ONOS checkin based on commit tag e796610b1f721d02f9b0e213cf6f7790c10ecd60

Change-Id: Ife8810491034fe7becdba75dda20de4267bd15cd

1 files changed, 124 insertions, 0 deletions

diff --git a/framework/src/onos/core/api/src/main/java/org/onosproject/cluster/LeadershipService.java b/framework/src/onos/core/api/src/main/java/org/onosproject/cluster/LeadershipService.java
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+/*
+ * 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);
+
+}