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 akka.actor.Status;
  16 import com.google.common.annotations.VisibleForTesting;
  17 import com.google.common.base.Optional;
  18 import com.google.common.base.Preconditions;
  19 import com.google.common.base.Verify;
  20 import com.google.common.collect.Lists;
  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.ApplyState;
  38 import org.opendaylight.controller.cluster.raft.base.messages.CheckConsensusReached;
  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.messages.RequestLeadership;
  54 import org.opendaylight.controller.cluster.raft.persisted.ApplyJournalEntries;
  55 import org.opendaylight.controller.cluster.raft.persisted.NoopPayload;
  56 import org.opendaylight.controller.cluster.raft.persisted.ServerConfigurationPayload;
  57 import org.opendaylight.controller.cluster.raft.persisted.SimpleReplicatedLogEntry;
  58 import org.opendaylight.controller.cluster.raft.protobuff.client.messages.Payload;
  59 import org.opendaylight.yangtools.concepts.Identifier;
  60 import org.opendaylight.yangtools.concepts.Immutable;
  61
  62 /**
  63  * RaftActor encapsulates a state machine that needs to be kept synchronized
  64  * in a cluster. It implements the RAFT algorithm as described in the paper
  65  * <a href='https://ramcloud.stanford.edu/wiki/download/attachments/11370504/raft.pdf'>
  66  * In Search of an Understandable Consensus Algorithm</a>
  67  *
  68  * <p>
  69  * RaftActor has 3 states and each state has a certain behavior associated
  70  * with it. A Raft actor can behave as,
  71  * <ul>
  72  * <li> A Leader </li>
  73  * <li> A Follower (or) </li>
  74  * <li> A Candidate </li>
  75  * </ul>
  76  *
  77  * <p>
  78  * A RaftActor MUST be a Leader in order to accept requests from clients to
  79  * change the state of it's encapsulated state machine. Once a RaftActor becomes
  80  * a Leader it is also responsible for ensuring that all followers ultimately
  81  * have the same log and therefore the same state machine as itself.
  82  *
  83  * <p>
  84  * The current behavior of a RaftActor determines how election for leadership
  85  * is initiated and how peer RaftActors react to request for votes.
  86  *
  87  * <p>
  88  * Each RaftActor also needs to know the current election term. It uses this
  89  * information for a couple of things. One is to simply figure out who it
  90  * voted for in the last election. Another is to figure out if the message
  91  * it received to update it's state is stale.
  92  *
  93  * <p>
  94  * The RaftActor uses akka-persistence to store it's replicated log.
  95  * Furthermore through it's behaviors a Raft Actor determines
  96  * <ul>
  97  * <li> when a log entry should be persisted </li>
  98  * <li> when a log entry should be applied to the state machine (and) </li>
  99  * <li> when a snapshot should be saved </li>
 100  * </ul>
 101  */
 102 public abstract class RaftActor extends AbstractUntypedPersistentActor {
 103
 104     private static final long APPLY_STATE_DELAY_THRESHOLD_IN_NANOS = TimeUnit.MILLISECONDS.toNanos(50L); // 50 millis
 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;
 113
 114     private final PersistentDataProvider persistentProvider;
 115
 116     private final BehaviorStateTracker behaviorStateTracker = new BehaviorStateTracker();
 117
 118     private RaftActorRecoverySupport raftRecovery;
 119
 120     private RaftActorSnapshotMessageSupport snapshotSupport;
 121
 122     private RaftActorServerConfigurationSupport serverConfigurationSupport;
 123
 124     private RaftActorLeadershipTransferCohort leadershipTransferInProgress;
 125
 126     private boolean shuttingDown;
 127
