opendaylight/md-sal/sal-akka-raft/src/main/java/org/opendaylight/controller/cluster/raft/RaftActor.java

   1 /*
   2  * Copyright (c) 2014 Cisco Systems, Inc. and others.  All rights reserved.
   3  * Copyright (c) 2015 Brocade Communications Systems, Inc. and others.  All rights reserved.
   4  *
   5  * This program and the accompanying materials are made available under the
   6  * terms of the Eclipse Public License v1.0 which accompanies this distribution,
   7  * and is available at http://www.eclipse.org/legal/epl-v10.html
   8  */
   9
  10 package org.opendaylight.controller.cluster.raft;
  11
  12 import akka.actor.ActorRef;
  13 import akka.actor.ActorSelection;
  14 import akka.japi.Procedure;
  15 import com.google.common.annotations.VisibleForTesting;
  16 import com.google.common.base.Objects;
  17 import com.google.common.base.Optional;
  18 import com.google.common.base.Supplier;
  19 import com.google.common.collect.Lists;
  20 import java.io.Serializable;
  21 import java.util.Collection;
  22 import java.util.HashMap;
  23 import java.util.List;
  24 import java.util.Map;
  25 import java.util.concurrent.TimeUnit;
  26 import javax.annotation.Nonnull;
  27 import org.apache.commons.lang3.time.DurationFormatUtils;
  28 import org.opendaylight.controller.cluster.DataPersistenceProvider;
  29 import org.opendaylight.controller.cluster.DelegatingPersistentDataProvider;
  30 import org.opendaylight.controller.cluster.NonPersistentDataProvider;
  31 import org.opendaylight.controller.cluster.PersistentDataProvider;
  32 import org.opendaylight.controller.cluster.common.actor.AbstractUntypedPersistentActor;
  33 import org.opendaylight.controller.cluster.notifications.LeaderStateChanged;
  34 import org.opendaylight.controller.cluster.notifications.RoleChanged;
  35 import org.opendaylight.controller.cluster.raft.base.messages.ApplyJournalEntries;
  36 import org.opendaylight.controller.cluster.raft.base.messages.ApplyState;
  37 import org.opendaylight.controller.cluster.raft.base.messages.InitiateCaptureSnapshot;
  38 import org.opendaylight.controller.cluster.raft.base.messages.Replicate;
  39 import org.opendaylight.controller.cluster.raft.base.messages.SwitchBehavior;
  40 import org.opendaylight.controller.cluster.raft.behaviors.AbstractLeader;
  41 import org.opendaylight.controller.cluster.raft.behaviors.DelegatingRaftActorBehavior;
  42 import org.opendaylight.controller.cluster.raft.behaviors.Follower;
  43 import org.opendaylight.controller.cluster.raft.behaviors.RaftActorBehavior;
  44 import org.opendaylight.controller.cluster.raft.client.messages.FindLeader;
  45 import org.opendaylight.controller.cluster.raft.client.messages.FindLeaderReply;
  46 import org.opendaylight.controller.cluster.raft.client.messages.FollowerInfo;
  47 import org.opendaylight.controller.cluster.raft.client.messages.GetOnDemandRaftState;
  48 import org.opendaylight.controller.cluster.raft.client.messages.OnDemandRaftState;
  49 import org.opendaylight.controller.cluster.raft.protobuff.client.messages.Payload;
  50 import org.slf4j.Logger;
  51 import org.slf4j.LoggerFactory;
  52
  53 /**
  54  * RaftActor encapsulates a state machine that needs to be kept synchronized
  55  * in a cluster. It implements the RAFT algorithm as described in the paper
  56  * <a href='https://ramcloud.stanford.edu/wiki/download/attachments/11370504/raft.pdf'>
  57  * In Search of an Understandable Consensus Algorithm</a>
  58  * <p/>
  59  * RaftActor has 3 states and each state has a certain behavior associated
  60  * with it. A Raft actor can behave as,
  61  * <ul>
  62  * <li> A Leader </li>
  63  * <li> A Follower (or) </li>
  64  * <li> A Candidate </li>
  65  * </ul>
  66  * <p/>
  67  * <p/>
  68  * A RaftActor MUST be a Leader in order to accept requests from clients to
  69  * change the state of it's encapsulated state machine. Once a RaftActor becomes
  70  * a Leader it is also responsible for ensuring that all followers ultimately
  71  * have the same log and therefore the same state machine as itself.
