Package org.elasticsearch.cluster.coordination

Class ElectionSchedulerFactory

java.lang.Object

org.elasticsearch.cluster.coordination.ElectionSchedulerFactory

public class ElectionSchedulerFactory
extends java.lang.Object

It's provably impossible to guarantee that any leader election algorithm ever elects a leader, but they generally work (with probability that approaches 1 over time) as long as elections occur sufficiently infrequently, compared to the time it takes to send a message to another node and receive a response back. We do not know the round-trip latency here, but we can approximate it by attempting elections randomly at reasonably high frequency and backing off (linearly) until one of them succeeds. We also place an upper bound on the backoff so that if elections are failing due to a network partition that lasts for a long time then when the partition heals there is an election attempt reasonably quickly.

Field Summary

Fields

Modifier and Type	Field	Description
static Setting<TimeValue>	ELECTION_BACK_OFF_TIME_SETTING
static Setting<TimeValue>	ELECTION_DURATION_SETTING
static Setting<TimeValue>	ELECTION_INITIAL_TIMEOUT_SETTING
static Setting<TimeValue>	ELECTION_MAX_TIMEOUT_SETTING

Constructor Summary

Constructors

Constructor	Description
ElectionSchedulerFactory(Settings settings, java.util.Random random, ThreadPool threadPool)

Method Summary

Modifier and Type	Method	Description
Releasable	startElectionScheduler(TimeValue gracePeriod, java.lang.Runnable scheduledRunnable)	Start the process to schedule repeated election attempts.
java.lang.String	toString()

Methods inherited from class java.lang.Object

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

Field Detail

ELECTION_INITIAL_TIMEOUT_SETTING

public static final Setting<TimeValue> ELECTION_INITIAL_TIMEOUT_SETTING

ELECTION_BACK_OFF_TIME_SETTING

public static final Setting<TimeValue> ELECTION_BACK_OFF_TIME_SETTING

ELECTION_MAX_TIMEOUT_SETTING

public static final Setting<TimeValue> ELECTION_MAX_TIMEOUT_SETTING

ELECTION_DURATION_SETTING

public static final Setting<TimeValue> ELECTION_DURATION_SETTING

Constructor Detail

ElectionSchedulerFactory

public ElectionSchedulerFactory(Settings settings,
                                java.util.Random random,
                                ThreadPool threadPool)

Method Detail

startElectionScheduler

public Releasable startElectionScheduler(TimeValue gracePeriod,
                                         java.lang.Runnable scheduledRunnable)

Start the process to schedule repeated election attempts.

Parameters:

gracePeriod - An initial period to wait before attempting the first election.

scheduledRunnable - The action to run each time an election should be attempted.

toString

public java.lang.String toString()

Overrides:

toString in class java.lang.Object