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.util.Collection;
  21 import java.util.HashMap;
  22 import java.util.List;
  23 import java.util.Map;
  24 import java.util.Objects;
  25 import java.util.concurrent.TimeUnit;
  26 import javax.annotation.Nonnull;
  27 import javax.annotation.Nullable;
  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.ApplyState;
  37 import org.opendaylight.controller.cluster.raft.base.messages.InitiateCaptureSnapshot;
  38 import org.opendaylight.controller.cluster.raft.base.messages.LeaderTransitioning;
  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.AbstractRaftActorBehavior;
  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.client.messages.Shutdown;
  51 import org.opendaylight.controller.cluster.raft.persisted.ApplyJournalEntries;
  52 import org.opendaylight.controller.cluster.raft.persisted.NoopPayload;
  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
  57 /**
  58  * RaftActor encapsulates a state machine that needs to be kept synchronized
  59  * in a cluster. It implements the RAFT algorithm as described in the paper
  60  * <a href='https://ramcloud.stanford.edu/wiki/download/attachments/11370504/raft.pdf'>
  61  * In Search of an Understandable Consensus Algorithm</a>
  62  *
  63  * <p>
  64  * RaftActor has 3 states and each state has a certain behavior associated
  65  * with it. A Raft actor can behave as,
  66  * <ul>
  67  * <li> A Leader </li>
  68  * <li> A Follower (or) </li>
  69  * <li> A Candidate </li>
  70  * </ul>
  71  *
  72  * <p>
  73  * A RaftActor MUST be a Leader in order to accept requests from clients to
  74  * change the state of it's encapsulated state machine. Once a RaftActor becomes
  75  * a Leader it is also responsible for ensuring that all followers ultimately
  76  * have the same log and therefore the same state machine as itself.
  77  *
  78  * <p>
  79  * The current behavior of a RaftActor determines how election for leadership
  80  * is initiated and how peer RaftActors react to request for votes.
  81  *
  82  * <p>
  83  * Each RaftActor also needs to know the current election term. It uses this
  84  * information for a couple of things. One is to simply figure out who it
  85  * voted for in the last election. Another is to figure out if the message
  86  * it received to update it's state is stale.
  87  *
  88  * <p>
  89  * The RaftActor uses akka-persistence to store it's replicated log.
  90  * Furthermore through it's behaviors a Raft Actor determines
  91  * <ul>
  92  * <li> when a log entry should be persisted </li>
  93  * <li> when a log entry should be applied to the state machine (and) </li>
  94  * <li> when a snapshot should be saved </li>
  95  * </ul>
  96  */
  97 public abstract class RaftActor extends AbstractUntypedPersistentActor {
  98
  99     private static final long APPLY_STATE_DELAY_THRESHOLD_IN_NANOS = TimeUnit.MILLISECONDS.toNanos(50L); // 50 millis
 100
 101     /**
 102      * This context should NOT be passed directly to any other actor it is
 103      * only to be consumed by the RaftActorBehaviors.
 104      */
 105     private final RaftActorContextImpl context;
 106
 107     private final DelegatingPersistentDataProvider delegatingPersistenceProvider;
 108
 109     private final PersistentDataProvider persistentProvider;
 110
 111     private final BehaviorStateTracker behaviorStateTracker = new BehaviorStateTracker();
 112
 113     private RaftActorRecoverySupport raftRecovery;
 114
 115     private RaftActorSnapshotMessageSupport snapshotSupport;
 116
 117     private RaftActorServerConfigurationSupport serverConfigurationSupport;
 118
 119     private RaftActorLeadershipTransferCohort leadershipTransferInProgress;
 120
 121     private boolean shuttingDown;
 122
 123     protected RaftActor(String id, Map<String, String> peerAddresses,
 124          Optional<ConfigParams> configParams, short payloadVersion) {
 125
 126         persistentProvider = new PersistentDataProvider(this);
 127         delegatingPersistenceProvider = new RaftActorDelegatingPersistentDataProvider(null, persistentProvider);
 128
 129         context = new RaftActorContextImpl(this.getSelf(),
 130             this.getContext(), id, new ElectionTermImpl(persistentProvider, id, LOG),
 131             -1, -1, peerAddresses,
 132             configParams.isPresent() ? configParams.get() : new DefaultConfigParamsImpl(),
 133             delegatingPersistenceProvider, LOG);
 134
 135         context.setPayloadVersion(payloadVersion);
 136         context.setReplicatedLog(ReplicatedLogImpl.newInstance(context));
 137     }
 138
 139     @Override
 140     public void preStart() throws Exception {
 141         LOG.info("Starting recovery for {} with journal batch size {}", persistenceId(),
 142                 context.getConfigParams().getJournalRecoveryLogBatchSize());
 143
 144         super.preStart();
