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