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