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;
 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         delegatingPersistenceProvider = new RaftActorDelegatingPersistentDataProvider(null, persistentProvider);
 130
 131         context = new RaftActorContextImpl(this.getSelf(),
 132             this.getContext(), id, new ElectionTermImpl(persistentProvider, id, LOG),
 133             -1, -1, peerAddresses,
 134             (configParams.isPresent() ? configParams.get(): new DefaultConfigParamsImpl()),
 135             delegatingPersistenceProvider, LOG);
 136
 137         context.setPayloadVersion(payloadVersion);
 138         context.setReplicatedLog(ReplicatedLogImpl.newInstance(context, currentBehavior));
 139     }
 140
 141     @Override
 142     public void preStart() throws Exception {
 143         LOG.info("Starting recovery for {} with journal batch size {}", persistenceId(),
 144                 context.getConfigParams().getJournalRecoveryLogBatchSize());
 145
 146         super.preStart();
 147
 148         snapshotSupport = newRaftActorSnapshotMessageSupport();
 149         serverConfigurationSupport = new RaftActorServerConfigurationSupport(getRaftActorContext());
 150     }
 151
 152     @Override
 153     public void postStop() {
 154         if(currentBehavior.getDelegate() != null) {
 155             try {
 156                 currentBehavior.close();
 157             } catch (Exception e) {
 158                 LOG.debug("{}: Error closing behavior {}", persistenceId(), currentBehavior.state());
 159             }
 160         }
 161
 162         super.postStop();
 163     }
 164
 165     @Override
 166     public void handleRecover(Object message) {
 167         if(raftRecovery == null) {
 168             raftRecovery = newRaftActorRecoverySupport();
 169         }
 170
 171         boolean recoveryComplete = raftRecovery.handleRecoveryMessage(message, persistentProvider);
 172         if(recoveryComplete) {
 173             onRecoveryComplete();
 174
 175             initializeBehavior();
 176
 177             raftRecovery = null;
 178
 179             if (context.getReplicatedLog().size() > 0) {
 180                 self().tell(new InitiateCaptureSnapshot(), self());
 181                 LOG.info("{}: Snapshot capture initiated after recovery", persistenceId());
 182             } else {
 183                 LOG.info("{}: Snapshot capture NOT initiated after recovery, journal empty", persistenceId());
 184             }
 185         }
 186     }
 187
 188     protected RaftActorRecoverySupport newRaftActorRecoverySupport() {
 189         return new RaftActorRecoverySupport(context, currentBehavior, getRaftActorRecoveryCohort());
 190     }
 191
 192     protected void initializeBehavior(){
 193         changeCurrentBehavior(new Follower(context));
 194     }
 195
 196     protected void changeCurrentBehavior(RaftActorBehavior newBehavior){
 197         reusableBehaviorStateHolder.init(getCurrentBehavior());
 198         setCurrentBehavior(newBehavior);
 199         handleBehaviorChange(reusableBehaviorStateHolder, getCurrentBehavior());
 200     }
 201
 202     @Override
 203     public void handleCommand(final Object message) {
 204         if(serverConfigurationSupport.handleMessage(message, this, getSender())) {
 205             return;
 206         } else if (message instanceof ApplyState){
 207             ApplyState applyState = (ApplyState) message;
 208
 209             long elapsedTime = (System.nanoTime() - applyState.getStartTime());
 210             if(elapsedTime >= APPLY_STATE_DELAY_THRESHOLD_IN_NANOS){
 211                 LOG.warn("ApplyState took more time than expected. Elapsed Time = {} ms ApplyState = {}",
 212                         TimeUnit.NANOSECONDS.toMillis(elapsedTime), applyState);
 213             }
 214
 215             if(LOG.isDebugEnabled()) {
 216                 LOG.debug("{}: Applying state for log index {} data {}",
 217                     persistenceId(), applyState.getReplicatedLogEntry().getIndex(),
 218                     applyState.getReplicatedLogEntry().getData());
 219             }
 220
 221             applyState(applyState.getClientActor(), applyState.getIdentifier(),
 222                 applyState.getReplicatedLogEntry().getData());
 223
 224             if (!hasFollowers()) {
 225                 // for single node, the capture should happen after the apply state
 226                 // as we delete messages from the persistent journal which have made it to the snapshot
 227                 // capturing the snapshot before applying makes the persistent journal and snapshot out of sync
