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             if (context.getReplicatedLog().size() > 0) {
 178                 self().tell(new InitiateCaptureSnapshot(), self());
 179                 LOG.info("Snapshot capture initiated after recovery");
 180             } else {
 181                 LOG.info("Snapshot capture NOT initiated after recovery, journal empty");
 182             }
 183         }
 184     }
 185
 186     protected RaftActorRecoverySupport newRaftActorRecoverySupport() {
 187         return new RaftActorRecoverySupport(context, currentBehavior, getRaftActorRecoveryCohort());
 188     }
 189
 190     protected void initializeBehavior(){
 191         changeCurrentBehavior(new Follower(context));
 192     }
 193
 194     protected void changeCurrentBehavior(RaftActorBehavior newBehavior){
 195         reusableBehaviorStateHolder.init(getCurrentBehavior());
 196         setCurrentBehavior(newBehavior);
 197         handleBehaviorChange(reusableBehaviorStateHolder, getCurrentBehavior());
 198     }
 199
 200     @Override
 201     public void handleCommand(final Object message) {
 202         if(serverConfigurationSupport.handleMessage(message, this, getSender())) {
 203             return;
 204         } else if (message instanceof ApplyState){
 205             ApplyState applyState = (ApplyState) message;
 206
 207             long elapsedTime = (System.nanoTime() - applyState.getStartTime());
 208             if(elapsedTime >= APPLY_STATE_DELAY_THRESHOLD_IN_NANOS){
 209                 LOG.warn("ApplyState took more time than expected. Elapsed Time = {} ms ApplyState = {}",
 210                         TimeUnit.NANOSECONDS.toMillis(elapsedTime), applyState);
 211             }
 212
 213             if(LOG.isDebugEnabled()) {
 214                 LOG.debug("{}: Applying state for log index {} data {}",
 215                     persistenceId(), applyState.getReplicatedLogEntry().getIndex(),
 216                     applyState.getReplicatedLogEntry().getData());
 217             }
 218
 219             applyState(applyState.getClientActor(), applyState.getIdentifier(),
 220                 applyState.getReplicatedLogEntry().getData());
 221
 222             if (!hasFollowers()) {
 223                 // for single node, the capture should happen after the apply state
 224                 // as we delete messages from the persistent journal which have made it to the snapshot
 225                 // capturing the snapshot before applying makes the persistent journal and snapshot out of sync
 226                 // and recovery shows data missing
 227                 context.getReplicatedLog().captureSnapshotIfReady(applyState.getReplicatedLogEntry());
 228
 229                 context.getSnapshotManager().trimLog(context.getLastApplied(), currentBehavior);
 230             }
 231
 232         } else if (message instanceof ApplyJournalEntries){
 233             ApplyJournalEntries applyEntries = (ApplyJournalEntries) message;
 234             if(LOG.isDebugEnabled()) {
 235                 LOG.debug("{}: Persisting ApplyLogEntries with index={}", persistenceId(), applyEntries.getToIndex());
 236             }
 237
 238             persistence().persist(applyEntries, NoopProcedure.instance());
 239
 240         } else if (message instanceof FindLeader) {
 241             getSender().tell(
 242                 new FindLeaderReply(getLeaderAddress()),
 243                 getSelf()
 244             );
 245         } else if(message instanceof GetOnDemandRaftState) {
 246             onGetOnDemandRaftStats();
 247         } else if(message instanceof InitiateCaptureSnapshot) {
 248             captureSnapshot();
 249         } else if(message instanceof SwitchBehavior){
 250             switchBehavior(((SwitchBehavior) message));
 251         } else if(!snapshotSupport.handleSnapshotMessage(message)) {
 252             switchBehavior(reusableSwitchBehaviorSupplier.handleMessage(getSender(), message));
 253         }
 254     }
 255
 256     private void switchBehavior(SwitchBehavior message) {
 257         if(!getRaftActorContext().getRaftPolicy().automaticElectionsEnabled()) {
 258             RaftState newState = message.getNewState();
 259             if( newState == RaftState.Leader || newState == RaftState.Follower) {
 260                 switchBehavior(reusableSwitchBehaviorSupplier.handleMessage(getSender(), message));
 261                 getRaftActorContext().getTermInformation().updateAndPersist(message.getNewTerm(), "");
 262             } else {
 263                 LOG.warn("Switching to behavior : {} - not supported", newState);
 264             }
 265         }
 266     }
 267
 268     private void switchBehavior(Supplier<RaftActorBehavior> supplier){
 269         reusableBehaviorStateHolder.init(getCurrentBehavior());
 270
 271         setCurrentBehavior(supplier.get());
 272
 273         handleBehaviorChange(reusableBehaviorStateHolder, getCurrentBehavior());
 274     }
 275
 276     protected RaftActorSnapshotMessageSupport newRaftActorSnapshotMessageSupport() {
 277         return new RaftActorSnapshotMessageSupport(context, currentBehavior,
 278                 getRaftActorSnapshotCohort());
 279     }
 280
 281     private void onGetOnDemandRaftStats() {
 282         // Debugging message to retrieve raft stats.
