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.actor.PoisonPill;
  15 import com.google.common.annotations.VisibleForTesting;
  16 import com.google.common.base.Optional;
  17 import com.google.common.base.Preconditions;
  18 import com.google.common.base.Verify;
  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.Objects;
  26 import java.util.concurrent.TimeUnit;
  27 import javax.annotation.Nonnull;
  28 import javax.annotation.Nullable;
  29 import org.apache.commons.lang3.time.DurationFormatUtils;
  30 import org.opendaylight.controller.cluster.DataPersistenceProvider;
  31 import org.opendaylight.controller.cluster.DelegatingPersistentDataProvider;
  32 import org.opendaylight.controller.cluster.NonPersistentDataProvider;
  33 import org.opendaylight.controller.cluster.PersistentDataProvider;
  34 import org.opendaylight.controller.cluster.common.actor.AbstractUntypedPersistentActor;
  35 import org.opendaylight.controller.cluster.notifications.LeaderStateChanged;
  36 import org.opendaylight.controller.cluster.notifications.RoleChanged;
  37 import org.opendaylight.controller.cluster.raft.base.messages.ApplyJournalEntries;
  38 import org.opendaylight.controller.cluster.raft.base.messages.ApplyState;
  39 import org.opendaylight.controller.cluster.raft.base.messages.InitiateCaptureSnapshot;
  40 import org.opendaylight.controller.cluster.raft.base.messages.LeaderTransitioning;
  41 import org.opendaylight.controller.cluster.raft.base.messages.Replicate;
  42 import org.opendaylight.controller.cluster.raft.base.messages.SwitchBehavior;
  43 import org.opendaylight.controller.cluster.raft.behaviors.AbstractLeader;
  44 import org.opendaylight.controller.cluster.raft.behaviors.AbstractRaftActorBehavior;
  45 import org.opendaylight.controller.cluster.raft.behaviors.Follower;
  46 import org.opendaylight.controller.cluster.raft.behaviors.RaftActorBehavior;
  47 import org.opendaylight.controller.cluster.raft.client.messages.FindLeader;
  48 import org.opendaylight.controller.cluster.raft.client.messages.FindLeaderReply;
  49 import org.opendaylight.controller.cluster.raft.client.messages.FollowerInfo;
  50 import org.opendaylight.controller.cluster.raft.client.messages.GetOnDemandRaftState;
  51 import org.opendaylight.controller.cluster.raft.client.messages.OnDemandRaftState;
  52 import org.opendaylight.controller.cluster.raft.client.messages.Shutdown;
  53 import org.opendaylight.controller.cluster.raft.protobuff.client.messages.Payload;
  54 import org.opendaylight.yangtools.concepts.Identifier;
  55 import org.opendaylight.yangtools.concepts.Immutable;
  56 import org.slf4j.Logger;
  57 import org.slf4j.LoggerFactory;
  58
  59 /**
  60  * RaftActor encapsulates a state machine that needs to be kept synchronized
  61  * in a cluster. It implements the RAFT algorithm as described in the paper
  62  * <a href='https://ramcloud.stanford.edu/wiki/download/attachments/11370504/raft.pdf'>
  63  * In Search of an Understandable Consensus Algorithm</a>
  64  * <p/>
  65  * RaftActor has 3 states and each state has a certain behavior associated
  66  * with it. A Raft actor can behave as,
  67  * <ul>
  68  * <li> A Leader </li>
  69  * <li> A Follower (or) </li>
  70  * <li> A Candidate </li>
  71  * </ul>
  72  * <p/>
  73  * <p/>
  74  * A RaftActor MUST be a Leader in order to accept requests from clients to
  75  * change the state of it's encapsulated state machine. Once a RaftActor becomes
  76  * a Leader it is also responsible for ensuring that all followers ultimately
  77  * have the same log and therefore the same state machine as itself.
  78  * <p/>
  79  * <p/>
  80  * The current behavior of a RaftActor determines how election for leadership
  81  * is initiated and how peer RaftActors react to request for votes.
  82  * <p/>
  83  * <p/>
  84  * Each RaftActor also needs to know the current election term. It uses this
  85  * information for a couple of things. One is to simply figure out who it
  86  * voted for in the last election. Another is to figure out if the message
  87  * it received to update it's state is stale.
  88  * <p/>
  89  * <p/>
  90  * The RaftActor uses akka-persistence to store it's replicated log.
