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()),
 128             delegatingPersistenceProvider, LOG);
 129
 130         context.setReplicatedLog(ReplicatedLogImpl.newInstance(context, delegatingPersistenceProvider, 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(delegatingPersistenceProvider, context, currentBehavior,
 183                 getRaftActorRecoveryCohort());
 184     }
 185
 186     protected void initializeBehavior(){
 187         changeCurrentBehavior(new Follower(context));
 188     }
 189
 190     protected void changeCurrentBehavior(RaftActorBehavior newBehavior){
 191         reusableBehaviorStateHolder.init(getCurrentBehavior());
 192         setCurrentBehavior(newBehavior);
 193         handleBehaviorChange(reusableBehaviorStateHolder, getCurrentBehavior());
 194     }
 195
 196     @Override
 197     public void handleCommand(Object message) {
 198         if (message instanceof ApplyState){
 199             ApplyState applyState = (ApplyState) message;
 200
 201             long elapsedTime = (System.nanoTime() - applyState.getStartTime());
 202             if(elapsedTime >= APPLY_STATE_DELAY_THRESHOLD_IN_NANOS){
 203                 LOG.warn("ApplyState took more time than expected. Elapsed Time = {} ms ApplyState = {}",
 204                         TimeUnit.NANOSECONDS.toMillis(elapsedTime), applyState);
 205             }
 206
 207             if(LOG.isDebugEnabled()) {
 208                 LOG.debug("{}: Applying state for log index {} data {}",
 209                     persistenceId(), applyState.getReplicatedLogEntry().getIndex(),
 210                     applyState.getReplicatedLogEntry().getData());
 211             }
 212
 213             applyState(applyState.getClientActor(), applyState.getIdentifier(),
 214                 applyState.getReplicatedLogEntry().getData());
 215
 216         } else if (message instanceof ApplyJournalEntries){
 217             ApplyJournalEntries applyEntries = (ApplyJournalEntries) message;
 218             if(LOG.isDebugEnabled()) {
 219                 LOG.debug("{}: Persisting ApplyLogEntries with index={}", persistenceId(), applyEntries.getToIndex());
 220             }
 221
 222             persistence().persist(applyEntries, NoopProcedure.instance());
 223
 224         } else if (message instanceof FindLeader) {
 225             getSender().tell(
 226                 new FindLeaderReply(getLeaderAddress()),
 227                 getSelf()
 228             );
 229         } else if(message instanceof GetOnDemandRaftState) {
 230             onGetOnDemandRaftStats();
 231         } else if(!snapshotSupport.handleSnapshotMessage(message)) {
 232             reusableBehaviorStateHolder.init(getCurrentBehavior());
 233
 234             setCurrentBehavior(currentBehavior.handleMessage(getSender(), message));
 235
 236             handleBehaviorChange(reusableBehaviorStateHolder, getCurrentBehavior());
 237         }
 238     }
 239
 240     protected RaftActorSnapshotMessageSupport newRaftActorSnapshotMessageSupport() {
 241         return new RaftActorSnapshotMessageSupport(delegatingPersistenceProvider, context,
 242                 currentBehavior, getRaftActorSnapshotCohort());
 243     }
 244
 245     private void onGetOnDemandRaftStats() {
 246         // Debugging message to retrieve raft stats.
