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     private RaftActorServerConfigurationSupport serverConfigurationSupport;
 124
 125     public RaftActor(String id, Map<String, String> peerAddresses,
 126          Optional<ConfigParams> configParams, short payloadVersion) {
 127
 128         persistentProvider = new PersistentDataProvider(this);
 129         context = new RaftActorContextImpl(this.getSelf(),
 130             this.getContext(), id, new ElectionTermImpl(persistentProvider, id, LOG),
 131             -1, -1, peerAddresses,
 132             (configParams.isPresent() ? configParams.get(): new DefaultConfigParamsImpl()),
 133             delegatingPersistenceProvider, LOG);
 134
 135         context.setPayloadVersion(payloadVersion);
 136         context.setReplicatedLog(ReplicatedLogImpl.newInstance(context, currentBehavior));
 137     }
 138
 139     @Override
 140     public void preStart() throws Exception {
 141         LOG.info("Starting recovery for {} with journal batch size {}", persistenceId(),
 142                 context.getConfigParams().getJournalRecoveryLogBatchSize());
 143
 144         super.preStart();
 145
 146         snapshotSupport = newRaftActorSnapshotMessageSupport();
 147         serverConfigurationSupport = new RaftActorServerConfigurationSupport(getRaftActorContext());
 148     }
 149
 150     @Override
 151     public void postStop() {
 152         if(currentBehavior.getDelegate() != null) {
 153             try {
 154                 currentBehavior.close();
 155             } catch (Exception e) {
 156                 LOG.debug("{}: Error closing behavior {}", persistenceId(), currentBehavior.state());
 157             }
 158         }
 159
 160         super.postStop();
 161     }
 162
 163     @Override
 164     public void handleRecover(Object message) {
 165         if(raftRecovery == null) {
 166             raftRecovery = newRaftActorRecoverySupport();
 167         }
 168
 169         boolean recoveryComplete = raftRecovery.handleRecoveryMessage(message, persistentProvider);
 170         if(recoveryComplete) {
 171             onRecoveryComplete();
 172
 173             initializeBehavior();
 174
 175             raftRecovery = null;
 176         }
 177     }
 178
 179     protected RaftActorRecoverySupport newRaftActorRecoverySupport() {
 180         return new RaftActorRecoverySupport(context, currentBehavior, getRaftActorRecoveryCohort());
 181     }
 182
 183     protected void initializeBehavior(){
 184         changeCurrentBehavior(new Follower(context));
 185     }
 186
 187     protected void changeCurrentBehavior(RaftActorBehavior newBehavior){
 188         reusableBehaviorStateHolder.init(getCurrentBehavior());
 189         setCurrentBehavior(newBehavior);
 190         handleBehaviorChange(reusableBehaviorStateHolder, getCurrentBehavior());
 191     }
 192
 193     @Override
 194     public void handleCommand(final Object message) {
 195         if(serverConfigurationSupport.handleMessage(message, this, getSender())) {
 196             return;
 197         } else if (message instanceof ApplyState){
 198             ApplyState applyState = (ApplyState) message;
 199
 200             long elapsedTime = (System.nanoTime() - applyState.getStartTime());
 201             if(elapsedTime >= APPLY_STATE_DELAY_THRESHOLD_IN_NANOS){
 202                 LOG.warn("ApplyState took more time than expected. Elapsed Time = {} ms ApplyState = {}",
 203                         TimeUnit.NANOSECONDS.toMillis(elapsedTime), applyState);
 204             }
 205
 206             if(LOG.isDebugEnabled()) {
 207                 LOG.debug("{}: Applying state for log index {} data {}",
 208                     persistenceId(), applyState.getReplicatedLogEntry().getIndex(),
 209                     applyState.getReplicatedLogEntry().getData());
 210             }
 211
 212             applyState(applyState.getClientActor(), applyState.getIdentifier(),
 213                 applyState.getReplicatedLogEntry().getData());
 214
 215             if (!hasFollowers()) {
 216                 // for single node, the capture should happen after the apply state
 217                 // as we delete messages from the persistent journal which have made it to the snapshot
 218                 // capturing the snapshot before applying makes the persistent journal and snapshot out of sync
 219                 // and recovery shows data missing