  91  * Furthermore through it's behaviors a Raft Actor determines
  92  * <p/>
  93  * <ul>
  94  * <li> when a log entry should be persisted </li>
  95  * <li> when a log entry should be applied to the state machine (and) </li>
  96  * <li> when a snapshot should be saved </li>
  97  * </ul>
  98  */
  99 public abstract class RaftActor extends AbstractUntypedPersistentActor {
 100
 101     private static final long APPLY_STATE_DELAY_THRESHOLD_IN_NANOS = TimeUnit.MILLISECONDS.toNanos(50L); // 50 millis
 102
 103     protected final Logger LOG = LoggerFactory.getLogger(getClass());
 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 final BehaviorStateTracker behaviorStateTracker = new BehaviorStateTracker();
 116
 117     private RaftActorRecoverySupport raftRecovery;
 118
 119     private RaftActorSnapshotMessageSupport snapshotSupport;
 120
 121     private RaftActorServerConfigurationSupport serverConfigurationSupport;
 122
 123     private RaftActorLeadershipTransferCohort leadershipTransferInProgress;
 124
 125     private boolean shuttingDown;
 126
 127     public RaftActor(String id, Map<String, String> peerAddresses,
 128          Optional<ConfigParams> configParams, short payloadVersion) {
 129
 130         persistentProvider = new PersistentDataProvider(this);
 131         delegatingPersistenceProvider = new RaftActorDelegatingPersistentDataProvider(null, persistentProvider);
 132
 133         context = new RaftActorContextImpl(this.getSelf(),
 134             this.getContext(), id, new ElectionTermImpl(persistentProvider, id, LOG),
 135             -1, -1, peerAddresses,
 136             (configParams.isPresent() ? configParams.get(): new DefaultConfigParamsImpl()),
 137             delegatingPersistenceProvider, LOG);
 138
 139         context.setPayloadVersion(payloadVersion);
 140         context.setReplicatedLog(ReplicatedLogImpl.newInstance(context));
 141     }
 142
 143     @Override
 144     public void preStart() throws Exception {
 145         LOG.info("Starting recovery for {} with journal batch size {}", persistenceId(),
 146                 context.getConfigParams().getJournalRecoveryLogBatchSize());
 147
 148         super.preStart();
 149
 150         snapshotSupport = newRaftActorSnapshotMessageSupport();
 151         serverConfigurationSupport = new RaftActorServerConfigurationSupport(this);
 152     }
 153
 154     @Override
 155     public void postStop() {
 156         context.close();
 157         super.postStop();
 158     }
 159
 160     @Override
 161     protected void handleRecover(Object message) {
 162         if(raftRecovery == null) {
 163             raftRecovery = newRaftActorRecoverySupport();
 164         }
 165
 166         boolean recoveryComplete = raftRecovery.handleRecoveryMessage(message, persistentProvider);
 167         if(recoveryComplete) {
 168             onRecoveryComplete();
 169
 170             initializeBehavior();
 171
 172             raftRecovery = null;
 173
 174             if (context.getReplicatedLog().size() > 0) {
 175                 self().tell(new InitiateCaptureSnapshot(), self());
 176                 LOG.info("{}: Snapshot capture initiated after recovery", persistenceId());
 177             } else {
 178                 LOG.info("{}: Snapshot capture NOT initiated after recovery, journal empty", persistenceId());
 179             }
 180         }
 181     }
 182
 183     protected RaftActorRecoverySupport newRaftActorRecoverySupport() {
 184         return new RaftActorRecoverySupport(context, getRaftActorRecoveryCohort());
 185     }
 186
 187     @VisibleForTesting
 188     void initializeBehavior(){
 189         changeCurrentBehavior(new Follower(context));
 190     }
 191
 192     @VisibleForTesting
 193     protected void changeCurrentBehavior(RaftActorBehavior newBehavior) {
 194         final RaftActorBehavior currentBehavior = getCurrentBehavior();
 195         if (currentBehavior != null) {
 196             try {
 197                 currentBehavior.close();
 198             } catch (Exception e) {
 199                 LOG.warn("{}: Error closing behavior {}", persistence(), currentBehavior, e);
 200             }
 201         }
 202
 203         final BehaviorState state = behaviorStateTracker.capture(currentBehavior);
 204         setCurrentBehavior(newBehavior);
 205         handleBehaviorChange(state, newBehavior);
 206     }
 207
 208     /**
 209      * Method exposed for subclasses to plug-in their logic. This method is invoked by {@link #handleCommand(Object)}
 210      * for messages which are not handled by this class. Subclasses overriding this class should fall back to this
 211      * implementation for messages which they do not handle
 212      *
 213      * @param message Incoming command message
 214      */
 215     protected void handleNonRaftCommand(final Object message) {
 216         unhandled(message);
 217     }
 218
 219     /**
 220      * @deprecated This method is not final for testing purposes. DO NOT OVERRIDE IT, override
 221      * {@link #handleNonRaftCommand(Object)} instead.
