Package org.apache.storm.nimbus

Interface ILeaderElector

All Superinterfaces:

AutoCloseable

All Known Implementing Classes:

LeaderElectorImp, MockLeaderElector

public interface ILeaderElector
extends AutoCloseable

The interface for leader election.

Method Summary

Modifier and Type	Method	Description
void	addToLeaderLockQueue()	queue up for leadership lock.
boolean	awaitLeadership(long timeout, TimeUnit timeUnit)	Wait for the caller to gain leadership.
void	close()	Method called to allow for cleanup.
List<NimbusInfo>	getAllNimbuses()	Get list of current nimbus addresses.
NimbusInfo	getLeader()	Get the current leader's address.
boolean	isLeader()	Decide if the caller currently has the leader lock.
void	prepare(Map<String,Object> conf)	Method guaranteed to be called as part of initialization of leader elector instance.
void	quitElectionFor(int delayMs)	Removes the caller from leadership election, relinquishing leadership if acquired, then requeues for leadership after the specified delay.

Method Detail

prepare

void prepare(Map<String,Object> conf)

Method guaranteed to be called as part of initialization of leader elector instance.

Parameters:

conf - configuration

addToLeaderLockQueue

void addToLeaderLockQueue()
                   throws Exception

queue up for leadership lock. The call returns immediately and the caller must check isLeader() to perform any leadership action. This method can be called multiple times so it needs to be idempotent.

Throws:

Exception

quitElectionFor

void quitElectionFor(int delayMs)
              throws Exception

Removes the caller from leadership election, relinquishing leadership if acquired, then requeues for leadership after the specified delay.

Parameters:

delayMs - The delay to wait before re-entering the election

Throws:

Exception

isLeader

boolean isLeader()
          throws Exception

Decide if the caller currently has the leader lock.

Returns:

true if the caller currently has the leader lock.

Throws:

Exception

getLeader

NimbusInfo getLeader()

Get the current leader's address.

Returns:

the current leader's address, may return null if no one has the lock.

awaitLeadership

boolean awaitLeadership(long timeout,
                        TimeUnit timeUnit)
                 throws InterruptedException

Wait for the caller to gain leadership. This should only be used in single-Nimbus clusters, and is only useful to allow testing code to wait for a LocalCluster's Nimbus to gain leadership before trying to submit topologies.

Returns:

true is leadership was acquired, false otherwise

Throws:

InterruptedException

getAllNimbuses

List<NimbusInfo> getAllNimbuses()
                         throws Exception

Get list of current nimbus addresses.

Returns:

list of current nimbus addresses, includes leader.

Throws:

Exception

close

void close()
    throws Exception

Method called to allow for cleanup. Relinquishes leadership if owned by the caller.

Specified by:

close in interface AutoCloseable

Throws:

Exception