opendaylight/md-sal/sal-akka-raft/src/main/java/org/opendaylight/controller/cluster/raft/RaftActor.java

   1 /*
   2  * Copyright (c) 2014 Cisco Systems, Inc. and others.  All rights reserved.
   3  * Copyright (c) 2015 Brocade Communications Systems, Inc. and others.  All rights reserved.
   4  *
   5  * This program and the accompanying materials are made available under the
   6  * terms of the Eclipse Public License v1.0 which accompanies this distribution,
   7  * and is available at http://www.eclipse.org/legal/epl-v10.html
   8  */
   9
  10 package org.opendaylight.controller.cluster.raft;
  11
  12 import akka.actor.ActorRef;
  13 import akka.actor.ActorSelection;
  14 import akka.japi.Procedure;
  15 import akka.persistence.SnapshotSelectionCriteria;
  16 import com.google.common.annotations.VisibleForTesting;
  17 import com.google.common.base.Objects;
  18 import com.google.common.base.Optional;
  19 import com.google.common.base.Supplier;
  20 import com.google.common.collect.Lists;
  21 import java.io.Serializable;
  22 import java.util.Collection;
  23 import java.util.HashMap;
  24 import java.util.List;
  25 import java.util.Map;
  26 import java.util.concurrent.TimeUnit;
  27 import javax.annotation.Nonnull;
  28 import org.apache.commons.lang3.time.DurationFormatUtils;
  29 import org.opendaylight.controller.cluster.DataPersistenceProvider;
  30 import org.opendaylight.controller.cluster.DelegatingPersistentDataProvider;
  31 import org.opendaylight.controller.cluster.NonPersistentDataProvider;
  32 import org.opendaylight.controller.cluster.PersistentDataProvider;
  33 import org.opendaylight.controller.cluster.common.actor.AbstractUntypedPersistentActor;
  34 import org.opendaylight.controller.cluster.notifications.LeaderStateChanged;
  35 import org.opendaylight.controller.cluster.notifications.RoleChanged;
  36 import org.opendaylight.controller.cluster.raft.base.messages.ApplyJournalEntries;
  37 import org.opendaylight.controller.cluster.raft.base.messages.ApplyState;
  38 import org.opendaylight.controller.cluster.raft.base.messages.InitiateCaptureSnapshot;
  39 import org.opendaylight.controller.cluster.raft.base.messages.Replicate;
  40 import org.opendaylight.controller.cluster.raft.base.messages.SwitchBehavior;
  41 import org.opendaylight.controller.cluster.raft.behaviors.AbstractLeader;
  42 import org.opendaylight.controller.cluster.raft.behaviors.DelegatingRaftActorBehavior;
  43 import org.opendaylight.controller.cluster.raft.behaviors.Follower;
  44 import org.opendaylight.controller.cluster.raft.behaviors.RaftActorBehavior;
  45 import org.opendaylight.controller.cluster.raft.client.messages.FindLeader;
  46 import org.opendaylight.controller.cluster.raft.client.messages.FindLeaderReply;
  47 import org.opendaylight.controller.cluster.raft.client.messages.FollowerInfo;
  48 import org.opendaylight.controller.cluster.raft.client.messages.GetOnDemandRaftState;
  49 import org.opendaylight.controller.cluster.raft.client.messages.OnDemandRaftState;
  50 import org.opendaylight.controller.cluster.raft.protobuff.client.messages.Payload;
  51 import org.slf4j.Logger;
  52 import org.slf4j.LoggerFactory;
  53
  54 /**
  55  * RaftActor encapsulates a state machine that needs to be kept synchronized
  56  * in a cluster. It implements the RAFT algorithm as described in the paper
  57  * <a href='https://ramcloud.stanford.edu/wiki/download/attachments/11370504/raft.pdf'>
  58  * In Search of an Understandable Consensus Algorithm</a>
  59  * <p/>
  60  * RaftActor has 3 states and each state has a certain behavior associated
  61  * with it. A Raft actor can behave as,
  62  * <ul>
  63  * <li> A Leader </li>
  64  * <li> A Follower (or) </li>
  65  * <li> A Candidate </li>
  66  * </ul>
  67  * <p/>
  68  * <p/>
  69  * A RaftActor MUST be a Leader in order to accept requests from clients to
  70  * change the state of it's encapsulated state machine. Once a RaftActor becomes
  71  * a Leader it is also responsible for ensuring that all followers ultimately
  72  * have the same log and therefore the same state machine as itself.