 222      */
 223     @Deprecated
 224     @Override
 225     // FIXME: make this method final once our unit tests do not need to override it
 226     protected void handleCommand(final Object message) {
 227         if (serverConfigurationSupport.handleMessage(message, getSender())) {
 228             return;
 229         }
 230         if (snapshotSupport.handleSnapshotMessage(message, getSender())) {
 231             return;
 232         }
 233
 234         if (message instanceof ApplyState) {
 235             ApplyState applyState = (ApplyState) message;
 236
 237             long startTime = System.nanoTime();
 238
 239             if(LOG.isDebugEnabled()) {
 240                 LOG.debug("{}: Applying state for log index {} data {}",
 241                     persistenceId(), applyState.getReplicatedLogEntry().getIndex(),
 242                     applyState.getReplicatedLogEntry().getData());
 243             }
 244
 245             applyState(applyState.getClientActor(), applyState.getIdentifier(),
 246                 applyState.getReplicatedLogEntry().getData());
 247
 248             long elapsedTime = System.nanoTime() - startTime;
 249             if(elapsedTime >= APPLY_STATE_DELAY_THRESHOLD_IN_NANOS){
 250                 LOG.debug("ApplyState took more time than expected. Elapsed Time = {} ms ApplyState = {}",
 251                         TimeUnit.NANOSECONDS.toMillis(elapsedTime), applyState);
 252             }
 253
 254             if (!hasFollowers()) {
 255                 // for single node, the capture should happen after the apply state
 256                 // as we delete messages from the persistent journal which have made it to the snapshot
 257                 // capturing the snapshot before applying makes the persistent journal and snapshot out of sync
 258                 // and recovery shows data missing
 259                 context.getReplicatedLog().captureSnapshotIfReady(applyState.getReplicatedLogEntry());
 260
 261                 context.getSnapshotManager().trimLog(context.getLastApplied());
 262             }
 263
 264         } else if (message instanceof ApplyJournalEntries) {
 265             ApplyJournalEntries applyEntries = (ApplyJournalEntries) message;
 266             if(LOG.isDebugEnabled()) {
 267                 LOG.debug("{}: Persisting ApplyJournalEntries with index={}", persistenceId(), applyEntries.getToIndex());
 268             }
 269
 270             persistence().persist(applyEntries, NoopProcedure.instance());
 271
 272         } else if (message instanceof FindLeader) {
 273             getSender().tell(
 274                 new FindLeaderReply(getLeaderAddress()),
 275                 getSelf()
 276             );
 277         } else if(message instanceof GetOnDemandRaftState) {
 278             onGetOnDemandRaftStats();
 279         } else if(message instanceof InitiateCaptureSnapshot) {
 280             captureSnapshot();
 281         } else if(message instanceof SwitchBehavior) {
 282             switchBehavior(((SwitchBehavior) message));
 283         } else if(message instanceof LeaderTransitioning) {
 284             onLeaderTransitioning();
 285         } else if(message instanceof Shutdown) {
 286             onShutDown();
 287         } else if(message instanceof Runnable) {
 288             ((Runnable)message).run();
 289         } else {
 290             // Processing the message may affect the state, hence we need to capture it
 291             final RaftActorBehavior currentBehavior = getCurrentBehavior();
 292             final BehaviorState state = behaviorStateTracker.capture(currentBehavior);
 293
 294             // A behavior indicates that it processed the change by returning a reference to the next behavior
 295             // to be used. A null return indicates it has not processed the message and we should be passing it to
 296             // the subclass for handling.
 297             final RaftActorBehavior nextBehavior = currentBehavior.handleMessage(getSender(), message);
 298             if (nextBehavior != null) {
 299                 switchBehavior(state, nextBehavior);
 300             } else {
 301                 handleNonRaftCommand(message);
 302             }
 303         }
 304     }
 305
 306     private void initiateLeadershipTransfer(final RaftActorLeadershipTransferCohort.OnComplete onComplete) {
 307         LOG.debug("{}: Initiating leader transfer", persistenceId());
 308
 309         if(leadershipTransferInProgress == null) {
 310             leadershipTransferInProgress = new RaftActorLeadershipTransferCohort(this);
 311             leadershipTransferInProgress.addOnComplete(new RaftActorLeadershipTransferCohort.OnComplete() {
 312                 @Override
 313                 public void onSuccess(ActorRef raftActorRef) {
 314                     leadershipTransferInProgress = null;
 315                 }
 316
 317                 @Override
 318                 public void onFailure(ActorRef raftActorRef) {
 319                     leadershipTransferInProgress = null;
 320                 }
 321             });
 322
 323             leadershipTransferInProgress.addOnComplete(onComplete);
 324             leadershipTransferInProgress.init();
 325         } else {
 326             LOG.debug("{}: prior leader transfer in progress - adding callback", persistenceId());
 327             leadershipTransferInProgress.addOnComplete(onComplete);
 328         }
 329     }
 330
 331     private void onShutDown() {
 332         LOG.debug("{}: onShutDown", persistenceId());
 333
 334         if(shuttingDown) {
 335             return;
 336         }
 337
 338         shuttingDown = true;
 339
 340         final RaftActorBehavior currentBehavior = context.getCurrentBehavior();
 341         if (currentBehavior.state() != RaftState.Leader) {
 342             // For non-leaders shutdown is a no-op
 343             self().tell(PoisonPill.getInstance(), self());
 344             return;
 345         }
 346
 347         if (context.hasFollowers()) {
 348             initiateLeadershipTransfer(new RaftActorLeadershipTransferCohort.OnComplete() {
 349                 @Override
 350                 public void onSuccess(ActorRef raftActorRef) {
 351                     LOG.debug("{}: leader transfer succeeded - sending PoisonPill", persistenceId());