 128     protected RaftActor(String id, Map<String, String> peerAddresses,
 129          Optional<ConfigParams> configParams, short payloadVersion) {
 130
 131         persistentProvider = new PersistentDataProvider(this);
 132         delegatingPersistenceProvider = new RaftActorDelegatingPersistentDataProvider(null, persistentProvider);
 133
 134         context = new RaftActorContextImpl(this.getSelf(),
 135             this.getContext(), id, new ElectionTermImpl(persistentProvider, id, LOG),
 136             -1, -1, peerAddresses,
 137             configParams.isPresent() ? configParams.get() : new DefaultConfigParamsImpl(),
 138             delegatingPersistenceProvider, this::handleApplyState, LOG);
 139
 140         context.setPayloadVersion(payloadVersion);
 141         context.setReplicatedLog(ReplicatedLogImpl.newInstance(context));
 142     }
 143
 144     @Override
 145     public void preStart() throws Exception {
 146         LOG.info("Starting recovery for {} with journal batch size {}", persistenceId(),
 147                 context.getConfigParams().getJournalRecoveryLogBatchSize());
 148
 149         super.preStart();
 150
 151         snapshotSupport = newRaftActorSnapshotMessageSupport();
 152         serverConfigurationSupport = new RaftActorServerConfigurationSupport(this);
 153     }
 154
 155     @Override
 156     public void postStop() {
 157         context.close();
 158         super.postStop();
 159     }
 160
 161     @Override
 162     protected void handleRecover(Object message) {
 163         if (raftRecovery == null) {
 164             raftRecovery = newRaftActorRecoverySupport();
 165         }
 166
 167         boolean recoveryComplete = raftRecovery.handleRecoveryMessage(message, persistentProvider);
 168         if (recoveryComplete) {
 169             onRecoveryComplete();
 170
 171             initializeBehavior();
 172
 173             raftRecovery = null;
 174         }
 175     }
 176
 177     protected RaftActorRecoverySupport newRaftActorRecoverySupport() {
 178         return new RaftActorRecoverySupport(context, getRaftActorRecoveryCohort());
 179     }
 180
 181     @VisibleForTesting
 182     void initializeBehavior() {
 183         changeCurrentBehavior(new Follower(context));
 184     }
 185
 186     @VisibleForTesting
 187     @SuppressWarnings("checkstyle:IllegalCatch")
 188     protected void changeCurrentBehavior(RaftActorBehavior newBehavior) {
 189         final RaftActorBehavior currentBehavior = getCurrentBehavior();
 190         if (currentBehavior != null) {
 191             try {
 192                 currentBehavior.close();
 193             } catch (Exception e) {
 194                 LOG.warn("{}: Error closing behavior {}", persistence(), currentBehavior, e);
 195             }
 196         }
 197
 198         final BehaviorState state = behaviorStateTracker.capture(currentBehavior);
 199         setCurrentBehavior(newBehavior);
 200         handleBehaviorChange(state, newBehavior);
 201     }
 202
 203     /**
 204      * Method exposed for subclasses to plug-in their logic. This method is invoked by {@link #handleCommand(Object)}
 205      * for messages which are not handled by this class. Subclasses overriding this class should fall back to this
 206      * implementation for messages which they do not handle
 207      *
 208      * @param message Incoming command message
 209      */
 210     protected void handleNonRaftCommand(final Object message) {
 211         unhandled(message);
 212     }
 213
 214     /**
 215      * Handles a message.
 216      *
 217      * @deprecated This method is not final for testing purposes. DO NOT OVERRIDE IT, override
 218      * {@link #handleNonRaftCommand(Object)} instead.