  73  * <p/>
  74  * <p/>
  75  * The current behavior of a RaftActor determines how election for leadership
  76  * is initiated and how peer RaftActors react to request for votes.
  77  * <p/>
  78  * <p/>
  79  * Each RaftActor also needs to know the current election term. It uses this
  80  * information for a couple of things. One is to simply figure out who it
  81  * voted for in the last election. Another is to figure out if the message
  82  * it received to update it's state is stale.
  83  * <p/>
  84  * <p/>
  85  * The RaftActor uses akka-persistence to store it's replicated log.
  86  * Furthermore through it's behaviors a Raft Actor determines
  87  * <p/>
  88  * <ul>
  89  * <li> when a log entry should be persisted </li>
  90  * <li> when a log entry should be applied to the state machine (and) </li>
  91  * <li> when a snapshot should be saved </li>
  92  * </ul>
  93  */
  94 public abstract class RaftActor extends AbstractUntypedPersistentActor {
  95
  96     private static final long APPLY_STATE_DELAY_THRESHOLD_IN_NANOS = TimeUnit.MILLISECONDS.toNanos(50L); // 50 millis
  97
  98     protected final Logger LOG = LoggerFactory.getLogger(getClass());
  99
 100     /**
 101      * The current state determines the current behavior of a RaftActor
 102      * A Raft Actor always starts off in the Follower State
 103      */
 104     private final DelegatingRaftActorBehavior currentBehavior = new DelegatingRaftActorBehavior();
 105
 106     /**
 107      * This context should NOT be passed directly to any other actor it is
 108      * only to be consumed by the RaftActorBehaviors
 109      */
 110     private final RaftActorContextImpl context;
 111
 112     private final DelegatingPersistentDataProvider delegatingPersistenceProvider = new DelegatingPersistentDataProvider(null);
 113
 114     private RaftActorRecoverySupport raftRecovery;
 115
 116     private RaftActorSnapshotMessageSupport snapshotSupport;
 117
 118     private final BehaviorStateHolder reusableBehaviorStateHolder = new BehaviorStateHolder();
 119
 120     private final SwitchBehaviorSupplier reusableSwitchBehaviorSupplier = new SwitchBehaviorSupplier();
 121
 122     public RaftActor(String id, Map<String, String> peerAddresses,
 123          Optional<ConfigParams> configParams, short payloadVersion) {
 124
 125         context = new RaftActorContextImpl(this.getSelf(),
 126             this.getContext(), id, new ElectionTermImpl(delegatingPersistenceProvider, id, LOG),
 127             -1, -1, peerAddresses,
 128             (configParams.isPresent() ? configParams.get(): new DefaultConfigParamsImpl()),
 129             delegatingPersistenceProvider, LOG);
 130
 131         context.setPayloadVersion(payloadVersion);
 132         context.setReplicatedLog(ReplicatedLogImpl.newInstance(context, currentBehavior));
 133     }
 134
 135     @Override
 136     public void preStart() throws Exception {
 137         LOG.info("Starting recovery for {} with journal batch size {}", persistenceId(),
 138                 context.getConfigParams().getJournalRecoveryLogBatchSize());
 139
 140         super.preStart();
 141
 142         snapshotSupport = newRaftActorSnapshotMessageSupport();
 143     }
 144
 145     @Override
 146     public void postStop() {
 147         if(currentBehavior.getDelegate() != null) {
 148             try {
 149                 currentBehavior.close();
 150             } catch (Exception e) {
 151                 LOG.debug("{}: Error closing behavior {}", persistenceId(), currentBehavior.state());
 152             }
 153         }
 154
 155         super.postStop();
 156     }
 157
 158     @Override
 159     public void handleRecover(Object message) {
 160         if(raftRecovery == null) {
 161             raftRecovery = newRaftActorRecoverySupport();
 162         }
 163
 164         boolean recoveryComplete = raftRecovery.handleRecoveryMessage(message);
 165         if(recoveryComplete) {
 166             if(!persistence().isRecoveryApplicable()) {
 167                 // Delete all the messages from the akka journal so that we do not end up with consistency issues