 228                 // and recovery shows data missing
 229                 context.getReplicatedLog().captureSnapshotIfReady(applyState.getReplicatedLogEntry());
 230
 231                 context.getSnapshotManager().trimLog(context.getLastApplied(), currentBehavior);
 232             }
 233
 234         } else if (message instanceof ApplyJournalEntries){
 235             ApplyJournalEntries applyEntries = (ApplyJournalEntries) message;
 236             if(LOG.isDebugEnabled()) {
 237                 LOG.debug("{}: Persisting ApplyLogEntries with index={}", persistenceId(), applyEntries.getToIndex());
 238             }
 239
 240             persistence().persist(applyEntries, NoopProcedure.instance());
 241
 242         } else if (message instanceof FindLeader) {
 243             getSender().tell(
 244                 new FindLeaderReply(getLeaderAddress()),
 245                 getSelf()
 246             );
 247         } else if(message instanceof GetOnDemandRaftState) {
 248             onGetOnDemandRaftStats();
 249         } else if(message instanceof InitiateCaptureSnapshot) {
 250             captureSnapshot();
 251         } else if(message instanceof SwitchBehavior){
 252             switchBehavior(((SwitchBehavior) message));
 253         } else if(!snapshotSupport.handleSnapshotMessage(message, getSender())) {
 254             switchBehavior(reusableSwitchBehaviorSupplier.handleMessage(getSender(), message));
 255         }
 256     }
 257
 258     private void switchBehavior(SwitchBehavior message) {
 259         if(!getRaftActorContext().getRaftPolicy().automaticElectionsEnabled()) {
 260             RaftState newState = message.getNewState();
 261             if( newState == RaftState.Leader || newState == RaftState.Follower) {
 262                 switchBehavior(reusableSwitchBehaviorSupplier.handleMessage(getSender(), message));
 263                 getRaftActorContext().getTermInformation().updateAndPersist(message.getNewTerm(), "");
 264             } else {
 265                 LOG.warn("Switching to behavior : {} - not supported", newState);
 266             }
 267         }
 268     }
 269
 270     private void switchBehavior(Supplier<RaftActorBehavior> supplier){
 271         reusableBehaviorStateHolder.init(getCurrentBehavior());
 272
 273         setCurrentBehavior(supplier.get());
 274
 275         handleBehaviorChange(reusableBehaviorStateHolder, getCurrentBehavior());
 276     }
 277
 278     protected RaftActorSnapshotMessageSupport newRaftActorSnapshotMessageSupport() {
 279         return new RaftActorSnapshotMessageSupport(context, currentBehavior,
 280                 getRaftActorSnapshotCohort());
 281     }
 282
 283     private void onGetOnDemandRaftStats() {
 284         // Debugging message to retrieve raft stats.
 285
 286         Map<String, String> peerAddresses = new HashMap<>();
 287         for(String peerId: context.getPeerIds()) {
 288             peerAddresses.put(peerId, context.getPeerAddress(peerId));
 289         }
 290
 291         OnDemandRaftState.Builder builder = OnDemandRaftState.builder()
 292                 .commitIndex(context.getCommitIndex())
 293                 .currentTerm(context.getTermInformation().getCurrentTerm())
 294                 .inMemoryJournalDataSize(replicatedLog().dataSize())
 295                 .inMemoryJournalLogSize(replicatedLog().size())
 296                 .isSnapshotCaptureInitiated(context.getSnapshotManager().isCapturing())
 297                 .lastApplied(context.getLastApplied())
 298                 .lastIndex(replicatedLog().lastIndex())
 299                 .lastTerm(replicatedLog().lastTerm())
 300                 .leader(getLeaderId())
 301                 .raftState(currentBehavior.state().toString())
 302                 .replicatedToAllIndex(currentBehavior.getReplicatedToAllIndex())
 303                 .snapshotIndex(replicatedLog().getSnapshotIndex())
 304                 .snapshotTerm(replicatedLog().getSnapshotTerm())
 305                 .votedFor(context.getTermInformation().getVotedFor())
 306                 .peerAddresses(peerAddresses)
 307                 .customRaftPolicyClassName(context.getConfigParams().getCustomRaftPolicyImplementationClass());
 308
 309         ReplicatedLogEntry lastLogEntry = getLastLogEntry();
 310         if (lastLogEntry != null) {
 311             builder.lastLogIndex(lastLogEntry.getIndex());
 312             builder.lastLogTerm(lastLogEntry.getTerm());
 313         }
 314
 315         if(getCurrentBehavior() instanceof AbstractLeader) {
