Package com.hazelcast.cluster

Enum Class ClusterState

java.lang.Object
java.lang.Enum<ClusterState>
com.hazelcast.cluster.ClusterState
All Implemented Interfaces:
Serializable, Comparable<ClusterState>, Constable
public enum ClusterState extends Enum<ClusterState>
ClusterState are several possible states of the cluster where each state can allow and/or deny specific actions and/or change behavior of specific actions.

There are 5 states:

  1. ACTIVE: Cluster will continue to operate without any restriction.
  2. NO_MIGRATION: Migrations (partition rebalancing) and backup replications are not allowed. Cluster will continue to operate without any restriction.
  3. FROZEN: New members are not allowed to join, partition table/assignments will be frozen. All other operations are allowed and will operate without any restriction. If some members leave the cluster while it is in FROZEN state, they can join back.
  4. PASSIVE: New members are not allowed to join. All operations, except the ones marked with AllowedDuringPassiveState, will be rejected immediately.
  5. IN_TRANSITION: Shows that ClusterState is in transition. This is a temporary & intermediate state, not allowed to be set explicitly.

By default, cluster will be in ACTIVE state. During split-brain merge process, state of the cluster, that is going to join to the major side, will be changed to FROZEN automatically before merge and will be set to the state of the new cluster after merge.

Since:
3.6
See Also:

  • Enum Constant Details

    • ACTIVE

      public static final ClusterState ACTIVE
      In ACTIVE state, cluster will continue to operate without any restriction. All operations are allowed. This is the default state of a cluster.

    • NO_MIGRATION

      public static final ClusterState NO_MIGRATION
      In NO_MIGRATION state of the cluster, migrations (partition rebalancing) and backup replications are not allowed.
      • When a new member joins, it will not be assigned any partitions until cluster state changes to ACTIVE.
      • When a member leaves, backups of primary replicas owned by that member will be promoted to primary. But missing backup replicas will not be created/replicated until cluster state changes to ACTIVE.
      Cluster will continue to operate without any restriction. All operations are allowed.
      Since:
      3.9

    • FROZEN

      public static final ClusterState FROZEN
      In FROZEN state of the cluster:
      • New members are not allowed to join, except the members left during FROZEN or PASSIVE state. For example, cluster has 3 nodes; A, B and C in FROZEN state. If member B leaves the cluster (either proper shutdown or crash), it will be allowed to re-join to the cluster. But another member D, won't be able to join.
      • Partition table/assignments will be frozen. When a member leaves the cluster, its partition assignments (as primary and backup) will remain the same, until either that member re-joins to the cluster or ClusterState changes back to ACTIVE. If that member re-joins while still in FROZEN, it will own all previously assigned partitions. If ClusterState changes to ACTIVE then partition re-balancing process will kick in and all unassigned partitions will be assigned to active members. It's not allowed to change ClusterState to FROZEN when there are pending migration/replication tasks in the system.
      • Nodes continue to stay in NodeState.ACTIVE state when cluster goes into the FROZEN state.
      • All other operations except migrations are allowed and will operate without any restriction.

    • PASSIVE

      public static final ClusterState PASSIVE
      In PASSIVE state of the cluster:
      • New members are not allowed to join, except the members left during FROZEN or PASSIVE state.
      • Partition table/assignments will be frozen. It's not allowed to change ClusterState to PASSIVE when there are pending migration/replication tasks in the system. If some nodes leave the cluster while cluster is in PASSIVE state, they will be removed from the partition table when cluster state moves back to ACTIVE.
      • When cluster state is moved to PASSIVE, nodes are moved to NodeState.PASSIVE too. Similarly when cluster state moves to another state from PASSIVE, nodes become NodeState.ACTIVE.
      • All operations, except the ones marked with AllowedDuringPassiveState, will be rejected immediately.

    • IN_TRANSITION

      public static final ClusterState IN_TRANSITION
      Shows that ClusterState is in transition. When a state change transaction is started, ClusterState will be shown as IN_TRANSITION while the transaction is in progress. After the transaction completes, cluster will be either in the new state or in the previous state, depending on transaction result.

      This is a temporary & intermediate state, not allowed to be set explicitly.

      • Similarly to the FROZEN state, new members are not allowed and migration/replication process will be paused.
      • If membership change occurs in the cluster, cluster state transition will fail and will be reverted back to the previous state.

  • Method Details

    • values

      public static ClusterState[] values()
      Returns an array containing the constants of this enum class, in the order they are declared.
      Returns:
      an array containing the constants of this enum class, in the order they are declared

    • valueOf

      public static ClusterState valueOf(String name)
      Returns the enum constant of this class with the specified name. The string must match exactly an identifier used to declare an enum constant in this class. (Extraneous whitespace characters are not permitted.)
      Parameters:
      name - the name of the enum constant to be returned.
      Returns:
      the enum constant with the specified name
      Throws:
      IllegalArgumentException - if this enum class has no constant with the specified name
      NullPointerException - if the argument is null

    • isJoinAllowed

      public boolean isJoinAllowed()
      Returns true, if joining of a new member is allowed in this state.
      Returns:
      true if joining of a new member is allowed in this state.

    • isMigrationAllowed

      public boolean isMigrationAllowed()
      Returns true, if migrations and replications are allowed in this state.
      Returns:
      true if migrations and replications are allowed in this state.

    • isPartitionPromotionAllowed

      public boolean isPartitionPromotionAllowed()
      Returns true, if partition promotions are allowed in this state.
      Returns:
      true if partition promotions are allowed in this state.

    • getId

      public byte getId()

    • getById

      public static ClusterState getById(int id)