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         this(id, peerAddresses, Optional.<ConfigParams>absent());
 119     }
 120
 121     public RaftActor(String id, Map<String, String> peerAddresses,
 122          Optional<ConfigParams> configParams) {
 123
 124         context = new RaftActorContextImpl(this.getSelf(),
 125             this.getContext(), id, new ElectionTermImpl(delegatingPersistenceProvider, id, LOG),
 126             -1, -1, peerAddresses,
 127             (configParams.isPresent() ? configParams.get(): new DefaultConfigParamsImpl()),
 128             delegatingPersistenceProvider, LOG);
 129
 130         context.setReplicatedLog(ReplicatedLogImpl.newInstance(context, currentBehavior));
 131     }
 132
 133     @Override
 134     public void preStart() throws Exception {
 135         LOG.info("Starting recovery for {} with journal batch size {}", persistenceId(),
 136                 context.getConfigParams().getJournalRecoveryLogBatchSize());
 137
 138         super.preStart();
 139
 140         snapshotSupport = newRaftActorSnapshotMessageSupport();
 141     }
 142
 143     @Override
 144     public void postStop() {
 145         if(currentBehavior.getDelegate() != null) {
 146             try {
 147                 currentBehavior.close();
 148             } catch (Exception e) {
 149                 LOG.debug("{}: Error closing behavior {}", persistenceId(), currentBehavior.state());
 150             }
 151         }
 152
 153         super.postStop();
 154     }
 155
 156     @Override
 157     public void handleRecover(Object message) {
 158         if(raftRecovery == null) {
 159             raftRecovery = newRaftActorRecoverySupport();
 160         }
 161
 162         boolean recoveryComplete = raftRecovery.handleRecoveryMessage(message);
 163         if(recoveryComplete) {
 164             if(!persistence().isRecoveryApplicable()) {
 165                 // Delete all the messages from the akka journal so that we do not end up with consistency issues
 166                 // Note I am not using the dataPersistenceProvider and directly using the akka api here
 167                 deleteMessages(lastSequenceNr());
 168
 169                 // Delete all the akka snapshots as they will not be needed
 170                 deleteSnapshots(new SnapshotSelectionCriteria(scala.Long.MaxValue(), scala.Long.MaxValue()));
 171             }
 172
 173             onRecoveryComplete();
 174
 175             initializeBehavior();
 176
 177             raftRecovery = null;
 178         }
 179     }
 180
 181     protected RaftActorRecoverySupport newRaftActorRecoverySupport() {
 182         return new RaftActorRecoverySupport(context, currentBehavior, getRaftActorRecoveryCohort());
 183     }
 184
 185     protected void initializeBehavior(){
 186         changeCurrentBehavior(new Follower(context));
 187     }
 188
 189     protected void changeCurrentBehavior(RaftActorBehavior newBehavior){
 190         reusableBehaviorStateHolder.init(getCurrentBehavior());
 191         setCurrentBehavior(newBehavior);
 192         handleBehaviorChange(reusableBehaviorStateHolder, getCurrentBehavior());
 193     }
 194
 195     @Override
 196     public void handleCommand(Object message) {
 197         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         } else if (message instanceof ApplyJournalEntries){
 216             ApplyJournalEntries applyEntries = (ApplyJournalEntries) message;
 217             if(LOG.isDebugEnabled()) {
 218                 LOG.debug("{}: Persisting ApplyLogEntries with index={}", persistenceId(), applyEntries.getToIndex());
 219             }
 220
 221             persistence().persist(applyEntries, NoopProcedure.instance());
 222
 223         } else if (message instanceof FindLeader) {
 224             getSender().tell(
 225                 new FindLeaderReply(getLeaderAddress()),
 226                 getSelf()
 227             );
 228         } else if(message instanceof GetOnDemandRaftState) {
 229             onGetOnDemandRaftStats();
 230         } else if(!snapshotSupport.handleSnapshotMessage(message)) {
 231             reusableBehaviorStateHolder.init(getCurrentBehavior());
 232
 233             setCurrentBehavior(currentBehavior.handleMessage(getSender(), message));
 234
 235             handleBehaviorChange(reusableBehaviorStateHolder, getCurrentBehavior());
 236         }
 237     }
 238
 239     protected RaftActorSnapshotMessageSupport newRaftActorSnapshotMessageSupport() {
 240         return new RaftActorSnapshotMessageSupport(context, currentBehavior,
 241                 getRaftActorSnapshotCohort());
 242     }
 243
 244     private void onGetOnDemandRaftStats() {
 245         // Debugging message to retrieve raft stats.