 219      */
 220     @Deprecated
 221     @Override
 222     // FIXME: make this method final once our unit tests do not need to override it
 223     protected void handleCommand(final Object message) {
 224         if (serverConfigurationSupport.handleMessage(message, getSender())) {
 225             return;
 226         }
 227         if (snapshotSupport.handleSnapshotMessage(message, getSender())) {
 228             return;
 229         }
 230         if (message instanceof ApplyState) {
 231             ApplyState applyState = (ApplyState) message;
 232
 233             if (!hasFollowers()) {
 234                 // for single node, the capture should happen after the apply state
 235                 // as we delete messages from the persistent journal which have made it to the snapshot
 236                 // capturing the snapshot before applying makes the persistent journal and snapshot out of sync
 237                 // and recovery shows data missing
 238                 context.getReplicatedLog().captureSnapshotIfReady(applyState.getReplicatedLogEntry());
 239
 240                 context.getSnapshotManager().trimLog(context.getLastApplied());
 241             }
 242
 243             possiblyHandleBehaviorMessage(message);
 244         } else if (message instanceof ApplyJournalEntries) {
 245             ApplyJournalEntries applyEntries = (ApplyJournalEntries) message;
 246             LOG.debug("{}: Persisting ApplyJournalEntries with index={}", persistenceId(), applyEntries.getToIndex());
 247
 248             persistence().persistAsync(applyEntries, NoopProcedure.instance());
 249
 250         } else if (message instanceof FindLeader) {
 251             getSender().tell(
 252                 new FindLeaderReply(getLeaderAddress()),
 253                 getSelf()
 254             );
 255         } else if (message instanceof GetOnDemandRaftState) {
 256             onGetOnDemandRaftStats();
 257         } else if (message instanceof InitiateCaptureSnapshot) {
 258             captureSnapshot();
 259         } else if (message instanceof SwitchBehavior) {
 260             switchBehavior((SwitchBehavior) message);
 261         } else if (message instanceof LeaderTransitioning) {
 262             onLeaderTransitioning((LeaderTransitioning)message);
 263         } else if (message instanceof Shutdown) {
 264             onShutDown();
 265         } else if (message instanceof Runnable) {
 266             ((Runnable)message).run();
 267         } else if (message instanceof NoopPayload) {
 268             persistData(null, null, (NoopPayload) message, false);
 269         } else if (message instanceof RequestLeadership) {
 270             onRequestLeadership((RequestLeadership) message);
 271         } else if (!possiblyHandleBehaviorMessage(message)) {
 272             handleNonRaftCommand(message);
 273         }
 274     }
 275
 276     private void onRequestLeadership(final RequestLeadership message) {
 277         LOG.debug("{}: onRequestLeadership {}", persistenceId(), message);
 278         if (!isLeader()) {
 279             // non-leader cannot satisfy leadership request
 280             LOG.warn("{}: onRequestLeadership {} was sent to non-leader."
 281                     + " Current behavior: {}. Sending failure response",
 282                     persistenceId(), getCurrentBehavior().state());
 283             message.getReplyTo().tell(new LeadershipTransferFailedException("Cannot transfer leader to "
 284                     + message.getRequestedFollowerId()
 285                     + ". RequestLeadership message was sent to non-leader " + persistenceId()), getSelf());
 286             return;
 287         }
 288
 289         final String requestedFollowerId = message.getRequestedFollowerId();
 290         final ActorRef replyTo = message.getReplyTo();
 291         initiateLeadershipTransfer(new RaftActorLeadershipTransferCohort.OnComplete() {
 292             @Override
 293             public void onSuccess(final ActorRef raftActorRef) {
 294                 // sanity check
 295                 if (!requestedFollowerId.equals(getLeaderId())) {
 296                     onFailure(raftActorRef);
 297                 }
 298
 299                 LOG.debug("{}: Leadership transferred successfully to {}", persistenceId(), requestedFollowerId);
 300                 replyTo.tell(new Status.Success(null), getSelf());
 301             }
 302
 303             @Override
 304             public void onFailure(final ActorRef raftActorRef) {
 305                 LOG.debug("{}: LeadershipTransfer request from {} failed", persistenceId(), requestedFollowerId);
 306                 replyTo.tell(new Status.Failure(
 307                         new LeadershipTransferFailedException(
 308                                 "Failed to transfer leadership to " + requestedFollowerId
 309                                         + ". Follower is not ready to become leader")),
 310                         getSelf());
 311             }
 312         }, message.getRequestedFollowerId());
 313     }
 314
 315     private boolean possiblyHandleBehaviorMessage(final Object message) {
 316         final RaftActorBehavior currentBehavior = getCurrentBehavior();
 317         final BehaviorState state = behaviorStateTracker.capture(currentBehavior);
 318
 319         // A behavior indicates that it processed the change by returning a reference to the next behavior
 320         // to be used. A null return indicates it has not processed the message and we should be passing it to
 321         // the subclass for handling.