 352                     raftActorRef.tell(PoisonPill.getInstance(), raftActorRef);
 353                 }
 354
 355                 @Override
 356                 public void onFailure(ActorRef raftActorRef) {
 357                     LOG.debug("{}: leader transfer failed - sending PoisonPill", persistenceId());
 358                     raftActorRef.tell(PoisonPill.getInstance(), raftActorRef);
 359                 }
 360             });
 361         } else {
 362             pauseLeader(new TimedRunnable(context.getConfigParams().getElectionTimeOutInterval(), this) {
 363                 @Override
 364                 protected void doRun() {
 365                     self().tell(PoisonPill.getInstance(), self());
 366                 }
 367
 368                 @Override
 369                 protected void doCancel() {
 370                     self().tell(PoisonPill.getInstance(), self());
 371                 }
 372             });
 373         }
 374     }
 375
 376     private void onLeaderTransitioning() {
 377         LOG.debug("{}: onLeaderTransitioning", persistenceId());
 378         Optional<ActorRef> roleChangeNotifier = getRoleChangeNotifier();
 379         if(getRaftState() == RaftState.Follower && roleChangeNotifier.isPresent()) {
 380             roleChangeNotifier.get().tell(newLeaderStateChanged(getId(), null,
 381                 getCurrentBehavior().getLeaderPayloadVersion()), getSelf());
 382         }
 383     }
 384
 385     private void switchBehavior(SwitchBehavior message) {
 386         if(!getRaftActorContext().getRaftPolicy().automaticElectionsEnabled()) {
 387             RaftState newState = message.getNewState();
 388             if( newState == RaftState.Leader || newState == RaftState.Follower) {
 389                 switchBehavior(behaviorStateTracker.capture(getCurrentBehavior()),
 390                     AbstractRaftActorBehavior.createBehavior(context, message.getNewState()));
 391                 getRaftActorContext().getTermInformation().updateAndPersist(message.getNewTerm(), "");
 392             } else {
 393                 LOG.warn("Switching to behavior : {} - not supported", newState);
 394             }
 395         }
 396     }
 397
 398     private void switchBehavior(final BehaviorState oldBehaviorState, final RaftActorBehavior nextBehavior) {
 399         setCurrentBehavior(nextBehavior);
 400         handleBehaviorChange(oldBehaviorState, nextBehavior);
 401     }
 402
 403     @VisibleForTesting
 404     RaftActorSnapshotMessageSupport newRaftActorSnapshotMessageSupport() {
 405         return new RaftActorSnapshotMessageSupport(context, getRaftActorSnapshotCohort());
 406     }
 407
 408     private void onGetOnDemandRaftStats() {
 409         // Debugging message to retrieve raft stats.
 410
 411         Map<String, String> peerAddresses = new HashMap<>();
 412         Map<String, Boolean> peerVotingStates = new HashMap<>();
 413         for(PeerInfo info: context.getPeers()) {
 414             peerVotingStates.put(info.getId(), info.isVoting());
 415             peerAddresses.put(info.getId(), info.getAddress() != null ? info.getAddress() : "");
 416         }
 417
 418         final RaftActorBehavior currentBehavior = context.getCurrentBehavior();
 419         OnDemandRaftState.Builder builder = OnDemandRaftState.builder()
 420                 .commitIndex(context.getCommitIndex())
 421                 .currentTerm(context.getTermInformation().getCurrentTerm())
 422                 .inMemoryJournalDataSize(replicatedLog().dataSize())
 423                 .inMemoryJournalLogSize(replicatedLog().size())
 424                 .isSnapshotCaptureInitiated(context.getSnapshotManager().isCapturing())
 425                 .lastApplied(context.getLastApplied())
 426                 .lastIndex(replicatedLog().lastIndex())
 427                 .lastTerm(replicatedLog().lastTerm())
 428                 .leader(getLeaderId())
 429                 .raftState(currentBehavior.state().toString())
 430                 .replicatedToAllIndex(currentBehavior.getReplicatedToAllIndex())
 431                 .snapshotIndex(replicatedLog().getSnapshotIndex())
 432                 .snapshotTerm(replicatedLog().getSnapshotTerm())
 433                 .votedFor(context.getTermInformation().getVotedFor())
 434                 .isVoting(context.isVotingMember())
 435                 .peerAddresses(peerAddresses)
 436                 .peerVotingStates(peerVotingStates)
 437                 .customRaftPolicyClassName(context.getConfigParams().getCustomRaftPolicyImplementationClass());
 438
 439         ReplicatedLogEntry lastLogEntry = replicatedLog().last();
 440         if (lastLogEntry != null) {
 441             builder.lastLogIndex(lastLogEntry.getIndex());
 442             builder.lastLogTerm(lastLogEntry.getTerm());
 443         }
 444
 445         if(getCurrentBehavior() instanceof AbstractLeader) {
 446             AbstractLeader leader = (AbstractLeader)getCurrentBehavior();
 447             Collection<String> followerIds = leader.getFollowerIds();
 448             List<FollowerInfo> followerInfoList = Lists.newArrayListWithCapacity(followerIds.size());
 449             for(String id: followerIds) {
 450                 final FollowerLogInformation info = leader.getFollower(id);
 451                 followerInfoList.add(new FollowerInfo(id, info.getNextIndex(), info.getMatchIndex(),
 452                         info.isFollowerActive(), DurationFormatUtils.formatDurationHMS(info.timeSinceLastActivity()),
 453                         context.getPeerInfo(info.getId()).isVoting()));
 454             }
 455
 456             builder.followerInfoList(followerInfoList);
 457         }
 458
 459         sender().tell(builder.build(), self());
 460
 461     }
 462
 463     private void handleBehaviorChange(BehaviorState oldBehaviorState, RaftActorBehavior currentBehavior) {
 464         RaftActorBehavior oldBehavior = oldBehaviorState.getBehavior();
 465
 466         if (oldBehavior != currentBehavior){
 467             onStateChanged();
 468         }
 469
 470         String lastValidLeaderId = oldBehavior == null ? null : oldBehaviorState.getLastValidLeaderId();
 471         String oldBehaviorStateName = oldBehavior == null ? null : oldBehavior.state().name();
 472
 473         // it can happen that the state has not changed but the leader has changed.
