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  *
   4  * This program and the accompanying materials are made available under the
   5  * terms of the Eclipse Public License v1.0 which accompanies this distribution,
   6  * and is available at http://www.eclipse.org/legal/epl-v10.html
   7  */
   8
   9 package org.opendaylight.controller.cluster.raft;
  10
  11 import akka.actor.ActorRef;
  12 import akka.actor.ActorSelection;
  13 import akka.japi.Procedure;
  14 import akka.persistence.SnapshotSelectionCriteria;
  15 import com.google.common.annotations.VisibleForTesting;
  16 import com.google.common.base.Objects;
  17 import com.google.common.base.Optional;
  18 import com.google.common.collect.ImmutableMap;
  19 import com.google.common.collect.Lists;
  20 import java.io.Serializable;
  21 import java.util.Collection;
  22 import java.util.List;
  23 import java.util.Map;
  24 import java.util.concurrent.TimeUnit;
  25 import javax.annotation.Nonnull;
  26 import org.apache.commons.lang3.time.DurationFormatUtils;
  27 import org.opendaylight.controller.cluster.DataPersistenceProvider;
  28 import org.opendaylight.controller.cluster.DelegatingPersistentDataProvider;
  29 import org.opendaylight.controller.cluster.NonPersistentDataProvider;
  30 import org.opendaylight.controller.cluster.PersistentDataProvider;
  31 import org.opendaylight.controller.cluster.common.actor.AbstractUntypedPersistentActor;
  32 import org.opendaylight.controller.cluster.notifications.LeaderStateChanged;
  33 import org.opendaylight.controller.cluster.notifications.RoleChanged;
  34 import org.opendaylight.controller.cluster.raft.base.messages.ApplyJournalEntries;
  35 import org.opendaylight.controller.cluster.raft.base.messages.ApplyState;
  36 import org.opendaylight.controller.cluster.raft.base.messages.Replicate;
  37 import org.opendaylight.controller.cluster.raft.behaviors.AbstractLeader;
  38 import org.opendaylight.controller.cluster.raft.behaviors.DelegatingRaftActorBehavior;
  39 import org.opendaylight.controller.cluster.raft.behaviors.Follower;
  40 import org.opendaylight.controller.cluster.raft.behaviors.RaftActorBehavior;
  41 import org.opendaylight.controller.cluster.raft.client.messages.FindLeader;
  42 import org.opendaylight.controller.cluster.raft.client.messages.FindLeaderReply;
  43 import org.opendaylight.controller.cluster.raft.client.messages.FollowerInfo;
  44 import org.opendaylight.controller.cluster.raft.client.messages.GetOnDemandRaftState;
  45 import org.opendaylight.controller.cluster.raft.client.messages.OnDemandRaftState;
  46 import org.opendaylight.controller.cluster.raft.protobuff.client.messages.Payload;
  47 import org.slf4j.Logger;
  48 import org.slf4j.LoggerFactory;
  49
  50 /**
  51  * RaftActor encapsulates a state machine that needs to be kept synchronized
  52  * in a cluster. It implements the RAFT algorithm as described in the paper
  53  * <a href='https://ramcloud.stanford.edu/wiki/download/attachments/11370504/raft.pdf'>
  54  * In Search of an Understandable Consensus Algorithm</a>
  55  * <p/>
  56  * RaftActor has 3 states and each state has a certain behavior associated
  57  * with it. A Raft actor can behave as,
  58  * <ul>
  59  * <li> A Leader </li>
  60  * <li> A Follower (or) </li>
  61  * <li> A Candidate </li>
  62  * </ul>
  63  * <p/>
  64  * <p/>
  65  * A RaftActor MUST be a Leader in order to accept requests from clients to
  66  * change the state of it's encapsulated state machine. Once a RaftActor becomes
  67  * a Leader it is also responsible for ensuring that all followers ultimately
  68  * have the same log and therefore the same state machine as itself.
  69  * <p/>
  70  * <p/>
  71  * The current behavior of a RaftActor determines how election for leadership
  72  * is initiated and how peer RaftActors react to request for votes.