 145
 146         snapshotSupport = newRaftActorSnapshotMessageSupport();
 147         serverConfigurationSupport = new RaftActorServerConfigurationSupport(this);
 148     }
 149
 150     @Override
 151     public void postStop() {
 152         context.close();
 153         super.postStop();
 154     }
 155
 156     @Override
 157     protected void handleRecover(Object message) {
 158         if (raftRecovery == null) {
 159             raftRecovery = newRaftActorRecoverySupport();
 160         }
 161
 162         boolean recoveryComplete = raftRecovery.handleRecoveryMessage(message, persistentProvider);
 163         if (recoveryComplete) {
 164             onRecoveryComplete();
 165
 166             initializeBehavior();
 167
 168             raftRecovery = null;
 169         }
 170     }
 171
 172     protected RaftActorRecoverySupport newRaftActorRecoverySupport() {
 173         return new RaftActorRecoverySupport(context, getRaftActorRecoveryCohort());
 174     }
 175
 176     @VisibleForTesting
 177     void initializeBehavior() {
 178         changeCurrentBehavior(new Follower(context));
 179     }
 180
 181     @VisibleForTesting
 182     @SuppressWarnings("checkstyle:IllegalCatch")
 183     protected void changeCurrentBehavior(RaftActorBehavior newBehavior) {
 184         final RaftActorBehavior currentBehavior = getCurrentBehavior();
 185         if (currentBehavior != null) {
 186             try {
 187                 currentBehavior.close();
 188             } catch (Exception e) {
 189                 LOG.warn("{}: Error closing behavior {}", persistence(), currentBehavior, e);
 190             }
 191         }
 192
 193         final BehaviorState state = behaviorStateTracker.capture(currentBehavior);
 194         setCurrentBehavior(newBehavior);
 195         handleBehaviorChange(state, newBehavior);
 196     }
 197
 198     /**
 199      * Method exposed for subclasses to plug-in their logic. This method is invoked by {@link #handleCommand(Object)}
 200      * for messages which are not handled by this class. Subclasses overriding this class should fall back to this
 201      * implementation for messages which they do not handle
 202      *
 203      * @param message Incoming command message
 204      */
 205     protected void handleNonRaftCommand(final Object message) {
 206         unhandled(message);
 207     }
 208
 209     /**
 210      * Handles a message.
 211      *
 212      * @deprecated This method is not final for testing purposes. DO NOT OVERRIDE IT, override
 213      * {@link #handleNonRaftCommand(Object)} instead.
 214      */
 215     @Deprecated
 216     @Override
 217     // FIXME: make this method final once our unit tests do not need to override it
 218     protected void handleCommand(final Object message) {
 219         if (serverConfigurationSupport.handleMessage(message, getSender())) {
 220             return;
 221         }
 222         if (snapshotSupport.handleSnapshotMessage(message, getSender())) {
 223             return;
 224         }
 225
 226         if (message instanceof ApplyState) {
 227             ApplyState applyState = (ApplyState) message;
 228
 229             long startTime = System.nanoTime();
 230
 231             if (LOG.isDebugEnabled()) {
 232                 LOG.debug("{}: Applying state for log index {} data {}",
 233                     persistenceId(), applyState.getReplicatedLogEntry().getIndex(),
 234                     applyState.getReplicatedLogEntry().getData());
 235             }
 236
 237             if (!(applyState.getReplicatedLogEntry().getData() instanceof NoopPayload)) {
 238                 applyState(applyState.getClientActor(), applyState.getIdentifier(),
 239                     applyState.getReplicatedLogEntry().getData());
 240             }
 241
 242             long elapsedTime = System.nanoTime() - startTime;
 243             if (elapsedTime >= APPLY_STATE_DELAY_THRESHOLD_IN_NANOS) {
 244                 LOG.debug("ApplyState took more time than expected. Elapsed Time = {} ms ApplyState = {}",
 245                         TimeUnit.NANOSECONDS.toMillis(elapsedTime), applyState);
 246             }
 247
 248             if (!hasFollowers()) {
 249                 // for single node, the capture should happen after the apply state
 250                 // as we delete messages from the persistent journal which have made it to the snapshot
 251                 // capturing the snapshot before applying makes the persistent journal and snapshot out of sync
 252                 // and recovery shows data missing
 253                 context.getReplicatedLog().captureSnapshotIfReady(applyState.getReplicatedLogEntry());
 254
 255                 context.getSnapshotManager().trimLog(context.getLastApplied());
 256             }
 257
 258             // Send it to the current behavior - some behaviors like PreLeader need to be notified of ApplyState.
