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 com.google.common.annotations.VisibleForTesting;
  16 import com.google.common.base.Objects;
  17 import com.google.common.base.Optional;
  18 import com.google.common.base.Supplier;
  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.InitiateCaptureSnapshot;
  38 import org.opendaylight.controller.cluster.raft.base.messages.Replicate;
  39 import org.opendaylight.controller.cluster.raft.base.messages.SwitchBehavior;
  40 import org.opendaylight.controller.cluster.raft.behaviors.AbstractLeader;
  41 import org.opendaylight.controller.cluster.raft.behaviors.DelegatingRaftActorBehavior;
  42 import org.opendaylight.controller.cluster.raft.behaviors.Follower;
  43 import org.opendaylight.controller.cluster.raft.behaviors.RaftActorBehavior;
  44 import org.opendaylight.controller.cluster.raft.client.messages.FindLeader;
  45 import org.opendaylight.controller.cluster.raft.client.messages.FindLeaderReply;
  46 import org.opendaylight.controller.cluster.raft.client.messages.FollowerInfo;
  47 import org.opendaylight.controller.cluster.raft.client.messages.GetOnDemandRaftState;
  48 import org.opendaylight.controller.cluster.raft.client.messages.OnDemandRaftState;
  49 import org.opendaylight.controller.cluster.raft.protobuff.client.messages.Payload;
  50 import org.slf4j.Logger;
  51 import org.slf4j.LoggerFactory;
  52
  53 /**
  54  * RaftActor encapsulates a state machine that needs to be kept synchronized
  55  * in a cluster. It implements the RAFT algorithm as described in the paper
  56  * <a href='https://ramcloud.stanford.edu/wiki/download/attachments/11370504/raft.pdf'>
  57  * In Search of an Understandable Consensus Algorithm</a>
  58  * <p/>
  59  * RaftActor has 3 states and each state has a certain behavior associated
  60  * with it. A Raft actor can behave as,
  61  * <ul>
  62  * <li> A Leader </li>
  63  * <li> A Follower (or) </li>
  64  * <li> A Candidate </li>
  65  * </ul>
  66  * <p/>
  67  * <p/>
  68  * A RaftActor MUST be a Leader in order to accept requests from clients to
  69  * change the state of it's encapsulated state machine. Once a RaftActor becomes
  70  * a Leader it is also responsible for ensuring that all followers ultimately
  71  * have the same log and therefore the same state machine as itself.
  72  * <p/>
  73  * <p/>
  74  * The current behavior of a RaftActor determines how election for leadership
  75  * is initiated and how peer RaftActors react to request for votes.
  76  * <p/>
  77  * <p/>
  78  * Each RaftActor also needs to know the current election term. It uses this
  79  * information for a couple of things. One is to simply figure out who it
  80  * voted for in the last election. Another is to figure out if the message
  81  * it received to update it's state is stale.
  82  * <p/>
  83  * <p/>
  84  * The RaftActor uses akka-persistence to store it's replicated log.