 220                 context.getReplicatedLog().captureSnapshotIfReady(applyState.getReplicatedLogEntry());
 221
 222                 context.getSnapshotManager().trimLog(context.getLastApplied(), currentBehavior);
 223             }
 224
 225         } else if (message instanceof ApplyJournalEntries){
 226             ApplyJournalEntries applyEntries = (ApplyJournalEntries) message;
 227             if(LOG.isDebugEnabled()) {
 228                 LOG.debug("{}: Persisting ApplyLogEntries with index={}", persistenceId(), applyEntries.getToIndex());
 229             }
 230
 231             persistence().persist(applyEntries, NoopProcedure.instance());
 232
 233         } else if (message instanceof FindLeader) {
 234             getSender().tell(
 235                 new FindLeaderReply(getLeaderAddress()),
 236                 getSelf()
 237             );
 238         } else if(message instanceof GetOnDemandRaftState) {
 239             onGetOnDemandRaftStats();
 240         } else if(message instanceof InitiateCaptureSnapshot) {
 241             captureSnapshot();
 242         } else if(message instanceof SwitchBehavior){
 243             switchBehavior(((SwitchBehavior) message));
 244         } else if(!snapshotSupport.handleSnapshotMessage(message)) {
 245             switchBehavior(reusableSwitchBehaviorSupplier.handleMessage(getSender(), message));
 246         }
 247     }
 248
 249     private void switchBehavior(SwitchBehavior message) {
 250         if(!getRaftActorContext().getRaftPolicy().automaticElectionsEnabled()) {
 251             RaftState newState = message.getNewState();
 252             if( newState == RaftState.Leader || newState == RaftState.Follower) {
 253                 switchBehavior(reusableSwitchBehaviorSupplier.handleMessage(getSender(), message));
 254                 getRaftActorContext().getTermInformation().updateAndPersist(message.getNewTerm(), "");
 255             } else {
 256                 LOG.warn("Switching to behavior : {} - not supported", newState);
 257             }
 258         }
 259     }
 260
 261     private void switchBehavior(Supplier<RaftActorBehavior> supplier){
 262         reusableBehaviorStateHolder.init(getCurrentBehavior());
 263
 264         setCurrentBehavior(supplier.get());
 265
 266         handleBehaviorChange(reusableBehaviorStateHolder, getCurrentBehavior());
 267     }
 268
 269     protected RaftActorSnapshotMessageSupport newRaftActorSnapshotMessageSupport() {
 270         return new RaftActorSnapshotMessageSupport(context, currentBehavior,
 271                 getRaftActorSnapshotCohort());
 272     }
 273
 274     private void onGetOnDemandRaftStats() {
 275         // Debugging message to retrieve raft stats.
 276
 277         OnDemandRaftState.Builder builder = OnDemandRaftState.builder()
 278                 .commitIndex(context.getCommitIndex())
 279                 .currentTerm(context.getTermInformation().getCurrentTerm())
 280                 .inMemoryJournalDataSize(replicatedLog().dataSize())
 281                 .inMemoryJournalLogSize(replicatedLog().size())
 282                 .isSnapshotCaptureInitiated(context.getSnapshotManager().isCapturing())
 283                 .lastApplied(context.getLastApplied())
 284                 .lastIndex(replicatedLog().lastIndex())
 285                 .lastTerm(replicatedLog().lastTerm())
 286                 .leader(getLeaderId())
 287                 .raftState(currentBehavior.state().toString())
 288                 .replicatedToAllIndex(currentBehavior.getReplicatedToAllIndex())
 289                 .snapshotIndex(replicatedLog().getSnapshotIndex())
 290                 .snapshotTerm(replicatedLog().getSnapshotTerm())
 291                 .votedFor(context.getTermInformation().getVotedFor())
 292                 .peerAddresses(new HashMap<>(context.getPeerAddresses()));
 293
 294         ReplicatedLogEntry lastLogEntry = getLastLogEntry();
 295         if (lastLogEntry != null) {
 296             builder.lastLogIndex(lastLogEntry.getIndex());
 297             builder.lastLogTerm(lastLogEntry.getTerm());
 298         }
 299
 300         if(getCurrentBehavior() instanceof AbstractLeader) {
 301             AbstractLeader leader = (AbstractLeader)getCurrentBehavior();
 302             Collection<String> followerIds = leader.getFollowerIds();
 303             List<FollowerInfo> followerInfoList = Lists.newArrayListWithCapacity(followerIds.size());