 168                 // Note I am not using the dataPersistenceProvider and directly using the akka api here
 169                 deleteMessages(lastSequenceNr());
 170
 171                 // Delete all the akka snapshots as they will not be needed
 172                 deleteSnapshots(new SnapshotSelectionCriteria(scala.Long.MaxValue(), scala.Long.MaxValue()));
 173             }
 174
 175             onRecoveryComplete();
 176
 177             initializeBehavior();
 178
 179             raftRecovery = null;
 180         }
 181     }
 182
 183     protected RaftActorRecoverySupport newRaftActorRecoverySupport() {
 184         return new RaftActorRecoverySupport(context, currentBehavior, getRaftActorRecoveryCohort());
 185     }
 186
 187     protected void initializeBehavior(){
 188         changeCurrentBehavior(new Follower(context));
 189     }
 190
 191     protected void changeCurrentBehavior(RaftActorBehavior newBehavior){
 192         reusableBehaviorStateHolder.init(getCurrentBehavior());
 193         setCurrentBehavior(newBehavior);
 194         handleBehaviorChange(reusableBehaviorStateHolder, getCurrentBehavior());
 195     }
 196
 197     @Override
 198     public void handleCommand(final Object message) {
 199         if (message instanceof ApplyState){
 200             ApplyState applyState = (ApplyState) message;
 201
 202             long elapsedTime = (System.nanoTime() - applyState.getStartTime());
 203             if(elapsedTime >= APPLY_STATE_DELAY_THRESHOLD_IN_NANOS){
 204                 LOG.warn("ApplyState took more time than expected. Elapsed Time = {} ms ApplyState = {}",
 205                         TimeUnit.NANOSECONDS.toMillis(elapsedTime), applyState);
 206             }
 207
 208             if(LOG.isDebugEnabled()) {
 209                 LOG.debug("{}: Applying state for log index {} data {}",
 210                     persistenceId(), applyState.getReplicatedLogEntry().getIndex(),
 211                     applyState.getReplicatedLogEntry().getData());
 212             }
 213
 214             applyState(applyState.getClientActor(), applyState.getIdentifier(),
 215                 applyState.getReplicatedLogEntry().getData());
 216
 217             if (!hasFollowers()) {
 218                 // for single node, the capture should happen after the apply state
 219                 // as we delete messages from the persistent journal which have made it to the snapshot
 220                 // capturing the snapshot before applying makes the persistent journal and snapshot out of sync
 221                 // and recovery shows data missing
 222                 context.getReplicatedLog().captureSnapshotIfReady(applyState.getReplicatedLogEntry());
 223
 224                 context.getSnapshotManager().trimLog(context.getLastApplied(), currentBehavior);
 225             }
 226
 227         } else if (message instanceof ApplyJournalEntries){
 228             ApplyJournalEntries applyEntries = (ApplyJournalEntries) message;
 229             if(LOG.isDebugEnabled()) {
 230                 LOG.debug("{}: Persisting ApplyLogEntries with index={}", persistenceId(), applyEntries.getToIndex());
 231             }
 232
 233             persistence().persist(applyEntries, NoopProcedure.instance());
 234
 235         } else if (message instanceof FindLeader) {
 236             getSender().tell(
 237                 new FindLeaderReply(getLeaderAddress()),
 238                 getSelf()
 239             );
 240         } else if(message instanceof GetOnDemandRaftState) {
 241             onGetOnDemandRaftStats();
 242         } else if(message instanceof InitiateCaptureSnapshot) {
 243             captureSnapshot();
 244         } else if(message instanceof SwitchBehavior){
 245             switchBehavior(((SwitchBehavior) message));
 246         } else if(!snapshotSupport.handleSnapshotMessage(message)) {
 247             switchBehavior(reusableSwitchBehaviorSupplier.handleMessage(getSender(), message));
 248         }
 249     }
 250
 251     private void switchBehavior(SwitchBehavior message) {
