com.hazelcast.cluster

Interface Cluster

public interface Cluster

Hazelcast cluster interface. It provides access to the members in the cluster and one can register for changes in the cluster members.

All the methods on the Cluster are thread-safe.

Method Summary

Modifier and Type	Method and Description
UUID	addMembershipListener(MembershipListener listener) Adds MembershipListener to listen for membership updates.
void	changeClusterState(ClusterState newState) Changes state of the cluster to the given state transactionally.
void	changeClusterState(ClusterState newState, TransactionOptions transactionOptions) Changes state of the cluster to the given state transactionally.
void	changeClusterVersion(Version version) Changes the cluster version transactionally.
void	changeClusterVersion(Version version, TransactionOptions options) Changes the cluster version transactionally, with the transaction options provided.
ClusterState	getClusterState() Returns the state of the cluster.
long	getClusterTime() Returns the cluster-wide time in milliseconds.
Version	getClusterVersion() The cluster version indicates the operating version of the cluster.
HotRestartService	getHotRestartService() Returns the Hot Restart service for interacting with Hot Restart.
Member	getLocalMember() Returns this Hazelcast instance member.
Set<Member>	getMembers() Set of the current members in the cluster.
void	promoteLocalLiteMember() Promotes local lite member to data member.
boolean	removeMembershipListener(UUID registrationId) Removes the specified MembershipListener.
void	shutdown() Changes state of the cluster to the ClusterState.PASSIVE transactionally, then triggers the shutdown process on each node.
void	shutdown(TransactionOptions transactionOptions) Changes state of the cluster to the ClusterState.PASSIVE transactionally, then triggers the shutdown process on each node.

Method Detail

addMembershipListener

UUID addMembershipListener(@Nonnull
                           MembershipListener listener)

Adds MembershipListener to listen for membership updates.

The addMembershipListener method returns a register ID. This ID is needed to remove the MembershipListener using the removeMembershipListener(UUID) method.

If the MembershipListener implements the InitialMembershipListener interface, it will also receive the InitialMembershipEvent.

There is no check for duplicate registrations, so if you register the listener twice, it will get events twice.

Parameters:

listener - membership listener

Returns:

the registration ID

Throws:

NullPointerException - if listener is null

See Also:

removeMembershipListener(UUID)

removeMembershipListener

boolean removeMembershipListener(@Nonnull
                                 UUID registrationId)

Removes the specified MembershipListener.

If the same MembershipListener is registered multiple times, it needs to be removed multiple times. This method can safely be called multiple times for the same registration ID; subsequent calls are ignored.

Parameters:

registrationId - the registrationId of MembershipListener to remove

Returns:

true if the registration is removed, false otherwise

Throws:

NullPointerException - if the registration ID is null

See Also:

addMembershipListener(MembershipListener)

getMembers

Set<Member> getMembers()

Set of the current members in the cluster. The returned set is an immutable set; it can't be modified.

The returned set is backed by an ordered set. Every member in the cluster returns the 'members' in the same order. To obtain the oldest member (the master) in the cluster, you can retrieve the first item in the set using 'getMembers().iterator().next()'.

Returns:

current members in the cluster

getLocalMember

Member getLocalMember()

Returns this Hazelcast instance member.

The returned value will never be null, but it may change when local lite member is promoted to a data member via promoteLocalLiteMember() or when this member merges to a new cluster after split-brain detected. Returned value should not be cached but instead this method should be called each time when local member is needed.

Returns:

this Hazelcast instance member

promoteLocalLiteMember

void promoteLocalLiteMember()

Promotes local lite member to data member. When this method returns both getLocalMember() and getMembers() reflects the promotion.

Throws:

IllegalStateException - when member is not a lite member or mastership claim in progress or local member cannot be identified as a member of the cluster or cluster state doesn't allow migrations/repartitioning

Since:

3.9

getClusterTime

long getClusterTime()

Returns the cluster-wide time in milliseconds.

Cluster tries to keep a cluster-wide time which might be different than the member's own system time. Cluster-wide time is -almost- the same on all members of the cluster.

Returns:

cluster-wide time

getClusterState

@Nonnull
ClusterState getClusterState()

Returns the state of the cluster.