 474         Optional<ActorRef> roleChangeNotifier = getRoleChangeNotifier();
 475         if(!Objects.equals(lastValidLeaderId, currentBehavior.getLeaderId()) ||
 476            oldBehaviorState.getLeaderPayloadVersion() != currentBehavior.getLeaderPayloadVersion()) {
 477             if(roleChangeNotifier.isPresent()) {
 478                 roleChangeNotifier.get().tell(newLeaderStateChanged(getId(), currentBehavior.getLeaderId(),
 479                         currentBehavior.getLeaderPayloadVersion()), getSelf());
 480             }
 481
 482             onLeaderChanged(lastValidLeaderId, currentBehavior.getLeaderId());
 483
 484             if(leadershipTransferInProgress != null) {
 485                 leadershipTransferInProgress.onNewLeader(currentBehavior.getLeaderId());
 486             }
 487
 488             serverConfigurationSupport.onNewLeader(currentBehavior.getLeaderId());
 489         }
 490
 491         if (roleChangeNotifier.isPresent() &&
 492                 (oldBehavior == null || (oldBehavior.state() != currentBehavior.state()))) {
 493             roleChangeNotifier.get().tell(new RoleChanged(getId(), oldBehaviorStateName ,
 494                     currentBehavior.state().name()), getSelf());
 495         }
 496     }
 497
 498     protected LeaderStateChanged newLeaderStateChanged(String memberId, String leaderId, short leaderPayloadVersion) {
 499         return new LeaderStateChanged(memberId, leaderId, leaderPayloadVersion);
 500     }
 501
 502     @Override
 503     public long snapshotSequenceNr() {
 504         // When we do a snapshot capture, we also capture and save the sequence-number of the persistent journal,
 505         // so that we can delete the persistent journal based on the saved sequence-number
 506         // However , when akka replays the journal during recovery, it replays it from the sequence number when the snapshot
 507         // was saved and not the number we saved.
 508         // We would want to override it , by asking akka to use the last-sequence number known to us.
 509         return context.getSnapshotManager().getLastSequenceNumber();
 510     }
 511
 512     /**
 513      * When a derived RaftActor needs to persist something it must call
 514      * persistData.
 515      *
 516      * @param clientActor
 517      * @param identifier
 518      * @param data
 519      */
 520     protected final void persistData(final ActorRef clientActor, final Identifier identifier, final Payload data) {
 521
 522         ReplicatedLogEntry replicatedLogEntry = new ReplicatedLogImplEntry(
 523             context.getReplicatedLog().lastIndex() + 1,
 524             context.getTermInformation().getCurrentTerm(), data);
 525
 526         if(LOG.isDebugEnabled()) {
 527             LOG.debug("{}: Persist data {}", persistenceId(), replicatedLogEntry);
 528         }
 529
 530         final RaftActorContext raftContext = getRaftActorContext();
 531
 532         replicatedLog().appendAndPersist(replicatedLogEntry, replicatedLogEntry1 -> {
 533             if (!hasFollowers()){
 534                 // Increment the Commit Index and the Last Applied values
 535                 raftContext.setCommitIndex(replicatedLogEntry1.getIndex());
 536                 raftContext.setLastApplied(replicatedLogEntry1.getIndex());
 537
 538                 // Apply the state immediately.
 539                 self().tell(new ApplyState(clientActor, identifier, replicatedLogEntry1), self());
 540
 541                 // Send a ApplyJournalEntries message so that we write the fact that we applied
 542                 // the state to durable storage
 543                 self().tell(new ApplyJournalEntries(replicatedLogEntry1.getIndex()), self());
 544
 545             } else if (clientActor != null) {
 546                 context.getReplicatedLog().captureSnapshotIfReady(replicatedLogEntry1);
 547
 548                 // Send message for replication
 549                 getCurrentBehavior().handleMessage(getSelf(),
 550                         new Replicate(clientActor, identifier, replicatedLogEntry1));
 551             }
 552         });
 553     }
 554
 555     private ReplicatedLog replicatedLog() {
 556         return context.getReplicatedLog();
 557     }
 558
 559     protected String getId() {
 560         return context.getId();
 561     }
 562
 563     @VisibleForTesting
 564     void setCurrentBehavior(RaftActorBehavior behavior) {
 565         context.setCurrentBehavior(behavior);
 566     }
 567
 568     protected RaftActorBehavior getCurrentBehavior() {
 569         return context.getCurrentBehavior();
 570     }
 571
 572     /**
 573      * Derived actors can call the isLeader method to check if the current
 574      * RaftActor is the Leader or not
 575      *
 576      * @return true it this RaftActor is a Leader false otherwise
 577      */
 578     protected boolean isLeader() {
 579         return context.getId().equals(getCurrentBehavior().getLeaderId());
 580     }
 581
 582     protected final boolean isLeaderActive() {
 583         return getRaftState() != RaftState.IsolatedLeader && !shuttingDown &&
 584                 !isLeadershipTransferInProgress();
 585     }
 586
 587     private boolean isLeadershipTransferInProgress() {
 588         return leadershipTransferInProgress != null && leadershipTransferInProgress.isTransferring();
 589     }
 590
 591     /**
 592      * Derived actor can call getLeader if they need a reference to the Leader.