  73  * <p/>
  74  * <p/>
  75  * Each RaftActor also needs to know the current election term. It uses this
  76  * information for a couple of things. One is to simply figure out who it
  77  * voted for in the last election. Another is to figure out if the message
  78  * it received to update it's state is stale.
  79  * <p/>
  80  * <p/>
  81  * The RaftActor uses akka-persistence to store it's replicated log.
  82  * Furthermore through it's behaviors a Raft Actor determines
  83  * <p/>
  84  * <ul>
  85  * <li> when a log entry should be persisted </li>
  86  * <li> when a log entry should be applied to the state machine (and) </li>
  87  * <li> when a snapshot should be saved </li>
  88  * </ul>
  89  */
  90 public abstract class RaftActor extends AbstractUntypedPersistentActor {
  91
  92     private static final long APPLY_STATE_DELAY_THRESHOLD_IN_NANOS = TimeUnit.MILLISECONDS.toNanos(50L); // 50 millis
  93
  94     protected final Logger LOG = LoggerFactory.getLogger(getClass());
  95
  96     /**
  97      * The current state determines the current behavior of a RaftActor
  98      * A Raft Actor always starts off in the Follower State
  99      */
 100     private final DelegatingRaftActorBehavior currentBehavior = new DelegatingRaftActorBehavior();
 101
 102     /**
 103      * This context should NOT be passed directly to any other actor it is
 104      * only to be consumed by the RaftActorBehaviors
 105      */
 106     private final RaftActorContextImpl context;
 107
 108     private final DelegatingPersistentDataProvider delegatingPersistenceProvider = new DelegatingPersistentDataProvider(null);
 109
 110     private RaftActorRecoverySupport raftRecovery;
 111
 112     private RaftActorSnapshotMessageSupport snapshotSupport;
 113
 114     private final BehaviorStateHolder reusableBehaviorStateHolder = new BehaviorStateHolder();
 115
 116     public RaftActor(String id, Map<String, String> peerAddresses) {
 117         this(id, peerAddresses, Optional.<ConfigParams>absent());
 118     }
 119
 120     public RaftActor(String id, Map<String, String> peerAddresses,
 121          Optional<ConfigParams> configParams) {
 122
 123         context = new RaftActorContextImpl(this.getSelf(),
 124             this.getContext(), id, new ElectionTermImpl(delegatingPersistenceProvider, id, LOG),
 125             -1, -1, peerAddresses,
 126             (configParams.isPresent() ? configParams.get(): new DefaultConfigParamsImpl()), LOG);
 127
 128         context.setReplicatedLog(ReplicatedLogImpl.newInstance(context, delegatingPersistenceProvider, currentBehavior));
 129     }
 130
 131     @Override
 132     public void preStart() throws Exception {
 133         LOG.info("Starting recovery for {} with journal batch size {}", persistenceId(),
 134                 context.getConfigParams().getJournalRecoveryLogBatchSize());
 135
 136         super.preStart();
 137     }
 138
 139     @Override
 140     public void postStop() {
 141         if(currentBehavior.getDelegate() != null) {
 142             try {
 143                 currentBehavior.close();
 144             } catch (Exception e) {
 145                 LOG.debug("{}: Error closing behavior {}", persistenceId(), currentBehavior.state());
 146             }
 147         }
 148
 149         super.postStop();
 150     }
 151
 152     @Override
 153     public void handleRecover(Object message) {
 154         if(raftRecovery == null) {
 155             raftRecovery = new RaftActorRecoverySupport(delegatingPersistenceProvider, context, currentBehavior,
 156                     getRaftActorRecoveryCohort());
 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 void initializeBehavior(){
 179         changeCurrentBehavior(new Follower(context));
 180     }
 181
 182     protected void changeCurrentBehavior(RaftActorBehavior newBehavior){
 183         reusableBehaviorStateHolder.init(getCurrentBehavior());
 184         setCurrentBehavior(newBehavior);
 185         handleBehaviorChange(reusableBehaviorStateHolder, getCurrentBehavior());
 186     }
 187
 188     @Override
 189     public void handleCommand(Object message) {
 190         if(snapshotSupport == null) {
 191             snapshotSupport = new RaftActorSnapshotMessageSupport(delegatingPersistenceProvider, context,
 192                     currentBehavior, getRaftActorSnapshotCohort(), self());
 193         }
 194
 195         boolean handled = snapshotSupport.handleSnapshotMessage(message);
 196         if(handled) {
 197             return;
 198         }
 199
 200         if (message instanceof ApplyState){
 201             ApplyState applyState = (ApplyState) message;
 202
 203             long elapsedTime = (System.nanoTime() - applyState.getStartTime());