If cluster state change is in process, ClusterState.IN_TRANSITION will be returned.

This is a local operation, state will be read directly from local member.

Returns:

state of the cluster

Since:

3.6

changeClusterState

void changeClusterState(@Nonnull
                        ClusterState newState)

Changes state of the cluster to the given state transactionally. Transaction will be TWO_PHASE and will have 1 durability by default. If you want to override transaction options, use changeClusterState(ClusterState, TransactionOptions).

If the given state is already same as current state of the cluster, then this method will have no effect.

If there's an ongoing state change transaction in the cluster, this method will fail immediately with a TransactionException.

If a membership change occurs in the cluster during state change, a new member joins or an existing member leaves, then this method will fail with an IllegalStateException.

If there are ongoing/pending migration/replication operations, because of re-balancing due to member join or leave, then trying to change from ACTIVE to FROZEN or PASSIVE will fail with an IllegalStateException.

If transaction timeouts during state change, then this method will fail with a TransactionException.

Parameters:

newState - new state of the cluster

Throws:

NullPointerException - if newState is null

IllegalArgumentException - if newState is ClusterState.IN_TRANSITION

IllegalStateException - if member-list changes during the transaction or there are ongoing/pending migration operations

TransactionException - if there's already an ongoing transaction or this transaction fails or this transaction timeouts

Since:

3.6

changeClusterState

void changeClusterState(@Nonnull
                        ClusterState newState,
                        @Nonnull
                        TransactionOptions transactionOptions)

Changes state of the cluster to the given state transactionally. Transaction must be a TWO_PHASE transaction.

If the given state is already same as current state of the cluster, then this method will have no effect.

If there's an ongoing state change transaction in the cluster, this method will fail immediately with a TransactionException.

If a membership change occurs in the cluster during state change, a new member joins or an existing member leaves, then this method will fail with an IllegalStateException.

If there are ongoing/pending migration/replication operations, because of re-balancing due to member join or leave, then trying to change from ACTIVE to FROZEN or PASSIVE will fail with an IllegalStateException.

If transaction timeouts during state change, then this method will fail with a TransactionException.

Parameters:

newState - new state of the cluster

transactionOptions - transaction options

Throws:

NullPointerException - if newState is null

IllegalArgumentException - if newState is ClusterState.IN_TRANSITION or transaction type is not TWO_PHASE

IllegalStateException - if member-list changes during the transaction or there are ongoing/pending migration operations

TransactionException - if there's already an ongoing transaction or this transaction fails or this transaction timeouts

Since:

3.6

getClusterVersion

Version getClusterVersion()

The cluster version indicates the operating version of the cluster. It is separate from each node's codebase version, as it may be acceptable for a node to operate at a different compatibility version than its codebase version. This method may return Version.UNKNOWN if invoked after the ClusterService is constructed and before the node forms a cluster, either by joining existing members or becoming master of its standalone cluster if it is the first node on the cluster. Importantly, this is the time during which a lifecycle event with state LifecycleEvent.LifecycleState.STARTING is triggered.

For example, consider a cluster comprised of nodes running on hazelcast-3.8.0.jar. Each node's codebase version is 3.8.0 and on startup the cluster version is 3.8. After a while, another node joins, running on hazelcast-3.9.jar; this node's codebase version is 3.9.0. If deemed compatible, it is allowed to join the cluster. At this point, the cluster version is still 3.8 and the 3.9.0 member should be able to adapt its behaviour to be compatible with the other 3.8.0 members. Once all 3.8.0 members have been shutdown and replaced by other members on codebase version 3.9.0, still the cluster version will be 3.8. At this point, it is possible to update the cluster version to 3.9, since all cluster members will be compatible with the new cluster version. Once cluster version is updated to 3.9, further communication among members will take place in 3.9 and all new features and functionality of version 3.9 will be available.

Returns:

the version at which this cluster operates.

Since:

3.8

getHotRestartService

HotRestartService getHotRestartService()

Returns the Hot Restart service for interacting with Hot Restart.

Returns:

the hot restart service

Throws:

UnsupportedOperationException - if the hot restart service is not supported on this instance (e.g. on client)

shutdown

void shutdown()

Changes state of the cluster to the ClusterState.PASSIVE transactionally, then triggers the shutdown process on each node. Transaction will be TWO_PHASE and will have 1 durability by default. If you want to override transaction options, use shutdown(TransactionOptions).