 322         final RaftActorBehavior nextBehavior = currentBehavior.handleMessage(getSender(), message);
 323         if (nextBehavior != null) {
 324             switchBehavior(state, nextBehavior);
 325             return true;
 326         }
 327
 328         return false;
 329     }
 330
 331     private void initiateLeadershipTransfer(final RaftActorLeadershipTransferCohort.OnComplete onComplete) {
 332         initiateLeadershipTransfer(onComplete, null);
 333     }
 334
 335     private void initiateLeadershipTransfer(final RaftActorLeadershipTransferCohort.OnComplete onComplete,
 336                                             final String followerId) {
 337         LOG.debug("{}: Initiating leader transfer", persistenceId());
 338
 339         if (leadershipTransferInProgress == null) {
 340             leadershipTransferInProgress = new RaftActorLeadershipTransferCohort(this, followerId);
 341             leadershipTransferInProgress.addOnComplete(new RaftActorLeadershipTransferCohort.OnComplete() {
 342                 @Override
 343                 public void onSuccess(ActorRef raftActorRef) {
 344                     leadershipTransferInProgress = null;
 345                 }
 346
 347                 @Override
 348                 public void onFailure(ActorRef raftActorRef) {
 349                     leadershipTransferInProgress = null;
 350                 }
 351             });
 352
 353             leadershipTransferInProgress.addOnComplete(onComplete);
 354             leadershipTransferInProgress.init();
 355         } else {
 356             LOG.debug("{}: prior leader transfer in progress - adding callback", persistenceId());
 357             leadershipTransferInProgress.addOnComplete(onComplete);
 358         }
 359     }
 360
 361     private void onShutDown() {
 362         LOG.debug("{}: onShutDown", persistenceId());
 363
 364         if (shuttingDown) {
 365             return;
 366         }
 367
 368         shuttingDown = true;
 369
 370         final RaftActorBehavior currentBehavior = context.getCurrentBehavior();
 371         if (currentBehavior.state() != RaftState.Leader) {
 372             // For non-leaders shutdown is a no-op
 373             self().tell(PoisonPill.getInstance(), self());
 374             return;
 375         }
 376
 377         if (context.hasFollowers()) {
 378             initiateLeadershipTransfer(new RaftActorLeadershipTransferCohort.OnComplete() {
 379                 @Override
 380                 public void onSuccess(ActorRef raftActorRef) {
 381                     LOG.debug("{}: leader transfer succeeded - sending PoisonPill", persistenceId());
 382                     raftActorRef.tell(PoisonPill.getInstance(), raftActorRef);
 383                 }
 384
 385                 @Override
 386                 public void onFailure(ActorRef raftActorRef) {
 387                     LOG.debug("{}: leader transfer failed - sending PoisonPill", persistenceId());
 388                     raftActorRef.tell(PoisonPill.getInstance(), raftActorRef);
 389                 }
 390             });
 391         } else {
 392             pauseLeader(new TimedRunnable(context.getConfigParams().getElectionTimeOutInterval(), this) {
 393                 @Override
 394                 protected void doRun() {
 395                     self().tell(PoisonPill.getInstance(), self());
 396                 }
 397
 398                 @Override
 399                 protected void doCancel() {
 400                     self().tell(PoisonPill.getInstance(), self());
 401                 }
 402             });
 403         }
 404     }
 405
 406     private void onLeaderTransitioning(final LeaderTransitioning leaderTransitioning) {
 407         LOG.debug("{}: onLeaderTransitioning: {}", persistenceId(), leaderTransitioning);
 408         Optional<ActorRef> roleChangeNotifier = getRoleChangeNotifier();
 409         if (getRaftState() == RaftState.Follower && roleChangeNotifier.isPresent()
 410                 && leaderTransitioning.getLeaderId().equals(getCurrentBehavior().getLeaderId())) {
 411             roleChangeNotifier.get().tell(newLeaderStateChanged(getId(), null,
 412                 getCurrentBehavior().getLeaderPayloadVersion()), getSelf());
 413         }
 414     }
 415
 416     private void switchBehavior(SwitchBehavior message) {
 417         if (!getRaftActorContext().getRaftPolicy().automaticElectionsEnabled()) {
 418             RaftState newState = message.getNewState();
 419             if (newState == RaftState.Leader || newState == RaftState.Follower) {
 420                 switchBehavior(behaviorStateTracker.capture(getCurrentBehavior()),
 421                     AbstractRaftActorBehavior.createBehavior(context, message.getNewState()));
 422                 getRaftActorContext().getTermInformation().updateAndPersist(message.getNewTerm(), "");
 423             } else {
 424                 LOG.warn("Switching to behavior : {} - not supported", newState);
 425             }
 426         }
 427     }
 428
 429     private void switchBehavior(final BehaviorState oldBehaviorState, final RaftActorBehavior nextBehavior) {
 430         setCurrentBehavior(nextBehavior);
 431         handleBehaviorChange(oldBehaviorState, nextBehavior);
 432     }
 433
 434     @VisibleForTesting
 435     RaftActorSnapshotMessageSupport newRaftActorSnapshotMessageSupport() {
 436         return new RaftActorSnapshotMessageSupport(context, getRaftActorSnapshotCohort());
 437     }
 438
 439     private void onGetOnDemandRaftStats() {
 440         // Debugging message to retrieve raft stats.
