org.onosproject.cluster

Interface LeadershipService

All Superinterfaces:

ListenerService<LeadershipEvent,LeadershipEventListener>

public interface LeadershipService
extends ListenerService<LeadershipEvent,LeadershipEventListener>

Service for leader election.

Leadership contests are organized around topics. A instance can join the leadership race for a topic or withdraw from a race it has previously joined.

Listeners can be added to receive notifications asynchronously for various leadership contests.

When a node gets elected as a leader for a topic, all nodes receive notifications indicating a change in leadership.

Method Summary

Modifier and Type	Method and Description
default List<NodeId>	getCandidates(String topic) Returns the candidate nodes for a given topic.
default NodeId	getLeader(String topic) Returns the node identifier that is the current leader for a topic.
Leadership	getLeadership(String topic) Returns the current leadership for a topic.
Set<String>	ownedTopics(NodeId nodeId) Returns the set of topics owned by the specified node.
Leadership	runForLeadership(String topic) Enters a leadership contest.
void	withdraw(String topic) Withdraws from a leadership contest.

Methods inherited from interface org.onosproject.event.ListenerService

addListener, removeListener

Method Detail

getLeader

default NodeId getLeader(String topic)

Returns the node identifier that is the current leader for a topic.

Parameters:

topic - leadership topic

Returns:

node identifier of the current leader; null if there is no leader for the topic

getLeadership

Leadership getLeadership(String topic)

Returns the current leadership for a topic.

Parameters:

topic - leadership topic

Returns:

leadership or null if no such topic exists

ownedTopics

Set<String> ownedTopics(NodeId nodeId)

Returns the set of topics owned by the specified node.

Parameters:

nodeId - node identifier.

Returns:

set of topics for which this node is the current leader.

runForLeadership

Leadership runForLeadership(String topic)

Enters a leadership contest.

Parameters:

topic - leadership topic

Returns:

Leadership future

withdraw

void withdraw(String topic)

Withdraws from a leadership contest.

Parameters:

topic - leadership topic

getCandidates

default List<NodeId> getCandidates(String topic)

Returns the candidate nodes for a given topic.

Parameters:

topic - leadership topic

Returns:

A lists of nodeIds, which may be empty.