 304             for(String id: followerIds) {
 305                 final FollowerLogInformation info = leader.getFollower(id);
 306                 followerInfoList.add(new FollowerInfo(id, info.getNextIndex(), info.getMatchIndex(),
 307                         info.isFollowerActive(), DurationFormatUtils.formatDurationHMS(info.timeSinceLastActivity())));
 308             }
 309
 310             builder.followerInfoList(followerInfoList);
 311         }
 312
 313         sender().tell(builder.build(), self());
 314
 315     }
 316
 317     private void handleBehaviorChange(BehaviorStateHolder oldBehaviorState, RaftActorBehavior currentBehavior) {
 318         RaftActorBehavior oldBehavior = oldBehaviorState.getBehavior();
 319
 320         if (oldBehavior != currentBehavior){
 321             onStateChanged();
 322         }
 323
 324         String lastValidLeaderId = oldBehavior == null ? null : oldBehaviorState.getLastValidLeaderId();
 325         String oldBehaviorStateName = oldBehavior == null ? null : oldBehavior.state().name();
 326
 327         // it can happen that the state has not changed but the leader has changed.
 328         Optional<ActorRef> roleChangeNotifier = getRoleChangeNotifier();
 329         if(!Objects.equal(lastValidLeaderId, currentBehavior.getLeaderId()) ||
 330            oldBehaviorState.getLeaderPayloadVersion() != currentBehavior.getLeaderPayloadVersion()) {
 331             if(roleChangeNotifier.isPresent()) {
 332                 roleChangeNotifier.get().tell(newLeaderStateChanged(getId(), currentBehavior.getLeaderId(),
 333                         currentBehavior.getLeaderPayloadVersion()), getSelf());
 334             }
 335
 336             onLeaderChanged(lastValidLeaderId, currentBehavior.getLeaderId());
 337         }
 338
 339         if (roleChangeNotifier.isPresent() &&
 340                 (oldBehavior == null || (oldBehavior.state() != currentBehavior.state()))) {
 341             roleChangeNotifier.get().tell(new RoleChanged(getId(), oldBehaviorStateName ,
 342                     currentBehavior.state().name()), getSelf());
 343         }
 344     }
 345
 346     protected LeaderStateChanged newLeaderStateChanged(String memberId, String leaderId, short leaderPayloadVersion) {
 347         return new LeaderStateChanged(memberId, leaderId, leaderPayloadVersion);
 348     }
 349
 350     @Override
 351     public long snapshotSequenceNr() {
 352         // When we do a snapshot capture, we also capture and save the sequence-number of the persistent journal,
 353         // so that we can delete the persistent journal based on the saved sequence-number
 354         // However , when akka replays the journal during recovery, it replays it from the sequence number when the snapshot
 355         // was saved and not the number we saved.
 356         // We would want to override it , by asking akka to use the last-sequence number known to us.
 357         return context.getSnapshotManager().getLastSequenceNumber();
 358     }
 359
 360     /**
 361      * When a derived RaftActor needs to persist something it must call
 362      * persistData.
 363      *
 364      * @param clientActor
 365      * @param identifier
 366      * @param data
 367      */
 368     protected void persistData(final ActorRef clientActor, final String identifier,
 369         final Payload data) {
 370
 371         ReplicatedLogEntry replicatedLogEntry = new ReplicatedLogImplEntry(
 372             context.getReplicatedLog().lastIndex() + 1,
 373             context.getTermInformation().getCurrentTerm(), data);
 374
 375         if(LOG.isDebugEnabled()) {
 376             LOG.debug("{}: Persist data {}", persistenceId(), replicatedLogEntry);
 377         }
 378
 379         final RaftActorContext raftContext = getRaftActorContext();
 380
 381         replicatedLog().appendAndPersist(replicatedLogEntry, new Procedure<ReplicatedLogEntry>() {
 382             @Override
 383             public void apply(ReplicatedLogEntry replicatedLogEntry) throws Exception {
 384                 if (!hasFollowers()){
 385                     // Increment the Commit Index and the Last Applied values
 386                     raftContext.setCommitIndex(replicatedLogEntry.getIndex());
 387                     raftContext.setLastApplied(replicatedLogEntry.getIndex());
 388
 389                     // Apply the state immediately.