  85  * Furthermore through it's behaviors a Raft Actor determines
  86  * <p/>
  87  * <ul>
  88  * <li> when a log entry should be persisted </li>
  89  * <li> when a log entry should be applied to the state machine (and) </li>
  90  * <li> when a snapshot should be saved </li>
  91  * </ul>
  92  */
  93 public abstract class RaftActor extends AbstractUntypedPersistentActor {
  94
  95     private static final long APPLY_STATE_DELAY_THRESHOLD_IN_NANOS = TimeUnit.MILLISECONDS.toNanos(50L); // 50 millis
  96
  97     protected final Logger LOG = LoggerFactory.getLogger(getClass());
  98
  99     /**
 100      * The current state determines the current behavior of a RaftActor
 101      * A Raft Actor always starts off in the Follower State
 102      */
 103     private final DelegatingRaftActorBehavior currentBehavior = new DelegatingRaftActorBehavior();
 104
 105     /**
 106      * This context should NOT be passed directly to any other actor it is
 107      * only to be consumed by the RaftActorBehaviors
 108      */
 109     private final RaftActorContextImpl context;
 110
 111     private final DelegatingPersistentDataProvider delegatingPersistenceProvider = new DelegatingPersistentDataProvider(null);
 112
 113     private final PersistentDataProvider persistentProvider;
 114
 115     private RaftActorRecoverySupport raftRecovery;
 116
 117     private RaftActorSnapshotMessageSupport snapshotSupport;
 118
 119     private final BehaviorStateHolder reusableBehaviorStateHolder = new BehaviorStateHolder();
 120
 121     private final SwitchBehaviorSupplier reusableSwitchBehaviorSupplier = new SwitchBehaviorSupplier();
 122
 123     private RaftActorServerConfigurationSupport serverConfigurationSupport;
 124
 125     public RaftActor(String id, Map<String, String> peerAddresses,
 126          Optional<ConfigParams> configParams, short payloadVersion) {
 127
 128         persistentProvider = new PersistentDataProvider(this);
 129         context = new RaftActorContextImpl(this.getSelf(),
 130             this.getContext(), id, new ElectionTermImpl(persistentProvider, id, LOG),
 131             -1, -1, peerAddresses,
 132             (configParams.isPresent() ? configParams.get(): new DefaultConfigParamsImpl()),
 133             delegatingPersistenceProvider, LOG);
 134
 135         context.setPayloadVersion(payloadVersion);
 136         context.setReplicatedLog(ReplicatedLogImpl.newInstance(context, currentBehavior));
 137     }
 138
 139     @Override
 140     public void preStart() throws Exception {
 141         LOG.info("Starting recovery for {} with journal batch size {}", persistenceId(),
 142                 context.getConfigParams().getJournalRecoveryLogBatchSize());
 143
 144         super.preStart();
 145
 146         snapshotSupport = newRaftActorSnapshotMessageSupport();
 147         serverConfigurationSupport = new RaftActorServerConfigurationSupport(getRaftActorContext());
 148     }
 149
 150     @Override
 151     public void postStop() {
 152         if(currentBehavior.getDelegate() != null) {
 153             try {
 154                 currentBehavior.close();
 155             } catch (Exception e) {
 156                 LOG.debug("{}: Error closing behavior {}", persistenceId(), currentBehavior.state());
 157             }
 158         }
 159
 160         super.postStop();
 161     }
 162
 163     @Override
 164     public void handleRecover(Object message) {
 165         if(raftRecovery == null) {
 166             raftRecovery = newRaftActorRecoverySupport();
 167         }
 168
 169         boolean recoveryComplete = raftRecovery.handleRecoveryMessage(message, persistentProvider);
 170         if(recoveryComplete) {
 171             onRecoveryComplete();
 172
 173             initializeBehavior();
 174
 175             raftRecovery = null;
 176         }
 177     }
 178
 179     protected RaftActorRecoverySupport newRaftActorRecoverySupport() {
 180         return new RaftActorRecoverySupport(context, currentBehavior, 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(final Object message) {
 195         if (message instanceof ApplyState){
 196             ApplyState applyState = (ApplyState) message;
 197
 198             boolean result = serverConfigurationSupport.handleMessage(message, this, getSender());
 199             if(result){
 200                 return;
 201             }
 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             if (!hasFollowers()) {
 219                 // for single node, the capture should happen after the apply state
 220                 // as we delete messages from the persistent journal which have made it to the snapshot
 221                 // capturing the snapshot before applying makes the persistent journal and snapshot out of sync
 222                 // and recovery shows data missing
 223                 context.getReplicatedLog().captureSnapshotIfReady(applyState.getReplicatedLogEntry());
 224
 225                 context.getSnapshotManager().trimLog(context.getLastApplied(), currentBehavior);
 226             }
 227
 228         } else if (message instanceof ApplyJournalEntries){
 229             ApplyJournalEntries applyEntries = (ApplyJournalEntries) message;
 230             if(LOG.isDebugEnabled()) {