 259             possiblyHandleBehaviorMessage(message);
 260
 261         } else if (message instanceof ApplyJournalEntries) {
 262             ApplyJournalEntries applyEntries = (ApplyJournalEntries) message;
 263             LOG.debug("{}: Persisting ApplyJournalEntries with index={}", persistenceId(), applyEntries.getToIndex());
 264
 265             persistence().persist(applyEntries, NoopProcedure.instance());
 266
 267         } else if (message instanceof FindLeader) {
 268             getSender().tell(
 269                 new FindLeaderReply(getLeaderAddress()),
 270                 getSelf()
 271             );
 272         } else if (message instanceof GetOnDemandRaftState) {
 273             onGetOnDemandRaftStats();
 274         } else if (message instanceof InitiateCaptureSnapshot) {
 275             captureSnapshot();
 276         } else if (message instanceof SwitchBehavior) {
 277             switchBehavior((SwitchBehavior) message);
 278         } else if (message instanceof LeaderTransitioning) {
 279             onLeaderTransitioning();
 280         } else if (message instanceof Shutdown) {
 281             onShutDown();
 282         } else if (message instanceof Runnable) {
 283             ((Runnable)message).run();
 284         } else if (message instanceof NoopPayload) {
 285             persistData(null, null, (NoopPayload)message);
 286         } else if (!possiblyHandleBehaviorMessage(message)) {
 287             handleNonRaftCommand(message);
 288         }
 289     }
 290
 291     private boolean possiblyHandleBehaviorMessage(final Object message) {
 292         final RaftActorBehavior currentBehavior = getCurrentBehavior();
 293         final BehaviorState state = behaviorStateTracker.capture(currentBehavior);
 294
 295         // A behavior indicates that it processed the change by returning a reference to the next behavior
 296         // to be used. A null return indicates it has not processed the message and we should be passing it to
 297         // the subclass for handling.
 298         final RaftActorBehavior nextBehavior = currentBehavior.handleMessage(getSender(), message);
 299         if (nextBehavior != null) {
 300             switchBehavior(state, nextBehavior);
 301             return true;
 302         }
 303
 304         return false;
 305     }
 306
 307     private void initiateLeadershipTransfer(final RaftActorLeadershipTransferCohort.OnComplete onComplete) {
 308         LOG.debug("{}: Initiating leader transfer", persistenceId());
 309
 310         if (leadershipTransferInProgress == null) {
 311             leadershipTransferInProgress = new RaftActorLeadershipTransferCohort(this);
 312             leadershipTransferInProgress.addOnComplete(new RaftActorLeadershipTransferCohort.OnComplete() {
 313                 @Override
 314                 public void onSuccess(ActorRef raftActorRef) {
 315                     leadershipTransferInProgress = null;
 316                 }
 317
 318                 @Override
 319                 public void onFailure(ActorRef raftActorRef) {
 320                     leadershipTransferInProgress = null;
 321                 }
 322             });
 323
 324             leadershipTransferInProgress.addOnComplete(onComplete);
 325             leadershipTransferInProgress.init();
 326         } else {
 327             LOG.debug("{}: prior leader transfer in progress - adding callback", persistenceId());
 328             leadershipTransferInProgress.addOnComplete(onComplete);
 329         }
 330     }
 331
 332     private void onShutDown() {
 333         LOG.debug("{}: onShutDown", persistenceId());
 334
 335         if (shuttingDown) {
 336             return;
 337         }
 338
 339         shuttingDown = true;
 340
 341         final RaftActorBehavior currentBehavior = context.getCurrentBehavior();
 342         if (currentBehavior.state() != RaftState.Leader) {
 343             // For non-leaders shutdown is a no-op
 344             self().tell(PoisonPill.getInstance(), self());
 345             return;
 346         }
 347
 348         if (context.hasFollowers()) {
 349             initiateLeadershipTransfer(new RaftActorLeadershipTransferCohort.OnComplete() {
 350                 @Override
 351                 public void onSuccess(ActorRef raftActorRef) {
 352                     LOG.debug("{}: leader transfer succeeded - sending PoisonPill", persistenceId());
 353                     raftActorRef.tell(PoisonPill.getInstance(), raftActorRef);
 354                 }
 355
 356                 @Override
 357                 public void onFailure(ActorRef raftActorRef) {
 358                     LOG.debug("{}: leader transfer failed - sending PoisonPill", persistenceId());
 359                     raftActorRef.tell(PoisonPill.getInstance(), raftActorRef);
 360                 }
 361             });
 362         } else {
 363             pauseLeader(new TimedRunnable(context.getConfigParams().getElectionTimeOutInterval(), this) {
 364                 @Override
 365                 protected void doRun() {
 366                     self().tell(PoisonPill.getInstance(), self());
 367                 }
 368
 369                 @Override
 370                 protected void doCancel() {
 371                     self().tell(PoisonPill.getInstance(), self());
 372                 }
 373             });
 374         }
 375     }
 376
 377     private void onLeaderTransitioning() {