 390                     self().tell(new ApplyState(clientActor, identifier, replicatedLogEntry), self());
 391
 392                     // Send a ApplyJournalEntries message so that we write the fact that we applied
 393                     // the state to durable storage
 394                     self().tell(new ApplyJournalEntries(replicatedLogEntry.getIndex()), self());
 395
 396                 } else if (clientActor != null) {
 397                     context.getReplicatedLog().captureSnapshotIfReady(replicatedLogEntry);
 398
 399                     // Send message for replication
 400                     currentBehavior.handleMessage(getSelf(),
 401                             new Replicate(clientActor, identifier, replicatedLogEntry));
 402                 }
 403             }
 404         });
 405     }
 406
 407     private ReplicatedLog replicatedLog() {
 408         return context.getReplicatedLog();
 409     }
 410
 411     protected String getId() {
 412         return context.getId();
 413     }
 414
 415     @VisibleForTesting
 416     void setCurrentBehavior(RaftActorBehavior behavior) {
 417         currentBehavior.setDelegate(behavior);
 418     }
 419
 420     protected RaftActorBehavior getCurrentBehavior() {
 421         return currentBehavior.getDelegate();
 422     }
 423
 424     /**
 425      * Derived actors can call the isLeader method to check if the current
 426      * RaftActor is the Leader or not
 427      *
 428      * @return true it this RaftActor is a Leader false otherwise
 429      */
 430     protected boolean isLeader() {
 431         return context.getId().equals(currentBehavior.getLeaderId());
 432     }
 433
 434     /**
 435      * Derived actor can call getLeader if they need a reference to the Leader.
 436      * This would be useful for example in forwarding a request to an actor
 437      * which is the leader
 438      *
 439      * @return A reference to the leader if known, null otherwise
 440      */
 441     protected ActorSelection getLeader(){
 442         String leaderAddress = getLeaderAddress();
 443
 444         if(leaderAddress == null){
 445             return null;
 446         }
 447
 448         return context.actorSelection(leaderAddress);
 449     }
 450
 451     /**
 452      *
 453      * @return the current leader's id
 454      */
 455     protected String getLeaderId(){
 456         return currentBehavior.getLeaderId();
 457     }
 458
 459     protected RaftState getRaftState() {
 460         return currentBehavior.state();
 461     }
 462
 463     protected ReplicatedLogEntry getLastLogEntry() {
 464         return replicatedLog().last();
 465     }
 466
 467     protected Long getCurrentTerm(){
 468         return context.getTermInformation().getCurrentTerm();
 469     }
 470
 471     protected Long getCommitIndex(){
 472         return context.getCommitIndex();
 473     }
 474
 475     protected Long getLastApplied(){
 476         return context.getLastApplied();
 477     }
 478
 479     protected RaftActorContext getRaftActorContext() {
 480         return context;
 481     }
 482
 483     protected void updateConfigParams(ConfigParams configParams) {
 484         context.setConfigParams(configParams);
 485     }
 486
 487     public final DataPersistenceProvider persistence() {
 488         return delegatingPersistenceProvider.getDelegate();
 489     }
 490
 491     public void setPersistence(DataPersistenceProvider provider) {
 492         delegatingPersistenceProvider.setDelegate(provider);
 493     }
 494
 495     protected void setPersistence(boolean persistent) {
 496         if(persistent) {
 497             setPersistence(new PersistentDataProvider(this));
 498         } else {
 499             setPersistence(new NonPersistentDataProvider() {
 500                 /**
 501                  * The way snapshotting works is,
 502                  * <ol>
 503                  * <li> RaftActor calls createSnapshot on the Shard
 504                  * <li> Shard sends a CaptureSnapshotReply and RaftActor then calls saveSnapshot
 505                  * <li> When saveSnapshot is invoked on the akka-persistence API it uses the SnapshotStore to save
 506                  * the snapshot. The SnapshotStore sends SaveSnapshotSuccess or SaveSnapshotFailure. When the
 507                  * RaftActor gets SaveSnapshot success it commits the snapshot to the in-memory journal. This
 508                  * commitSnapshot is mimicking what is done in SaveSnapshotSuccess.
