com.hazelcast.crdt

Class CRDTReplicationMigrationService

java.lang.Object

com.hazelcast.crdt.CRDTReplicationMigrationService

All Implemented Interfaces:

GracefulShutdownAwareService, ManagedService, MembershipAwareService

public class CRDTReplicationMigrationService
extends Object
implements ManagedService, MembershipAwareService, GracefulShutdownAwareService

Service that handles replication and migration of CRDT data for all CRDT implementations. The CRDT implementations for which it performs replication and migration must implement CRDTReplicationAwareService.

The replication is performed periodically on an executor with the name "hz:CRDTReplicationMigration". You may configure this executor accordingly. The migration mechanism uses the same executor but it is performed only on membership changes and on CRDT state merge. The migration checks are triggered on CRDT state merge because CRDT states can get merged when a replica is shutting down and it is trying to replicate any previously unreplicated state to any member in the cluster, regardless of the configured replica count.

See Also:

CRDTReplicationConfig.getReplicationPeriodMillis(), CRDTReplicationConfig.getMaxConcurrentReplicationTargets()

Field Summary

Fields

Modifier and Type	Field and Description
static String	CRDT_REPLICATION_MIGRATION_EXECUTOR The executor for the CRDT replication and migration tasks
static String	SERVICE_NAME The name of this service

Constructor Summary

Constructors

Constructor and Description
CRDTReplicationMigrationService()

Method Summary

Modifier and Type	Method and Description
void	init(NodeEngine nodeEngine, Properties properties) Initializes this service.
void	memberAdded(MembershipServiceEvent event) Invoked when a new member is added to the cluster.
void	memberAttributeChanged(MemberAttributeServiceEvent event) Invoked when a member attribute is changed.
void	memberRemoved(MembershipServiceEvent event) Invoked when an existing member leaves the cluster.
boolean	onShutdown(long timeout, TimeUnit unit) Attempts to replicate only the unreplicated CRDT state to any non-local member in the cluster.
void	reset() Resets this service back to its initial state.
void	shutdown(boolean terminate) Shuts down this service.
String	toString()

Methods inherited from class java.lang.Object

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

Field Detail

SERVICE_NAME

public static final String SERVICE_NAME

The name of this service

See Also:

Constant Field Values

CRDT_REPLICATION_MIGRATION_EXECUTOR

public static final String CRDT_REPLICATION_MIGRATION_EXECUTOR

The executor for the CRDT replication and migration tasks

See Also:

Constant Field Values

Constructor Detail

CRDTReplicationMigrationService

public CRDTReplicationMigrationService()

Method Detail

init

public void init(NodeEngine nodeEngine,
                 Properties properties)

Description copied from interface: ManagedService

Initializes this service.

Specified by:

init in interface ManagedService

Parameters:

nodeEngine - the NodeEngine that this service belongs to

properties - the Properties (can be used to pass settings to the service)

reset

public void reset()

Description copied from interface: ManagedService

Resets this service back to its initial state.

TODO: what is the purpose of reset

Specified by:

reset in interface ManagedService

shutdown

public void shutdown(boolean terminate)

Description copied from interface: ManagedService

Shuts down this service.

TODO: what is the purpose of the terminate variable

Specified by:

shutdown in interface ManagedService

Parameters:

terminate - true to shut down this service

onShutdown

public boolean onShutdown(long timeout,
                          TimeUnit unit)

Attempts to replicate only the unreplicated CRDT state to any non-local member in the cluster. The state may be unreplicated because the CRDT state has been changed (via mutation or merge with an another CRDT) but has not yet been disseminated through the usual replication mechanism to any member. This method will iterate through the member list and try and replicate to at least one member. The method returns once all of the unreplicated state has been replicated successfully or when there are no more members to attempt processing. This method will replicate all of the unreplicated CRDT states to any data member in the cluster, regardless if that member is actually the replica for some CRDT (because of a configured replica count). It is the responsibility of that member to migrate the state for which it is not a replica. The configured replica count can therefore be broken during shutdown to increase the chance of survival of unreplicated CRDT data (if the actual replicas are unreachable).

Specified by:

onShutdown in interface GracefulShutdownAwareService

Parameters:

timeout - timeout for graceful shutdown

unit - time unit

Returns:

true if graceful shutdown is successful, false otherwise

See Also:

CRDTReplicationTask

memberAdded

public void memberAdded(MembershipServiceEvent event)

Description copied from interface: MembershipAwareService

Invoked when a new member is added to the cluster. Should be non-blocking.

Specified by:

memberAdded in interface MembershipAwareService

Parameters:

event - the event for a new member added to the cluster

memberRemoved

public void memberRemoved(MembershipServiceEvent event)

Description copied from interface: MembershipAwareService

Invoked when an existing member leaves the cluster. Should be non-blocking.

Specified by:

memberRemoved in interface MembershipAwareService

Parameters:

event - the event for an existing member leaving the cluster

memberAttributeChanged

public void memberAttributeChanged(MemberAttributeServiceEvent event)

Description copied from interface: MembershipAwareService

Invoked when a member attribute is changed.

Specified by:

memberAttributeChanged in interface MembershipAwareService

Parameters:

event - the event for a member attribute being changed

toString

public String toString()

Overrides:

toString in class Object