 204             if(elapsedTime >= APPLY_STATE_DELAY_THRESHOLD_IN_NANOS){
 205                 LOG.warn("ApplyState took more time than expected. Elapsed Time = {} ms ApplyState = {}",
 206                         TimeUnit.NANOSECONDS.toMillis(elapsedTime), applyState);
 207             }
 208
 209             if(LOG.isDebugEnabled()) {
 210                 LOG.debug("{}: Applying state for log index {} data {}",
 211                     persistenceId(), applyState.getReplicatedLogEntry().getIndex(),
 212                     applyState.getReplicatedLogEntry().getData());
 213             }
 214
 215             applyState(applyState.getClientActor(), applyState.getIdentifier(),
 216                 applyState.getReplicatedLogEntry().getData());
 217
 218         } else if (message instanceof ApplyJournalEntries){
 219             ApplyJournalEntries applyEntries = (ApplyJournalEntries) message;
 220             if(LOG.isDebugEnabled()) {
 221                 LOG.debug("{}: Persisting ApplyLogEntries with index={}", persistenceId(), applyEntries.getToIndex());
 222             }
 223
 224             persistence().persist(applyEntries, NoopProcedure.instance());
 225
 226         } else if (message instanceof FindLeader) {
 227             getSender().tell(
 228                 new FindLeaderReply(getLeaderAddress()),
 229                 getSelf()
 230             );
 231         } else if(message instanceof GetOnDemandRaftState) {
 232             onGetOnDemandRaftStats();
 233         } else {
 234             reusableBehaviorStateHolder.init(getCurrentBehavior());
 235
 236             setCurrentBehavior(currentBehavior.handleMessage(getSender(), message));
 237
 238             handleBehaviorChange(reusableBehaviorStateHolder, getCurrentBehavior());
 239         }
 240     }
 241
 242     private void onGetOnDemandRaftStats() {
 243         // Debugging message to retrieve raft stats.
 244
 245         OnDemandRaftState.Builder builder = OnDemandRaftState.builder()
 246                 .commitIndex(context.getCommitIndex())
 247                 .currentTerm(context.getTermInformation().getCurrentTerm())
 248                 .inMemoryJournalDataSize(replicatedLog().dataSize())
 249                 .inMemoryJournalLogSize(replicatedLog().size())
 250                 .isSnapshotCaptureInitiated(context.getSnapshotManager().isCapturing())
 251                 .lastApplied(context.getLastApplied())
 252                 .lastIndex(replicatedLog().lastIndex())
 253                 .lastTerm(replicatedLog().lastTerm())
 254                 .leader(getLeaderId())
 255                 .raftState(currentBehavior.state().toString())
 256                 .replicatedToAllIndex(currentBehavior.getReplicatedToAllIndex())
 257                 .snapshotIndex(replicatedLog().getSnapshotIndex())
 258                 .snapshotTerm(replicatedLog().getSnapshotTerm())
 259                 .votedFor(context.getTermInformation().getVotedFor())
 260                 .peerAddresses(ImmutableMap.copyOf(context.getPeerAddresses()));
 261
 262         ReplicatedLogEntry lastLogEntry = getLastLogEntry();
 263         if (lastLogEntry != null) {
 264             builder.lastLogIndex(lastLogEntry.getIndex());
 265             builder.lastLogTerm(lastLogEntry.getTerm());
 266         }
 267
 268         if(getCurrentBehavior() instanceof AbstractLeader) {
 269             AbstractLeader leader = (AbstractLeader)getCurrentBehavior();
 270             Collection<String> followerIds = leader.getFollowerIds();
 271             List<FollowerInfo> followerInfoList = Lists.newArrayListWithCapacity(followerIds.size());
 272             for(String id: followerIds) {
 273                 final FollowerLogInformation info = leader.getFollower(id);
 274                 followerInfoList.add(new FollowerInfo(id, info.getNextIndex(), info.getMatchIndex(),
 275                         info.isFollowerActive(), DurationFormatUtils.formatDurationHMS(info.timeSinceLastActivity())));
 276             }
 277
 278             builder.followerInfoList(followerInfoList);
 279         }
 280
 281         sender().tell(builder.build(), self());
 282
 283     }
 284
 285     private void handleBehaviorChange(BehaviorStateHolder oldBehaviorState, RaftActorBehavior currentBehavior) {
 286         RaftActorBehavior oldBehavior = oldBehaviorState.getBehavior();
 287
 288         if (oldBehavior != currentBehavior){
 289             onStateChanged();
 290         }
 291
 292         String oldBehaviorLeaderId = oldBehavior == null ? null : oldBehaviorState.getLeaderId();
 293         String oldBehaviorStateName = oldBehavior == null ? null : oldBehavior.state().name();
 294
 295         // it can happen that the state has not changed but the leader has changed.