 283
 284         Map<String, String> peerAddresses = new HashMap<>();
 285         for(String peerId: context.getPeerIds()) {
 286             peerAddresses.put(peerId, context.getPeerAddress(peerId));
 287         }
 288
 289         OnDemandRaftState.Builder builder = OnDemandRaftState.builder()
 290                 .commitIndex(context.getCommitIndex())
 291                 .currentTerm(context.getTermInformation().getCurrentTerm())
 292                 .inMemoryJournalDataSize(replicatedLog().dataSize())
 293                 .inMemoryJournalLogSize(replicatedLog().size())
 294                 .isSnapshotCaptureInitiated(context.getSnapshotManager().isCapturing())
 295                 .lastApplied(context.getLastApplied())
 296                 .lastIndex(replicatedLog().lastIndex())
 297                 .lastTerm(replicatedLog().lastTerm())
 298                 .leader(getLeaderId())
 299                 .raftState(currentBehavior.state().toString())
 300                 .replicatedToAllIndex(currentBehavior.getReplicatedToAllIndex())
 301                 .snapshotIndex(replicatedLog().getSnapshotIndex())
 302                 .snapshotTerm(replicatedLog().getSnapshotTerm())
 303                 .votedFor(context.getTermInformation().getVotedFor())
 304                 .peerAddresses(peerAddresses);
 305
 306         ReplicatedLogEntry lastLogEntry = getLastLogEntry();
 307         if (lastLogEntry != null) {
 308             builder.lastLogIndex(lastLogEntry.getIndex());
 309             builder.lastLogTerm(lastLogEntry.getTerm());
 310         }
 311
 312         if(getCurrentBehavior() instanceof AbstractLeader) {
 313             AbstractLeader leader = (AbstractLeader)getCurrentBehavior();
 314             Collection<String> followerIds = leader.getFollowerIds();
 315             List<FollowerInfo> followerInfoList = Lists.newArrayListWithCapacity(followerIds.size());
 316             for(String id: followerIds) {
 317                 final FollowerLogInformation info = leader.getFollower(id);
 318                 followerInfoList.add(new FollowerInfo(id, info.getNextIndex(), info.getMatchIndex(),
 319                         info.isFollowerActive(), DurationFormatUtils.formatDurationHMS(info.timeSinceLastActivity())));
 320             }
 321
 322             builder.followerInfoList(followerInfoList);
 323         }
 324
 325         sender().tell(builder.build(), self());
 326
 327     }
 328
 329     private void handleBehaviorChange(BehaviorStateHolder oldBehaviorState, RaftActorBehavior currentBehavior) {
 330         RaftActorBehavior oldBehavior = oldBehaviorState.getBehavior();
 331
 332         if (oldBehavior != currentBehavior){
 333             onStateChanged();
 334         }
 335
 336         String lastValidLeaderId = oldBehavior == null ? null : oldBehaviorState.getLastValidLeaderId();
 337         String oldBehaviorStateName = oldBehavior == null ? null : oldBehavior.state().name();
 338
 339         // it can happen that the state has not changed but the leader has changed.