 316             AbstractLeader leader = (AbstractLeader)getCurrentBehavior();
 317             Collection<String> followerIds = leader.getFollowerIds();
 318             List<FollowerInfo> followerInfoList = Lists.newArrayListWithCapacity(followerIds.size());
 319             for(String id: followerIds) {
 320                 final FollowerLogInformation info = leader.getFollower(id);
 321                 followerInfoList.add(new FollowerInfo(id, info.getNextIndex(), info.getMatchIndex(),
 322                         info.isFollowerActive(), DurationFormatUtils.formatDurationHMS(info.timeSinceLastActivity())));
 323             }
 324
 325             builder.followerInfoList(followerInfoList);
 326         }
 327
 328         sender().tell(builder.build(), self());
 329
 330     }
 331
 332     private void handleBehaviorChange(BehaviorStateHolder oldBehaviorState, RaftActorBehavior currentBehavior) {
 333         RaftActorBehavior oldBehavior = oldBehaviorState.getBehavior();
 334
 335         if (oldBehavior != currentBehavior){
 336             onStateChanged();
 337         }
 338
 339         String lastValidLeaderId = oldBehavior == null ? null : oldBehaviorState.getLastValidLeaderId();
 340         String oldBehaviorStateName = oldBehavior == null ? null : oldBehavior.state().name();
 341
 342         // it can happen that the state has not changed but the leader has changed.
 343         Optional<ActorRef> roleChangeNotifier = getRoleChangeNotifier();
 344         if(!Objects.equal(lastValidLeaderId, currentBehavior.getLeaderId()) ||
 345            oldBehaviorState.getLeaderPayloadVersion() != currentBehavior.getLeaderPayloadVersion()) {
 346             if(roleChangeNotifier.isPresent()) {
 347                 roleChangeNotifier.get().tell(newLeaderStateChanged(getId(), currentBehavior.getLeaderId(),
 348                         currentBehavior.getLeaderPayloadVersion()), getSelf());
 349             }
 350
 351             onLeaderChanged(lastValidLeaderId, currentBehavior.getLeaderId());
 352         }
 353
 354         if (roleChangeNotifier.isPresent() &&
 355                 (oldBehavior == null || (oldBehavior.state() != currentBehavior.state()))) {
 356             roleChangeNotifier.get().tell(new RoleChanged(getId(), oldBehaviorStateName ,
 357                     currentBehavior.state().name()), getSelf());
 358         }
 359     }
 360
 361     protected LeaderStateChanged newLeaderStateChanged(String memberId, String leaderId, short leaderPayloadVersion) {
 362         return new LeaderStateChanged(memberId, leaderId, leaderPayloadVersion);
 363     }
 364
 365     @Override
 366     public long snapshotSequenceNr() {
 367         // When we do a snapshot capture, we also capture and save the sequence-number of the persistent journal,
 368         // so that we can delete the persistent journal based on the saved sequence-number
 369         // However , when akka replays the journal during recovery, it replays it from the sequence number when the snapshot
 370         // was saved and not the number we saved.
 371         // We would want to override it , by asking akka to use the last-sequence number known to us.
 372         return context.getSnapshotManager().getLastSequenceNumber();
 373     }
 374
 375     /**
 376      * When a derived RaftActor needs to persist something it must call
 377      * persistData.
 378      *
 379      * @param clientActor
 380      * @param identifier
 381      * @param data
 382      */
 383     protected void persistData(final ActorRef clientActor, final String identifier,
 384         final Payload data) {
 385
 386         ReplicatedLogEntry replicatedLogEntry = new ReplicatedLogImplEntry(
 387             context.getReplicatedLog().lastIndex() + 1,
 388             context.getTermInformation().getCurrentTerm(), data);
 389
 390         if(LOG.isDebugEnabled()) {
 391             LOG.debug("{}: Persist data {}", persistenceId(), replicatedLogEntry);
 392         }
 393
 394         final RaftActorContext raftContext = getRaftActorContext();
 395
 396         replicatedLog().appendAndPersist(replicatedLogEntry, new Procedure<ReplicatedLogEntry>() {
 397             @Override
 398             public void apply(ReplicatedLogEntry replicatedLogEntry) {
 399                 if (!hasFollowers()){
 400                     // Increment the Commit Index and the Last Applied values
 401                     raftContext.setCommitIndex(replicatedLogEntry.getIndex());
 402                     raftContext.setLastApplied(replicatedLogEntry.getIndex());
 403
 404                     // Apply the state immediately.