 296         Optional<ActorRef> roleChangeNotifier = getRoleChangeNotifier();
 297         if(!Objects.equal(oldBehaviorLeaderId, currentBehavior.getLeaderId())) {
 298             if(roleChangeNotifier.isPresent()) {
 299                 roleChangeNotifier.get().tell(new LeaderStateChanged(getId(), currentBehavior.getLeaderId()), getSelf());
 300             }
 301
 302             onLeaderChanged(oldBehaviorLeaderId, currentBehavior.getLeaderId());
 303         }
 304
 305         if (roleChangeNotifier.isPresent() &&
 306                 (oldBehavior == null || (oldBehavior.state() != currentBehavior.state()))) {
 307             roleChangeNotifier.get().tell(new RoleChanged(getId(), oldBehaviorStateName ,
 308                     currentBehavior.state().name()), getSelf());
 309         }
 310     }
 311
 312     /**
 313      * When a derived RaftActor needs to persist something it must call
 314      * persistData.
 315      *
 316      * @param clientActor
 317      * @param identifier
 318      * @param data
 319      */
 320     protected void persistData(final ActorRef clientActor, final String identifier,
 321         final Payload data) {
 322
 323         ReplicatedLogEntry replicatedLogEntry = new ReplicatedLogImplEntry(
 324             context.getReplicatedLog().lastIndex() + 1,
 325             context.getTermInformation().getCurrentTerm(), data);
 326
 327         if(LOG.isDebugEnabled()) {
 328             LOG.debug("{}: Persist data {}", persistenceId(), replicatedLogEntry);
 329         }
 330
 331         final RaftActorContext raftContext = getRaftActorContext();
 332
 333         replicatedLog().appendAndPersist(replicatedLogEntry, new Procedure<ReplicatedLogEntry>() {
 334             @Override
 335             public void apply(ReplicatedLogEntry replicatedLogEntry) throws Exception {
 336                 if(!hasFollowers()){
 337                     // Increment the Commit Index and the Last Applied values
 338                     raftContext.setCommitIndex(replicatedLogEntry.getIndex());
 339                     raftContext.setLastApplied(replicatedLogEntry.getIndex());
 340
 341                     // Apply the state immediately
 342                     applyState(clientActor, identifier, data);
 343
 344                     // Send a ApplyJournalEntries message so that we write the fact that we applied
 345                     // the state to durable storage
 346                     self().tell(new ApplyJournalEntries(replicatedLogEntry.getIndex()), self());
 347
 348                     context.getSnapshotManager().trimLog(context.getLastApplied(), currentBehavior);
 349
 350                 } else if (clientActor != null) {
 351                     // Send message for replication
 352                     currentBehavior.handleMessage(getSelf(),
 353                             new Replicate(clientActor, identifier, replicatedLogEntry));
 354                 }
 355             }
 356         });
 357     }
 358
 359     private ReplicatedLog replicatedLog() {
 360         return context.getReplicatedLog();
 361     }
 362
 363     protected String getId() {
 364         return context.getId();
 365     }
 366
 367     @VisibleForTesting
 368     void setCurrentBehavior(RaftActorBehavior behavior) {
 369         currentBehavior.setDelegate(behavior);
 370     }
 371
 372     protected RaftActorBehavior getCurrentBehavior() {
 373         return currentBehavior.getDelegate();
 374     }
 375
 376     /**
 377      * Derived actors can call the isLeader method to check if the current
 378      * RaftActor is the Leader or not
 379      *
 380      * @return true it this RaftActor is a Leader false otherwise
 381      */
 382     protected boolean isLeader() {
 383         return context.getId().equals(currentBehavior.getLeaderId());
 384     }
 385
 386     /**
 387      * Derived actor can call getLeader if they need a reference to the Leader.