 593      * This would be useful for example in forwarding a request to an actor
 594      * which is the leader
 595      *
 596      * @return A reference to the leader if known, null otherwise
 597      */
 598     protected ActorSelection getLeader(){
 599         String leaderAddress = getLeaderAddress();
 600
 601         if(leaderAddress == null){
 602             return null;
 603         }
 604
 605         return context.actorSelection(leaderAddress);
 606     }
 607
 608     /**
 609      *
 610      * @return the current leader's id
 611      */
 612     protected final String getLeaderId(){
 613         return getCurrentBehavior().getLeaderId();
 614     }
 615
 616     @VisibleForTesting
 617     protected final RaftState getRaftState() {
 618         return getCurrentBehavior().state();
 619     }
 620
 621     protected Long getCurrentTerm(){
 622         return context.getTermInformation().getCurrentTerm();
 623     }
 624
 625     protected RaftActorContext getRaftActorContext() {
 626         return context;
 627     }
 628
 629     protected void updateConfigParams(ConfigParams configParams) {
 630
 631         // obtain the RaftPolicy for oldConfigParams and the updated one.
 632         String oldRaftPolicy = context.getConfigParams().
 633             getCustomRaftPolicyImplementationClass();
 634         String newRaftPolicy = configParams.
 635             getCustomRaftPolicyImplementationClass();
 636
 637         LOG.debug("{}: RaftPolicy used with prev.config {}, RaftPolicy used with newConfig {}", persistenceId(),
 638             oldRaftPolicy, newRaftPolicy);
 639         context.setConfigParams(configParams);
 640         if (!Objects.equals(oldRaftPolicy, newRaftPolicy)) {
 641             // The RaftPolicy was modified. If the current behavior is Follower then re-initialize to Follower
 642             // but transfer the previous leaderId so it doesn't immediately try to schedule an election. This
 643             // avoids potential disruption. Otherwise, switch to Follower normally.
 644             RaftActorBehavior behavior = getCurrentBehavior();
 645             if (behavior != null && behavior.state() == RaftState.Follower) {
 646                 String previousLeaderId = behavior.getLeaderId();
 647                 short previousLeaderPayloadVersion = behavior.getLeaderPayloadVersion();
 648
 649                 LOG.debug("{}: Re-initializing to Follower with previous leaderId {}", persistenceId(), previousLeaderId);
 650
 651                 changeCurrentBehavior(new Follower(context, previousLeaderId, previousLeaderPayloadVersion));
 652             } else {
 653                 initializeBehavior();
 654             }
 655         }
 656     }
 657
 658     public final DataPersistenceProvider persistence() {
 659         return delegatingPersistenceProvider.getDelegate();
 660     }
 661
 662     public void setPersistence(DataPersistenceProvider provider) {
 663         delegatingPersistenceProvider.setDelegate(provider);
 664     }
 665
 666     protected void setPersistence(boolean persistent) {
 667         if(persistent) {
 668             setPersistence(new PersistentDataProvider(this));
 669         } else {
 670             setPersistence(new NonPersistentDataProvider() {
 671                 /**
 672                  * The way snapshotting works is,
 673                  * <ol>
 674                  * <li> RaftActor calls createSnapshot on the Shard
 675                  * <li> Shard sends a CaptureSnapshotReply and RaftActor then calls saveSnapshot
 676                  * <li> When saveSnapshot is invoked on the akka-persistence API it uses the SnapshotStore to save
 677                  * the snapshot. The SnapshotStore sends SaveSnapshotSuccess or SaveSnapshotFailure. When the
 678                  * RaftActor gets SaveSnapshot success it commits the snapshot to the in-memory journal. This
 679                  * commitSnapshot is mimicking what is done in SaveSnapshotSuccess.
 680                  * </ol>
 681                  */
 682                 @Override
 683                 public void saveSnapshot(Object o) {
 684                     // Make saving Snapshot successful
 685                     // Committing the snapshot here would end up calling commit in the creating state which would
 686                     // be a state violation. That's why now we send a message to commit the snapshot.
 687                     self().tell(RaftActorSnapshotMessageSupport.COMMIT_SNAPSHOT, self());
 688                 }
 689             });
 690         }
 691     }
 692
 693     /**
 694      * setPeerAddress sets the address of a known peer at a later time.