 405                     self().tell(new ApplyState(clientActor, identifier, replicatedLogEntry), self());
 406
 407                     // Send a ApplyJournalEntries message so that we write the fact that we applied
 408                     // the state to durable storage
 409                     self().tell(new ApplyJournalEntries(replicatedLogEntry.getIndex()), self());
 410
 411                 } else if (clientActor != null) {
 412                     context.getReplicatedLog().captureSnapshotIfReady(replicatedLogEntry);
 413
 414                     // Send message for replication
 415                     currentBehavior.handleMessage(getSelf(),
 416                             new Replicate(clientActor, identifier, replicatedLogEntry));
 417                 }
 418             }
 419         });
 420     }
 421
 422     private ReplicatedLog replicatedLog() {
 423         return context.getReplicatedLog();
 424     }
 425
 426     protected String getId() {
 427         return context.getId();
 428     }
 429
 430     @VisibleForTesting
 431     void setCurrentBehavior(RaftActorBehavior behavior) {
 432         currentBehavior.setDelegate(behavior);
 433     }
 434
 435     protected RaftActorBehavior getCurrentBehavior() {
 436         return currentBehavior.getDelegate();
 437     }
 438
 439     /**
 440      * Derived actors can call the isLeader method to check if the current
 441      * RaftActor is the Leader or not
 442      *
 443      * @return true it this RaftActor is a Leader false otherwise
 444      */
 445     protected boolean isLeader() {
 446         return context.getId().equals(currentBehavior.getLeaderId());
 447     }
 448
 449     /**
 450      * Derived actor can call getLeader if they need a reference to the Leader.
 451      * This would be useful for example in forwarding a request to an actor
 452      * which is the leader
 453      *
 454      * @return A reference to the leader if known, null otherwise
 455      */
 456     protected ActorSelection getLeader(){
 457         String leaderAddress = getLeaderAddress();
 458
 459         if(leaderAddress == null){
 460             return null;
 461         }
 462
 463         return context.actorSelection(leaderAddress);
 464     }
 465
 466     /**
 467      *
 468      * @return the current leader's id
 469      */
 470     protected String getLeaderId(){
 471         return currentBehavior.getLeaderId();
 472     }
 473
 474     protected RaftState getRaftState() {
 475         return currentBehavior.state();
 476     }
 477
 478     protected ReplicatedLogEntry getLastLogEntry() {
 479         return replicatedLog().last();
 480     }
 481
 482     protected Long getCurrentTerm(){
 483         return context.getTermInformation().getCurrentTerm();
 484     }
 485
 486     protected Long getCommitIndex(){
 487         return context.getCommitIndex();
 488     }
 489
 490     protected Long getLastApplied(){
 491         return context.getLastApplied();
 492     }
 493
 494     protected RaftActorContext getRaftActorContext() {
 495         return context;
 496     }
 497
 498     protected void updateConfigParams(ConfigParams configParams) {
 499
 500         // obtain the RaftPolicy for oldConfigParams and the updated one.
 501         String oldRaftPolicy = context.getConfigParams().
 502             getCustomRaftPolicyImplementationClass();
 503         String newRaftPolicy = configParams.
 504             getCustomRaftPolicyImplementationClass();
 505
 506         LOG.debug("{}: RaftPolicy used with prev.config {}, RaftPolicy used with newConfig {}", persistenceId(),
 507             oldRaftPolicy, newRaftPolicy);
 508         context.setConfigParams(configParams);
 509         if (!Objects.equal(oldRaftPolicy, newRaftPolicy)) {
 510             // The RaftPolicy was modified. If the current behavior is Follower then re-initialize to Follower
 511             // but transfer the previous leaderId so it doesn't immediately try to schedule an election. This
 512             // avoids potential disruption. Otherwise, switch to Follower normally.