 247
 248         OnDemandRaftState.Builder builder = OnDemandRaftState.builder()
 249                 .commitIndex(context.getCommitIndex())
 250                 .currentTerm(context.getTermInformation().getCurrentTerm())
 251                 .inMemoryJournalDataSize(replicatedLog().dataSize())
 252                 .inMemoryJournalLogSize(replicatedLog().size())
 253                 .isSnapshotCaptureInitiated(context.getSnapshotManager().isCapturing())
 254                 .lastApplied(context.getLastApplied())
 255                 .lastIndex(replicatedLog().lastIndex())
 256                 .lastTerm(replicatedLog().lastTerm())
 257                 .leader(getLeaderId())
 258                 .raftState(currentBehavior.state().toString())
 259                 .replicatedToAllIndex(currentBehavior.getReplicatedToAllIndex())
 260                 .snapshotIndex(replicatedLog().getSnapshotIndex())
 261                 .snapshotTerm(replicatedLog().getSnapshotTerm())
 262                 .votedFor(context.getTermInformation().getVotedFor())
 263                 .peerAddresses(ImmutableMap.copyOf(context.getPeerAddresses()));
 264
 265         ReplicatedLogEntry lastLogEntry = getLastLogEntry();
 266         if (lastLogEntry != null) {
 267             builder.lastLogIndex(lastLogEntry.getIndex());
 268             builder.lastLogTerm(lastLogEntry.getTerm());
 269         }
 270
 271         if(getCurrentBehavior() instanceof AbstractLeader) {
 272             AbstractLeader leader = (AbstractLeader)getCurrentBehavior();
 273             Collection<String> followerIds = leader.getFollowerIds();
 274             List<FollowerInfo> followerInfoList = Lists.newArrayListWithCapacity(followerIds.size());
 275             for(String id: followerIds) {
 276                 final FollowerLogInformation info = leader.getFollower(id);
 277                 followerInfoList.add(new FollowerInfo(id, info.getNextIndex(), info.getMatchIndex(),
 278                         info.isFollowerActive(), DurationFormatUtils.formatDurationHMS(info.timeSinceLastActivity())));
 279             }
 280
 281             builder.followerInfoList(followerInfoList);
 282         }
 283
 284         sender().tell(builder.build(), self());
 285
 286     }
 287
 288     private void handleBehaviorChange(BehaviorStateHolder oldBehaviorState, RaftActorBehavior currentBehavior) {
 289         RaftActorBehavior oldBehavior = oldBehaviorState.getBehavior();
 290
 291         if (oldBehavior != currentBehavior){
 292             onStateChanged();
 293         }
 294
 295         String oldBehaviorLeaderId = oldBehavior == null ? null : oldBehaviorState.getLeaderId();
 296         String oldBehaviorStateName = oldBehavior == null ? null : oldBehavior.state().name();
 297
 298         // it can happen that the state has not changed but the leader has changed.
 299         Optional<ActorRef> roleChangeNotifier = getRoleChangeNotifier();
 300         if(!Objects.equal(oldBehaviorLeaderId, currentBehavior.getLeaderId())) {
 301             if(roleChangeNotifier.isPresent()) {
 302                 roleChangeNotifier.get().tell(new LeaderStateChanged(getId(), currentBehavior.getLeaderId()), getSelf());
 303             }
 304
 305             onLeaderChanged(oldBehaviorLeaderId, currentBehavior.getLeaderId());
 306         }
 307
 308         if (roleChangeNotifier.isPresent() &&
 309                 (oldBehavior == null || (oldBehavior.state() != currentBehavior.state()))) {
 310             roleChangeNotifier.get().tell(new RoleChanged(getId(), oldBehaviorStateName ,
 311                     currentBehavior.state().name()), getSelf());
 312         }
 313     }
 314
 315     /**
 316      * When a derived RaftActor needs to persist something it must call
 317      * persistData.
 318      *
 319      * @param clientActor
 320      * @param identifier
 321      * @param data
 322      */
 323     protected void persistData(final ActorRef clientActor, final String identifier,
 324         final Payload data) {
 325
 326         ReplicatedLogEntry replicatedLogEntry = new ReplicatedLogImplEntry(
 327             context.getReplicatedLog().lastIndex() + 1,
 328             context.getTermInformation().getCurrentTerm(), data);
 329
 330         if(LOG.isDebugEnabled()) {
 331             LOG.debug("{}: Persist data {}", persistenceId(), replicatedLogEntry);
 332         }
 333
 334         final RaftActorContext raftContext = getRaftActorContext();
 335
 336         replicatedLog().appendAndPersist(replicatedLogEntry, new Procedure<ReplicatedLogEntry>() {
 337             @Override
 338             public void apply(ReplicatedLogEntry replicatedLogEntry) throws Exception {
 339                 if(!hasFollowers()){
 340                     // Increment the Commit Index and the Last Applied values
 341                     raftContext.setCommitIndex(replicatedLogEntry.getIndex());
 342                     raftContext.setLastApplied(replicatedLogEntry.getIndex());
 343
 344                     // Apply the state immediately
 345                     applyState(clientActor, identifier, data);
 346
 347                     // Send a ApplyJournalEntries message so that we write the fact that we applied
 348                     // the state to durable storage
 349                     self().tell(new ApplyJournalEntries(replicatedLogEntry.getIndex()), self());
 350
 351                     context.getSnapshotManager().trimLog(context.getLastApplied(), currentBehavior);
 352
 353                 } else if (clientActor != null) {
 354                     // Send message for replication
 355                     currentBehavior.handleMessage(getSelf(),
 356                             new Replicate(clientActor, identifier, replicatedLogEntry));
 357                 }
 358             }
 359         });
 360     }
 361
 362     private ReplicatedLog replicatedLog() {
 363         return context.getReplicatedLog();
 364     }
 365
 366     protected String getId() {
 367         return context.getId();
 368     }
 369
 370     @VisibleForTesting
 371     void setCurrentBehavior(RaftActorBehavior behavior) {
 372         currentBehavior.setDelegate(behavior);
 373     }
 374
 375     protected RaftActorBehavior getCurrentBehavior() {
 376         return currentBehavior.getDelegate();
 377     }
 378
 379     /**
 380      * Derived actors can call the isLeader method to check if the current
 381      * RaftActor is the Leader or not
 382      *
 383      * @return true it this RaftActor is a Leader false otherwise
 384      */
 385     protected boolean isLeader() {
 386         return context.getId().equals(currentBehavior.getLeaderId());
 387     }
 388
 389     /**
 390      * Derived actor can call getLeader if they need a reference to the Leader.