 231                 LOG.debug("{}: Persisting ApplyLogEntries with index={}", persistenceId(), applyEntries.getToIndex());
 232             }
 233
 234             persistence().persist(applyEntries, NoopProcedure.instance());
 235
 236         } else if (message instanceof FindLeader) {
 237             getSender().tell(
 238                 new FindLeaderReply(getLeaderAddress()),
 239                 getSelf()
 240             );
 241         } else if(message instanceof GetOnDemandRaftState) {
 242             onGetOnDemandRaftStats();
 243         } else if(message instanceof InitiateCaptureSnapshot) {
 244             captureSnapshot();
 245         } else if(message instanceof SwitchBehavior){
 246             switchBehavior(((SwitchBehavior) message));
 247         } else if(!snapshotSupport.handleSnapshotMessage(message) &&
 248                 !serverConfigurationSupport.handleMessage(message, this, getSender())) {
 249             switchBehavior(reusableSwitchBehaviorSupplier.handleMessage(getSender(), message));
 250         }
 251     }
 252
 253     private void switchBehavior(SwitchBehavior message) {
 254         if(!getRaftActorContext().getRaftPolicy().automaticElectionsEnabled()) {
 255             RaftState newState = message.getNewState();
 256             if( newState == RaftState.Leader || newState == RaftState.Follower) {
 257                 switchBehavior(reusableSwitchBehaviorSupplier.handleMessage(getSender(), message));
 258                 getRaftActorContext().getTermInformation().updateAndPersist(message.getNewTerm(), "");
 259             } else {
 260                 LOG.warn("Switching to behavior : {} - not supported", newState);
 261             }
 262         }
 263     }
 264
 265     private void switchBehavior(Supplier<RaftActorBehavior> supplier){
 266         reusableBehaviorStateHolder.init(getCurrentBehavior());
 267
 268         setCurrentBehavior(supplier.get());
 269
 270         handleBehaviorChange(reusableBehaviorStateHolder, getCurrentBehavior());
 271     }
 272
 273     protected RaftActorSnapshotMessageSupport newRaftActorSnapshotMessageSupport() {
 274         return new RaftActorSnapshotMessageSupport(context, currentBehavior,
 275                 getRaftActorSnapshotCohort());
 276     }
 277
 278     private void onGetOnDemandRaftStats() {
 279         // Debugging message to retrieve raft stats.
 280
 281         OnDemandRaftState.Builder builder = OnDemandRaftState.builder()
 282                 .commitIndex(context.getCommitIndex())
 283                 .currentTerm(context.getTermInformation().getCurrentTerm())
 284                 .inMemoryJournalDataSize(replicatedLog().dataSize())
 285                 .inMemoryJournalLogSize(replicatedLog().size())
 286                 .isSnapshotCaptureInitiated(context.getSnapshotManager().isCapturing())
 287                 .lastApplied(context.getLastApplied())
 288                 .lastIndex(replicatedLog().lastIndex())
 289                 .lastTerm(replicatedLog().lastTerm())
 290                 .leader(getLeaderId())
 291                 .raftState(currentBehavior.state().toString())
 292                 .replicatedToAllIndex(currentBehavior.getReplicatedToAllIndex())
 293                 .snapshotIndex(replicatedLog().getSnapshotIndex())
 294                 .snapshotTerm(replicatedLog().getSnapshotTerm())
 295                 .votedFor(context.getTermInformation().getVotedFor())
 296                 .peerAddresses(new HashMap<>(context.getPeerAddresses()));
 297
 298         ReplicatedLogEntry lastLogEntry = getLastLogEntry();
 299         if (lastLogEntry != null) {
 300             builder.lastLogIndex(lastLogEntry.getIndex());
 301             builder.lastLogTerm(lastLogEntry.getTerm());
 302         }
 303
 304         if(getCurrentBehavior() instanceof AbstractLeader) {
 305             AbstractLeader leader = (AbstractLeader)getCurrentBehavior();
 306             Collection<String> followerIds = leader.getFollowerIds();
 307             List<FollowerInfo> followerInfoList = Lists.newArrayListWithCapacity(followerIds.size());
 308             for(String id: followerIds) {
 309                 final FollowerLogInformation info = leader.getFollower(id);
 310                 followerInfoList.add(new FollowerInfo(id, info.getNextIndex(), info.getMatchIndex(),
 311                         info.isFollowerActive(), DurationFormatUtils.formatDurationHMS(info.timeSinceLastActivity())));
 312             }
 313
 314             builder.followerInfoList(followerInfoList);
 315         }
 316
 317         sender().tell(builder.build(), self());
 318
 319     }
 320
 321     private void handleBehaviorChange(BehaviorStateHolder oldBehaviorState, RaftActorBehavior currentBehavior) {
 322         RaftActorBehavior oldBehavior = oldBehaviorState.getBehavior();
 323
 324         if (oldBehavior != currentBehavior){
 325             onStateChanged();
 326         }
 327
 328         String lastValidLeaderId = oldBehavior == null ? null : oldBehaviorState.getLastValidLeaderId();
 329         String oldBehaviorStateName = oldBehavior == null ? null : oldBehavior.state().name();
 330
 331         // it can happen that the state has not changed but the leader has changed.