 441
 442         Map<String, String> peerAddresses = new HashMap<>();
 443         Map<String, Boolean> peerVotingStates = new HashMap<>();
 444         for (PeerInfo info: context.getPeers()) {
 445             peerVotingStates.put(info.getId(), info.isVoting());
 446             peerAddresses.put(info.getId(), info.getAddress() != null ? info.getAddress() : "");
 447         }
 448
 449         final RaftActorBehavior currentBehavior = context.getCurrentBehavior();
 450         OnDemandRaftState.AbstractBuilder<?> builder = newOnDemandRaftStateBuilder()
 451                 .commitIndex(context.getCommitIndex())
 452                 .currentTerm(context.getTermInformation().getCurrentTerm())
 453                 .inMemoryJournalDataSize(replicatedLog().dataSize())
 454                 .inMemoryJournalLogSize(replicatedLog().size())
 455                 .isSnapshotCaptureInitiated(context.getSnapshotManager().isCapturing())
 456                 .lastApplied(context.getLastApplied())
 457                 .lastIndex(replicatedLog().lastIndex())
 458                 .lastTerm(replicatedLog().lastTerm())
 459                 .leader(getLeaderId())
 460                 .raftState(currentBehavior.state().toString())
 461                 .replicatedToAllIndex(currentBehavior.getReplicatedToAllIndex())
 462                 .snapshotIndex(replicatedLog().getSnapshotIndex())
 463                 .snapshotTerm(replicatedLog().getSnapshotTerm())
 464                 .votedFor(context.getTermInformation().getVotedFor())
 465                 .isVoting(context.isVotingMember())
 466                 .peerAddresses(peerAddresses)
 467                 .peerVotingStates(peerVotingStates)
 468                 .customRaftPolicyClassName(context.getConfigParams().getCustomRaftPolicyImplementationClass());
 469
 470         ReplicatedLogEntry lastLogEntry = replicatedLog().last();
 471         if (lastLogEntry != null) {
 472             builder.lastLogIndex(lastLogEntry.getIndex());
 473             builder.lastLogTerm(lastLogEntry.getTerm());
 474         }
 475
 476         if (getCurrentBehavior() instanceof AbstractLeader) {
 477             AbstractLeader leader = (AbstractLeader)getCurrentBehavior();
 478             Collection<String> followerIds = leader.getFollowerIds();
 479             List<FollowerInfo> followerInfoList = Lists.newArrayListWithCapacity(followerIds.size());
 480             for (String id: followerIds) {
 481                 final FollowerLogInformation info = leader.getFollower(id);
 482                 followerInfoList.add(new FollowerInfo(id, info.getNextIndex(), info.getMatchIndex(),
 483                         info.isFollowerActive(), DurationFormatUtils.formatDurationHMS(info.timeSinceLastActivity()),
 484                         context.getPeerInfo(info.getId()).isVoting()));
 485             }
 486
 487             builder.followerInfoList(followerInfoList);
 488         }
 489
 490         sender().tell(builder.build(), self());
 491
 492     }
 493
 494     protected OnDemandRaftState.AbstractBuilder<?> newOnDemandRaftStateBuilder() {
 495         return OnDemandRaftState.builder();
 496     }
 497
 498     private void handleBehaviorChange(BehaviorState oldBehaviorState, RaftActorBehavior currentBehavior) {
 499         RaftActorBehavior oldBehavior = oldBehaviorState.getBehavior();
 500
 501         if (oldBehavior != currentBehavior) {
 502             onStateChanged();
 503         }
 504
 505         String lastLeaderId = oldBehavior == null ? null : oldBehaviorState.getLastLeaderId();
 506         String lastValidLeaderId = oldBehavior == null ? null : oldBehaviorState.getLastValidLeaderId();
 507         String oldBehaviorStateName = oldBehavior == null ? null : oldBehavior.state().name();
 508
 509         // it can happen that the state has not changed but the leader has changed.