  72  * <p/>
  73  * <p/>
  74  * The current behavior of a RaftActor determines how election for leadership
  75  * is initiated and how peer RaftActors react to request for votes.
  76  * <p/>
  77  * <p/>
  78  * Each RaftActor also needs to know the current election term. It uses this
  79  * information for a couple of things. One is to simply figure out who it
  80  * voted for in the last election. Another is to figure out if the message
  81  * it received to update it's state is stale.
  82  * <p/>
  83  * <p/>
  84  * The RaftActor uses akka-persistence to store it's replicated log.
  85  * Furthermore through it's behaviors a Raft Actor determines
  86  * <p/>
  87  * <ul>
  88  * <li> when a log entry should be persisted </li>
  89  * <li> when a log entry should be applied to the state machine (and) </li>
  90  * <li> when a snapshot should be saved </li>
  91  * </ul>
  92  */
  93 public abstract class RaftActor extends AbstractUntypedPersistentActor {
  94
  95     private static final long APPLY_STATE_DELAY_THRESHOLD_IN_NANOS = TimeUnit.MILLISECONDS.toNanos(50L); // 50 millis
  96
  97     protected final Logger LOG = LoggerFactory.getLogger(getClass());
  98
  99     /**
 100      * The current state determines the current behavior of a RaftActor
 101      * A Raft Actor always starts off in the Follower State
 102      */
 103     private final DelegatingRaftActorBehavior currentBehavior = new DelegatingRaftActorBehavior();
 104
 105     /**
 106      * This context should NOT be passed directly to any other actor it is
 107      * only to be consumed by the RaftActorBehaviors
 108      */
 109     private final RaftActorContextImpl context;
 110
 111     private final DelegatingPersistentDataProvider delegatingPersistenceProvider = new DelegatingPersistentDataProvider(null);
 112
 113     private final PersistentDataProvider persistentProvider;
 114
 115     private RaftActorRecoverySupport raftRecovery;
 116
 117     private RaftActorSnapshotMessageSupport snapshotSupport;
 118
 119     private final BehaviorStateHolder reusableBehaviorStateHolder = new BehaviorStateHolder();
 120
 121     private final SwitchBehaviorSupplier reusableSwitchBehaviorSupplier = new SwitchBehaviorSupplier();
 122
 123     public RaftActor(String id, Map<String, String> peerAddresses,
 124          Optional<ConfigParams> configParams, short payloadVersion) {
 125
 126         persistentProvider = new PersistentDataProvider(this);
 127         context = new RaftActorContextImpl(this.getSelf(),
 128             this.getContext(), id, new ElectionTermImpl(persistentProvider, id, LOG),
 129             -1, -1, peerAddresses,
 130             (configParams.isPresent() ? configParams.get(): new DefaultConfigParamsImpl()),
 131             delegatingPersistenceProvider, LOG);
 132
 133         context.setPayloadVersion(payloadVersion);
 134         context.setReplicatedLog(ReplicatedLogImpl.newInstance(context, currentBehavior));
 135     }
 136
 137     @Override
 138     public void preStart() throws Exception {
 139         LOG.info("Starting recovery for {} with journal batch size {}", persistenceId(),
 140                 context.getConfigParams().getJournalRecoveryLogBatchSize());
 141
 142         super.preStart();
 143
 144         snapshotSupport = newRaftActorSnapshotMessageSupport();
 145     }
 146
 147     @Override
 148     public void postStop() {
 149         if(currentBehavior.getDelegate() != null) {
 150             try {
 151                 currentBehavior.close();
 152             } catch (Exception e) {
 153                 LOG.debug("{}: Error closing behavior {}", persistenceId(), currentBehavior.state());
 154             }
 155         }
 156
 157         super.postStop();
 158     }
 159
 160     @Override
 161     public void handleRecover(Object message) {
 162         if(raftRecovery == null) {
 163             raftRecovery = newRaftActorRecoverySupport();
 164         }
 165