 509                  * </ol>
 510                  */
 511                 @Override
 512                 public void saveSnapshot(Object o) {
 513                     // Make saving Snapshot successful
 514                     // Committing the snapshot here would end up calling commit in the creating state which would
 515                     // be a state violation. That's why now we send a message to commit the snapshot.
 516                     self().tell(RaftActorSnapshotMessageSupport.COMMIT_SNAPSHOT, self());
 517                 }
 518             });
 519         }
 520     }
 521
 522     /**
 523      * setPeerAddress sets the address of a known peer at a later time.
 524      * <p>
 525      * This is to account for situations where a we know that a peer
 526      * exists but we do not know an address up-front. This may also be used in
 527      * situations where a known peer starts off in a different location and we
 528      * need to change it's address
 529      * <p>
 530      * Note that if the peerId does not match the list of peers passed to
 531      * this actor during construction an IllegalStateException will be thrown.
 532      *
 533      * @param peerId
 534      * @param peerAddress
 535      */
 536     protected void setPeerAddress(String peerId, String peerAddress){
 537         context.setPeerAddress(peerId, peerAddress);
 538     }
 539
 540     /**
 541      * The applyState method will be called by the RaftActor when some data
 542      * needs to be applied to the actor's state
 543      *
 544      * @param clientActor A reference to the client who sent this message. This
 545      *                    is the same reference that was passed to persistData
 546      *                    by the derived actor. clientActor may be null when
 547      *                    the RaftActor is behaving as a follower or during
 548      *                    recovery.
 549      * @param identifier  The identifier of the persisted data. This is also
 550      *                    the same identifier that was passed to persistData by
 551      *                    the derived actor. identifier may be null when
 552      *                    the RaftActor is behaving as a follower or during
 553      *                    recovery
 554      * @param data        A piece of data that was persisted by the persistData call.
 555      *                    This should NEVER be null.
 556      */
 557     protected abstract void applyState(ActorRef clientActor, String identifier,
 558         Object data);
 559
 560     /**
 561      * Returns the RaftActorRecoveryCohort to participate in persistence recovery.
 562      */
 563     @Nonnull
 564     protected abstract RaftActorRecoveryCohort getRaftActorRecoveryCohort();
 565
 566     /**
 567      * This method is called when recovery is complete.
 568      */
 569     protected abstract void onRecoveryComplete();
 570
 571     /**
 572      * Returns the RaftActorSnapshotCohort to participate in persistence recovery.
 573      */
 574     @Nonnull
 575     protected abstract RaftActorSnapshotCohort getRaftActorSnapshotCohort();
 576
 577     /**
 578      * This method will be called by the RaftActor when the state of the
 579      * RaftActor changes. The derived actor can then use methods like
 580      * isLeader or getLeader to do something useful
 581      */
 582     protected abstract void onStateChanged();
 583
 584     /**
 585      * Notifier Actor for this RaftActor to notify when a role change happens
 586      * @return ActorRef - ActorRef of the notifier or Optional.absent if none.