 252         if(!getRaftActorContext().getRaftPolicy().automaticElectionsEnabled()) {
 253             RaftState newState = message.getNewState();
 254             if( newState == RaftState.Leader || newState == RaftState.Follower) {
 255                 switchBehavior(reusableSwitchBehaviorSupplier.handleMessage(getSender(), message));
 256                 getRaftActorContext().getTermInformation().updateAndPersist(message.getNewTerm(), "");
 257             } else {
 258                 LOG.warn("Switching to behavior : {} - not supported", newState);
 259             }
 260         }
 261     }
 262
 263     private void switchBehavior(Supplier<RaftActorBehavior> supplier){
 264         reusableBehaviorStateHolder.init(getCurrentBehavior());
 265
 266         setCurrentBehavior(supplier.get());
 267
 268         handleBehaviorChange(reusableBehaviorStateHolder, getCurrentBehavior());
 269     }
 270
 271     protected RaftActorSnapshotMessageSupport newRaftActorSnapshotMessageSupport() {
 272         return new RaftActorSnapshotMessageSupport(context, currentBehavior,
 273                 getRaftActorSnapshotCohort());
 274     }
 275
 276     private void onGetOnDemandRaftStats() {
 277         // Debugging message to retrieve raft stats.
 278
 279         OnDemandRaftState.Builder builder = OnDemandRaftState.builder()
 280                 .commitIndex(context.getCommitIndex())
 281                 .currentTerm(context.getTermInformation().getCurrentTerm())
 282                 .inMemoryJournalDataSize(replicatedLog().dataSize())
 283                 .inMemoryJournalLogSize(replicatedLog().size())
 284                 .isSnapshotCaptureInitiated(context.getSnapshotManager().isCapturing())
 285                 .lastApplied(context.getLastApplied())
 286                 .lastIndex(replicatedLog().lastIndex())
 287                 .lastTerm(replicatedLog().lastTerm())
 288                 .leader(getLeaderId())
 289                 .raftState(currentBehavior.state().toString())
 290                 .replicatedToAllIndex(currentBehavior.getReplicatedToAllIndex())
 291                 .snapshotIndex(replicatedLog().getSnapshotIndex())
 292                 .snapshotTerm(replicatedLog().getSnapshotTerm())
 293                 .votedFor(context.getTermInformation().getVotedFor())
 294                 .peerAddresses(new HashMap<>(context.getPeerAddresses()));
 295
 296         ReplicatedLogEntry lastLogEntry = getLastLogEntry();
 297         if (lastLogEntry != null) {
 298             builder.lastLogIndex(lastLogEntry.getIndex());
 299             builder.lastLogTerm(lastLogEntry.getTerm());
 300         }
 301
 302         if(getCurrentBehavior() instanceof AbstractLeader) {
 303             AbstractLeader leader = (AbstractLeader)getCurrentBehavior();
 304             Collection<String> followerIds = leader.getFollowerIds();
 305             List<FollowerInfo> followerInfoList = Lists.newArrayListWithCapacity(followerIds.size());
 306             for(String id: followerIds) {
 307                 final FollowerLogInformation info = leader.getFollower(id);
 308                 followerInfoList.add(new FollowerInfo(id, info.getNextIndex(), info.getMatchIndex(),
 309                         info.isFollowerActive(), DurationFormatUtils.formatDurationHMS(info.timeSinceLastActivity())));
 310             }
 311
 312             builder.followerInfoList(followerInfoList);
 313         }
 314
 315         sender().tell(builder.build(), self());
 316
 317     }
 318
 319     private void handleBehaviorChange(BehaviorStateHolder oldBehaviorState, RaftActorBehavior currentBehavior) {
 320         RaftActorBehavior oldBehavior = oldBehaviorState.getBehavior();
 321
 322         if (oldBehavior != currentBehavior){
 323             onStateChanged();
 324         }
 325
 326         String lastValidLeaderId = oldBehavior == null ? null : oldBehaviorState.getLastValidLeaderId();
 327         String oldBehaviorStateName = oldBehavior == null ? null : oldBehavior.state().name();
 328
 329         // it can happen that the state has not changed but the leader has changed.