 695      * <p>
 696      * This is to account for situations where a we know that a peer
 697      * exists but we do not know an address up-front. This may also be used in
 698      * situations where a known peer starts off in a different location and we
 699      * need to change it's address
 700      * <p>
 701      * Note that if the peerId does not match the list of peers passed to
 702      * this actor during construction an IllegalStateException will be thrown.
 703      *
 704      * @param peerId
 705      * @param peerAddress
 706      */
 707     protected void setPeerAddress(String peerId, String peerAddress){
 708         context.setPeerAddress(peerId, peerAddress);
 709     }
 710
 711     /**
 712      * The applyState method will be called by the RaftActor when some data
 713      * needs to be applied to the actor's state
 714      *
 715      * @param clientActor A reference to the client who sent this message. This
 716      *                    is the same reference that was passed to persistData
 717      *                    by the derived actor. clientActor may be null when
 718      *                    the RaftActor is behaving as a follower or during
 719      *                    recovery.
 720      * @param identifier  The identifier of the persisted data. This is also
 721      *                    the same identifier that was passed to persistData by
 722      *                    the derived actor. identifier may be null when
 723      *                    the RaftActor is behaving as a follower or during
 724      *                    recovery
 725      * @param data        A piece of data that was persisted by the persistData call.
 726      *                    This should NEVER be null.
 727      */
 728     protected abstract void applyState(ActorRef clientActor, Identifier identifier, Object data);
 729
 730     /**
 731      * Returns the RaftActorRecoveryCohort to participate in persistence recovery.
 732      */
 733     @Nonnull
 734     protected abstract RaftActorRecoveryCohort getRaftActorRecoveryCohort();
 735
 736     /**
 737      * This method is called when recovery is complete.
 738      */
 739     protected abstract void onRecoveryComplete();
 740
 741     /**
 742      * Returns the RaftActorSnapshotCohort to participate in persistence recovery.
 743      */
 744     @Nonnull
 745     protected abstract RaftActorSnapshotCohort getRaftActorSnapshotCohort();
 746
 747     /**
 748      * This method will be called by the RaftActor when the state of the
 749      * RaftActor changes. The derived actor can then use methods like
 750      * isLeader or getLeader to do something useful
 751      */
 752     protected abstract void onStateChanged();
 753
 754     /**
 755      * Notifier Actor for this RaftActor to notify when a role change happens
 756      * @return ActorRef - ActorRef of the notifier or Optional.absent if none.
 757      */
 758     protected abstract Optional<ActorRef> getRoleChangeNotifier();
 759
 760     /**
 761      * This method is called prior to operations such as leadership transfer and actor shutdown when the leader
 762      * must pause or stop its duties. This method allows derived classes to gracefully pause or finish current
 763      * work prior to performing the operation. On completion of any work, the run method must be called on the
 764      * given Runnable to proceed with the given operation. <b>Important:</b> the run method must be called on
 765      * this actor's thread dispatcher as as it modifies internal state.
 766      * <p>
 767      * The default implementation immediately runs the operation.
 768      *
 769      * @param operation the operation to run
 770      */
 771     protected void pauseLeader(Runnable operation) {
 772         operation.run();
 773     }
 774
 775     protected void onLeaderChanged(String oldLeader, String newLeader) {
 776
 777     };
 778
 779     private String getLeaderAddress(){
 780         if(isLeader()){
 781             return getSelf().path().toString();
 782         }
 783         String leaderId = getLeaderId();
 784         if (leaderId == null) {
 785             return null;
 786         }
 787         String peerAddress = context.getPeerAddress(leaderId);
 788         if(LOG.isDebugEnabled()) {
 789             LOG.debug("{}: getLeaderAddress leaderId = {} peerAddress = {}",
 790                     persistenceId(), leaderId, peerAddress);
 791         }
 792
 793         return peerAddress;
 794     }
 795
 796     protected boolean hasFollowers(){
 797         return getRaftActorContext().hasFollowers();
 798     }
 799
 800     private void captureSnapshot() {
 801         SnapshotManager snapshotManager = context.getSnapshotManager();
 802
 803         if (!snapshotManager.isCapturing()) {
 804             final long idx = getCurrentBehavior().getReplicatedToAllIndex();
 805             LOG.debug("Take a snapshot of current state. lastReplicatedLog is {} and replicatedToAllIndex is {}",
 806                 replicatedLog().last(), idx);
 807
 808             snapshotManager.capture(replicatedLog().last(), idx);
 809         }
 810     }
 811
 812     /**
 813      * Switch this member to non-voting status. This is a no-op for all behaviors except when we are the leader,
 814      * in which case we need to step down.
 815      */
 816     void becomeNonVoting() {
 817         if (isLeader()) {
 818             initiateLeadershipTransfer(new RaftActorLeadershipTransferCohort.OnComplete() {
 819                 @Override
 820                 public void onSuccess(ActorRef raftActorRef) {
 821                     LOG.debug("{}: leader transfer succeeded after change to non-voting", persistenceId());
 822                     ensureFollowerState();
 823                 }
 824
 825                 @Override
 826                 public void onFailure(ActorRef raftActorRef) {
 827                     LOG.debug("{}: leader transfer failed after change to non-voting", persistenceId());
 828                     ensureFollowerState();
 829                 }
 830
 831                 private void ensureFollowerState() {
 832                     // Whether or not leadership transfer succeeded, we have to step down as leader and
 833                     // switch to Follower so ensure that.