 587      */
 588     protected abstract Optional<ActorRef> getRoleChangeNotifier();
 589
 590     protected void onLeaderChanged(String oldLeader, String newLeader){};
 591
 592     private String getLeaderAddress(){
 593         if(isLeader()){
 594             return getSelf().path().toString();
 595         }
 596         String leaderId = currentBehavior.getLeaderId();
 597         if (leaderId == null) {
 598             return null;
 599         }
 600         String peerAddress = context.getPeerAddress(leaderId);
 601         if(LOG.isDebugEnabled()) {
 602             LOG.debug("{}: getLeaderAddress leaderId = {} peerAddress = {}",
 603                     persistenceId(), leaderId, peerAddress);
 604         }
 605
 606         return peerAddress;
 607     }
 608
 609     protected boolean hasFollowers(){
 610         return getRaftActorContext().hasFollowers();
 611     }
 612
 613     private void captureSnapshot() {
 614         SnapshotManager snapshotManager = context.getSnapshotManager();
 615
 616         if(!snapshotManager.isCapturing()) {
 617             LOG.debug("Take a snapshot of current state. lastReplicatedLog is {} and replicatedToAllIndex is {}",
 618                 replicatedLog().last(), currentBehavior.getReplicatedToAllIndex());
 619
 620             snapshotManager.capture(replicatedLog().last(), currentBehavior.getReplicatedToAllIndex());
 621         }
 622     }
 623
 624     /**
 625      * @deprecated Deprecated in favor of {@link org.opendaylight.controller.cluster.raft.base.messages.DeleteEntries}
 626      *             whose type for fromIndex is long instead of int. This class was kept for backwards
 627      *             compatibility with Helium.
 628      */
 629     // Suppressing this warning as we can't set serialVersionUID to maintain backwards compatibility.
 630     @SuppressWarnings("serial")
 631     @Deprecated
 632     static class DeleteEntries implements Serializable {
 633         private final int fromIndex;
 634
 635         public DeleteEntries(int fromIndex) {
 636             this.fromIndex = fromIndex;
 637         }
 638
 639         public int getFromIndex() {
 640             return fromIndex;
 641         }
 642     }
 643
 644     /**
 645      * @deprecated Deprecated in favor of non-inner class {@link org.opendaylight.controller.cluster.raft.base.messages.UpdateElectionTerm}
 646      *             which has serialVersionUID set. This class was kept for backwards compatibility with Helium.
 647      */
 648     // Suppressing this warning as we can't set serialVersionUID to maintain backwards compatibility.
 649     @SuppressWarnings("serial")
 650     @Deprecated
 651     static class UpdateElectionTerm implements Serializable {
 652         private final long currentTerm;
 653         private final String votedFor;
 654
 655         public UpdateElectionTerm(long currentTerm, String votedFor) {
 656             this.currentTerm = currentTerm;
 657             this.votedFor = votedFor;
 658         }
 659
 660         public long getCurrentTerm() {
 661             return currentTerm;
 662         }
 663
 664         public String getVotedFor() {
 665             return votedFor;
 666         }
 667     }
 668
 669     private static class BehaviorStateHolder {
 670         private RaftActorBehavior behavior;
 671         private String lastValidLeaderId;
 672         private short leaderPayloadVersion;
 673
 674         void init(RaftActorBehavior behavior) {
 675             this.behavior = behavior;
 676             this.leaderPayloadVersion = behavior != null ? behavior.getLeaderPayloadVersion() : -1;
 677
 678             String behaviorLeaderId = behavior != null ? behavior.getLeaderId() : null;
 679             if(behaviorLeaderId != null) {
 680                 this.lastValidLeaderId = behaviorLeaderId;
 681             }
 682         }
 683
 684         RaftActorBehavior getBehavior() {
 685             return behavior;
 686         }
 687
 688         String getLastValidLeaderId() {
 689             return lastValidLeaderId;
 690         }
 691
 692         short getLeaderPayloadVersion() {
 693             return leaderPayloadVersion;
 694         }
 695     }
 696
 697     private class SwitchBehaviorSupplier implements Supplier<RaftActorBehavior> {
 698         private Object message;
 699         private ActorRef sender;
 700
 701         public SwitchBehaviorSupplier handleMessage(ActorRef sender, Object message){
 702             this.sender = sender;
 703             this.message = message;
 704             return this;
 705         }
 706
 707         @Override
 708         public RaftActorBehavior get() {
 709             if(this.message instanceof SwitchBehavior){
 710                 return ((SwitchBehavior) message).getNewState().createBehavior(getRaftActorContext());
 711             }
 712             return currentBehavior.handleMessage(sender, message);
 713         }
 714     }
 715 }