 378         LOG.debug("{}: onLeaderTransitioning", persistenceId());
 379         Optional<ActorRef> roleChangeNotifier = getRoleChangeNotifier();
 380         if (getRaftState() == RaftState.Follower && roleChangeNotifier.isPresent()) {
 381             roleChangeNotifier.get().tell(newLeaderStateChanged(getId(), null,
 382                 getCurrentBehavior().getLeaderPayloadVersion()), getSelf());
 383         }
 384     }
 385
 386     private void switchBehavior(SwitchBehavior message) {
 387         if (!getRaftActorContext().getRaftPolicy().automaticElectionsEnabled()) {
 388             RaftState newState = message.getNewState();
 389             if ( newState == RaftState.Leader || newState == RaftState.Follower) {
 390                 switchBehavior(behaviorStateTracker.capture(getCurrentBehavior()),
 391                     AbstractRaftActorBehavior.createBehavior(context, message.getNewState()));
 392                 getRaftActorContext().getTermInformation().updateAndPersist(message.getNewTerm(), "");
 393             } else {
 394                 LOG.warn("Switching to behavior : {} - not supported", newState);
 395             }
 396         }
 397     }
 398
 399     private void switchBehavior(final BehaviorState oldBehaviorState, final RaftActorBehavior nextBehavior) {
 400         setCurrentBehavior(nextBehavior);
 401         handleBehaviorChange(oldBehaviorState, nextBehavior);
 402     }
 403
 404     @VisibleForTesting
 405     RaftActorSnapshotMessageSupport newRaftActorSnapshotMessageSupport() {
 406         return new RaftActorSnapshotMessageSupport(context, getRaftActorSnapshotCohort());
 407     }
 408
 409     private void onGetOnDemandRaftStats() {
 410         // Debugging message to retrieve raft stats.
 411
 412         Map<String, String> peerAddresses = new HashMap<>();
 413         Map<String, Boolean> peerVotingStates = new HashMap<>();
 414         for (PeerInfo info: context.getPeers()) {
 415             peerVotingStates.put(info.getId(), info.isVoting());
 416             peerAddresses.put(info.getId(), info.getAddress() != null ? info.getAddress() : "");
 417         }
 418
 419         final RaftActorBehavior currentBehavior = context.getCurrentBehavior();
 420         OnDemandRaftState.Builder builder = OnDemandRaftState.builder()
 421                 .commitIndex(context.getCommitIndex())
 422                 .currentTerm(context.getTermInformation().getCurrentTerm())
 423                 .inMemoryJournalDataSize(replicatedLog().dataSize())
 424                 .inMemoryJournalLogSize(replicatedLog().size())
 425                 .isSnapshotCaptureInitiated(context.getSnapshotManager().isCapturing())
 426                 .lastApplied(context.getLastApplied())
 427                 .lastIndex(replicatedLog().lastIndex())
 428                 .lastTerm(replicatedLog().lastTerm())
 429                 .leader(getLeaderId())
 430                 .raftState(currentBehavior.state().toString())
 431                 .replicatedToAllIndex(currentBehavior.getReplicatedToAllIndex())
 432                 .snapshotIndex(replicatedLog().getSnapshotIndex())
 433                 .snapshotTerm(replicatedLog().getSnapshotTerm())
 434                 .votedFor(context.getTermInformation().getVotedFor())
 435                 .isVoting(context.isVotingMember())
 436                 .peerAddresses(peerAddresses)
 437                 .peerVotingStates(peerVotingStates)
 438                 .customRaftPolicyClassName(context.getConfigParams().getCustomRaftPolicyImplementationClass());
 439
 440         ReplicatedLogEntry lastLogEntry = replicatedLog().last();
 441         if (lastLogEntry != null) {
 442             builder.lastLogIndex(lastLogEntry.getIndex());
 443             builder.lastLogTerm(lastLogEntry.getTerm());
 444         }
 445
 446         if (getCurrentBehavior() instanceof AbstractLeader) {
 447             AbstractLeader leader = (AbstractLeader)getCurrentBehavior();
 448             Collection<String> followerIds = leader.getFollowerIds();
 449             List<FollowerInfo> followerInfoList = Lists.newArrayListWithCapacity(followerIds.size());
 450             for (String id: followerIds) {
 451                 final FollowerLogInformation info = leader.getFollower(id);
 452                 followerInfoList.add(new FollowerInfo(id, info.getNextIndex(), info.getMatchIndex(),
 453                         info.isFollowerActive(), DurationFormatUtils.formatDurationHMS(info.timeSinceLastActivity()),
 454                         context.getPeerInfo(info.getId()).isVoting()));
 455             }
 456
 457             builder.followerInfoList(followerInfoList);
 458         }
 459
 460         sender().tell(builder.build(), self());
 461
 462     }
 463
 464     private void handleBehaviorChange(BehaviorState oldBehaviorState, RaftActorBehavior currentBehavior) {
 465         RaftActorBehavior oldBehavior = oldBehaviorState.getBehavior();
 466
 467         if (oldBehavior != currentBehavior) {
 468             onStateChanged();
 469         }
 470
 471         String lastLeaderId = oldBehavior == null ? null : oldBehaviorState.getLastLeaderId();
 472         String lastValidLeaderId = oldBehavior == null ? null : oldBehaviorState.getLastValidLeaderId();
 473         String oldBehaviorStateName = oldBehavior == null ? null : oldBehavior.state().name();
 474
 475         // it can happen that the state has not changed but the leader has changed.