 246
 247         OnDemandRaftState.Builder builder = OnDemandRaftState.builder()
 248                 .commitIndex(context.getCommitIndex())
 249                 .currentTerm(context.getTermInformation().getCurrentTerm())
 250                 .inMemoryJournalDataSize(replicatedLog().dataSize())
 251                 .inMemoryJournalLogSize(replicatedLog().size())
 252                 .isSnapshotCaptureInitiated(context.getSnapshotManager().isCapturing())
 253                 .lastApplied(context.getLastApplied())
 254                 .lastIndex(replicatedLog().lastIndex())
 255                 .lastTerm(replicatedLog().lastTerm())
 256                 .leader(getLeaderId())
 257                 .raftState(currentBehavior.state().toString())
 258                 .replicatedToAllIndex(currentBehavior.getReplicatedToAllIndex())
 259                 .snapshotIndex(replicatedLog().getSnapshotIndex())
 260                 .snapshotTerm(replicatedLog().getSnapshotTerm())
 261                 .votedFor(context.getTermInformation().getVotedFor())
 262                 .peerAddresses(new HashMap<>(context.getPeerAddresses()));
 263
 264         ReplicatedLogEntry lastLogEntry = getLastLogEntry();
 265         if (lastLogEntry != null) {
 266             builder.lastLogIndex(lastLogEntry.getIndex());
 267             builder.lastLogTerm(lastLogEntry.getTerm());
 268         }
 269
 270         if(getCurrentBehavior() instanceof AbstractLeader) {
 271             AbstractLeader leader = (AbstractLeader)getCurrentBehavior();
 272             Collection<String> followerIds = leader.getFollowerIds();
 273             List<FollowerInfo> followerInfoList = Lists.newArrayListWithCapacity(followerIds.size());
 274             for(String id: followerIds) {
 275                 final FollowerLogInformation info = leader.getFollower(id);
 276                 followerInfoList.add(new FollowerInfo(id, info.getNextIndex(), info.getMatchIndex(),
 277                         info.isFollowerActive(), DurationFormatUtils.formatDurationHMS(info.timeSinceLastActivity())));
 278             }
 279
 280             builder.followerInfoList(followerInfoList);
 281         }
 282
 283         sender().tell(builder.build(), self());
 284
 285     }
 286
 287     private void handleBehaviorChange(BehaviorStateHolder oldBehaviorState, RaftActorBehavior currentBehavior) {
 288         RaftActorBehavior oldBehavior = oldBehaviorState.getBehavior();
 289
 290         if (oldBehavior != currentBehavior){
 291             onStateChanged();
 292         }
 293
 294         String oldBehaviorLeaderId = oldBehavior == null ? null : oldBehaviorState.getLeaderId();
 295         String oldBehaviorStateName = oldBehavior == null ? null : oldBehavior.state().name();
 296
 297         // it can happen that the state has not changed but the leader has changed.