 166         boolean recoveryComplete = raftRecovery.handleRecoveryMessage(message, persistentProvider);
 167         if(recoveryComplete) {
 168             onRecoveryComplete();
 169
 170             initializeBehavior();
 171
 172             raftRecovery = null;
 173         }
 174     }
 175
 176     protected RaftActorRecoverySupport newRaftActorRecoverySupport() {
 177         return new RaftActorRecoverySupport(context, currentBehavior, getRaftActorRecoveryCohort());
 178     }
 179
 180     protected void initializeBehavior(){
 181         changeCurrentBehavior(new Follower(context));
 182     }
 183
 184     protected void changeCurrentBehavior(RaftActorBehavior newBehavior){
 185         reusableBehaviorStateHolder.init(getCurrentBehavior());
 186         setCurrentBehavior(newBehavior);
 187         handleBehaviorChange(reusableBehaviorStateHolder, getCurrentBehavior());
 188     }
 189
 190     @Override
 191     public void handleCommand(final Object message) {
 192         if (message instanceof ApplyState){
 193             ApplyState applyState = (ApplyState) message;
 194
 195             long elapsedTime = (System.nanoTime() - applyState.getStartTime());
 196             if(elapsedTime >= APPLY_STATE_DELAY_THRESHOLD_IN_NANOS){
 197                 LOG.warn("ApplyState took more time than expected. Elapsed Time = {} ms ApplyState = {}",
 198                         TimeUnit.NANOSECONDS.toMillis(elapsedTime), applyState);
 199             }
 200
 201             if(LOG.isDebugEnabled()) {
 202                 LOG.debug("{}: Applying state for log index {} data {}",
 203                     persistenceId(), applyState.getReplicatedLogEntry().getIndex(),
 204                     applyState.getReplicatedLogEntry().getData());
 205             }
 206
 207             applyState(applyState.getClientActor(), applyState.getIdentifier(),
 208                 applyState.getReplicatedLogEntry().getData());
 209
 210             if (!hasFollowers()) {
 211                 // for single node, the capture should happen after the apply state
 212                 // as we delete messages from the persistent journal which have made it to the snapshot
 213                 // capturing the snapshot before applying makes the persistent journal and snapshot out of sync
 214                 // and recovery shows data missing
 215                 context.getReplicatedLog().captureSnapshotIfReady(applyState.getReplicatedLogEntry());
 216
 217                 context.getSnapshotManager().trimLog(context.getLastApplied(), currentBehavior);
 218             }
 219
 220         } else if (message instanceof ApplyJournalEntries){
 221             ApplyJournalEntries applyEntries = (ApplyJournalEntries) message;
 222             if(LOG.isDebugEnabled()) {
 223                 LOG.debug("{}: Persisting ApplyLogEntries with index={}", persistenceId(), applyEntries.getToIndex());
 224             }
 225
 226             persistence().persist(applyEntries, NoopProcedure.instance());
 227
 228         } else if (message instanceof FindLeader) {
 229             getSender().tell(
 230                 new FindLeaderReply(getLeaderAddress()),
 231                 getSelf()
 232             );
 233         } else if(message instanceof GetOnDemandRaftState) {
 234             onGetOnDemandRaftStats();
 235         } else if(message instanceof InitiateCaptureSnapshot) {
 236             captureSnapshot();
 237         } else if(message instanceof SwitchBehavior){
 238             switchBehavior(((SwitchBehavior) message));
 239         } else if(!snapshotSupport.handleSnapshotMessage(message)) {
 240             switchBehavior(reusableSwitchBehaviorSupplier.handleMessage(getSender(), message));
 241         }
 242     }
 243
 244     private void switchBehavior(SwitchBehavior message) {
 245         if(!getRaftActorContext().getRaftPolicy().automaticElectionsEnabled()) {
 246             RaftState newState = message.getNewState();