 388      * This would be useful for example in forwarding a request to an actor
 389      * which is the leader
 390      *
 391      * @return A reference to the leader if known, null otherwise
 392      */
 393     protected ActorSelection getLeader(){
 394         String leaderAddress = getLeaderAddress();
 395
 396         if(leaderAddress == null){
 397             return null;
 398         }
 399
 400         return context.actorSelection(leaderAddress);
 401     }
 402
 403     /**
 404      *
 405      * @return the current leader's id
 406      */
 407     protected String getLeaderId(){
 408         return currentBehavior.getLeaderId();
 409     }
 410
 411     protected RaftState getRaftState() {
 412         return currentBehavior.state();
 413     }
 414
 415     protected ReplicatedLogEntry getLastLogEntry() {
 416         return replicatedLog().last();
 417     }
 418
 419     protected Long getCurrentTerm(){
 420         return context.getTermInformation().getCurrentTerm();
 421     }
 422
 423     protected Long getCommitIndex(){
 424         return context.getCommitIndex();
 425     }
 426
 427     protected Long getLastApplied(){
 428         return context.getLastApplied();
 429     }
 430
 431     protected RaftActorContext getRaftActorContext() {
 432         return context;
 433     }
 434
 435     protected void updateConfigParams(ConfigParams configParams) {
 436         context.setConfigParams(configParams);
 437     }
 438
 439     public final DataPersistenceProvider persistence() {
 440         return delegatingPersistenceProvider.getDelegate();
 441     }
 442
 443     public void setPersistence(DataPersistenceProvider provider) {
 444         delegatingPersistenceProvider.setDelegate(provider);
 445     }
 446
 447     protected void setPersistence(boolean persistent) {
 448         if(persistent) {
 449             setPersistence(new PersistentDataProvider(this));
 450         } else {
 451             setPersistence(new NonPersistentDataProvider() {
 452                 /**
 453                  * The way snapshotting works is,
 454                  * <ol>
 455                  * <li> RaftActor calls createSnapshot on the Shard
 456                  * <li> Shard sends a CaptureSnapshotReply and RaftActor then calls saveSnapshot
 457                  * <li> When saveSnapshot is invoked on the akka-persistence API it uses the SnapshotStore to save
 458                  * the snapshot. The SnapshotStore sends SaveSnapshotSuccess or SaveSnapshotFailure. When the
 459                  * RaftActor gets SaveSnapshot success it commits the snapshot to the in-memory journal. This
 460                  * commitSnapshot is mimicking what is done in SaveSnapshotSuccess.
 461                  * </ol>
 462                  */
 463                 @Override
 464                 public void saveSnapshot(Object o) {
 465                     // Make saving Snapshot successful
 466                     // Committing the snapshot here would end up calling commit in the creating state which would
 467                     // be a state violation. That's why now we send a message to commit the snapshot.
 468                     self().tell(RaftActorSnapshotMessageSupport.COMMIT_SNAPSHOT, self());
 469                 }
 470             });
 471         }
 472     }
 473
 474     /**
 475      * setPeerAddress sets the address of a known peer at a later time.
 476      * <p>
 477      * This is to account for situations where a we know that a peer
 478      * exists but we do not know an address up-front. This may also be used in
 479      * situations where a known peer starts off in a different location and we
 480      * need to change it's address
 481      * <p>
 482      * Note that if the peerId does not match the list of peers passed to
 483      * this actor during construction an IllegalStateException will be thrown.