If the cluster is already in ClusterState.PASSIVE, shutdown process begins immediately. All the node join / leave rules described in ClusterState.PASSIVE state also applies here.

Any node can start the shutdown process. A shutdown command is sent to other nodes periodically until either all other nodes leave the cluster or a configurable timeout occurs (see ClusterProperty.CLUSTER_SHUTDOWN_TIMEOUT_SECONDS). If some of the nodes do not shutdown before the timeout duration, shutdown can be also invoked on them.

Throws:

IllegalStateException - if member-list changes during the transaction or there are ongoing/pending migration operations or shutdown process times out

TransactionException - if there's already an ongoing transaction or this transaction fails or this transaction timeouts

Since:

3.6

See Also:

ClusterProperty.CLUSTER_SHUTDOWN_TIMEOUT_SECONDS, changeClusterState(ClusterState), ClusterState.PASSIVE

shutdown

void shutdown(@Nullable
              TransactionOptions transactionOptions)

Changes state of the cluster to the ClusterState.PASSIVE transactionally, then triggers the shutdown process on each node. Transaction must be a TWO_PHASE transaction.

If the cluster is already in ClusterState.PASSIVE, shutdown process begins immediately. All the node join / leave rules described in ClusterState.PASSIVE state also applies here.

Any node can start the shutdown process. A shutdown command is sent to other nodes periodically until either all other nodes leave the cluster or a configurable timeout occurs (see ClusterProperty.CLUSTER_SHUTDOWN_TIMEOUT_SECONDS). If some of the nodes do not shutdown before the timeout duration, shutdown can be also invoked on them.

Parameters:

transactionOptions - transaction options

Throws:

IllegalStateException - if member-list changes during the transaction or there are ongoing/pending migration operations or shutdown process times out

TransactionException - if there's already an ongoing transaction or this transaction fails or this transaction timeouts

Since:

3.6

See Also:

ClusterProperty.CLUSTER_SHUTDOWN_TIMEOUT_SECONDS, changeClusterState(ClusterState), ClusterState.PASSIVE

changeClusterVersion

void changeClusterVersion(@Nonnull
                          Version version)

Changes the cluster version transactionally. Internally this method uses the same transaction infrastructure as changeClusterState(ClusterState) and the transaction defaults are the same in this case as well (TWO_PHASE transaction with durability 1 by default).

If the requested cluster version is same as the current one, nothing happens.

If a member of the cluster is not compatible with the given cluster version, as implemented by NodeExtension.isNodeVersionCompatibleWith(Version), then a VersionMismatchException is thrown.

If an invalid version transition is requested, for example changing to a different major version, an IllegalArgumentException is thrown.

If a membership change occurs in the cluster during locking phase, a new member joins or an existing member leaves, then this method will fail with an IllegalStateException.

Likewise, once locking phase is completed successfully, getClusterState() will report being ClusterState.IN_TRANSITION, disallowing membership changes until the new cluster version is committed.

Parameters:

version - new version of the cluster

Since:

3.8

changeClusterVersion

void changeClusterVersion(@Nonnull
                          Version version,
                          @Nonnull
                          TransactionOptions options)

Changes the cluster version transactionally, with the transaction options provided. Internally this method uses the same transaction infrastructure as changeClusterState(ClusterState, TransactionOptions). The transaction options must specify a TWO_PHASE transaction.

If the requested cluster version is same as the current one, nothing happens.

If a member of the cluster is not compatible with the given cluster version, as implemented by NodeExtension.isNodeVersionCompatibleWith(Version), then a VersionMismatchException is thrown.

If an invalid version transition is requested, for example changing to a different major version, an IllegalArgumentException is thrown.

If a membership change occurs in the cluster during locking phase, a new member joins or an existing member leaves, then this method will fail with an IllegalStateException.

Likewise, once locking phase is completed successfully, getClusterState() will report being ClusterState.IN_TRANSITION, disallowing membership changes until the new cluster version is committed.

Parameters:

version - new version of the cluster

options - options by which to execute the transaction

Since:

3.8