 298         Optional<ActorRef> roleChangeNotifier = getRoleChangeNotifier();
 299         if(!Objects.equal(oldBehaviorLeaderId, currentBehavior.getLeaderId())) {
 300             if(roleChangeNotifier.isPresent()) {
 301                 roleChangeNotifier.get().tell(new LeaderStateChanged(getId(), currentBehavior.getLeaderId()), getSelf());
 302             }
 303
 304             onLeaderChanged(oldBehaviorLeaderId, currentBehavior.getLeaderId());
 305         }
 306
 307         if (roleChangeNotifier.isPresent() &&
 308                 (oldBehavior == null || (oldBehavior.state() != currentBehavior.state()))) {
 309             roleChangeNotifier.get().tell(new RoleChanged(getId(), oldBehaviorStateName ,
 310                     currentBehavior.state().name()), getSelf());
 311         }
 312     }
 313
 314     /**
 315      * When a derived RaftActor needs to persist something it must call
 316      * persistData.
 317      *
 318      * @param clientActor
 319      * @param identifier
 320      * @param data
 321      */
 322     protected void persistData(final ActorRef clientActor, final String identifier,
 323         final Payload data) {
 324
 325         ReplicatedLogEntry replicatedLogEntry = new ReplicatedLogImplEntry(
 326             context.getReplicatedLog().lastIndex() + 1,
 327             context.getTermInformation().getCurrentTerm(), data);
 328
 329         if(LOG.isDebugEnabled()) {
 330             LOG.debug("{}: Persist data {}", persistenceId(), replicatedLogEntry);
 331         }
 332
 333         final RaftActorContext raftContext = getRaftActorContext();
 334
 335         replicatedLog().appendAndPersist(replicatedLogEntry, new Procedure<ReplicatedLogEntry>() {
 336             @Override
 337             public void apply(ReplicatedLogEntry replicatedLogEntry) throws Exception {
 338                 if(!hasFollowers()){
 339                     // Increment the Commit Index and the Last Applied values
 340                     raftContext.setCommitIndex(replicatedLogEntry.getIndex());
 341                     raftContext.setLastApplied(replicatedLogEntry.getIndex());
 342
 343                     // Apply the state immediately
 344                     applyState(clientActor, identifier, data);
 345
 346                     // Send a ApplyJournalEntries message so that we write the fact that we applied
 347                     // the state to durable storage
 348                     self().tell(new ApplyJournalEntries(replicatedLogEntry.getIndex()), self());
 349
 350                     context.getSnapshotManager().trimLog(context.getLastApplied(), currentBehavior);
 351
 352                 } else if (clientActor != null) {
 353                     // Send message for replication
 354                     currentBehavior.handleMessage(getSelf(),
 355                             new Replicate(clientActor, identifier, replicatedLogEntry));
 356                 }
 357             }
 358         });
 359     }
 360
 361     private ReplicatedLog replicatedLog() {
 362         return context.getReplicatedLog();
 363     }
 364
 365     protected String getId() {
 366         return context.getId();
 367     }
 368
 369     @VisibleForTesting
 370     void setCurrentBehavior(RaftActorBehavior behavior) {
 371         currentBehavior.setDelegate(behavior);
 372     }
 373
 374     protected RaftActorBehavior getCurrentBehavior() {
 375         return currentBehavior.getDelegate();
 376     }
 377
 378     /**
 379      * Derived actors can call the isLeader method to check if the current
 380      * RaftActor is the Leader or not
 381      *
 382      * @return true it this RaftActor is a Leader false otherwise
 383      */
 384     protected boolean isLeader() {
 385         return context.getId().equals(currentBehavior.getLeaderId());
 386     }
 387
 388     /**
 389      * Derived actor can call getLeader if they need a reference to the Leader.