 476         Optional<ActorRef> roleChangeNotifier = getRoleChangeNotifier();
 477         if (!Objects.equals(lastLeaderId, currentBehavior.getLeaderId())
 478                 || oldBehaviorState.getLeaderPayloadVersion() != currentBehavior.getLeaderPayloadVersion()) {
 479             if (roleChangeNotifier.isPresent()) {
 480                 roleChangeNotifier.get().tell(newLeaderStateChanged(getId(), currentBehavior.getLeaderId(),
 481                         currentBehavior.getLeaderPayloadVersion()), getSelf());
 482             }
 483
 484             onLeaderChanged(lastValidLeaderId, currentBehavior.getLeaderId());
 485
 486             if (leadershipTransferInProgress != null) {
 487                 leadershipTransferInProgress.onNewLeader(currentBehavior.getLeaderId());
 488             }
 489
 490             serverConfigurationSupport.onNewLeader(currentBehavior.getLeaderId());
 491         }
 492
 493         if (roleChangeNotifier.isPresent()
 494                 && (oldBehavior == null || oldBehavior.state() != currentBehavior.state())) {
 495             roleChangeNotifier.get().tell(new RoleChanged(getId(), oldBehaviorStateName ,
 496                     currentBehavior.state().name()), getSelf());
 497         }
 498     }
 499
 500     protected LeaderStateChanged newLeaderStateChanged(String memberId, String leaderId, short leaderPayloadVersion) {
 501         return new LeaderStateChanged(memberId, leaderId, leaderPayloadVersion);
 502     }
 503
 504     @Override
 505     public long snapshotSequenceNr() {
 506         // When we do a snapshot capture, we also capture and save the sequence-number of the persistent journal,
 507         // so that we can delete the persistent journal based on the saved sequence-number
 508         // However , when akka replays the journal during recovery, it replays it from the sequence number when the
 509         // snapshot was saved and not the number we saved. We would want to override it , by asking akka to use the
 510         // last-sequence number known to us.
 511         return context.getSnapshotManager().getLastSequenceNumber();
 512     }
 513
 514     /**
 515      * When a derived RaftActor needs to persist something it must call
 516      * persistData.
 517      */
 518     protected final void persistData(final ActorRef clientActor, final Identifier identifier, final Payload data) {
 519
 520         ReplicatedLogEntry replicatedLogEntry = new ReplicatedLogImplEntry(
 521             context.getReplicatedLog().lastIndex() + 1,
 522             context.getTermInformation().getCurrentTerm(), data);
 523
 524         LOG.debug("{}: Persist data {}", persistenceId(), replicatedLogEntry);
 525
 526         final RaftActorContext raftContext = getRaftActorContext();
 527
 528         replicatedLog().appendAndPersist(replicatedLogEntry, replicatedLogEntry1 -> {
 529             if (!hasFollowers()) {
 530                 // Increment the Commit Index and the Last Applied values
 531                 raftContext.setCommitIndex(replicatedLogEntry1.getIndex());
 532                 raftContext.setLastApplied(replicatedLogEntry1.getIndex());
 533
 534                 // Apply the state immediately.
 535                 self().tell(new ApplyState(clientActor, identifier, replicatedLogEntry1), self());
 536
 537                 // Send a ApplyJournalEntries message so that we write the fact that we applied
 538                 // the state to durable storage
 539                 self().tell(new ApplyJournalEntries(replicatedLogEntry1.getIndex()), self());
 540
 541             } else {
 542                 context.getReplicatedLog().captureSnapshotIfReady(replicatedLogEntry1);
 543
 544                 // Send message for replication
 545                 getCurrentBehavior().handleMessage(getSelf(),
 546                         new Replicate(clientActor, identifier, replicatedLogEntry1));
 547             }
 548         });
 549     }
 550
 551     private ReplicatedLog replicatedLog() {
 552         return context.getReplicatedLog();
 553     }
 554
 555     protected String getId() {
 556         return context.getId();
 557     }
 558
 559     @VisibleForTesting
 560     void setCurrentBehavior(RaftActorBehavior behavior) {
 561         context.setCurrentBehavior(behavior);
 562     }
 563
 564     protected RaftActorBehavior getCurrentBehavior() {
 565         return context.getCurrentBehavior();
 566     }
 567
 568     /**
 569      * Derived actors can call the isLeader method to check if the current
 570      * RaftActor is the Leader or not.
