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.ImmutableMap;
  20 import com.google.common.collect.Lists;
  21 import java.io.Serializable;
  22 import java.util.Collection;
  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()), LOG);
 128
 129         context.setReplicatedLog(ReplicatedLogImpl.newInstance(context, delegatingPersistenceProvider, currentBehavior));
 130     }
 131
 132     @Override
 133     public void preStart() throws Exception {
 134         LOG.info("Starting recovery for {} with journal batch size {}", persistenceId(),
 135                 context.getConfigParams().getJournalRecoveryLogBatchSize());
 136
 137         super.preStart();
 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(delegatingPersistenceProvider, context, currentBehavior,
 180                 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(snapshotSupport == null) {
 196             snapshotSupport = new RaftActorSnapshotMessageSupport(delegatingPersistenceProvider, context,
 197                     currentBehavior, getRaftActorSnapshotCohort(), self());
 198         }
 199
 200         boolean handled = snapshotSupport.handleSnapshotMessage(message);
 201         if(handled) {
 202             return;
 203         }
 204
 205         if (message instanceof ApplyState){
 206             ApplyState applyState = (ApplyState) message;
 207
 208             long elapsedTime = (System.nanoTime() - applyState.getStartTime());
 209             if(elapsedTime >= APPLY_STATE_DELAY_THRESHOLD_IN_NANOS){
 210                 LOG.warn("ApplyState took more time than expected. Elapsed Time = {} ms ApplyState = {}",
 211                         TimeUnit.NANOSECONDS.toMillis(elapsedTime), applyState);
 212             }
 213
 214             if(LOG.isDebugEnabled()) {
 215                 LOG.debug("{}: Applying state for log index {} data {}",
 216                     persistenceId(), applyState.getReplicatedLogEntry().getIndex(),
 217                     applyState.getReplicatedLogEntry().getData());
 218             }
 219
 220             applyState(applyState.getClientActor(), applyState.getIdentifier(),
 221                 applyState.getReplicatedLogEntry().getData());
 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 {
 239             reusableBehaviorStateHolder.init(getCurrentBehavior());
 240
 241             setCurrentBehavior(currentBehavior.handleMessage(getSender(), message));
 242
 243             handleBehaviorChange(reusableBehaviorStateHolder, getCurrentBehavior());
 244         }
 245     }
 246
 247     private void onGetOnDemandRaftStats() {
 248         // Debugging message to retrieve raft stats.
 249
 250         OnDemandRaftState.Builder builder = OnDemandRaftState.builder()
 251                 .commitIndex(context.getCommitIndex())
 252                 .currentTerm(context.getTermInformation().getCurrentTerm())
 253                 .inMemoryJournalDataSize(replicatedLog().dataSize())
 254                 .inMemoryJournalLogSize(replicatedLog().size())
 255                 .isSnapshotCaptureInitiated(context.getSnapshotManager().isCapturing())
 256                 .lastApplied(context.getLastApplied())
 257                 .lastIndex(replicatedLog().lastIndex())
 258                 .lastTerm(replicatedLog().lastTerm())
 259                 .leader(getLeaderId())
 260                 .raftState(currentBehavior.state().toString())
 261                 .replicatedToAllIndex(currentBehavior.getReplicatedToAllIndex())
 262                 .snapshotIndex(replicatedLog().getSnapshotIndex())
 263                 .snapshotTerm(replicatedLog().getSnapshotTerm())
 264                 .votedFor(context.getTermInformation().getVotedFor())
 265                 .peerAddresses(ImmutableMap.copyOf(context.getPeerAddresses()));
 266
 267         ReplicatedLogEntry lastLogEntry = getLastLogEntry();
 268         if (lastLogEntry != null) {
 269             builder.lastLogIndex(lastLogEntry.getIndex());
 270             builder.lastLogTerm(lastLogEntry.getTerm());
 271         }
 272
 273         if(getCurrentBehavior() instanceof AbstractLeader) {
 274             AbstractLeader leader = (AbstractLeader)getCurrentBehavior();
 275             Collection<String> followerIds = leader.getFollowerIds();
 276             List<FollowerInfo> followerInfoList = Lists.newArrayListWithCapacity(followerIds.size());
 277             for(String id: followerIds) {
 278                 final FollowerLogInformation info = leader.getFollower(id);
 279                 followerInfoList.add(new FollowerInfo(id, info.getNextIndex(), info.getMatchIndex(),
 280                         info.isFollowerActive(), DurationFormatUtils.formatDurationHMS(info.timeSinceLastActivity())));
 281             }
 282
 283             builder.followerInfoList(followerInfoList);
 284         }
 285
 286         sender().tell(builder.build(), self());
 287
 288     }
 289
 290     private void handleBehaviorChange(BehaviorStateHolder oldBehaviorState, RaftActorBehavior currentBehavior) {
 291         RaftActorBehavior oldBehavior = oldBehaviorState.getBehavior();
 292
 293         if (oldBehavior != currentBehavior){
 294             onStateChanged();
 295         }
 296
 297         String oldBehaviorLeaderId = oldBehavior == null ? null : oldBehaviorState.getLeaderId();
 298         String oldBehaviorStateName = oldBehavior == null ? null : oldBehavior.state().name();
 299
 300         // it can happen that the state has not changed but the leader has changed.