 390      * This would be useful for example in forwarding a request to an actor
 391      * which is the leader
 392      *
 393      * @return A reference to the leader if known, null otherwise
 394      */
 395     protected ActorSelection getLeader(){
 396         String leaderAddress = getLeaderAddress();
 397
 398         if(leaderAddress == null){
 399             return null;
 400         }
 401
 402         return context.actorSelection(leaderAddress);
 403     }
 404
 405     /**
 406      *
 407      * @return the current leader's id
 408      */
 409     protected String getLeaderId(){
 410         return currentBehavior.getLeaderId();
 411     }
 412
 413     protected RaftState getRaftState() {
 414         return currentBehavior.state();
 415     }
 416
 417     protected ReplicatedLogEntry getLastLogEntry() {
 418         return replicatedLog().last();
 419     }
 420
 421     protected Long getCurrentTerm(){
 422         return context.getTermInformation().getCurrentTerm();
 423     }
 424
 425     protected Long getCommitIndex(){
 426         return context.getCommitIndex();
 427     }
 428
 429     protected Long getLastApplied(){
 430         return context.getLastApplied();
 431     }
 432
 433     protected RaftActorContext getRaftActorContext() {
 434         return context;
 435     }
 436
 437     protected void updateConfigParams(ConfigParams configParams) {
 438         context.setConfigParams(configParams);
 439     }
 440
 441     public final DataPersistenceProvider persistence() {
 442         return delegatingPersistenceProvider.getDelegate();
 443     }
 444
 445     public void setPersistence(DataPersistenceProvider provider) {
 446         delegatingPersistenceProvider.setDelegate(provider);
 447     }
 448
 449     protected void setPersistence(boolean persistent) {
 450         if(persistent) {
 451             setPersistence(new PersistentDataProvider(this));
 452         } else {
 453             setPersistence(new NonPersistentDataProvider() {
 454                 /**
 455                  * The way snapshotting works is,
 456                  * <ol>
 457                  * <li> RaftActor calls createSnapshot on the Shard
 458                  * <li> Shard sends a CaptureSnapshotReply and RaftActor then calls saveSnapshot
 459                  * <li> When saveSnapshot is invoked on the akka-persistence API it uses the SnapshotStore to save
 460                  * the snapshot. The SnapshotStore sends SaveSnapshotSuccess or SaveSnapshotFailure. When the
 461                  * RaftActor gets SaveSnapshot success it commits the snapshot to the in-memory journal. This
 462                  * commitSnapshot is mimicking what is done in SaveSnapshotSuccess.
 463                  * </ol>
 464                  */
 465                 @Override
 466                 public void saveSnapshot(Object o) {
 467                     // Make saving Snapshot successful
 468                     // Committing the snapshot here would end up calling commit in the creating state which would
 469                     // be a state violation. That's why now we send a message to commit the snapshot.
 470                     self().tell(RaftActorSnapshotMessageSupport.COMMIT_SNAPSHOT, self());
 471                 }
 472             });
 473         }
 474     }
 475
 476     /**
 477      * setPeerAddress sets the address of a known peer at a later time.
 478      * <p>
 479      * This is to account for situations where a we know that a peer
 480      * exists but we do not know an address up-front. This may also be used in
 481      * situations where a known peer starts off in a different location and we
 482      * need to change it's address
 483      * <p>
 484      * Note that if the peerId does not match the list of peers passed to
 485      * this actor during construction an IllegalStateException will be thrown.
 486      *
 487      * @param peerId
 488      * @param peerAddress
 489      */
 490     protected void setPeerAddress(String peerId, String peerAddress){
 491         context.setPeerAddress(peerId, peerAddress);
 492     }
 493
 494     /**
 495      * The applyState method will be called by the RaftActor when some data
 496      * needs to be applied to the actor's state
 497      *
 498      * @param clientActor A reference to the client who sent this message. This
 499      *                    is the same reference that was passed to persistData
 500      *                    by the derived actor. clientActor may be null when
 501      *                    the RaftActor is behaving as a follower or during
 502      *                    recovery.
 503      * @param identifier  The identifier of the persisted data. This is also
 504      *                    the same identifier that was passed to persistData by
 505      *                    the derived actor. identifier may be null when
 506      *                    the RaftActor is behaving as a follower or during
 507      *                    recovery
 508      * @param data        A piece of data that was persisted by the persistData call.