 332         Optional<ActorRef> roleChangeNotifier = getRoleChangeNotifier();
 333         if(!Objects.equal(lastValidLeaderId, currentBehavior.getLeaderId()) ||
 334            oldBehaviorState.getLeaderPayloadVersion() != currentBehavior.getLeaderPayloadVersion()) {
 335             if(roleChangeNotifier.isPresent()) {
 336                 roleChangeNotifier.get().tell(newLeaderStateChanged(getId(), currentBehavior.getLeaderId(),
 337                         currentBehavior.getLeaderPayloadVersion()), getSelf());
 338             }
 339
 340             onLeaderChanged(lastValidLeaderId, currentBehavior.getLeaderId());
 341         }
 342
 343         if (roleChangeNotifier.isPresent() &&
 344                 (oldBehavior == null || (oldBehavior.state() != currentBehavior.state()))) {
 345             roleChangeNotifier.get().tell(new RoleChanged(getId(), oldBehaviorStateName ,
 346                     currentBehavior.state().name()), getSelf());
 347         }
 348     }
 349
 350     protected LeaderStateChanged newLeaderStateChanged(String memberId, String leaderId, short leaderPayloadVersion) {
 351         return new LeaderStateChanged(memberId, leaderId, leaderPayloadVersion);
 352     }
 353
 354     @Override
 355     public long snapshotSequenceNr() {
 356         // When we do a snapshot capture, we also capture and save the sequence-number of the persistent journal,
 357         // so that we can delete the persistent journal based on the saved sequence-number
 358         // However , when akka replays the journal during recovery, it replays it from the sequence number when the snapshot
 359         // was saved and not the number we saved.
 360         // We would want to override it , by asking akka to use the last-sequence number known to us.
 361         return context.getSnapshotManager().getLastSequenceNumber();
 362     }
 363
 364     /**
 365      * When a derived RaftActor needs to persist something it must call
 366      * persistData.
 367      *
 368      * @param clientActor
 369      * @param identifier
 370      * @param data
 371      */
 372     protected void persistData(final ActorRef clientActor, final String identifier,
 373         final Payload data) {
 374
 375         ReplicatedLogEntry replicatedLogEntry = new ReplicatedLogImplEntry(
 376             context.getReplicatedLog().lastIndex() + 1,
 377             context.getTermInformation().getCurrentTerm(), data);
 378
 379         if(LOG.isDebugEnabled()) {
 380             LOG.debug("{}: Persist data {}", persistenceId(), replicatedLogEntry);
 381         }
 382
 383         final RaftActorContext raftContext = getRaftActorContext();
 384
 385         replicatedLog().appendAndPersist(replicatedLogEntry, new Procedure<ReplicatedLogEntry>() {
 386             @Override
 387             public void apply(ReplicatedLogEntry replicatedLogEntry) throws Exception {
 388                 if (!hasFollowers()){
 389                     // Increment the Commit Index and the Last Applied values
 390                     raftContext.setCommitIndex(replicatedLogEntry.getIndex());
 391                     raftContext.setLastApplied(replicatedLogEntry.getIndex());
 392
 393                     // Apply the state immediately.