 391      * This would be useful for example in forwarding a request to an actor
 392      * which is the leader
 393      *
 394      * @return A reference to the leader if known, null otherwise
 395      */
 396     protected ActorSelection getLeader(){
 397         String leaderAddress = getLeaderAddress();
 398
 399         if(leaderAddress == null){
 400             return null;
 401         }
 402
 403         return context.actorSelection(leaderAddress);
 404     }
 405
 406     /**
 407      *
 408      * @return the current leader's id
 409      */
 410     protected String getLeaderId(){
 411         return currentBehavior.getLeaderId();
 412     }
 413
 414     protected RaftState getRaftState() {
 415         return currentBehavior.state();
 416     }
 417
 418     protected ReplicatedLogEntry getLastLogEntry() {
 419         return replicatedLog().last();
 420     }
 421
 422     protected Long getCurrentTerm(){
 423         return context.getTermInformation().getCurrentTerm();
 424     }
 425
 426     protected Long getCommitIndex(){
 427         return context.getCommitIndex();
 428     }
 429
 430     protected Long getLastApplied(){
 431         return context.getLastApplied();
 432     }
 433
 434     protected RaftActorContext getRaftActorContext() {
 435         return context;
 436     }
 437
 438     protected void updateConfigParams(ConfigParams configParams) {
 439         context.setConfigParams(configParams);
 440     }
 441
 442     public final DataPersistenceProvider persistence() {
 443         return delegatingPersistenceProvider.getDelegate();
 444     }
 445
 446     public void setPersistence(DataPersistenceProvider provider) {
 447         delegatingPersistenceProvider.setDelegate(provider);
 448     }
 449
 450     protected void setPersistence(boolean persistent) {
 451         if(persistent) {
 452             setPersistence(new PersistentDataProvider(this));
 453         } else {
 454             setPersistence(new NonPersistentDataProvider() {
 455                 /**
 456                  * The way snapshotting works is,
 457                  * <ol>
 458                  * <li> RaftActor calls createSnapshot on the Shard
 459                  * <li> Shard sends a CaptureSnapshotReply and RaftActor then calls saveSnapshot
 460                  * <li> When saveSnapshot is invoked on the akka-persistence API it uses the SnapshotStore to save
 461                  * the snapshot. The SnapshotStore sends SaveSnapshotSuccess or SaveSnapshotFailure. When the
 462                  * RaftActor gets SaveSnapshot success it commits the snapshot to the in-memory journal. This
 463                  * commitSnapshot is mimicking what is done in SaveSnapshotSuccess.
 464                  * </ol>
 465                  */
 466                 @Override
 467                 public void saveSnapshot(Object o) {
 468                     // Make saving Snapshot successful
 469                     // Committing the snapshot here would end up calling commit in the creating state which would
 470                     // be a state violation. That's why now we send a message to commit the snapshot.
 471                     self().tell(RaftActorSnapshotMessageSupport.COMMIT_SNAPSHOT, self());
 472                 }
 473             });
 474         }
 475     }
 476
 477     /**
 478      * setPeerAddress sets the address of a known peer at a later time.
 479      * <p>
 480      * This is to account for situations where a we know that a peer
 481      * exists but we do not know an address up-front. This may also be used in
 482      * situations where a known peer starts off in a different location and we
 483      * need to change it's address
 484      * <p>
 485      * Note that if the peerId does not match the list of peers passed to
 486      * this actor during construction an IllegalStateException will be thrown.