 513             RaftActorBehavior behavior = currentBehavior.getDelegate();
 514             if(behavior instanceof Follower) {
 515                 String previousLeaderId = ((Follower)behavior).getLeaderId();
 516
 517                 LOG.debug("{}: Re-initializing to Follower with previous leaderId {}", persistenceId(), previousLeaderId);
 518
 519                 changeCurrentBehavior(new Follower(context, previousLeaderId));
 520             } else {
 521                 initializeBehavior();
 522             }
 523         }
 524     }
 525
 526     public final DataPersistenceProvider persistence() {
 527         return delegatingPersistenceProvider.getDelegate();
 528     }
 529
 530     public void setPersistence(DataPersistenceProvider provider) {
 531         delegatingPersistenceProvider.setDelegate(provider);
 532     }
 533
 534     protected void setPersistence(boolean persistent) {
 535         if(persistent) {
 536             setPersistence(new PersistentDataProvider(this));
 537         } else {
 538             setPersistence(new NonPersistentDataProvider() {
 539                 /**
 540                  * The way snapshotting works is,
 541                  * <ol>
 542                  * <li> RaftActor calls createSnapshot on the Shard
 543                  * <li> Shard sends a CaptureSnapshotReply and RaftActor then calls saveSnapshot
 544                  * <li> When saveSnapshot is invoked on the akka-persistence API it uses the SnapshotStore to save
 545                  * the snapshot. The SnapshotStore sends SaveSnapshotSuccess or SaveSnapshotFailure. When the
 546                  * RaftActor gets SaveSnapshot success it commits the snapshot to the in-memory journal. This
 547                  * commitSnapshot is mimicking what is done in SaveSnapshotSuccess.
 548                  * </ol>
 549                  */
 550                 @Override
 551                 public void saveSnapshot(Object o) {
 552                     // Make saving Snapshot successful
 553                     // Committing the snapshot here would end up calling commit in the creating state which would
 554                     // be a state violation. That's why now we send a message to commit the snapshot.
 555                     self().tell(RaftActorSnapshotMessageSupport.COMMIT_SNAPSHOT, self());
 556                 }
 557             });
 558         }
 559     }
 560
 561     /**
 562      * setPeerAddress sets the address of a known peer at a later time.
 563      * <p>
 564      * This is to account for situations where a we know that a peer
 565      * exists but we do not know an address up-front. This may also be used in
 566      * situations where a known peer starts off in a different location and we
 567      * need to change it's address
 568      * <p>
 569      * Note that if the peerId does not match the list of peers passed to
 570      * this actor during construction an IllegalStateException will be thrown.
 571      *
 572      * @param peerId
 573      * @param peerAddress
 574      */
 575     protected void setPeerAddress(String peerId, String peerAddress){
 576         context.setPeerAddress(peerId, peerAddress);
 577     }
 578
 579     /**
 580      * The applyState method will be called by the RaftActor when some data
 581      * needs to be applied to the actor's state
 582      *
 583      * @param clientActor A reference to the client who sent this message. This
 584      *                    is the same reference that was passed to persistData
 585      *                    by the derived actor. clientActor may be null when
 586      *                    the RaftActor is behaving as a follower or during
 587      *                    recovery.
 588      * @param identifier  The identifier of the persisted data. This is also
 589      *                    the same identifier that was passed to persistData by
 590      *                    the derived actor. identifier may be null when
 591      *                    the RaftActor is behaving as a follower or during
 592      *                    recovery
 593      * @param data        A piece of data that was persisted by the persistData call.
 594      *                    This should NEVER be null.
 595      */
 596     protected abstract void applyState(ActorRef clientActor, String identifier,
 597         Object data);
 598
 599     /**
 600      * Returns the RaftActorRecoveryCohort to participate in persistence recovery.
 601      */
 602     @Nonnull
 603     protected abstract RaftActorRecoveryCohort getRaftActorRecoveryCohort();
 604
 605     /**
 606      * This method is called when recovery is complete.
 607      */
 608     protected abstract void onRecoveryComplete();
 609
 610     /**
 611      * Returns the RaftActorSnapshotCohort to participate in persistence recovery.
 612      */
 613     @Nonnull
 614     protected abstract RaftActorSnapshotCohort getRaftActorSnapshotCohort();
 615
 616     /**
 617      * This method will be called by the RaftActor when the state of the
 618      * RaftActor changes. The derived actor can then use methods like
 619      * isLeader or getLeader to do something useful
 620      */
 621     protected abstract void onStateChanged();
 622
 623     /**
 624      * Notifier Actor for this RaftActor to notify when a role change happens
 625      * @return ActorRef - ActorRef of the notifier or Optional.absent if none.