 394                     self().tell(new ApplyState(clientActor, identifier, replicatedLogEntry), self());
 395
 396                     // Send a ApplyJournalEntries message so that we write the fact that we applied
 397                     // the state to durable storage
 398                     self().tell(new ApplyJournalEntries(replicatedLogEntry.getIndex()), self());
 399
 400                 } else if (clientActor != null) {
 401                     context.getReplicatedLog().captureSnapshotIfReady(replicatedLogEntry);
 402
 403                     // Send message for replication
 404                     currentBehavior.handleMessage(getSelf(),
 405                             new Replicate(clientActor, identifier, replicatedLogEntry));
 406                 }
 407             }
 408         });
 409     }
 410
 411     private ReplicatedLog replicatedLog() {
 412         return context.getReplicatedLog();
 413     }
 414
 415     protected String getId() {
 416         return context.getId();
 417     }
 418
 419     @VisibleForTesting
 420     void setCurrentBehavior(RaftActorBehavior behavior) {
 421         currentBehavior.setDelegate(behavior);
 422     }
 423
 424     protected RaftActorBehavior getCurrentBehavior() {
 425         return currentBehavior.getDelegate();
 426     }
 427
 428     /**
 429      * Derived actors can call the isLeader method to check if the current
 430      * RaftActor is the Leader or not
 431      *
 432      * @return true it this RaftActor is a Leader false otherwise
 433      */
 434     protected boolean isLeader() {
 435         return context.getId().equals(currentBehavior.getLeaderId());
 436     }
 437
 438     /**
 439      * Derived actor can call getLeader if they need a reference to the Leader.
 440      * This would be useful for example in forwarding a request to an actor
 441      * which is the leader
 442      *
 443      * @return A reference to the leader if known, null otherwise
 444      */
 445     protected ActorSelection getLeader(){
 446         String leaderAddress = getLeaderAddress();
 447
 448         if(leaderAddress == null){
 449             return null;
 450         }
 451
 452         return context.actorSelection(leaderAddress);
 453     }
 454
 455     /**
 456      *
 457      * @return the current leader's id
 458      */
 459     protected String getLeaderId(){
 460         return currentBehavior.getLeaderId();
 461     }
 462
 463     protected RaftState getRaftState() {
 464         return currentBehavior.state();
 465     }
 466
 467     protected ReplicatedLogEntry getLastLogEntry() {
 468         return replicatedLog().last();
 469     }
 470
 471     protected Long getCurrentTerm(){
 472         return context.getTermInformation().getCurrentTerm();
 473     }
 474
 475     protected Long getCommitIndex(){
 476         return context.getCommitIndex();
 477     }
 478
 479     protected Long getLastApplied(){
 480         return context.getLastApplied();
 481     }
 482
 483     protected RaftActorContext getRaftActorContext() {
 484         return context;
 485     }
 486
 487     protected void updateConfigParams(ConfigParams configParams) {
 488         context.setConfigParams(configParams);
 489     }
 490
 491     public final DataPersistenceProvider persistence() {
 492         return delegatingPersistenceProvider.getDelegate();
 493     }
 494
 495     public void setPersistence(DataPersistenceProvider provider) {
 496         delegatingPersistenceProvider.setDelegate(provider);
 497     }
 498
 499     protected void setPersistence(boolean persistent) {
 500         if(persistent) {
 501             setPersistence(new PersistentDataProvider(this));
 502         } else {
 503             setPersistence(new NonPersistentDataProvider() {
 504                 /**
 505                  * The way snapshotting works is,
 506                  * <ol>
 507                  * <li> RaftActor calls createSnapshot on the Shard
 508                  * <li> Shard sends a CaptureSnapshotReply and RaftActor then calls saveSnapshot
 509                  * <li> When saveSnapshot is invoked on the akka-persistence API it uses the SnapshotStore to save
 510                  * the snapshot. The SnapshotStore sends SaveSnapshotSuccess or SaveSnapshotFailure. When the
 511                  * RaftActor gets SaveSnapshot success it commits the snapshot to the in-memory journal. This
 512                  * commitSnapshot is mimicking what is done in SaveSnapshotSuccess.