 484      *
 485      * @param peerId
 486      * @param peerAddress
 487      */
 488     protected void setPeerAddress(String peerId, String peerAddress){
 489         context.setPeerAddress(peerId, peerAddress);
 490     }
 491
 492     /**
 493      * The applyState method will be called by the RaftActor when some data
 494      * needs to be applied to the actor's state
 495      *
 496      * @param clientActor A reference to the client who sent this message. This
 497      *                    is the same reference that was passed to persistData
 498      *                    by the derived actor. clientActor may be null when
 499      *                    the RaftActor is behaving as a follower or during
 500      *                    recovery.
 501      * @param identifier  The identifier of the persisted data. This is also
 502      *                    the same identifier that was passed to persistData by
 503      *                    the derived actor. identifier may be null when
 504      *                    the RaftActor is behaving as a follower or during
 505      *                    recovery
 506      * @param data        A piece of data that was persisted by the persistData call.
 507      *                    This should NEVER be null.
 508      */
 509     protected abstract void applyState(ActorRef clientActor, String identifier,
 510         Object data);
 511
 512     /**
 513      * Returns the RaftActorRecoveryCohort to participate in persistence recovery.
 514      */
 515     @Nonnull
 516     protected abstract RaftActorRecoveryCohort getRaftActorRecoveryCohort();
 517
 518     /**
 519      * This method is called when recovery is complete.
 520      */
 521     protected abstract void onRecoveryComplete();
 522
 523     /**
 524      * Returns the RaftActorSnapshotCohort to participate in persistence recovery.
 525      */
 526     @Nonnull
 527     protected abstract RaftActorSnapshotCohort getRaftActorSnapshotCohort();
 528
 529     /**
 530      * This method will be called by the RaftActor when the state of the
 531      * RaftActor changes. The derived actor can then use methods like
 532      * isLeader or getLeader to do something useful
 533      */
 534     protected abstract void onStateChanged();
 535
 536     /**
 537      * Notifier Actor for this RaftActor to notify when a role change happens
 538      * @return ActorRef - ActorRef of the notifier or Optional.absent if none.
 539      */
 540     protected abstract Optional<ActorRef> getRoleChangeNotifier();
 541
 542     protected void onLeaderChanged(String oldLeader, String newLeader){};
 543
 544     private String getLeaderAddress(){
 545         if(isLeader()){
 546             return getSelf().path().toString();
 547         }
 548         String leaderId = currentBehavior.getLeaderId();
 549         if (leaderId == null) {
 550             return null;
 551         }
 552         String peerAddress = context.getPeerAddress(leaderId);
 553         if(LOG.isDebugEnabled()) {
 554             LOG.debug("{}: getLeaderAddress leaderId = {} peerAddress = {}",
 555                     persistenceId(), leaderId, peerAddress);
 556         }
 557
 558         return peerAddress;
 559     }
 560
 561     protected boolean hasFollowers(){
 562         return getRaftActorContext().hasFollowers();
 563     }
 564
 565     static class DeleteEntries implements Serializable {
 566         private static final long serialVersionUID = 1L;
 567         private final int fromIndex;
 568
 569         public DeleteEntries(int fromIndex) {
 570             this.fromIndex = fromIndex;
 571         }
 572
 573         public int getFromIndex() {
 574             return fromIndex;
 575         }
 576     }
 577
 578     static class UpdateElectionTerm implements Serializable {
 579         private static final long serialVersionUID = 1L;
 580         private final long currentTerm;
 581         private final String votedFor;
 582
 583         public UpdateElectionTerm(long currentTerm, String votedFor) {
 584             this.currentTerm = currentTerm;
 585             this.votedFor = votedFor;
 586         }
 587
 588         public long getCurrentTerm() {
 589             return currentTerm;
 590         }
 591
 592         public String getVotedFor() {
 593             return votedFor;
 594         }
 595     }
 596
 597     private static class BehaviorStateHolder {
 598         private RaftActorBehavior behavior;
 599         private String leaderId;
 600
 601         void init(RaftActorBehavior behavior) {
 602             this.behavior = behavior;
 603             this.leaderId = behavior != null ? behavior.getLeaderId() : null;
 604         }
 605
 606         RaftActorBehavior getBehavior() {
 607             return behavior;
 608         }
 609
 610         String getLeaderId() {
 611             return leaderId;
 612         }
 613     }
 614 }