 301         Optional<ActorRef> roleChangeNotifier = getRoleChangeNotifier();
 302         if(!Objects.equal(oldBehaviorLeaderId, currentBehavior.getLeaderId())) {
 303             if(roleChangeNotifier.isPresent()) {
 304                 roleChangeNotifier.get().tell(new LeaderStateChanged(getId(), currentBehavior.getLeaderId()), getSelf());
 305             }
 306
 307             onLeaderChanged(oldBehaviorLeaderId, currentBehavior.getLeaderId());
 308         }
 309
 310         if (roleChangeNotifier.isPresent() &&
 311                 (oldBehavior == null || (oldBehavior.state() != currentBehavior.state()))) {
 312             roleChangeNotifier.get().tell(new RoleChanged(getId(), oldBehaviorStateName ,
 313                     currentBehavior.state().name()), getSelf());
 314         }
 315     }
 316
 317     /**
 318      * When a derived RaftActor needs to persist something it must call
 319      * persistData.
 320      *
 321      * @param clientActor
 322      * @param identifier
 323      * @param data
 324      */
 325     protected void persistData(final ActorRef clientActor, final String identifier,
 326         final Payload data) {
 327
 328         ReplicatedLogEntry replicatedLogEntry = new ReplicatedLogImplEntry(
 329             context.getReplicatedLog().lastIndex() + 1,
 330             context.getTermInformation().getCurrentTerm(), data);
 331
 332         if(LOG.isDebugEnabled()) {
 333             LOG.debug("{}: Persist data {}", persistenceId(), replicatedLogEntry);
 334         }
 335
 336         final RaftActorContext raftContext = getRaftActorContext();
 337
 338         replicatedLog().appendAndPersist(replicatedLogEntry, new Procedure<ReplicatedLogEntry>() {
 339             @Override
 340             public void apply(ReplicatedLogEntry replicatedLogEntry) throws Exception {
 341                 if(!hasFollowers()){
 342                     // Increment the Commit Index and the Last Applied values
 343                     raftContext.setCommitIndex(replicatedLogEntry.getIndex());
 344                     raftContext.setLastApplied(replicatedLogEntry.getIndex());
 345
 346                     // Apply the state immediately
 347                     applyState(clientActor, identifier, data);
 348
 349                     // Send a ApplyJournalEntries message so that we write the fact that we applied
 350                     // the state to durable storage
 351                     self().tell(new ApplyJournalEntries(replicatedLogEntry.getIndex()), self());
 352
 353                     context.getSnapshotManager().trimLog(context.getLastApplied(), currentBehavior);
 354
 355                 } else if (clientActor != null) {
 356                     // Send message for replication
 357                     currentBehavior.handleMessage(getSelf(),
 358                             new Replicate(clientActor, identifier, replicatedLogEntry));
 359                 }
 360             }
 361         });
 362     }
 363
 364     private ReplicatedLog replicatedLog() {
 365         return context.getReplicatedLog();
 366     }
 367
 368     protected String getId() {
 369         return context.getId();
 370     }
 371
 372     @VisibleForTesting
 373     void setCurrentBehavior(RaftActorBehavior behavior) {
 374         currentBehavior.setDelegate(behavior);
 375     }
 376
 377     protected RaftActorBehavior getCurrentBehavior() {
 378         return currentBehavior.getDelegate();
 379     }
 380
 381     /**
 382      * Derived actors can call the isLeader method to check if the current
 383      * RaftActor is the Leader or not
 384      *
 385      * @return true it this RaftActor is a Leader false otherwise
 386      */
 387     protected boolean isLeader() {
 388         return context.getId().equals(currentBehavior.getLeaderId());
 389     }
 390
 391     /**
 392      * Derived actor can call getLeader if they need a reference to the Leader.