 513                  * </ol>
 514                  */
 515                 @Override
 516                 public void saveSnapshot(Object o) {
 517                     // Make saving Snapshot successful
 518                     // Committing the snapshot here would end up calling commit in the creating state which would
 519                     // be a state violation. That's why now we send a message to commit the snapshot.
 520                     self().tell(RaftActorSnapshotMessageSupport.COMMIT_SNAPSHOT, self());
 521                 }
 522             });
 523         }
 524     }
 525
 526     /**
 527      * setPeerAddress sets the address of a known peer at a later time.
 528      * <p>
 529      * This is to account for situations where a we know that a peer
 530      * exists but we do not know an address up-front. This may also be used in
 531      * situations where a known peer starts off in a different location and we
 532      * need to change it's address
 533      * <p>
 534      * Note that if the peerId does not match the list of peers passed to
 535      * this actor during construction an IllegalStateException will be thrown.
 536      *
 537      * @param peerId
 538      * @param peerAddress
 539      */
 540     protected void setPeerAddress(String peerId, String peerAddress){
 541         context.setPeerAddress(peerId, peerAddress);
 542     }
 543
 544     /**
 545      * The applyState method will be called by the RaftActor when some data
 546      * needs to be applied to the actor's state
 547      *
 548      * @param clientActor A reference to the client who sent this message. This
 549      *                    is the same reference that was passed to persistData
 550      *                    by the derived actor. clientActor may be null when
 551      *                    the RaftActor is behaving as a follower or during
 552      *                    recovery.
 553      * @param identifier  The identifier of the persisted data. This is also
 554      *                    the same identifier that was passed to persistData by
 555      *                    the derived actor. identifier may be null when
 556      *                    the RaftActor is behaving as a follower or during
 557      *                    recovery
 558      * @param data        A piece of data that was persisted by the persistData call.
 559      *                    This should NEVER be null.
 560      */
 561     protected abstract void applyState(ActorRef clientActor, String identifier,
 562         Object data);
 563
 564     /**
 565      * Returns the RaftActorRecoveryCohort to participate in persistence recovery.
 566      */
 567     @Nonnull
 568     protected abstract RaftActorRecoveryCohort getRaftActorRecoveryCohort();
 569
 570     /**
 571      * This method is called when recovery is complete.
 572      */
 573     protected abstract void onRecoveryComplete();
 574
 575     /**
 576      * Returns the RaftActorSnapshotCohort to participate in persistence recovery.
 577      */
 578     @Nonnull
 579     protected abstract RaftActorSnapshotCohort getRaftActorSnapshotCohort();
 580
 581     /**
 582      * This method will be called by the RaftActor when the state of the
 583      * RaftActor changes. The derived actor can then use methods like
 584      * isLeader or getLeader to do something useful
 585      */
 586     protected abstract void onStateChanged();
 587
 588     /**
 589      * Notifier Actor for this RaftActor to notify when a role change happens
 590      * @return ActorRef - ActorRef of the notifier or Optional.absent if none.