 571      *
 572      * @return true it this RaftActor is a Leader false otherwise
 573      */
 574     protected boolean isLeader() {
 575         return context.getId().equals(getCurrentBehavior().getLeaderId());
 576     }
 577
 578     protected final boolean isLeaderActive() {
 579         return getRaftState() != RaftState.IsolatedLeader && getRaftState() != RaftState.PreLeader
 580                 && !shuttingDown && !isLeadershipTransferInProgress();
 581     }
 582
 583     private boolean isLeadershipTransferInProgress() {
 584         return leadershipTransferInProgress != null && leadershipTransferInProgress.isTransferring();
 585     }
 586
 587     /**
 588      * Derived actor can call getLeader if they need a reference to the Leader.
 589      * This would be useful for example in forwarding a request to an actor
 590      * which is the leader
 591      *
 592      * @return A reference to the leader if known, null otherwise
 593      */
 594     public ActorSelection getLeader() {
 595         String leaderAddress = getLeaderAddress();
 596
 597         if (leaderAddress == null) {
 598             return null;
 599         }
 600
 601         return context.actorSelection(leaderAddress);
 602     }
 603
 604     /**
 605      * Returns the id of the current leader.
 606      *
 607      * @return the current leader's id
 608      */
 609     protected final String getLeaderId() {
 610         return getCurrentBehavior().getLeaderId();
 611     }
 612
 613     @VisibleForTesting
 614     protected final RaftState getRaftState() {
 615         return getCurrentBehavior().state();
 616     }
 617
 618     protected Long getCurrentTerm() {
 619         return context.getTermInformation().getCurrentTerm();
 620     }
 621
 622     protected RaftActorContext getRaftActorContext() {
 623         return context;
 624     }
 625
 626     protected void updateConfigParams(ConfigParams configParams) {
 627
 628         // obtain the RaftPolicy for oldConfigParams and the updated one.
 629         String oldRaftPolicy = context.getConfigParams().getCustomRaftPolicyImplementationClass();
 630         String newRaftPolicy = configParams.getCustomRaftPolicyImplementationClass();
 631
 632         LOG.debug("{}: RaftPolicy used with prev.config {}, RaftPolicy used with newConfig {}", persistenceId(),
 633             oldRaftPolicy, newRaftPolicy);
 634         context.setConfigParams(configParams);
 635         if (!Objects.equals(oldRaftPolicy, newRaftPolicy)) {
 636             // The RaftPolicy was modified. If the current behavior is Follower then re-initialize to Follower
 637             // but transfer the previous leaderId so it doesn't immediately try to schedule an election. This
 638             // avoids potential disruption. Otherwise, switch to Follower normally.
 639             RaftActorBehavior behavior = getCurrentBehavior();
 640             if (behavior != null && behavior.state() == RaftState.Follower) {
 641                 String previousLeaderId = behavior.getLeaderId();
 642                 short previousLeaderPayloadVersion = behavior.getLeaderPayloadVersion();
 643
 644                 LOG.debug("{}: Re-initializing to Follower with previous leaderId {}", persistenceId(),
 645                         previousLeaderId);
 646
 647                 changeCurrentBehavior(new Follower(context, previousLeaderId, previousLeaderPayloadVersion));
 648             } else {
 649                 initializeBehavior();
 650             }
 651         }
 652     }
 653
 654     public final DataPersistenceProvider persistence() {
 655         return delegatingPersistenceProvider.getDelegate();
 656     }
 657
 658     public void setPersistence(DataPersistenceProvider provider) {
 659         delegatingPersistenceProvider.setDelegate(provider);
 660     }
 661
 662     protected void setPersistence(boolean persistent) {
 663         DataPersistenceProvider currentPersistence = persistence();
 664         if (persistent && (currentPersistence == null || !currentPersistence.isRecoveryApplicable())) {
 665             setPersistence(new PersistentDataProvider(this));
 666
 667             if (getCurrentBehavior() != null) {
 668                 LOG.info("{}: Persistence has been enabled - capturing snapshot", persistenceId());
 669                 captureSnapshot();
 670             }
 671         } else if (!persistent && (currentPersistence == null || currentPersistence.isRecoveryApplicable())) {
 672             setPersistence(new NonPersistentDataProvider() {
 673                 /**
 674                  * The way snapshotting works is,
 675                  * <ol>
 676                  * <li> RaftActor calls createSnapshot on the Shard
 677                  * <li> Shard sends a CaptureSnapshotReply and RaftActor then calls saveSnapshot
 678                  * <li> When saveSnapshot is invoked on the akka-persistence API it uses the SnapshotStore to save
 679                  * the snapshot. The SnapshotStore sends SaveSnapshotSuccess or SaveSnapshotFailure. When the
 680                  * RaftActor gets SaveSnapshot success it commits the snapshot to the in-memory journal. This
 681                  * commitSnapshot is mimicking what is done in SaveSnapshotSuccess.