 247             if( newState == RaftState.Leader || newState == RaftState.Follower) {
 248                 switchBehavior(reusableSwitchBehaviorSupplier.handleMessage(getSender(), message));
 249                 getRaftActorContext().getTermInformation().updateAndPersist(message.getNewTerm(), "");
 250             } else {
 251                 LOG.warn("Switching to behavior : {} - not supported", newState);
 252             }
 253         }
 254     }
 255
 256     private void switchBehavior(Supplier<RaftActorBehavior> supplier){
 257         reusableBehaviorStateHolder.init(getCurrentBehavior());
 258
 259         setCurrentBehavior(supplier.get());
 260
 261         handleBehaviorChange(reusableBehaviorStateHolder, getCurrentBehavior());
 262     }
 263
 264     protected RaftActorSnapshotMessageSupport newRaftActorSnapshotMessageSupport() {
 265         return new RaftActorSnapshotMessageSupport(context, currentBehavior,
 266                 getRaftActorSnapshotCohort());
 267     }
 268
 269     private void onGetOnDemandRaftStats() {
 270         // Debugging message to retrieve raft stats.
 271
 272         OnDemandRaftState.Builder builder = OnDemandRaftState.builder()
 273                 .commitIndex(context.getCommitIndex())
 274                 .currentTerm(context.getTermInformation().getCurrentTerm())
 275                 .inMemoryJournalDataSize(replicatedLog().dataSize())
 276                 .inMemoryJournalLogSize(replicatedLog().size())
 277                 .isSnapshotCaptureInitiated(context.getSnapshotManager().isCapturing())
 278                 .lastApplied(context.getLastApplied())
 279                 .lastIndex(replicatedLog().lastIndex())
 280                 .lastTerm(replicatedLog().lastTerm())
 281                 .leader(getLeaderId())
 282                 .raftState(currentBehavior.state().toString())
 283                 .replicatedToAllIndex(currentBehavior.getReplicatedToAllIndex())
 284                 .snapshotIndex(replicatedLog().getSnapshotIndex())
 285                 .snapshotTerm(replicatedLog().getSnapshotTerm())
 286                 .votedFor(context.getTermInformation().getVotedFor())
 287                 .peerAddresses(new HashMap<>(context.getPeerAddresses()));
 288
 289         ReplicatedLogEntry lastLogEntry = getLastLogEntry();
 290         if (lastLogEntry != null) {
 291             builder.lastLogIndex(lastLogEntry.getIndex());
 292             builder.lastLogTerm(lastLogEntry.getTerm());
 293         }
 294
 295         if(getCurrentBehavior() instanceof AbstractLeader) {
 296             AbstractLeader leader = (AbstractLeader)getCurrentBehavior();
 297             Collection<String> followerIds = leader.getFollowerIds();
 298             List<FollowerInfo> followerInfoList = Lists.newArrayListWithCapacity(followerIds.size());
 299             for(String id: followerIds) {
 300                 final FollowerLogInformation info = leader.getFollower(id);
 301                 followerInfoList.add(new FollowerInfo(id, info.getNextIndex(), info.getMatchIndex(),
 302                         info.isFollowerActive(), DurationFormatUtils.formatDurationHMS(info.timeSinceLastActivity())));
 303             }
 304
 305             builder.followerInfoList(followerInfoList);
 306         }
 307
 308         sender().tell(builder.build(), self());
 309
 310     }
 311
 312     private void handleBehaviorChange(BehaviorStateHolder oldBehaviorState, RaftActorBehavior currentBehavior) {
 313         RaftActorBehavior oldBehavior = oldBehaviorState.getBehavior();
 314
 315         if (oldBehavior != currentBehavior){
 316             onStateChanged();
 317         }
 318
 319         String lastValidLeaderId = oldBehavior == null ? null : oldBehaviorState.getLastValidLeaderId();
 320         String oldBehaviorStateName = oldBehavior == null ? null : oldBehavior.state().name();
 321
 322         // it can happen that the state has not changed but the leader has changed.