 340         Optional<ActorRef> roleChangeNotifier = getRoleChangeNotifier();
 341         if(!Objects.equal(lastValidLeaderId, currentBehavior.getLeaderId()) ||
 342            oldBehaviorState.getLeaderPayloadVersion() != currentBehavior.getLeaderPayloadVersion()) {
 343             if(roleChangeNotifier.isPresent()) {
 344                 roleChangeNotifier.get().tell(newLeaderStateChanged(getId(), currentBehavior.getLeaderId(),
 345                         currentBehavior.getLeaderPayloadVersion()), getSelf());
 346             }
 347
 348             onLeaderChanged(lastValidLeaderId, currentBehavior.getLeaderId());
 349         }
 350
 351         if (roleChangeNotifier.isPresent() &&
 352                 (oldBehavior == null || (oldBehavior.state() != currentBehavior.state()))) {
 353             roleChangeNotifier.get().tell(new RoleChanged(getId(), oldBehaviorStateName ,
 354                     currentBehavior.state().name()), getSelf());
 355         }
 356     }
 357
 358     protected LeaderStateChanged newLeaderStateChanged(String memberId, String leaderId, short leaderPayloadVersion) {
 359         return new LeaderStateChanged(memberId, leaderId, leaderPayloadVersion);
 360     }
 361
 362     @Override
 363     public long snapshotSequenceNr() {
 364         // When we do a snapshot capture, we also capture and save the sequence-number of the persistent journal,
 365         // so that we can delete the persistent journal based on the saved sequence-number
 366         // However , when akka replays the journal during recovery, it replays it from the sequence number when the snapshot
 367         // was saved and not the number we saved.
 368         // We would want to override it , by asking akka to use the last-sequence number known to us.
 369         return context.getSnapshotManager().getLastSequenceNumber();
 370     }
 371
 372     /**
 373      * When a derived RaftActor needs to persist something it must call
 374      * persistData.
 375      *
 376      * @param clientActor
 377      * @param identifier
 378      * @param data
 379      */
 380     protected void persistData(final ActorRef clientActor, final String identifier,
 381         final Payload data) {
 382
 383         ReplicatedLogEntry replicatedLogEntry = new ReplicatedLogImplEntry(
 384             context.getReplicatedLog().lastIndex() + 1,
 385             context.getTermInformation().getCurrentTerm(), data);
 386
 387         if(LOG.isDebugEnabled()) {
 388             LOG.debug("{}: Persist data {}", persistenceId(), replicatedLogEntry);
 389         }
 390
 391         final RaftActorContext raftContext = getRaftActorContext();
 392
 393         replicatedLog().appendAndPersist(replicatedLogEntry, new Procedure<ReplicatedLogEntry>() {
 394             @Override
 395             public void apply(ReplicatedLogEntry replicatedLogEntry) {
 396                 if (!hasFollowers()){
 397                     // Increment the Commit Index and the Last Applied values
 398                     raftContext.setCommitIndex(replicatedLogEntry.getIndex());
 399                     raftContext.setLastApplied(replicatedLogEntry.getIndex());
 400
 401                     // Apply the state immediately.