 509      *                    This should NEVER be null.
 510      */
 511     protected abstract void applyState(ActorRef clientActor, String identifier,
 512         Object data);
 513
 514     /**
 515      * Returns the RaftActorRecoveryCohort to participate in persistence recovery.
 516      */
 517     @Nonnull
 518     protected abstract RaftActorRecoveryCohort getRaftActorRecoveryCohort();
 519
 520     /**
 521      * This method is called when recovery is complete.
 522      */
 523     protected abstract void onRecoveryComplete();
 524
 525     /**
 526      * Returns the RaftActorSnapshotCohort to participate in persistence recovery.
 527      */
 528     @Nonnull
 529     protected abstract RaftActorSnapshotCohort getRaftActorSnapshotCohort();
 530
 531     /**
 532      * This method will be called by the RaftActor when the state of the
 533      * RaftActor changes. The derived actor can then use methods like
 534      * isLeader or getLeader to do something useful
 535      */
 536     protected abstract void onStateChanged();
 537
 538     /**
 539      * Notifier Actor for this RaftActor to notify when a role change happens
 540      * @return ActorRef - ActorRef of the notifier or Optional.absent if none.
 541      */
 542     protected abstract Optional<ActorRef> getRoleChangeNotifier();
 543
 544     protected void onLeaderChanged(String oldLeader, String newLeader){};
 545
 546     private String getLeaderAddress(){
 547         if(isLeader()){
 548             return getSelf().path().toString();
 549         }
 550         String leaderId = currentBehavior.getLeaderId();
 551         if (leaderId == null) {
 552             return null;
 553         }
 554         String peerAddress = context.getPeerAddress(leaderId);
 555         if(LOG.isDebugEnabled()) {
 556             LOG.debug("{}: getLeaderAddress leaderId = {} peerAddress = {}",
 557                     persistenceId(), leaderId, peerAddress);
 558         }
 559
 560         return peerAddress;
 561     }
 562
 563     protected boolean hasFollowers(){
 564         return getRaftActorContext().hasFollowers();
 565     }
 566
 567     /**
 568      * @deprecated Deprecated in favor of {@link org.opendaylight.controller.cluster.raft.base.messages.DeleteEntriesTest}
 569      *             whose type for fromIndex is long instead of int. This class was kept for backwards
 570      *             compatibility with Helium.
 571      */
 572     @Deprecated
 573     static class DeleteEntries implements Serializable {
 574         private static final long serialVersionUID = 1L;
 575         private final int fromIndex;
 576
 577         public DeleteEntries(int fromIndex) {
 578             this.fromIndex = fromIndex;
 579         }
 580
 581         public int getFromIndex() {
 582             return fromIndex;
 583         }
 584     }
 585
 586     static class UpdateElectionTerm implements Serializable {
 587         private static final long serialVersionUID = 1L;
 588         private final long currentTerm;
 589         private final String votedFor;
 590
 591         public UpdateElectionTerm(long currentTerm, String votedFor) {
 592             this.currentTerm = currentTerm;
 593             this.votedFor = votedFor;
 594         }
 595
 596         public long getCurrentTerm() {
 597             return currentTerm;
 598         }
 599
 600         public String getVotedFor() {
 601             return votedFor;
 602         }
 603     }
 604
 605     private static class BehaviorStateHolder {
 606         private RaftActorBehavior behavior;
 607         private String leaderId;
 608
 609         void init(RaftActorBehavior behavior) {
 610             this.behavior = behavior;
 611             this.leaderId = behavior != null ? behavior.getLeaderId() : null;
 612         }
 613
 614         RaftActorBehavior getBehavior() {
 615             return behavior;
 616         }
 617
 618         String getLeaderId() {
 619             return leaderId;
 620         }
 621     }
 622 }