 330         Optional<ActorRef> roleChangeNotifier = getRoleChangeNotifier();
 331         if(!Objects.equal(lastValidLeaderId, currentBehavior.getLeaderId()) ||
 332            oldBehaviorState.getLeaderPayloadVersion() != currentBehavior.getLeaderPayloadVersion()) {
 333             if(roleChangeNotifier.isPresent()) {
 334                 roleChangeNotifier.get().tell(newLeaderStateChanged(getId(), currentBehavior.getLeaderId(),
 335                         currentBehavior.getLeaderPayloadVersion()), getSelf());
 336             }
 337
 338             onLeaderChanged(lastValidLeaderId, currentBehavior.getLeaderId());
 339         }
 340
 341         if (roleChangeNotifier.isPresent() &&
 342                 (oldBehavior == null || (oldBehavior.state() != currentBehavior.state()))) {
 343             roleChangeNotifier.get().tell(new RoleChanged(getId(), oldBehaviorStateName ,
 344                     currentBehavior.state().name()), getSelf());
 345         }
 346     }
 347
 348     protected LeaderStateChanged newLeaderStateChanged(String memberId, String leaderId, short leaderPayloadVersion) {
 349         return new LeaderStateChanged(memberId, leaderId, leaderPayloadVersion);
 350     }
 351
 352     @Override
 353     public long snapshotSequenceNr() {
 354         // When we do a snapshot capture, we also capture and save the sequence-number of the persistent journal,
 355         // so that we can delete the persistent journal based on the saved sequence-number
 356         // However , when akka replays the journal during recovery, it replays it from the sequence number when the snapshot
 357         // was saved and not the number we saved.
 358         // We would want to override it , by asking akka to use the last-sequence number known to us.
 359         return context.getSnapshotManager().getLastSequenceNumber();
 360     }
 361
 362     /**
 363      * When a derived RaftActor needs to persist something it must call
 364      * persistData.
 365      *
 366      * @param clientActor
 367      * @param identifier
 368      * @param data
 369      */
 370     protected void persistData(final ActorRef clientActor, final String identifier,
 371         final Payload data) {
 372
 373         ReplicatedLogEntry replicatedLogEntry = new ReplicatedLogImplEntry(
 374             context.getReplicatedLog().lastIndex() + 1,
 375             context.getTermInformation().getCurrentTerm(), data);
 376
 377         if(LOG.isDebugEnabled()) {
 378             LOG.debug("{}: Persist data {}", persistenceId(), replicatedLogEntry);
 379         }
 380
 381         final RaftActorContext raftContext = getRaftActorContext();
 382
 383         replicatedLog().appendAndPersist(replicatedLogEntry, new Procedure<ReplicatedLogEntry>() {
 384             @Override
 385             public void apply(ReplicatedLogEntry replicatedLogEntry) throws Exception {
 386                 if (!hasFollowers()){
 387                     // Increment the Commit Index and the Last Applied values
 388                     raftContext.setCommitIndex(replicatedLogEntry.getIndex());
 389                     raftContext.setLastApplied(replicatedLogEntry.getIndex());
 390
 391                     // Apply the state immediately.
