com.hazelcast.cp.internal.raft

Enum QueryPolicy

java.lang.Object

java.lang.Enum<QueryPolicy>

com.hazelcast.cp.internal.raft.QueryPolicy

All Implemented Interfaces:

Serializable, Comparable<QueryPolicy>

public enum QueryPolicy
extends Enum<QueryPolicy>

Policy to query committed Raft state without appending a log entry but in some cases giving up strong consistency guarantees.

Enum Constant Summary

Enum Constants

Enum Constant and Description
ANY_LOCAL Query committed Raft state locally on any Raft group member.
LEADER_LOCAL Query committed Raft state locally only on Raft group leader.
LINEARIZABLE Query Raft state in a linearizable manner, either by appending a log entry to Raft log or using the algorithm defined in 6.4 Processing read-only queries more efficiently section of Raft dissertation.

Method Summary

Modifier and Type	Method and Description
static QueryPolicy	valueOf(String name) Returns the enum constant of this type with the specified name.
static QueryPolicy[]	values() Returns an array containing the constants of this enum type, in the order they are declared.

Methods inherited from class java.lang.Enum

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

Methods inherited from class java.lang.Object

getClass, notify, notifyAll, wait, wait, wait

Enum Constant Detail

LEADER_LOCAL

public static final QueryPolicy LEADER_LOCAL

Query committed Raft state locally only on Raft group leader.

If the leader is split from the group and a new leader is elected already, stale values can be read until it realizes the split.

This policy is likely to hit more recent data when compared to ANY_LOCAL.

ANY_LOCAL

public static final QueryPolicy ANY_LOCAL

Query committed Raft state locally on any Raft group member.

Reading stale value is possible when a follower lags behind the leader or is split from rest of the group.

LEADER_LOCAL should be preferred if it's important to read up-to-date data mostly.

LINEARIZABLE

public static final QueryPolicy LINEARIZABLE

Query Raft state in a linearizable manner, either by appending a log entry to Raft log or using the algorithm defined in 6.4 Processing read-only queries more efficiently section of Raft dissertation.

Method Detail

values

public static QueryPolicy[] 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 (QueryPolicy c : QueryPolicy.values())
    System.out.println(c);

Returns:

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

valueOf

public static QueryPolicy 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