interface Phased

Specified by:

getPhase in interface SmartLifecycle

setPhase

public void setPhase(int phase)

Parameters:

phase - the phase

See Also:

SmartLifecycle

isAutoStartup

public boolean isAutoStartup()

Specified by:

isAutoStartup in interface SmartLifecycle

setAutoStartup

public void setAutoStartup(boolean autoStartup)

Parameters:

autoStartup - true to start automatically

See Also:

SmartLifecycle

getContext

public Context getContext()

Returns:

the context.

isPublishFailedEvents

public boolean isPublishFailedEvents()

setPublishFailedEvents

public void setPublishFailedEvents(boolean publishFailedEvents)

Enable or disable the publishing of failed events to the specified applicationEventPublisher. Because of the large number of failure events that can be published while attempting to get a mutex during leader election (in the case that another instance is holding the mutex), the default is set to false.

Parameters:

publishFailedEvents - boolean that if true, failed events will be published. If false, no failures will be published. Default is false.

Since:

5.0

start

public void start()

Start the registration of the candidate for leader election.

Specified by:

start in interface Lifecycle

destroy

public void destroy()

Specified by:

destroy in interface DisposableBean

stop

public void stop()

Stop the registration of the candidate for leader election. If the candidate is currently leader, its leadership will be revoked.

Specified by:

stop in interface Lifecycle