 323         Optional<ActorRef> roleChangeNotifier = getRoleChangeNotifier();
 324         if(!Objects.equal(lastValidLeaderId, currentBehavior.getLeaderId()) ||
 325            oldBehaviorState.getLeaderPayloadVersion() != currentBehavior.getLeaderPayloadVersion()) {
 326             if(roleChangeNotifier.isPresent()) {
 327                 roleChangeNotifier.get().tell(newLeaderStateChanged(getId(), currentBehavior.getLeaderId(),
 328                         currentBehavior.getLeaderPayloadVersion()), getSelf());
 329             }
 330
 331             onLeaderChanged(lastValidLeaderId, currentBehavior.getLeaderId());
 332         }
 333
 334         if (roleChangeNotifier.isPresent() &&
 335                 (oldBehavior == null || (oldBehavior.state() != currentBehavior.state()))) {
 336             roleChangeNotifier.get().tell(new RoleChanged(getId(), oldBehaviorStateName ,
 337                     currentBehavior.state().name()), getSelf());
 338         }
 339     }
 340
 341     protected LeaderStateChanged newLeaderStateChanged(String memberId, String leaderId, short leaderPayloadVersion) {
 342         return new LeaderStateChanged(memberId, leaderId, leaderPayloadVersion);
 343     }
 344
 345     @Override
 346     public long snapshotSequenceNr() {
 347         // When we do a snapshot capture, we also capture and save the sequence-number of the persistent journal,
 348         // so that we can delete the persistent journal based on the saved sequence-number
 349         // However , when akka replays the journal during recovery, it replays it from the sequence number when the snapshot
 350         // was saved and not the number we saved.
 351         // We would want to override it , by asking akka to use the last-sequence number known to us.
 352         return context.getSnapshotManager().getLastSequenceNumber();
 353     }
 354
 355     /**
 356      * When a derived RaftActor needs to persist something it must call
 357      * persistData.
 358      *
 359      * @param clientActor
 360      * @param identifier
 361      * @param data
 362      */
 363     protected void persistData(final ActorRef clientActor, final String identifier,
 364         final Payload data) {
 365
 366         ReplicatedLogEntry replicatedLogEntry = new ReplicatedLogImplEntry(
 367             context.getReplicatedLog().lastIndex() + 1,
 368             context.getTermInformation().getCurrentTerm(), data);
 369
 370         if(LOG.isDebugEnabled()) {
 371             LOG.debug("{}: Persist data {}", persistenceId(), replicatedLogEntry);
 372         }
 373
 374         final RaftActorContext raftContext = getRaftActorContext();
 375
 376         replicatedLog().appendAndPersist(replicatedLogEntry, new Procedure<ReplicatedLogEntry>() {
 377             @Override
 378             public void apply(ReplicatedLogEntry replicatedLogEntry) throws Exception {
 379                 if (!hasFollowers()){
 380                     // Increment the Commit Index and the Last Applied values
 381                     raftContext.setCommitIndex(replicatedLogEntry.getIndex());
 382                     raftContext.setLastApplied(replicatedLogEntry.getIndex());
 383
 384                     // Apply the state immediately.