 393      * This would be useful for example in forwarding a request to an actor
 394      * which is the leader
 395      *
 396      * @return A reference to the leader if known, null otherwise
 397      */
 398     protected ActorSelection getLeader(){
 399         String leaderAddress = getLeaderAddress();
 400
 401         if(leaderAddress == null){
 402             return null;
 403         }
 404
 405         return context.actorSelection(leaderAddress);
 406     }
 407
 408     /**
 409      *
 410      * @return the current leader's id
 411      */
 412     protected String getLeaderId(){
 413         return currentBehavior.getLeaderId();
 414     }
 415
 416     protected RaftState getRaftState() {
 417         return currentBehavior.state();
 418     }
 419
 420     protected ReplicatedLogEntry getLastLogEntry() {
 421         return replicatedLog().last();
 422     }
 423
 424     protected Long getCurrentTerm(){
 425         return context.getTermInformation().getCurrentTerm();
 426     }
 427
 428     protected Long getCommitIndex(){
 429         return context.getCommitIndex();
 430     }
 431
 432     protected Long getLastApplied(){
 433         return context.getLastApplied();
 434     }
 435
 436     protected RaftActorContext getRaftActorContext() {
 437         return context;
 438     }
 439
 440     protected void updateConfigParams(ConfigParams configParams) {
 441         context.setConfigParams(configParams);
 442     }
 443
 444     public final DataPersistenceProvider persistence() {
 445         return delegatingPersistenceProvider.getDelegate();
 446     }
 447
 448     public void setPersistence(DataPersistenceProvider provider) {
 449         delegatingPersistenceProvider.setDelegate(provider);
 450     }
 451
 452     protected void setPersistence(boolean persistent) {
 453         if(persistent) {
 454             setPersistence(new PersistentDataProvider(this));
 455         } else {
 456             setPersistence(new NonPersistentDataProvider() {
 457                 /**
 458                  * The way snapshotting works is,
 459                  * <ol>
 460                  * <li> RaftActor calls createSnapshot on the Shard
 461                  * <li> Shard sends a CaptureSnapshotReply and RaftActor then calls saveSnapshot
 462                  * <li> When saveSnapshot is invoked on the akka-persistence API it uses the SnapshotStore to save
 463                  * the snapshot. The SnapshotStore sends SaveSnapshotSuccess or SaveSnapshotFailure. When the
 464                  * RaftActor gets SaveSnapshot success it commits the snapshot to the in-memory journal. This
 465                  * commitSnapshot is mimicking what is done in SaveSnapshotSuccess.
 466                  * </ol>
 467                  */
 468                 @Override
 469                 public void saveSnapshot(Object o) {
 470                     // Make saving Snapshot successful
 471                     // Committing the snapshot here would end up calling commit in the creating state which would
 472                     // be a state violation. That's why now we send a message to commit the snapshot.
 473                     self().tell(RaftActorSnapshotMessageSupport.COMMIT_SNAPSHOT, self());
 474                 }
 475             });
 476         }
 477     }
 478
 479     /**
 480      * setPeerAddress sets the address of a known peer at a later time.
 481      * <p>
 482      * This is to account for situations where a we know that a peer
 483      * exists but we do not know an address up-front. This may also be used in
 484      * situations where a known peer starts off in a different location and we
 485      * need to change it's address
 486      * <p>
 487      * Note that if the peerId does not match the list of peers passed to
 488      * this actor during construction an IllegalStateException will be thrown.