 626      */
 627     protected abstract Optional<ActorRef> getRoleChangeNotifier();
 628
 629     protected void onLeaderChanged(String oldLeader, String newLeader){};
 630
 631     private String getLeaderAddress(){
 632         if(isLeader()){
 633             return getSelf().path().toString();
 634         }
 635         String leaderId = currentBehavior.getLeaderId();
 636         if (leaderId == null) {
 637             return null;
 638         }
 639         String peerAddress = context.getPeerAddress(leaderId);
 640         if(LOG.isDebugEnabled()) {
 641             LOG.debug("{}: getLeaderAddress leaderId = {} peerAddress = {}",
 642                     persistenceId(), leaderId, peerAddress);
 643         }
 644
 645         return peerAddress;
 646     }
 647
 648     protected boolean hasFollowers(){
 649         return getRaftActorContext().hasFollowers();
 650     }
 651
 652     private void captureSnapshot() {
 653         SnapshotManager snapshotManager = context.getSnapshotManager();
 654
 655         if(!snapshotManager.isCapturing()) {
 656             LOG.debug("Take a snapshot of current state. lastReplicatedLog is {} and replicatedToAllIndex is {}",
 657                 replicatedLog().last(), currentBehavior.getReplicatedToAllIndex());
 658
 659             snapshotManager.capture(replicatedLog().last(), currentBehavior.getReplicatedToAllIndex());
 660         }
 661     }
 662
 663     /**
 664      * @deprecated Deprecated in favor of {@link org.opendaylight.controller.cluster.raft.base.messages.DeleteEntries}
 665      *             whose type for fromIndex is long instead of int. This class was kept for backwards
 666      *             compatibility with Helium.
 667      */
 668     // Suppressing this warning as we can't set serialVersionUID to maintain backwards compatibility.
 669     @SuppressWarnings("serial")
 670     @Deprecated
 671     static class DeleteEntries implements Serializable {
 672         private final int fromIndex;
 673
 674         public DeleteEntries(int fromIndex) {
 675             this.fromIndex = fromIndex;
 676         }
 677
 678         public int getFromIndex() {
 679             return fromIndex;
 680         }
 681     }
 682
 683     /**
 684      * @deprecated Deprecated in favor of non-inner class {@link org.opendaylight.controller.cluster.raft.base.messages.UpdateElectionTerm}
 685      *             which has serialVersionUID set. This class was kept for backwards compatibility with Helium.
 686      */
 687     // Suppressing this warning as we can't set serialVersionUID to maintain backwards compatibility.
 688     @SuppressWarnings("serial")
 689     @Deprecated
 690     static class UpdateElectionTerm implements Serializable {
 691         private final long currentTerm;
 692         private final String votedFor;
 693
 694         public UpdateElectionTerm(long currentTerm, String votedFor) {
 695             this.currentTerm = currentTerm;
 696             this.votedFor = votedFor;
 697         }
 698
 699         public long getCurrentTerm() {
 700             return currentTerm;
 701         }
 702
 703         public String getVotedFor() {
 704             return votedFor;
 705         }
 706     }
 707
 708     private static class BehaviorStateHolder {
 709         private RaftActorBehavior behavior;
 710         private String lastValidLeaderId;
 711         private short leaderPayloadVersion;
 712
 713         void init(RaftActorBehavior behavior) {
 714             this.behavior = behavior;
 715             this.leaderPayloadVersion = behavior != null ? behavior.getLeaderPayloadVersion() : -1;
 716
 717             String behaviorLeaderId = behavior != null ? behavior.getLeaderId() : null;
 718             if(behaviorLeaderId != null) {
 719                 this.lastValidLeaderId = behaviorLeaderId;
 720             }
 721         }
 722
 723         RaftActorBehavior getBehavior() {
 724             return behavior;
 725         }
 726
 727         String getLastValidLeaderId() {
 728             return lastValidLeaderId;
 729         }
 730
 731         short getLeaderPayloadVersion() {
 732             return leaderPayloadVersion;
 733         }
 734     }
 735
 736     private class SwitchBehaviorSupplier implements Supplier<RaftActorBehavior> {
 737         private Object message;
 738         private ActorRef sender;
 739
 740         public SwitchBehaviorSupplier handleMessage(ActorRef sender, Object message){
 741             this.sender = sender;
 742             this.message = message;
 743             return this;
 744         }
 745
 746         @Override
 747         public RaftActorBehavior get() {
 748             if(this.message instanceof SwitchBehavior){
 749                 return ((SwitchBehavior) message).getNewState().createBehavior(getRaftActorContext());
 750             }
 751             return currentBehavior.handleMessage(sender, message);
 752         }
 753     }
 754 }