 385                     self().tell(new ApplyState(clientActor, identifier, replicatedLogEntry), self());
 386
 387                     // Send a ApplyJournalEntries message so that we write the fact that we applied
 388                     // the state to durable storage
 389                     self().tell(new ApplyJournalEntries(replicatedLogEntry.getIndex()), self());
 390
 391                 } else if (clientActor != null) {
 392                     context.getReplicatedLog().captureSnapshotIfReady(replicatedLogEntry);
 393
 394                     // Send message for replication
 395                     currentBehavior.handleMessage(getSelf(),
 396                             new Replicate(clientActor, identifier, replicatedLogEntry));
 397                 }
 398             }
 399         });
 400     }
 401
 402     private ReplicatedLog replicatedLog() {
 403         return context.getReplicatedLog();
 404     }
 405
 406     protected String getId() {
 407         return context.getId();
 408     }
 409
 410     @VisibleForTesting
 411     void setCurrentBehavior(RaftActorBehavior behavior) {
 412         currentBehavior.setDelegate(behavior);
 413     }
 414
 415     protected RaftActorBehavior getCurrentBehavior() {
 416         return currentBehavior.getDelegate();
 417     }
 418
 419     /**
 420      * Derived actors can call the isLeader method to check if the current
 421      * RaftActor is the Leader or not
 422      *
 423      * @return true it this RaftActor is a Leader false otherwise
 424      */
 425     protected boolean isLeader() {
 426         return context.getId().equals(currentBehavior.getLeaderId());
 427     }
 428
 429     /**
 430      * Derived actor can call getLeader if they need a reference to the Leader.
 431      * This would be useful for example in forwarding a request to an actor
 432      * which is the leader
 433      *
 434      * @return A reference to the leader if known, null otherwise
 435      */
 436     protected ActorSelection getLeader(){
 437         String leaderAddress = getLeaderAddress();
 438
 439         if(leaderAddress == null){
 440             return null;
 441         }
 442
 443         return context.actorSelection(leaderAddress);
 444     }
 445
 446     /**
 447      *
 448      * @return the current leader's id
 449      */
 450     protected String getLeaderId(){
 451         return currentBehavior.getLeaderId();
 452     }
 453
 454     protected RaftState getRaftState() {
 455         return currentBehavior.state();
 456     }
 457
 458     protected ReplicatedLogEntry getLastLogEntry() {
 459         return replicatedLog().last();
 460     }
 461
 462     protected Long getCurrentTerm(){
 463         return context.getTermInformation().getCurrentTerm();
 464     }
 465
 466     protected Long getCommitIndex(){
 467         return context.getCommitIndex();
 468     }
 469
 470     protected Long getLastApplied(){
 471         return context.getLastApplied();
 472     }
 473
 474     protected RaftActorContext getRaftActorContext() {
 475         return context;
 476     }
 477
 478     protected void updateConfigParams(ConfigParams configParams) {
 479         context.setConfigParams(configParams);
 480     }
 481
 482     public final DataPersistenceProvider persistence() {
 483         return delegatingPersistenceProvider.getDelegate();
 484     }
 485
 486     public void setPersistence(DataPersistenceProvider provider) {
 487         delegatingPersistenceProvider.setDelegate(provider);
 488     }
 489
 490     protected void setPersistence(boolean persistent) {
 491         if(persistent) {
 492             setPersistence(new PersistentDataProvider(this));
 493         } else {
 494             setPersistence(new NonPersistentDataProvider() {
 495                 /**
 496                  * The way snapshotting works is,
 497                  * <ol>
 498                  * <li> RaftActor calls createSnapshot on the Shard
 499                  * <li> Shard sends a CaptureSnapshotReply and RaftActor then calls saveSnapshot
 500                  * <li> When saveSnapshot is invoked on the akka-persistence API it uses the SnapshotStore to save
 501                  * the snapshot. The SnapshotStore sends SaveSnapshotSuccess or SaveSnapshotFailure. When the
 502                  * RaftActor gets SaveSnapshot success it commits the snapshot to the in-memory journal. This
 503                  * commitSnapshot is mimicking what is done in SaveSnapshotSuccess.