 489      *
 490      * @param peerId
 491      * @param peerAddress
 492      */
 493     protected void setPeerAddress(String peerId, String peerAddress){
 494         context.setPeerAddress(peerId, peerAddress);
 495     }
 496
 497     /**
 498      * The applyState method will be called by the RaftActor when some data
 499      * needs to be applied to the actor's state
 500      *
 501      * @param clientActor A reference to the client who sent this message. This
 502      *                    is the same reference that was passed to persistData
 503      *                    by the derived actor. clientActor may be null when
 504      *                    the RaftActor is behaving as a follower or during
 505      *                    recovery.
 506      * @param identifier  The identifier of the persisted data. This is also
 507      *                    the same identifier that was passed to persistData by
 508      *                    the derived actor. identifier may be null when
 509      *                    the RaftActor is behaving as a follower or during
 510      *                    recovery
 511      * @param data        A piece of data that was persisted by the persistData call.
 512      *                    This should NEVER be null.
 513      */
 514     protected abstract void applyState(ActorRef clientActor, String identifier,
 515         Object data);
 516
 517     /**
 518      * Returns the RaftActorRecoveryCohort to participate in persistence recovery.
 519      */
 520     @Nonnull
 521     protected abstract RaftActorRecoveryCohort getRaftActorRecoveryCohort();
 522
 523     /**
 524      * This method is called when recovery is complete.
 525      */
 526     protected abstract void onRecoveryComplete();
 527
 528     /**
 529      * Returns the RaftActorSnapshotCohort to participate in persistence recovery.
 530      */
 531     @Nonnull
 532     protected abstract RaftActorSnapshotCohort getRaftActorSnapshotCohort();
 533
 534     /**
 535      * This method will be called by the RaftActor when the state of the
 536      * RaftActor changes. The derived actor can then use methods like
 537      * isLeader or getLeader to do something useful
 538      */
 539     protected abstract void onStateChanged();
 540
 541     /**
 542      * Notifier Actor for this RaftActor to notify when a role change happens
 543      * @return ActorRef - ActorRef of the notifier or Optional.absent if none.
 544      */
 545     protected abstract Optional<ActorRef> getRoleChangeNotifier();
 546
 547     protected void onLeaderChanged(String oldLeader, String newLeader){};
 548
 549     private String getLeaderAddress(){
 550         if(isLeader()){
 551             return getSelf().path().toString();
 552         }
 553         String leaderId = currentBehavior.getLeaderId();
 554         if (leaderId == null) {
 555             return null;
 556         }
 557         String peerAddress = context.getPeerAddress(leaderId);
 558         if(LOG.isDebugEnabled()) {
 559             LOG.debug("{}: getLeaderAddress leaderId = {} peerAddress = {}",
 560                     persistenceId(), leaderId, peerAddress);
 561         }
 562
 563         return peerAddress;
 564     }
 565
 566     protected boolean hasFollowers(){
 567         return getRaftActorContext().hasFollowers();
 568     }
 569
 570     static class DeleteEntries implements Serializable {
 571         private static final long serialVersionUID = 1L;
 572         private final int fromIndex;
 573
 574         public DeleteEntries(int fromIndex) {
 575             this.fromIndex = fromIndex;
 576         }
 577
 578         public int getFromIndex() {
 579             return fromIndex;
 580         }
 581     }
 582
 583     static class UpdateElectionTerm implements Serializable {
 584         private static final long serialVersionUID = 1L;
 585         private final long currentTerm;
 586         private final String votedFor;
 587
 588         public UpdateElectionTerm(long currentTerm, String votedFor) {
 589             this.currentTerm = currentTerm;
 590             this.votedFor = votedFor;
 591         }
 592
 593         public long getCurrentTerm() {
 594             return currentTerm;
 595         }
 596
 597         public String getVotedFor() {
 598             return votedFor;
 599         }
 600     }
 601
 602     private static class BehaviorStateHolder {
 603         private RaftActorBehavior behavior;
 604         private String leaderId;
 605
 606         void init(RaftActorBehavior behavior) {
 607             this.behavior = behavior;
 608             this.leaderId = behavior != null ? behavior.getLeaderId() : null;
 609         }
 610
 611         RaftActorBehavior getBehavior() {
 612             return behavior;
 613         }
 614
 615         String getLeaderId() {
 616             return leaderId;
 617         }
 618     }
 619 }