 392                     self().tell(new ApplyState(clientActor, identifier, replicatedLogEntry), self());
 393
 394                     // Send a ApplyJournalEntries message so that we write the fact that we applied
 395                     // the state to durable storage
 396                     self().tell(new ApplyJournalEntries(replicatedLogEntry.getIndex()), self());
 397
 398                 } else if (clientActor != null) {
 399                     context.getReplicatedLog().captureSnapshotIfReady(replicatedLogEntry);
 400
 401                     // Send message for replication
 402                     currentBehavior.handleMessage(getSelf(),
 403                             new Replicate(clientActor, identifier, replicatedLogEntry));
 404                 }
 405             }
 406         });
 407     }
 408
 409     private ReplicatedLog replicatedLog() {
 410         return context.getReplicatedLog();
 411     }
 412
 413     protected String getId() {
 414         return context.getId();
 415     }
 416
 417     @VisibleForTesting
 418     void setCurrentBehavior(RaftActorBehavior behavior) {
 419         currentBehavior.setDelegate(behavior);
 420     }
 421
 422     protected RaftActorBehavior getCurrentBehavior() {
 423         return currentBehavior.getDelegate();
 424     }
 425
 426     /**
 427      * Derived actors can call the isLeader method to check if the current
 428      * RaftActor is the Leader or not
 429      *
 430      * @return true it this RaftActor is a Leader false otherwise
 431      */
 432     protected boolean isLeader() {
 433         return context.getId().equals(currentBehavior.getLeaderId());
 434     }
 435
 436     /**
 437      * Derived actor can call getLeader if they need a reference to the Leader.
 438      * This would be useful for example in forwarding a request to an actor
 439      * which is the leader
 440      *
 441      * @return A reference to the leader if known, null otherwise
 442      */
 443     protected ActorSelection getLeader(){
 444         String leaderAddress = getLeaderAddress();
 445
 446         if(leaderAddress == null){
 447             return null;
 448         }
 449
 450         return context.actorSelection(leaderAddress);
 451     }
 452
 453     /**
 454      *
 455      * @return the current leader's id
 456      */
 457     protected String getLeaderId(){
 458         return currentBehavior.getLeaderId();
 459     }
 460
 461     protected RaftState getRaftState() {
 462         return currentBehavior.state();
 463     }
 464
 465     protected ReplicatedLogEntry getLastLogEntry() {
 466         return replicatedLog().last();
 467     }
 468
 469     protected Long getCurrentTerm(){
 470         return context.getTermInformation().getCurrentTerm();
 471     }
 472
 473     protected Long getCommitIndex(){
 474         return context.getCommitIndex();
 475     }
 476
 477     protected Long getLastApplied(){
 478         return context.getLastApplied();
 479     }
 480
 481     protected RaftActorContext getRaftActorContext() {
 482         return context;
 483     }
 484
 485     protected void updateConfigParams(ConfigParams configParams) {
 486         context.setConfigParams(configParams);
 487     }
 488
 489     public final DataPersistenceProvider persistence() {
 490         return delegatingPersistenceProvider.getDelegate();
 491     }
 492
 493     public void setPersistence(DataPersistenceProvider provider) {
 494         delegatingPersistenceProvider.setDelegate(provider);
 495     }
 496
 497     protected void setPersistence(boolean persistent) {
 498         if(persistent) {
 499             setPersistence(new PersistentDataProvider(this));
 500         } else {
 501             setPersistence(new NonPersistentDataProvider() {
 502                 /**
 503                  * The way snapshotting works is,
 504                  * <ol>
 505                  * <li> RaftActor calls createSnapshot on the Shard
 506                  * <li> Shard sends a CaptureSnapshotReply and RaftActor then calls saveSnapshot
 507                  * <li> When saveSnapshot is invoked on the akka-persistence API it uses the SnapshotStore to save
 508                  * the snapshot. The SnapshotStore sends SaveSnapshotSuccess or SaveSnapshotFailure. When the
 509                  * RaftActor gets SaveSnapshot success it commits the snapshot to the in-memory journal. This
 510                  * commitSnapshot is mimicking what is done in SaveSnapshotSuccess.
