com.hazelcast.quorum.impl

Class QuorumServiceImpl

java.lang.Object

com.hazelcast.quorum.impl.QuorumServiceImpl

All Implemented Interfaces:

HeartbeatAware, PingAware, QuorumService, EventPublishingService<QuorumEvent,QuorumListener>, MembershipAwareService

public class QuorumServiceImpl
extends Object
implements EventPublishingService<QuorumEvent,QuorumListener>, MembershipAwareService, QuorumService, HeartbeatAware, PingAware

Service containing logic for cluster quorum. IMPORTANT: The term "quorum" simply refers to the count of members in the cluster required for an operation to succeed. It does NOT refer to an implementation of Paxos or Raft protocols as used in many NoSQL and distributed systems. The mechanism it provides in Hazelcast protects the user in case the number of nodes in a cluster drops below the specified one.

Field Summary

Fields

Modifier and Type	Field and Description
static String	SERVICE_NAME

Constructor Summary

Constructors

Constructor and Description
QuorumServiceImpl(NodeEngineImpl nodeEngine)

Method Summary

Modifier and Type	Method and Description
void	addQuorumListener(String name, QuorumListener listener)
void	dispatchEvent(QuorumEvent event, QuorumListener listener) Notifies the service of a published event.
void	ensureQuorumPresent(Operation op) Ensures that the quorum for the given operation is present.
void	ensureQuorumPresent(String quorumName, QuorumType requiredQuorumPermissionType) Ensures that the quorum with the given name is present.
Quorum	getQuorum(String quorumName) Returns the Quorum instance for a given quorum name.
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.
void	onHeartbeat(Member member, long timestamp) Notifies of a received heartbeat.
void	onPingLost(Member member) Notifies the QuorumFunction of ping loss.
void	onPingRestored(Member member) Notifies the QuorumFunction of a successful ping after one or more pings to that member were lost.
void	start()

Methods inherited from class java.lang.Object

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

Field Detail

SERVICE_NAME

public static final String SERVICE_NAME

See Also:

Constant Field Values

Constructor Detail

QuorumServiceImpl

public QuorumServiceImpl(NodeEngineImpl nodeEngine)

Method Detail

start

public void start()

addQuorumListener

public void addQuorumListener(String name,
                              QuorumListener listener)

ensureQuorumPresent

public void ensureQuorumPresent(Operation op)

Ensures that the quorum for the given operation is present. This requires that there is a quorum configured under the name which is returned by the operation service. This in turn requires that the operation is named and that the operation service is a QuorumAwareService.

Parameters:

op - the operation for which the quorum should be present

Throws:

QuorumException - if the operation requires a quorum and the quorum is not present

ensureQuorumPresent

public void ensureQuorumPresent(String quorumName,
                                QuorumType requiredQuorumPermissionType)

Description copied from interface: QuorumService

Ensures that the quorum with the given name is present. Throws a QuorumException if quorum not present. Does not throw exception if quorumName null or quorum undefined. If (requiredQuorumPermissionType == READ) -> will check for presence of READ or READ_WRITE quorum
If (requiredQuorumPermissionType == WRITE) -> will check for presence of WRITE or READ_WRITE quorum
If (requiredQuorumPermissionType == READ_WRITE) -> will check for presence of READ_WRITE quorum

Specified by:

ensureQuorumPresent in interface QuorumService

Parameters:

quorumName - quorum name to ensure, can be null or empty

requiredQuorumPermissionType - type of quorum required

dispatchEvent

public void dispatchEvent(QuorumEvent event,
                          QuorumListener listener)

Description copied from interface: EventPublishingService

Notifies the service of a published event.

Specified by:

dispatchEvent in interface EventPublishingService<QuorumEvent,QuorumListener>

Parameters:

event - the published event

listener - the listener registered for this event

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

getQuorum

public Quorum getQuorum(String quorumName)

Description copied from interface: QuorumService

Returns the Quorum instance for a given quorum name.

Specified by:

getQuorum in interface QuorumService

Parameters:

quorumName - name of the quorum

Returns:

Quorum

onHeartbeat

public void onHeartbeat(Member member,
                        long timestamp)

Description copied from interface: HeartbeatAware

Notifies of a received heartbeat. This method is always invoked before QuorumFunction.apply(Collection) so the QuorumFunction can update its internal state before deciding on quorum presence.

Specified by:

onHeartbeat in interface HeartbeatAware

Parameters:

member - member from which heartbeat was received

timestamp - timestmap on which heartbeat was received

onPingLost

public void onPingLost(Member member)

Description copied from interface: PingAware

Notifies the QuorumFunction of ping loss.

Specified by:

onPingLost in interface PingAware

Parameters:

member - member which was not pinged successfully

onPingRestored

public void onPingRestored(Member member)

Description copied from interface: PingAware

Notifies the QuorumFunction of a successful ping after one or more pings to that member were lost.

Specified by:

onPingRestored in interface PingAware

Parameters:

member - member which was pinged successfully