 402                     self().tell(new ApplyState(clientActor, identifier, replicatedLogEntry), self());
 403
 404                     // Send a ApplyJournalEntries message so that we write the fact that we applied
 405                     // the state to durable storage
 406                     self().tell(new ApplyJournalEntries(replicatedLogEntry.getIndex()), self());
 407
 408                 } else if (clientActor != null) {
 409                     context.getReplicatedLog().captureSnapshotIfReady(replicatedLogEntry);
 410
 411                     // Send message for replication
 412                     currentBehavior.handleMessage(getSelf(),
 413                             new Replicate(clientActor, identifier, replicatedLogEntry));
 414                 }
 415             }
 416         });
 417     }
 418
 419     private ReplicatedLog replicatedLog() {
 420         return context.getReplicatedLog();
 421     }
 422
 423     protected String getId() {
 424         return context.getId();
 425     }
 426
 427     @VisibleForTesting
 428     void setCurrentBehavior(RaftActorBehavior behavior) {
 429         currentBehavior.setDelegate(behavior);
 430     }
 431
 432     protected RaftActorBehavior getCurrentBehavior() {
 433         return currentBehavior.getDelegate();
 434     }
 435
 436     /**
 437      * Derived actors can call the isLeader method to check if the current
 438      * RaftActor is the Leader or not
 439      *
 440      * @return true it this RaftActor is a Leader false otherwise
 441      */
 442     protected boolean isLeader() {
 443         return context.getId().equals(currentBehavior.getLeaderId());
 444     }
 445
 446     /**
 447      * Derived actor can call getLeader if they need a reference to the Leader.
 448      * This would be useful for example in forwarding a request to an actor
 449      * which is the leader
 450      *
 451      * @return A reference to the leader if known, null otherwise
 452      */
 453     protected ActorSelection getLeader(){
 454         String leaderAddress = getLeaderAddress();
 455
 456         if(leaderAddress == null){
 457             return null;
 458         }
 459
 460         return context.actorSelection(leaderAddress);
 461     }
 462
 463     /**
 464      *
 465      * @return the current leader's id
 466      */
 467     protected String getLeaderId(){
 468         return currentBehavior.getLeaderId();
 469     }
 470
 471     protected RaftState getRaftState() {
 472         return currentBehavior.state();
 473     }
 474
 475     protected ReplicatedLogEntry getLastLogEntry() {
 476         return replicatedLog().last();
 477     }
 478
 479     protected Long getCurrentTerm(){
 480         return context.getTermInformation().getCurrentTerm();
 481     }
 482
 483     protected Long getCommitIndex(){
 484         return context.getCommitIndex();
 485     }
 486
 487     protected Long getLastApplied(){
 488         return context.getLastApplied();
 489     }
 490
 491     protected RaftActorContext getRaftActorContext() {
 492         return context;
 493     }
 494
 495     protected void updateConfigParams(ConfigParams configParams) {
 496
 497         // obtain the RaftPolicy for oldConfigParams and the updated one.
 498         String oldRaftPolicy = context.getConfigParams().
 499             getCustomRaftPolicyImplementationClass();
 500         String newRaftPolicy = configParams.
 501             getCustomRaftPolicyImplementationClass();
 502
 503         LOG.debug ("RaftPolicy used with prev.config {}, RaftPolicy used with newConfig {}",
 504             oldRaftPolicy, newRaftPolicy);
 505         context.setConfigParams(configParams);
 506         if (!Objects.equal(oldRaftPolicy, newRaftPolicy)) {
 507             //RaftPolicy is modifed for the Actor. Re-initialize its current behaviour
 508             initializeBehavior();
 509         }
 510     }
 511
 512     public final DataPersistenceProvider persistence() {
 513         return delegatingPersistenceProvider.getDelegate();
 514     }
 515
 516     public void setPersistence(DataPersistenceProvider provider) {
 517         delegatingPersistenceProvider.setDelegate(provider);
 518     }
 519
 520     protected void setPersistence(boolean persistent) {
 521         if(persistent) {
 522             setPersistence(new PersistentDataProvider(this));
 523         } else {
 524             setPersistence(new NonPersistentDataProvider() {
 525                 /**
 526                  * The way snapshotting works is,
 527                  * <ol>
 528                  * <li> RaftActor calls createSnapshot on the Shard
 529                  * <li> Shard sends a CaptureSnapshotReply and RaftActor then calls saveSnapshot
 530                  * <li> When saveSnapshot is invoked on the akka-persistence API it uses the SnapshotStore to save
 531                  * the snapshot. The SnapshotStore sends SaveSnapshotSuccess or SaveSnapshotFailure. When the
 532                  * RaftActor gets SaveSnapshot success it commits the snapshot to the in-memory journal. This
 533                  * commitSnapshot is mimicking what is done in SaveSnapshotSuccess.
