org.neo4j.kernel.ha.cluster

Enum HighAvailabilityMemberState

java.lang.Object

java.lang.Enum<HighAvailabilityMemberState>

org.neo4j.kernel.ha.cluster.HighAvailabilityMemberState

All Implemented Interfaces:

Serializable, Comparable<HighAvailabilityMemberState>

public enum HighAvailabilityMemberState
extends Enum<HighAvailabilityMemberState>

This represents the different states that a cluster member can have internally. Since transitioning to master or slave can take significant time those states are explicitly modeled. Most common transitions: PENDING -> TO_MASTER -> MASTER PENDING -> TO_SLAVE -> SLAVE MASTER/SLAVE -> PENDING

Enum Constant Summary

Enum Constants

Enum Constant and Description
ILLEGAL
MASTER Cluster member is available as master for other cluster members to use.
PENDING This state is the initial state, and is also the state used when leaving the cluster.
SLAVE Cluster member is ready as a slave
TO_MASTER The cluster member knows that it has been elected as master, and starts the transitioning process.
TO_SLAVE Member now knows that a master is available, and is transitioning itself to become a slave to that master.

Method Summary

Modifier and Type	Method and Description
String	errorMessage()
abstract boolean	isAccessAllowed()
abstract boolean	isEligibleForElection() The purpose of this is that an instance cannot vote in an election while becoming a slave, as it is copying stores.
abstract HighAvailabilityMemberState	masterIsAvailable(HighAvailabilityMemberContext context, org.neo4j.cluster.InstanceId masterId, URI masterHaURI)
abstract HighAvailabilityMemberState	masterIsElected(HighAvailabilityMemberContext context, org.neo4j.cluster.InstanceId masterId)
abstract HighAvailabilityMemberState	slaveIsAvailable(HighAvailabilityMemberContext context, org.neo4j.cluster.InstanceId slaveId, URI slaveUri)
static HighAvailabilityMemberState	valueOf(String name) Returns the enum constant of this type with the specified name.
static HighAvailabilityMemberState[]	values() Returns an array containing the constants of this enum type, in the order they are declared.

Methods inherited from class java.lang.Enum

compareTo, equals, getDeclaringClass, hashCode, name, ordinal, toString, valueOf

Methods inherited from class java.lang.Object

getClass, notify, notifyAll, wait, wait, wait

Enum Constant Detail

PENDING

public static final HighAvailabilityMemberState PENDING

This state is the initial state, and is also the state used when leaving the cluster.

Here we are waiting for events that transitions this member either to becoming a master or slave.

TO_SLAVE

public static final HighAvailabilityMemberState TO_SLAVE

Member now knows that a master is available, and is transitioning itself to become a slave to that master. It is performing the transition process here, and so is not yet available as a slave.

TO_MASTER

public static final HighAvailabilityMemberState TO_MASTER

The cluster member knows that it has been elected as master, and starts the transitioning process.

MASTER

public static final HighAvailabilityMemberState MASTER

Cluster member is available as master for other cluster members to use.

SLAVE

public static final HighAvailabilityMemberState SLAVE

Cluster member is ready as a slave

ILLEGAL

public static final HighAvailabilityMemberState ILLEGAL

Method Detail

values

public static HighAvailabilityMemberState[] values()

Returns an array containing the constants of this enum type, in the order they are declared. This method may be used to iterate over the constants as follows:

for (HighAvailabilityMemberState c : HighAvailabilityMemberState.values())
    System.out.println(c);

Returns:

an array containing the constants of this enum type, in the order they are declared

valueOf

public static HighAvailabilityMemberState valueOf(String name)

Returns the enum constant of this type with the specified name. The string must match exactly an identifier used to declare an enum constant in this type. (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 type has no constant with the specified name

NullPointerException - if the argument is null

masterIsElected

public abstract HighAvailabilityMemberState masterIsElected(HighAvailabilityMemberContext context,
                                                            org.neo4j.cluster.InstanceId masterId)

masterIsAvailable

public abstract HighAvailabilityMemberState masterIsAvailable(HighAvailabilityMemberContext context,
                                                              org.neo4j.cluster.InstanceId masterId,
                                                              URI masterHaURI)

slaveIsAvailable

public abstract HighAvailabilityMemberState slaveIsAvailable(HighAvailabilityMemberContext context,
                                                             org.neo4j.cluster.InstanceId slaveId,
                                                             URI slaveUri)

isEligibleForElection

public abstract boolean isEligibleForElection()

The purpose of this is that an instance cannot vote in an election while becoming a slave, as it is copying stores.

Returns:

whether the instance is eligible or not

isAccessAllowed

public abstract boolean isAccessAllowed()

errorMessage

public String errorMessage()