 511                  * </ol>
 512                  */
 513                 @Override
 514                 public void saveSnapshot(Object o) {
 515                     // Make saving Snapshot successful
 516                     // Committing the snapshot here would end up calling commit in the creating state which would
 517                     // be a state violation. That's why now we send a message to commit the snapshot.
 518                     self().tell(RaftActorSnapshotMessageSupport.COMMIT_SNAPSHOT, self());
 519                 }
 520             });
 521         }
 522     }
 523
 524     /**
 525      * setPeerAddress sets the address of a known peer at a later time.
 526      * <p>
 527      * This is to account for situations where a we know that a peer
 528      * exists but we do not know an address up-front. This may also be used in
 529      * situations where a known peer starts off in a different location and we
 530      * need to change it's address
 531      * <p>
 532      * Note that if the peerId does not match the list of peers passed to
 533      * this actor during construction an IllegalStateException will be thrown.
 534      *
 535      * @param peerId
 536      * @param peerAddress
 537      */
 538     protected void setPeerAddress(String peerId, String peerAddress){
 539         context.setPeerAddress(peerId, peerAddress);
 540     }
 541
 542     /**
 543      * The applyState method will be called by the RaftActor when some data
 544      * needs to be applied to the actor's state
 545      *
 546      * @param clientActor A reference to the client who sent this message. This
 547      *                    is the same reference that was passed to persistData
 548      *                    by the derived actor. clientActor may be null when
 549      *                    the RaftActor is behaving as a follower or during
 550      *                    recovery.
 551      * @param identifier  The identifier of the persisted data. This is also
 552      *                    the same identifier that was passed to persistData by
 553      *                    the derived actor. identifier may be null when
 554      *                    the RaftActor is behaving as a follower or during
 555      *                    recovery
 556      * @param data        A piece of data that was persisted by the persistData call.
 557      *                    This should NEVER be null.
 558      */
 559     protected abstract void applyState(ActorRef clientActor, String identifier,
 560         Object data);
 561
 562     /**
 563      * Returns the RaftActorRecoveryCohort to participate in persistence recovery.
 564      */
 565     @Nonnull
 566     protected abstract RaftActorRecoveryCohort getRaftActorRecoveryCohort();
 567
 568     /**
 569      * This method is called when recovery is complete.
 570      */
 571     protected abstract void onRecoveryComplete();
 572
 573     /**
 574      * Returns the RaftActorSnapshotCohort to participate in persistence recovery.
 575      */
 576     @Nonnull
 577     protected abstract RaftActorSnapshotCohort getRaftActorSnapshotCohort();
 578
 579     /**
 580      * This method will be called by the RaftActor when the state of the
 581      * RaftActor changes. The derived actor can then use methods like
 582      * isLeader or getLeader to do something useful
 583      */
 584     protected abstract void onStateChanged();
 585
 586     /**
 587      * Notifier Actor for this RaftActor to notify when a role change happens
 588      * @return ActorRef - ActorRef of the notifier or Optional.absent if none.