 682                  * </ol>
 683                  */
 684                 @Override
 685                 public void saveSnapshot(Object object) {
 686                     // Make saving Snapshot successful
 687                     // Committing the snapshot here would end up calling commit in the creating state which would
 688                     // be a state violation. That's why now we send a message to commit the snapshot.
 689                     self().tell(RaftActorSnapshotMessageSupport.COMMIT_SNAPSHOT, self());
 690                 }
 691             });
 692         }
 693     }
 694
 695     /**
 696      * setPeerAddress sets the address of a known peer at a later time.
 697      *
 698      * <p>
 699      * This is to account for situations where a we know that a peer
 700      * exists but we do not know an address up-front. This may also be used in
 701      * situations where a known peer starts off in a different location and we
 702      * need to change it's address
 703      *
 704      * <p>
 705      * Note that if the peerId does not match the list of peers passed to
 706      * this actor during construction an IllegalStateException will be thrown.
 707      */
 708     protected void setPeerAddress(String peerId, String peerAddress) {
 709         context.setPeerAddress(peerId, peerAddress);
 710     }
 711
 712     /**
 713      * The applyState method will be called by the RaftActor when some data
 714      * needs to be applied to the actor's state.
 715      *
 716      * @param clientActor A reference to the client who sent this message. This
 717      *                    is the same reference that was passed to persistData
 718      *                    by the derived actor. clientActor may be null when
 719      *                    the RaftActor is behaving as a follower or during
 720      *                    recovery.
 721      * @param identifier  The identifier of the persisted data. This is also
 722      *                    the same identifier that was passed to persistData by
 723      *                    the derived actor. identifier may be null when
 724      *                    the RaftActor is behaving as a follower or during
 725      *                    recovery
 726      * @param data        A piece of data that was persisted by the persistData call.
 727      *                    This should NEVER be null.
 728      */
 729     protected abstract void applyState(ActorRef clientActor, Identifier identifier, Object data);
 730
 731     /**
 732      * Returns the RaftActorRecoveryCohort to participate in persistence recovery.
 733      */
 734     @Nonnull
 735     protected abstract RaftActorRecoveryCohort getRaftActorRecoveryCohort();
 736
 737     /**
 738      * This method is called when recovery is complete.
 739      */
 740     protected abstract void onRecoveryComplete();
 741
 742     /**
 743      * Returns the RaftActorSnapshotCohort to participate in persistence recovery.
 744      */
 745     @Nonnull
 746     protected abstract RaftActorSnapshotCohort getRaftActorSnapshotCohort();
 747
 748     /**
 749      * This method will be called by the RaftActor when the state of the
 750      * RaftActor changes. The derived actor can then use methods like
 751      * isLeader or getLeader to do something useful
 752      */
 753     protected abstract void onStateChanged();
 754
 755     /**
 756      * Notifier Actor for this RaftActor to notify when a role change happens.
 757      *
 758      * @return ActorRef - ActorRef of the notifier or Optional.absent if none.
 759      */
 760     protected abstract Optional<ActorRef> getRoleChangeNotifier();
 761
 762     /**
 763      * This method is called prior to operations such as leadership transfer and actor shutdown when the leader
 764      * must pause or stop its duties. This method allows derived classes to gracefully pause or finish current
 765      * work prior to performing the operation. On completion of any work, the run method must be called on the
 766      * given Runnable to proceed with the given operation. <b>Important:</b> the run method must be called on
 767      * this actor's thread dispatcher as as it modifies internal state.
 768      *
 769      * <p>
 770      * The default implementation immediately runs the operation.
 771      *
 772      * @param operation the operation to run
 773      */
 774     protected void pauseLeader(Runnable operation) {
 775         operation.run();
 776     }
 777
 778     protected void onLeaderChanged(String oldLeader, String newLeader) {
 779     }
 780
 781     private String getLeaderAddress() {
 782         if (isLeader()) {
 783             return getSelf().path().toString();
 784         }
 785         String leaderId = getLeaderId();
 786         if (leaderId == null) {
 787             return null;
 788         }
 789         String peerAddress = context.getPeerAddress(leaderId);
 790         LOG.debug("{}: getLeaderAddress leaderId = {} peerAddress = {}", persistenceId(), leaderId, peerAddress);
 791
 792         return peerAddress;
 793     }
 794
 795     protected boolean hasFollowers() {
 796         return getRaftActorContext().hasFollowers();
 797     }
 798
 799     private void captureSnapshot() {
 800         SnapshotManager snapshotManager = context.getSnapshotManager();
 801
 802         if (!snapshotManager.isCapturing()) {
 803             final long idx = getCurrentBehavior().getReplicatedToAllIndex();
 804             LOG.debug("Take a snapshot of current state. lastReplicatedLog is {} and replicatedToAllIndex is {}",
 805                 replicatedLog().last(), idx);
 806
 807             snapshotManager.capture(replicatedLog().last(), idx);
 808         }
 809     }
 810
 811     /**
 812      * Switch this member to non-voting status. This is a no-op for all behaviors except when we are the leader,
 813      * in which case we need to step down.