 534                  * </ol>
 535                  */
 536                 @Override
 537                 public void saveSnapshot(Object o) {
 538                     // Make saving Snapshot successful
 539                     // Committing the snapshot here would end up calling commit in the creating state which would
 540                     // be a state violation. That's why now we send a message to commit the snapshot.
 541                     self().tell(RaftActorSnapshotMessageSupport.COMMIT_SNAPSHOT, self());
 542                 }
 543             });
 544         }
 545     }
 546
 547     /**
 548      * setPeerAddress sets the address of a known peer at a later time.
 549      * <p>
 550      * This is to account for situations where a we know that a peer
 551      * exists but we do not know an address up-front. This may also be used in
 552      * situations where a known peer starts off in a different location and we
 553      * need to change it's address
 554      * <p>
 555      * Note that if the peerId does not match the list of peers passed to
 556      * this actor during construction an IllegalStateException will be thrown.
 557      *
 558      * @param peerId
 559      * @param peerAddress
 560      */
 561     protected void setPeerAddress(String peerId, String peerAddress){
 562         context.setPeerAddress(peerId, peerAddress);
 563     }
 564
 565     /**
 566      * The applyState method will be called by the RaftActor when some data
 567      * needs to be applied to the actor's state
 568      *
 569      * @param clientActor A reference to the client who sent this message. This
 570      *                    is the same reference that was passed to persistData
 571      *                    by the derived actor. clientActor may be null when
 572      *                    the RaftActor is behaving as a follower or during
 573      *                    recovery.
 574      * @param identifier  The identifier of the persisted data. This is also
 575      *                    the same identifier that was passed to persistData by
 576      *                    the derived actor. identifier may be null when
 577      *                    the RaftActor is behaving as a follower or during
 578      *                    recovery
 579      * @param data        A piece of data that was persisted by the persistData call.
 580      *                    This should NEVER be null.
 581      */
 582     protected abstract void applyState(ActorRef clientActor, String identifier,
 583         Object data);
 584
 585     /**
 586      * Returns the RaftActorRecoveryCohort to participate in persistence recovery.
 587      */
 588     @Nonnull
 589     protected abstract RaftActorRecoveryCohort getRaftActorRecoveryCohort();
 590
 591     /**
 592      * This method is called when recovery is complete.
 593      */
 594     protected abstract void onRecoveryComplete();
 595
 596     /**
 597      * Returns the RaftActorSnapshotCohort to participate in persistence recovery.
 598      */
 599     @Nonnull
 600     protected abstract RaftActorSnapshotCohort getRaftActorSnapshotCohort();
 601
 602     /**
 603      * This method will be called by the RaftActor when the state of the
 604      * RaftActor changes. The derived actor can then use methods like
 605      * isLeader or getLeader to do something useful
 606      */
 607     protected abstract void onStateChanged();
 608
 609     /**
 610      * Notifier Actor for this RaftActor to notify when a role change happens
 611      * @return ActorRef - ActorRef of the notifier or Optional.absent if none.