 504                  * </ol>
 505                  */
 506                 @Override
 507                 public void saveSnapshot(Object o) {
 508                     // Make saving Snapshot successful
 509                     // Committing the snapshot here would end up calling commit in the creating state which would
 510                     // be a state violation. That's why now we send a message to commit the snapshot.
 511                     self().tell(RaftActorSnapshotMessageSupport.COMMIT_SNAPSHOT, self());
 512                 }
 513             });
 514         }
 515     }
 516
 517     /**
 518      * setPeerAddress sets the address of a known peer at a later time.
 519      * <p>
 520      * This is to account for situations where a we know that a peer
 521      * exists but we do not know an address up-front. This may also be used in
 522      * situations where a known peer starts off in a different location and we
 523      * need to change it's address
 524      * <p>
 525      * Note that if the peerId does not match the list of peers passed to
 526      * this actor during construction an IllegalStateException will be thrown.
 527      *
 528      * @param peerId
 529      * @param peerAddress
 530      */
 531     protected void setPeerAddress(String peerId, String peerAddress){
 532         context.setPeerAddress(peerId, peerAddress);
 533     }
 534
 535     /**
 536      * The applyState method will be called by the RaftActor when some data
 537      * needs to be applied to the actor's state
 538      *
 539      * @param clientActor A reference to the client who sent this message. This
 540      *                    is the same reference that was passed to persistData
 541      *                    by the derived actor. clientActor may be null when
 542      *                    the RaftActor is behaving as a follower or during
 543      *                    recovery.
 544      * @param identifier  The identifier of the persisted data. This is also
 545      *                    the same identifier that was passed to persistData by
 546      *                    the derived actor. identifier may be null when
 547      *                    the RaftActor is behaving as a follower or during
 548      *                    recovery
 549      * @param data        A piece of data that was persisted by the persistData call.
 550      *                    This should NEVER be null.
 551      */
 552     protected abstract void applyState(ActorRef clientActor, String identifier,
 553         Object data);
 554
 555     /**
 556      * Returns the RaftActorRecoveryCohort to participate in persistence recovery.
 557      */
 558     @Nonnull
 559     protected abstract RaftActorRecoveryCohort getRaftActorRecoveryCohort();
 560
 561     /**
 562      * This method is called when recovery is complete.
 563      */
 564     protected abstract void onRecoveryComplete();
 565
 566     /**
 567      * Returns the RaftActorSnapshotCohort to participate in persistence recovery.
 568      */
 569     @Nonnull
 570     protected abstract RaftActorSnapshotCohort getRaftActorSnapshotCohort();
 571
 572     /**
 573      * This method will be called by the RaftActor when the state of the
 574      * RaftActor changes. The derived actor can then use methods like
 575      * isLeader or getLeader to do something useful
 576      */
 577     protected abstract void onStateChanged();
 578
 579     /**
 580      * Notifier Actor for this RaftActor to notify when a role change happens
 581      * @return ActorRef - ActorRef of the notifier or Optional.absent if none.
