2 * Copyright (c) 2015 Brocade Communications Systems, Inc. and others. All rights reserved.
4 * This program and the accompanying materials are made available under the
5 * terms of the Eclipse Public License v1.0 which accompanies this distribution,
6 * and is available at http://www.eclipse.org/legal/epl-v10.html
8 package org.opendaylight.controller.cluster.raft;
10 import akka.actor.ActorRef;
11 import akka.actor.ActorSelection;
12 import akka.actor.Cancellable;
13 import com.google.common.annotations.VisibleForTesting;
14 import com.google.common.base.Optional;
15 import com.google.common.base.Stopwatch;
16 import java.util.ArrayList;
17 import java.util.List;
18 import java.util.concurrent.TimeUnit;
19 import org.opendaylight.controller.cluster.raft.base.messages.LeaderTransitioning;
20 import org.opendaylight.controller.cluster.raft.behaviors.Leader;
21 import org.opendaylight.controller.cluster.raft.behaviors.RaftActorBehavior;
22 import org.slf4j.Logger;
23 import org.slf4j.LoggerFactory;
24 import scala.concurrent.duration.FiniteDuration;
27 * A raft actor support class that participates in leadership transfer. An instance is created upon
28 * initialization of leadership transfer.
31 * The transfer process is as follows:
33 * <li>Send a LeaderStateChanged message with a null leader Id to the local RoleChangeNotifier to notify
34 * clients that we no longer have a working leader.</li>
35 * <li>Send a LeaderTransitioning message to each follower so each can send LeaderStateChanged messages to
36 * their local RoleChangeNotifiers.</li>
37 * <li>Call {@link RaftActor#pauseLeader} passing this RaftActorLeadershipTransferCohort
38 * instance. This allows derived classes to perform work prior to transferring leadership.</li>
39 * <li>When the pause is complete, the run method is called which in turn calls
40 * {@link Leader#transferLeadership(RaftActorLeadershipTransferCohort)}.</li>
41 * <li>The Leader calls {@link #transferComplete} on successful completion.</li>
42 * <li>Wait a short period of time for the new leader to be elected to give the derived class a chance to
43 * possibly complete work that was suspended while we were transferring.</li>
44 * <li>On notification of the new leader from the RaftActor or on time out, notify {@link OnComplete} callbacks.</li>
48 * NOTE: All methods on this class must be called on the actor's thread dispatcher as they may access/modify
51 * @author Thomas Pantelis
53 public class RaftActorLeadershipTransferCohort {
54 private static final Logger LOG = LoggerFactory.getLogger(RaftActorLeadershipTransferCohort.class);
56 private final RaftActor raftActor;
57 private Cancellable newLeaderTimer;
58 private final List<OnComplete> onCompleteCallbacks = new ArrayList<>();
59 private long newLeaderTimeoutInMillis = 2000;
60 private final Stopwatch transferTimer = Stopwatch.createUnstarted();
61 private boolean isTransferring;
63 RaftActorLeadershipTransferCohort(RaftActor raftActor) {
64 this.raftActor = raftActor;
68 RaftActorContext context = raftActor.getRaftActorContext();
69 RaftActorBehavior currentBehavior = raftActor.getCurrentBehavior();
71 transferTimer.start();
73 Optional<ActorRef> roleChangeNotifier = raftActor.getRoleChangeNotifier();
74 if (roleChangeNotifier.isPresent()) {
75 roleChangeNotifier.get().tell(raftActor.newLeaderStateChanged(context.getId(), null,
76 currentBehavior.getLeaderPayloadVersion()), raftActor.self());
79 for (String peerId: context.getPeerIds()) {
80 ActorSelection followerActor = context.getPeerActorSelection(peerId);
81 if (followerActor != null) {
82 followerActor.tell(new LeaderTransitioning(context.getId()), context.getActor());
86 raftActor.pauseLeader(new TimedRunnable(context.getConfigParams().getElectionTimeOutInterval(), raftActor) {
88 protected void doRun() {
93 protected void doCancel() {
94 LOG.debug("{}: pauseLeader timed out - aborting transfer", raftActor.persistenceId());
101 * This method is invoked to perform the leadership transfer.
105 RaftActorBehavior behavior = raftActor.getCurrentBehavior();
107 if (behavior instanceof Leader) {
108 isTransferring = true;
109 ((Leader)behavior).transferLeadership(this);
111 LOG.debug("{}: No longer the leader - skipping transfer", raftActor.persistenceId());
117 * This method is invoked to abort leadership transfer on failure.
119 public void abortTransfer() {
120 LOG.debug("{}: leader transfer aborted", raftActor.persistenceId());
125 * This method is invoked when leadership transfer was carried out and complete.
127 public void transferComplete() {
128 LOG.debug("{}: leader transfer complete - waiting for new leader", raftActor.persistenceId());
130 // We'll give it a little time for the new leader to be elected to give the derived class a
131 // chance to possibly complete work that was suspended while we were transferring. The
132 // RequestVote message from the new leader candidate should cause us to step down as leader
133 // and convert to follower due to higher term. We should then get an AppendEntries heart
134 // beat with the new leader id.
136 // Add a timer in case we don't get a leader change - 2 sec should be plenty of time if a new
137 // leader is elected. Note: the Runnable is sent as a message to the raftActor which executes it
138 // safely run on the actor's thread dispatcher.
139 FiniteDuration timeout = FiniteDuration.create(newLeaderTimeoutInMillis, TimeUnit.MILLISECONDS);
140 newLeaderTimer = raftActor.getContext().system().scheduler().scheduleOnce(timeout, raftActor.self(),
142 LOG.debug("{}: leader not elected in time", raftActor.persistenceId());
144 }, raftActor.getContext().system().dispatcher(), raftActor.self());
147 void onNewLeader(String newLeader) {
148 if (newLeader != null && newLeaderTimer != null) {
149 LOG.debug("{}: leader changed to {}", raftActor.persistenceId(), newLeader);
150 newLeaderTimer.cancel();
155 private void finish(boolean success) {
156 isTransferring = false;
157 if (transferTimer.isRunning()) {
158 transferTimer.stop();
160 LOG.info("{}: Successfully transferred leadership to {} in {}", raftActor.persistenceId(),
161 raftActor.getLeaderId(), transferTimer);
163 LOG.warn("{}: Failed to transfer leadership in {}", raftActor.persistenceId(), transferTimer);
167 for (OnComplete onComplete: onCompleteCallbacks) {
169 onComplete.onSuccess(raftActor.self());
171 onComplete.onFailure(raftActor.self());
176 void addOnComplete(OnComplete onComplete) {
177 onCompleteCallbacks.add(onComplete);
180 boolean isTransferring() {
181 return isTransferring;
185 void setNewLeaderTimeoutInMillis(long newLeaderTimeoutInMillis) {
186 this.newLeaderTimeoutInMillis = newLeaderTimeoutInMillis;
189 interface OnComplete {
190 void onSuccess(ActorRef raftActorRef);
192 void onFailure(ActorRef raftActorRef);