 589      */
 590     protected abstract Optional<ActorRef> getRoleChangeNotifier();
 591
 592     protected void onLeaderChanged(String oldLeader, String newLeader){};
 593
 594     private String getLeaderAddress(){
 595         if(isLeader()){
 596             return getSelf().path().toString();
 597         }
 598         String leaderId = currentBehavior.getLeaderId();
 599         if (leaderId == null) {
 600             return null;
 601         }
 602         String peerAddress = context.getPeerAddress(leaderId);
 603         if(LOG.isDebugEnabled()) {
 604             LOG.debug("{}: getLeaderAddress leaderId = {} peerAddress = {}",
 605                     persistenceId(), leaderId, peerAddress);
 606         }
 607
 608         return peerAddress;
 609     }
 610
 611     protected boolean hasFollowers(){
 612         return getRaftActorContext().hasFollowers();
 613     }
 614
 615     private void captureSnapshot() {
 616         SnapshotManager snapshotManager = context.getSnapshotManager();
 617
 618         if(!snapshotManager.isCapturing()) {
 619             LOG.debug("Take a snapshot of current state. lastReplicatedLog is {} and replicatedToAllIndex is {}",
 620                 replicatedLog().last(), currentBehavior.getReplicatedToAllIndex());
 621
 622             snapshotManager.capture(replicatedLog().last(), currentBehavior.getReplicatedToAllIndex());
 623         }
 624     }
 625
 626     /**
 627      * @deprecated Deprecated in favor of {@link org.opendaylight.controller.cluster.raft.base.messages.DeleteEntries}
 628      *             whose type for fromIndex is long instead of int. This class was kept for backwards
 629      *             compatibility with Helium.
 630      */
 631     // Suppressing this warning as we can't set serialVersionUID to maintain backwards compatibility.
 632     @SuppressWarnings("serial")
 633     @Deprecated
 634     static class DeleteEntries implements Serializable {
 635         private final int fromIndex;
 636
 637         public DeleteEntries(int fromIndex) {
 638             this.fromIndex = fromIndex;
 639         }
 640
 641         public int getFromIndex() {
 642             return fromIndex;
 643         }
 644     }
 645
 646     /**
 647      * @deprecated Deprecated in favor of non-inner class {@link org.opendaylight.controller.cluster.raft.base.messages.UpdateElectionTerm}
 648      *             which has serialVersionUID set. This class was kept for backwards compatibility with Helium.
 649      */
 650     // Suppressing this warning as we can't set serialVersionUID to maintain backwards compatibility.
 651     @SuppressWarnings("serial")
 652     @Deprecated
 653     static class UpdateElectionTerm implements Serializable {
 654         private final long currentTerm;
 655         private final String votedFor;
 656
 657         public UpdateElectionTerm(long currentTerm, String votedFor) {
 658             this.currentTerm = currentTerm;
 659             this.votedFor = votedFor;
 660         }
 661
 662         public long getCurrentTerm() {
 663             return currentTerm;
 664         }
 665
 666         public String getVotedFor() {
 667             return votedFor;
 668         }
 669     }
 670
 671     private static class BehaviorStateHolder {
 672         private RaftActorBehavior behavior;
 673         private String lastValidLeaderId;
 674         private short leaderPayloadVersion;
 675
 676         void init(RaftActorBehavior behavior) {
 677             this.behavior = behavior;
 678             this.leaderPayloadVersion = behavior != null ? behavior.getLeaderPayloadVersion() : -1;
 679
 680             String behaviorLeaderId = behavior != null ? behavior.getLeaderId() : null;
 681             if(behaviorLeaderId != null) {
 682                 this.lastValidLeaderId = behaviorLeaderId;
 683             }
 684         }
 685
 686         RaftActorBehavior getBehavior() {
 687             return behavior;
 688         }
 689
 690         String getLastValidLeaderId() {
 691             return lastValidLeaderId;
 692         }
 693
 694         short getLeaderPayloadVersion() {
 695             return leaderPayloadVersion;
 696         }
 697     }
 698
 699     private class SwitchBehaviorSupplier implements Supplier<RaftActorBehavior> {
 700         private Object message;
 701         private ActorRef sender;
 702
 703         public SwitchBehaviorSupplier handleMessage(ActorRef sender, Object message){
 704             this.sender = sender;
 705             this.message = message;
 706             return this;
 707         }
 708
 709         @Override
 710         public RaftActorBehavior get() {
 711             if(this.message instanceof SwitchBehavior){
 712                 return ((SwitchBehavior) message).getNewState().createBehavior(getRaftActorContext());
 713             }
 714             return currentBehavior.handleMessage(sender, message);
 715         }
 716     }
 717 }