 612      */
 613     protected abstract Optional<ActorRef> getRoleChangeNotifier();
 614
 615     protected void onLeaderChanged(String oldLeader, String newLeader){};
 616
 617     private String getLeaderAddress(){
 618         if(isLeader()){
 619             return getSelf().path().toString();
 620         }
 621         String leaderId = currentBehavior.getLeaderId();
 622         if (leaderId == null) {
 623             return null;
 624         }
 625         String peerAddress = context.getPeerAddress(leaderId);
 626         if(LOG.isDebugEnabled()) {
 627             LOG.debug("{}: getLeaderAddress leaderId = {} peerAddress = {}",
 628                     persistenceId(), leaderId, peerAddress);
 629         }
 630
 631         return peerAddress;
 632     }
 633
 634     protected boolean hasFollowers(){
 635         return getRaftActorContext().hasFollowers();
 636     }
 637
 638     private void captureSnapshot() {
 639         SnapshotManager snapshotManager = context.getSnapshotManager();
 640
 641         if(!snapshotManager.isCapturing()) {
 642             LOG.debug("Take a snapshot of current state. lastReplicatedLog is {} and replicatedToAllIndex is {}",
 643                 replicatedLog().last(), currentBehavior.getReplicatedToAllIndex());
 644
 645             snapshotManager.capture(replicatedLog().last(), currentBehavior.getReplicatedToAllIndex());
 646         }
 647     }
 648
 649     /**
 650      * @deprecated Deprecated in favor of {@link org.opendaylight.controller.cluster.raft.base.messages.DeleteEntries}
 651      *             whose type for fromIndex is long instead of int. This class was kept for backwards
 652      *             compatibility with Helium.
 653      */
 654     // Suppressing this warning as we can't set serialVersionUID to maintain backwards compatibility.
 655     @SuppressWarnings("serial")
 656     @Deprecated
 657     static class DeleteEntries implements Serializable {
 658         private final int fromIndex;
 659
 660         public DeleteEntries(int fromIndex) {
 661             this.fromIndex = fromIndex;
 662         }
 663
 664         public int getFromIndex() {
 665             return fromIndex;
 666         }
 667     }
 668
 669     /**
 670      * @deprecated Deprecated in favor of non-inner class {@link org.opendaylight.controller.cluster.raft.base.messages.UpdateElectionTerm}
 671      *             which has serialVersionUID set. This class was kept for backwards compatibility with Helium.
 672      */
 673     // Suppressing this warning as we can't set serialVersionUID to maintain backwards compatibility.
 674     @SuppressWarnings("serial")
 675     @Deprecated
 676     static class UpdateElectionTerm implements Serializable {
 677         private final long currentTerm;
 678         private final String votedFor;
 679
 680         public UpdateElectionTerm(long currentTerm, String votedFor) {
 681             this.currentTerm = currentTerm;
 682             this.votedFor = votedFor;
 683         }
 684
 685         public long getCurrentTerm() {
 686             return currentTerm;
 687         }
 688
 689         public String getVotedFor() {
 690             return votedFor;
 691         }
 692     }
 693
 694     private static class BehaviorStateHolder {
 695         private RaftActorBehavior behavior;
 696         private String lastValidLeaderId;
 697         private short leaderPayloadVersion;
 698
 699         void init(RaftActorBehavior behavior) {
 700             this.behavior = behavior;
 701             this.leaderPayloadVersion = behavior != null ? behavior.getLeaderPayloadVersion() : -1;
 702
 703             String behaviorLeaderId = behavior != null ? behavior.getLeaderId() : null;
 704             if(behaviorLeaderId != null) {
 705                 this.lastValidLeaderId = behaviorLeaderId;
 706             }
 707         }
 708
 709         RaftActorBehavior getBehavior() {
 710             return behavior;
 711         }
 712
 713         String getLastValidLeaderId() {
 714             return lastValidLeaderId;
 715         }
 716
 717         short getLeaderPayloadVersion() {
 718             return leaderPayloadVersion;
 719         }
 720     }
 721
 722     private class SwitchBehaviorSupplier implements Supplier<RaftActorBehavior> {
 723         private Object message;
 724         private ActorRef sender;
 725
 726         public SwitchBehaviorSupplier handleMessage(ActorRef sender, Object message){
 727             this.sender = sender;
 728             this.message = message;
 729             return this;
 730         }
 731
 732         @Override
 733         public RaftActorBehavior get() {
 734             if(this.message instanceof SwitchBehavior){
 735                 return ((SwitchBehavior) message).getNewState().createBehavior(getRaftActorContext());
 736             }
 737             return currentBehavior.handleMessage(sender, message);
 738         }
 739     }
 740 }