 487      *
 488      * @param peerId
 489      * @param peerAddress
 490      */
 491     protected void setPeerAddress(String peerId, String peerAddress){
 492         context.setPeerAddress(peerId, peerAddress);
 493     }
 494
 495     /**
 496      * The applyState method will be called by the RaftActor when some data
 497      * needs to be applied to the actor's state
 498      *
 499      * @param clientActor A reference to the client who sent this message. This
 500      *                    is the same reference that was passed to persistData
 501      *                    by the derived actor. clientActor may be null when
 502      *                    the RaftActor is behaving as a follower or during
 503      *                    recovery.
 504      * @param identifier  The identifier of the persisted data. This is also
 505      *                    the same identifier that was passed to persistData by
 506      *                    the derived actor. identifier may be null when
 507      *                    the RaftActor is behaving as a follower or during
 508      *                    recovery
 509      * @param data        A piece of data that was persisted by the persistData call.
 510      *                    This should NEVER be null.
 511      */
 512     protected abstract void applyState(ActorRef clientActor, String identifier,
 513         Object data);
 514
 515     /**
 516      * Returns the RaftActorRecoveryCohort to participate in persistence recovery.
 517      */
 518     @Nonnull
 519     protected abstract RaftActorRecoveryCohort getRaftActorRecoveryCohort();
 520
 521     /**
 522      * This method is called when recovery is complete.
 523      */
 524     protected abstract void onRecoveryComplete();
 525
 526     /**
 527      * Returns the RaftActorSnapshotCohort to participate in persistence recovery.
 528      */
 529     @Nonnull
 530     protected abstract RaftActorSnapshotCohort getRaftActorSnapshotCohort();
 531
 532     /**
 533      * This method will be called by the RaftActor when the state of the
 534      * RaftActor changes. The derived actor can then use methods like
 535      * isLeader or getLeader to do something useful
 536      */
 537     protected abstract void onStateChanged();
 538
 539     /**
 540      * Notifier Actor for this RaftActor to notify when a role change happens
 541      * @return ActorRef - ActorRef of the notifier or Optional.absent if none.
 542      */
 543     protected abstract Optional<ActorRef> getRoleChangeNotifier();
 544
 545     protected void onLeaderChanged(String oldLeader, String newLeader){};
 546
 547     private String getLeaderAddress(){
 548         if(isLeader()){
 549             return getSelf().path().toString();
 550         }
 551         String leaderId = currentBehavior.getLeaderId();
 552         if (leaderId == null) {
 553             return null;
 554         }
 555         String peerAddress = context.getPeerAddress(leaderId);
 556         if(LOG.isDebugEnabled()) {
 557             LOG.debug("{}: getLeaderAddress leaderId = {} peerAddress = {}",
 558                     persistenceId(), leaderId, peerAddress);
 559         }
 560
 561         return peerAddress;
 562     }
 563
 564     protected boolean hasFollowers(){
 565         return getRaftActorContext().hasFollowers();
 566     }
 567
 568     /**
 569      * @deprecated Deprecated in favor of {@link org.opendaylight.controller.cluster.raft.base.messages.DeleteEntriesTest}
 570      *             whose type for fromIndex is long instead of int. This class was kept for backwards
 571      *             compatibility with Helium.
 572      */
 573     @Deprecated
 574     static class DeleteEntries implements Serializable {
 575         private static final long serialVersionUID = 1L;
 576         private final int fromIndex;
 577
 578         public DeleteEntries(int fromIndex) {
 579             this.fromIndex = fromIndex;
 580         }
 581
 582         public int getFromIndex() {
 583             return fromIndex;
 584         }
 585     }
 586
 587     static class UpdateElectionTerm implements Serializable {
 588         private static final long serialVersionUID = 1L;
 589         private final long currentTerm;
 590         private final String votedFor;
 591
 592         public UpdateElectionTerm(long currentTerm, String votedFor) {
 593             this.currentTerm = currentTerm;
 594             this.votedFor = votedFor;
 595         }
 596
 597         public long getCurrentTerm() {
 598             return currentTerm;
 599         }
 600
 601         public String getVotedFor() {
 602             return votedFor;
 603         }
 604     }
 605
 606     private static class BehaviorStateHolder {
 607         private RaftActorBehavior behavior;
 608         private String leaderId;
 609
 610         void init(RaftActorBehavior behavior) {
 611             this.behavior = behavior;
 612             this.leaderId = behavior != null ? behavior.getLeaderId() : null;
 613         }
 614
 615         RaftActorBehavior getBehavior() {
 616             return behavior;
 617         }
 618
 619         String getLeaderId() {
 620             return leaderId;
 621         }
 622     }
 623 }