 582      */
 583     protected abstract Optional<ActorRef> getRoleChangeNotifier();
 584
 585     protected void onLeaderChanged(String oldLeader, String newLeader){};
 586
 587     private String getLeaderAddress(){
 588         if(isLeader()){
 589             return getSelf().path().toString();
 590         }
 591         String leaderId = currentBehavior.getLeaderId();
 592         if (leaderId == null) {
 593             return null;
 594         }
 595         String peerAddress = context.getPeerAddress(leaderId);
 596         if(LOG.isDebugEnabled()) {
 597             LOG.debug("{}: getLeaderAddress leaderId = {} peerAddress = {}",
 598                     persistenceId(), leaderId, peerAddress);
 599         }
 600
 601         return peerAddress;
 602     }
 603
 604     protected boolean hasFollowers(){
 605         return getRaftActorContext().hasFollowers();
 606     }
 607
 608     private void captureSnapshot() {
 609         SnapshotManager snapshotManager = context.getSnapshotManager();
 610
 611         if(!snapshotManager.isCapturing()) {
 612             LOG.debug("Take a snapshot of current state. lastReplicatedLog is {} and replicatedToAllIndex is {}",
 613                 replicatedLog().last(), currentBehavior.getReplicatedToAllIndex());
 614
 615             snapshotManager.capture(replicatedLog().last(), currentBehavior.getReplicatedToAllIndex());
 616         }
 617     }
 618
 619     /**
 620      * @deprecated Deprecated in favor of {@link org.opendaylight.controller.cluster.raft.base.messages.DeleteEntries}
 621      *             whose type for fromIndex is long instead of int. This class was kept for backwards
 622      *             compatibility with Helium.
 623      */
 624     // Suppressing this warning as we can't set serialVersionUID to maintain backwards compatibility.
 625     @SuppressWarnings("serial")
 626     @Deprecated
 627     static class DeleteEntries implements Serializable {
 628         private final int fromIndex;
 629
 630         public DeleteEntries(int fromIndex) {
 631             this.fromIndex = fromIndex;
 632         }
 633
 634         public int getFromIndex() {
 635             return fromIndex;
 636         }
 637     }
 638
 639     /**
 640      * @deprecated Deprecated in favor of non-inner class {@link org.opendaylight.controller.cluster.raft.base.messages.UpdateElectionTerm}
 641      *             which has serialVersionUID set. This class was kept for backwards compatibility with Helium.
 642      */
 643     // Suppressing this warning as we can't set serialVersionUID to maintain backwards compatibility.
 644     @SuppressWarnings("serial")
 645     @Deprecated
 646     static class UpdateElectionTerm implements Serializable {
 647         private final long currentTerm;
 648         private final String votedFor;
 649
 650         public UpdateElectionTerm(long currentTerm, String votedFor) {
 651             this.currentTerm = currentTerm;
 652             this.votedFor = votedFor;
 653         }
 654
 655         public long getCurrentTerm() {
 656             return currentTerm;
 657         }
 658
 659         public String getVotedFor() {
 660             return votedFor;
 661         }
 662     }
 663
 664     private static class BehaviorStateHolder {
 665         private RaftActorBehavior behavior;
 666         private String lastValidLeaderId;
 667         private short leaderPayloadVersion;
 668
 669         void init(RaftActorBehavior behavior) {
 670             this.behavior = behavior;
 671             this.leaderPayloadVersion = behavior != null ? behavior.getLeaderPayloadVersion() : -1;
 672
 673             String behaviorLeaderId = behavior != null ? behavior.getLeaderId() : null;
 674             if(behaviorLeaderId != null) {
 675                 this.lastValidLeaderId = behaviorLeaderId;
 676             }
 677         }
 678
 679         RaftActorBehavior getBehavior() {
 680             return behavior;
 681         }
 682
 683         String getLastValidLeaderId() {
 684             return lastValidLeaderId;
 685         }
 686
 687         short getLeaderPayloadVersion() {
 688             return leaderPayloadVersion;
 689         }
 690     }
 691
 692     private class SwitchBehaviorSupplier implements Supplier<RaftActorBehavior> {
 693         private Object message;
 694         private ActorRef sender;
 695
 696         public SwitchBehaviorSupplier handleMessage(ActorRef sender, Object message){
 697             this.sender = sender;
 698             this.message = message;
 699             return this;
 700         }
 701
 702         @Override
 703         public RaftActorBehavior get() {
 704             if(this.message instanceof SwitchBehavior){
 705                 return ((SwitchBehavior) message).getNewState().createBehavior(getRaftActorContext());
 706             }
 707             return currentBehavior.handleMessage(sender, message);
 708         }
 709     }
 710 }