 834                     if (getRaftState() != RaftState.Follower) {
 835                         initializeBehavior();
 836                     }
 837                 }
 838             });
 839         }
 840     }
 841
 842     /**
 843      * @deprecated Deprecated in favor of {@link org.opendaylight.controller.cluster.raft.base.messages.DeleteEntries}
 844      *             whose type for fromIndex is long instead of int. This class was kept for backwards
 845      *             compatibility with Helium.
 846      */
 847     // Suppressing this warning as we can't set serialVersionUID to maintain backwards compatibility.
 848     @SuppressWarnings("serial")
 849     @Deprecated
 850     static class DeleteEntries implements Serializable {
 851         private final int fromIndex;
 852
 853         public DeleteEntries(int fromIndex) {
 854             this.fromIndex = fromIndex;
 855         }
 856
 857         public int getFromIndex() {
 858             return fromIndex;
 859         }
 860     }
 861
 862     /**
 863      * @deprecated Deprecated in favor of non-inner class {@link org.opendaylight.controller.cluster.raft.base.messages.UpdateElectionTerm}
 864      *             which has serialVersionUID set. This class was kept for backwards compatibility with Helium.
 865      */
 866     // Suppressing this warning as we can't set serialVersionUID to maintain backwards compatibility.
 867     @SuppressWarnings("serial")
 868     @Deprecated
 869     static class UpdateElectionTerm implements Serializable {
 870         private final long currentTerm;
 871         private final String votedFor;
 872
 873         public UpdateElectionTerm(long currentTerm, String votedFor) {
 874             this.currentTerm = currentTerm;
 875             this.votedFor = votedFor;
 876         }
 877
 878         public long getCurrentTerm() {
 879             return currentTerm;
 880         }
 881
 882         public String getVotedFor() {
 883             return votedFor;
 884         }
 885     }
 886
 887     /**
 888      * A point-in-time capture of {@link RaftActorBehavior} state critical for transitioning between behaviors.
 889      */
 890     private static abstract class BehaviorState implements Immutable {
 891         @Nullable abstract RaftActorBehavior getBehavior();
 892         @Nullable abstract String getLastValidLeaderId();
 893         @Nullable abstract short getLeaderPayloadVersion();
 894     }
 895
 896     /**
 897      * A {@link BehaviorState} corresponding to non-null {@link RaftActorBehavior} state.
 898      */
 899     private static final class SimpleBehaviorState extends BehaviorState {
 900         private final RaftActorBehavior behavior;
 901         private final String lastValidLeaderId;
 902         private final short leaderPayloadVersion;
 903
 904         SimpleBehaviorState(final String lastValidLeaderId, final RaftActorBehavior behavior) {
 905             this.lastValidLeaderId = lastValidLeaderId;
 906             this.behavior = Preconditions.checkNotNull(behavior);
 907             this.leaderPayloadVersion = behavior.getLeaderPayloadVersion();
 908         }
 909
 910         @Override
 911         RaftActorBehavior getBehavior() {
 912             return behavior;
 913         }
 914
 915         @Override
 916         String getLastValidLeaderId() {
 917             return lastValidLeaderId;
 918         }
 919
 920         @Override
 921         short getLeaderPayloadVersion() {
 922             return leaderPayloadVersion;
 923         }
 924     }
 925
 926     /**
 927      * Class tracking behavior-related information, which we need to keep around and pass across behavior switches.
 928      * An instance is created for each RaftActor. It has two functions:
 929      * - it keeps track of the last leader ID we have encountered since we have been created
 930      * - it creates state capture needed to transition from one behavior to the next
 931      */
 932     private static final class BehaviorStateTracker {
 933         /**
 934          * A {@link BehaviorState} corresponding to null {@link RaftActorBehavior} state. Since null behavior is only
 935          * allowed before we receive the first message, we know the leader ID to be null.
 936          */
 937         private static final BehaviorState NULL_BEHAVIOR_STATE = new BehaviorState() {
 938             @Override
 939             RaftActorBehavior getBehavior() {
 940                 return null;
 941             }
 942
 943             @Override
 944             String getLastValidLeaderId() {
 945                 return null;
 946             }
 947
 948             @Override
 949             short getLeaderPayloadVersion() {
 950                 return -1;
 951             }
 952         };
 953
 954         private String lastValidLeaderId;
 955
 956         BehaviorState capture(final RaftActorBehavior behavior) {
 957             if (behavior == null) {
 958                 Verify.verify(lastValidLeaderId == null, "Null behavior with non-null last leader");
 959                 return NULL_BEHAVIOR_STATE;
 960             }
 961
 962             final String leaderId = behavior.getLeaderId();
 963             if (leaderId != null) {
 964                 lastValidLeaderId = leaderId;
 965             }
 966
 967             return new SimpleBehaviorState(lastValidLeaderId, behavior);
 968         }
 969     }
 970
 971 }