 591      */
 592     protected abstract Optional<ActorRef> getRoleChangeNotifier();
 593
 594     protected void onLeaderChanged(String oldLeader, String newLeader){};
 595
 596     private String getLeaderAddress(){
 597         if(isLeader()){
 598             return getSelf().path().toString();
 599         }
 600         String leaderId = currentBehavior.getLeaderId();
 601         if (leaderId == null) {
 602             return null;
 603         }
 604         String peerAddress = context.getPeerAddress(leaderId);
 605         if(LOG.isDebugEnabled()) {
 606             LOG.debug("{}: getLeaderAddress leaderId = {} peerAddress = {}",
 607                     persistenceId(), leaderId, peerAddress);
 608         }
 609
 610         return peerAddress;
 611     }
 612
 613     protected boolean hasFollowers(){
 614         return getRaftActorContext().hasFollowers();
 615     }
 616
 617     private void captureSnapshot() {
 618         SnapshotManager snapshotManager = context.getSnapshotManager();
 619
 620         if(!snapshotManager.isCapturing()) {
 621             LOG.debug("Take a snapshot of current state. lastReplicatedLog is {} and replicatedToAllIndex is {}",
 622                 replicatedLog().last(), currentBehavior.getReplicatedToAllIndex());
 623
 624             snapshotManager.capture(replicatedLog().last(), currentBehavior.getReplicatedToAllIndex());
 625         }
 626     }
 627
 628     /**
 629      * @deprecated Deprecated in favor of {@link org.opendaylight.controller.cluster.raft.base.messages.DeleteEntries}
 630      *             whose type for fromIndex is long instead of int. This class was kept for backwards
 631      *             compatibility with Helium.
 632      */
 633     // Suppressing this warning as we can't set serialVersionUID to maintain backwards compatibility.
 634     @SuppressWarnings("serial")
 635     @Deprecated
 636     static class DeleteEntries implements Serializable {
 637         private final int fromIndex;
 638
 639         public DeleteEntries(int fromIndex) {
 640             this.fromIndex = fromIndex;
 641         }
 642
 643         public int getFromIndex() {
 644             return fromIndex;
 645         }
 646     }
 647
 648     /**
 649      * @deprecated Deprecated in favor of non-inner class {@link org.opendaylight.controller.cluster.raft.base.messages.UpdateElectionTerm}
 650      *             which has serialVersionUID set. This class was kept for backwards compatibility with Helium.
 651      */
 652     // Suppressing this warning as we can't set serialVersionUID to maintain backwards compatibility.
 653     @SuppressWarnings("serial")
 654     @Deprecated
 655     static class UpdateElectionTerm implements Serializable {
 656         private final long currentTerm;
 657         private final String votedFor;
 658
 659         public UpdateElectionTerm(long currentTerm, String votedFor) {
 660             this.currentTerm = currentTerm;
 661             this.votedFor = votedFor;
 662         }
 663
 664         public long getCurrentTerm() {
 665             return currentTerm;
 666         }
 667
 668         public String getVotedFor() {
 669             return votedFor;
 670         }
 671     }
 672
 673     private static class BehaviorStateHolder {
 674         private RaftActorBehavior behavior;
 675         private String lastValidLeaderId;
 676         private short leaderPayloadVersion;
 677
 678         void init(RaftActorBehavior behavior) {
 679             this.behavior = behavior;
 680             this.leaderPayloadVersion = behavior != null ? behavior.getLeaderPayloadVersion() : -1;
 681
 682             String behaviorLeaderId = behavior != null ? behavior.getLeaderId() : null;
 683             if(behaviorLeaderId != null) {
 684                 this.lastValidLeaderId = behaviorLeaderId;
 685             }
 686         }
 687
 688         RaftActorBehavior getBehavior() {
 689             return behavior;
 690         }
 691
 692         String getLastValidLeaderId() {
 693             return lastValidLeaderId;
 694         }
 695
 696         short getLeaderPayloadVersion() {
 697             return leaderPayloadVersion;
 698         }
 699     }
 700
 701     private class SwitchBehaviorSupplier implements Supplier<RaftActorBehavior> {
 702         private Object message;
 703         private ActorRef sender;
 704
 705         public SwitchBehaviorSupplier handleMessage(ActorRef sender, Object message){
 706             this.sender = sender;
 707             this.message = message;
 708             return this;
 709         }
 710
 711         @Override
 712         public RaftActorBehavior get() {
 713             if(this.message instanceof SwitchBehavior){
 714                 return ((SwitchBehavior) message).getNewState().createBehavior(getRaftActorContext());
 715             }
 716             return currentBehavior.handleMessage(sender, message);
 717         }
 718     }
 719 }