 814      */
 815     void becomeNonVoting() {
 816         if (isLeader()) {
 817             initiateLeadershipTransfer(new RaftActorLeadershipTransferCohort.OnComplete() {
 818                 @Override
 819                 public void onSuccess(ActorRef raftActorRef) {
 820                     LOG.debug("{}: leader transfer succeeded after change to non-voting", persistenceId());
 821                     ensureFollowerState();
 822                 }
 823
 824                 @Override
 825                 public void onFailure(ActorRef raftActorRef) {
 826                     LOG.debug("{}: leader transfer failed after change to non-voting", persistenceId());
 827                     ensureFollowerState();
 828                 }
 829
 830                 private void ensureFollowerState() {
 831                     // Whether or not leadership transfer succeeded, we have to step down as leader and
 832                     // switch to Follower so ensure that.
 833                     if (getRaftState() != RaftState.Follower) {
 834                         initializeBehavior();
 835                     }
 836                 }
 837             });
 838         }
 839     }
 840
 841     /**
 842      * A point-in-time capture of {@link RaftActorBehavior} state critical for transitioning between behaviors.
 843      */
 844     private abstract static class BehaviorState implements Immutable {
 845         @Nullable abstract RaftActorBehavior getBehavior();
 846
 847         @Nullable abstract String getLastValidLeaderId();
 848
 849         @Nullable abstract String getLastLeaderId();
 850
 851         @Nullable abstract short getLeaderPayloadVersion();
 852     }
 853
 854     /**
 855      * A {@link BehaviorState} corresponding to non-null {@link RaftActorBehavior} state.
 856      */
 857     private static final class SimpleBehaviorState extends BehaviorState {
 858         private final RaftActorBehavior behavior;
 859         private final String lastValidLeaderId;
 860         private final String lastLeaderId;
 861         private final short leaderPayloadVersion;
 862
 863         SimpleBehaviorState(final String lastValidLeaderId, final String lastLeaderId,
 864                 final RaftActorBehavior behavior) {
 865             this.lastValidLeaderId = lastValidLeaderId;
 866             this.lastLeaderId = lastLeaderId;
 867             this.behavior = Preconditions.checkNotNull(behavior);
 868             this.leaderPayloadVersion = behavior.getLeaderPayloadVersion();
 869         }
 870
 871         @Override
 872         RaftActorBehavior getBehavior() {
 873             return behavior;
 874         }
 875
 876         @Override
 877         String getLastValidLeaderId() {
 878             return lastValidLeaderId;
 879         }
 880
 881         @Override
 882         short getLeaderPayloadVersion() {
 883             return leaderPayloadVersion;
 884         }
 885
 886         @Override
 887         String getLastLeaderId() {
 888             return lastLeaderId;
 889         }
 890     }
 891
 892     /**
 893      * Class tracking behavior-related information, which we need to keep around and pass across behavior switches.
 894      * An instance is created for each RaftActor. It has two functions:
 895      * - it keeps track of the last leader ID we have encountered since we have been created
 896      * - it creates state capture needed to transition from one behavior to the next
 897      */
 898     private static final class BehaviorStateTracker {
 899         /**
 900          * A {@link BehaviorState} corresponding to null {@link RaftActorBehavior} state. Since null behavior is only
 901          * allowed before we receive the first message, we know the leader ID to be null.
 902          */
 903         private static final BehaviorState NULL_BEHAVIOR_STATE = new BehaviorState() {
 904             @Override
 905             RaftActorBehavior getBehavior() {
 906                 return null;
 907             }
 908
 909             @Override
 910             String getLastValidLeaderId() {
 911                 return null;
 912             }
 913
 914             @Override
 915             short getLeaderPayloadVersion() {
 916                 return -1;
 917             }
 918
 919             @Override
 920             String getLastLeaderId() {
 921                 return null;
 922             }
 923         };
 924
 925         private String lastValidLeaderId;
 926         private String lastLeaderId;
 927
 928         BehaviorState capture(final RaftActorBehavior behavior) {
 929             if (behavior == null) {
 930                 Verify.verify(lastValidLeaderId == null, "Null behavior with non-null last leader");
 931                 return NULL_BEHAVIOR_STATE;
 932             }
 933
 934             lastLeaderId = behavior.getLeaderId();
 935             if (lastLeaderId != null) {
 936                 lastValidLeaderId = lastLeaderId;
 937             }
 938
 939             return new SimpleBehaviorState(lastValidLeaderId, lastLeaderId, behavior);
 940         }
 941     }
 942
 943 }