| /* |
| * Copyright 2014-2015 Open Networking Laboratory |
| * |
| * Licensed under the Apache License, Version 2.0 (the "License"); |
| * you may not use this file except in compliance with the License. |
| * You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| package org.onosproject.cluster; |
| |
| import org.onosproject.event.ListenerService; |
| |
| import java.util.List; |
| import java.util.Map; |
| import java.util.Set; |
| import java.util.concurrent.CompletableFuture; |
| |
| /** |
| * 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. |
| */ |
| public interface LeadershipService |
| extends ListenerService<LeadershipEvent, LeadershipEventListener> { |
| |
| /** |
| * Returns the current leader for the topic. |
| * |
| * @param path topic |
| * @return nodeId of the leader, null if so such topic exists. |
| */ |
| NodeId getLeader(String path); |
| |
| /** |
| * Returns the current leadership info for the topic. |
| * |
| * @param path topic |
| * @return leadership info or null if so such topic exists. |
| */ |
| Leadership getLeadership(String path); |
| |
| /** |
| * Returns the set of topics owned by the specified node. |
| * |
| * @param nodeId node Id. |
| * @return set of topics for which this node is the current leader. |
| */ |
| Set<String> ownedTopics(NodeId nodeId); |
| |
| /** |
| * Joins the leadership contest. |
| * |
| * @param path topic for which this controller node wishes to be a leader |
| * @return {@code Leadership} future |
| */ |
| CompletableFuture<Leadership> runForLeadership(String path); |
| |
| /** |
| * Withdraws from a leadership contest. |
| * |
| * @param path topic for which this controller node no longer wishes to be a leader |
| * @return future that is successfully completed when withdraw is done |
| */ |
| CompletableFuture<Void> withdraw(String path); |
| |
| /** |
| * If the local nodeId is the leader for specified topic, this method causes it to |
| * step down temporarily from leadership. |
| * <p> |
| * The node will continue to be in contention for leadership and can |
| * potentially become the leader again if and when it becomes the highest |
| * priority candidate |
| * <p> |
| * If the local nodeId is not the leader, this method will make no changes and |
| * simply return false. |
| * |
| * @param path topic for which this controller node should give up leadership |
| * @return true if this node stepped down from leadership, false otherwise |
| */ |
| boolean stepdown(String path); |
| |
| /** |
| * Moves the specified nodeId to the top of the candidates list for the topic. |
| * <p> |
| * If the node is not a candidate for this topic, this method will be a noop. |
| * |
| * @param path leadership topic |
| * @param nodeId nodeId to make the top candidate |
| * @return true if nodeId is now the top candidate, false otherwise |
| */ |
| boolean makeTopCandidate(String path, NodeId nodeId); |
| |
| /** |
| * Returns the current leader board. |
| * |
| * @return mapping from topic to leadership info. |
| */ |
| Map<String, Leadership> getLeaderBoard(); |
| |
| /** |
| * Returns the candidates for all known topics. |
| * |
| * @return A mapping from topics to corresponding list of candidates. |
| */ |
| Map<String, List<NodeId>> getCandidates(); |
| |
| /** |
| * Returns the candidates for a given topic. |
| * |
| * @param path topic |
| * @return A lists of NodeIds, which may be empty. |
| */ |
| List<NodeId> getCandidates(String path); |
| |
| } |