 510         Optional<ActorRef> roleChangeNotifier = getRoleChangeNotifier();
 511         if (!Objects.equals(lastLeaderId, currentBehavior.getLeaderId())
 512                 || oldBehaviorState.getLeaderPayloadVersion() != currentBehavior.getLeaderPayloadVersion()) {
 513             if (roleChangeNotifier.isPresent()) {
 514                 roleChangeNotifier.get().tell(newLeaderStateChanged(getId(), currentBehavior.getLeaderId(),
 515                         currentBehavior.getLeaderPayloadVersion()), getSelf());
 516             }
 517
 518             onLeaderChanged(lastValidLeaderId, currentBehavior.getLeaderId());
 519
 520             if (leadershipTransferInProgress != null) {
 521                 leadershipTransferInProgress.onNewLeader(currentBehavior.getLeaderId());
 522             }
 523
 524             serverConfigurationSupport.onNewLeader(currentBehavior.getLeaderId());
 525         }
 526
 527         if (roleChangeNotifier.isPresent()
 528                 && (oldBehavior == null || oldBehavior.state() != currentBehavior.state())) {
 529             roleChangeNotifier.get().tell(new RoleChanged(getId(), oldBehaviorStateName ,
 530                     currentBehavior.state().name()), getSelf());
 531         }
 532     }
 533
 534     private void handleApplyState(ApplyState applyState) {
 535         long startTime = System.nanoTime();
 536
 537         Payload payload = applyState.getReplicatedLogEntry().getData();
 538         if (LOG.isDebugEnabled()) {
 539             LOG.debug("{}: Applying state for log index {} data {}",
 540                 persistenceId(), applyState.getReplicatedLogEntry().getIndex(), payload);
 541         }
 542
 543         if (!(payload instanceof NoopPayload) && !(payload instanceof ServerConfigurationPayload)) {
 544             applyState(applyState.getClientActor(), applyState.getIdentifier(), payload);
 545         }
 546
 547         long elapsedTime = System.nanoTime() - startTime;
 548         if (elapsedTime >= APPLY_STATE_DELAY_THRESHOLD_IN_NANOS) {
 549             LOG.debug("ApplyState took more time than expected. Elapsed Time = {} ms ApplyState = {}",
 550                     TimeUnit.NANOSECONDS.toMillis(elapsedTime), applyState);
 551         }
 552
 553         // Send the ApplyState message back to self to handle further processing asynchronously.
 554         self().tell(applyState, self());
 555     }
 556
 557     protected LeaderStateChanged newLeaderStateChanged(String memberId, String leaderId, short leaderPayloadVersion) {
 558         return new LeaderStateChanged(memberId, leaderId, leaderPayloadVersion);
 559     }
 560
 561     @Override
 562     public long snapshotSequenceNr() {
 563         // When we do a snapshot capture, we also capture and save the sequence-number of the persistent journal,
 564         // so that we can delete the persistent journal based on the saved sequence-number
 565         // However , when akka replays the journal during recovery, it replays it from the sequence number when the
 566         // snapshot was saved and not the number we saved. We would want to override it , by asking akka to use the
 567         // last-sequence number known to us.
 568         return context.getSnapshotManager().getLastSequenceNumber();
 569     }
 570
 571     /**
 572      * Persists the given Payload in the journal and replicates to any followers. After successful completion,
 573      * {@link #applyState(ActorRef, Identifier, Object)} is notified.
 574      *
 575      * @param clientActor optional ActorRef that is provided via the applyState callback
 576      * @param identifier the payload identifier
 577      * @param data the payload data to persist
 578      * @param batchHint if true, an attempt is made to delay immediate replication and batch the payload with
 579      *        subsequent payloads for efficiency. Otherwise the payload is immediately replicated.
 580      */
 581     protected final void persistData(final ActorRef clientActor, final Identifier identifier, final Payload data,
 582             final boolean batchHint) {
 583         ReplicatedLogEntry replicatedLogEntry = new SimpleReplicatedLogEntry(
 584             context.getReplicatedLog().lastIndex() + 1,
 585             context.getTermInformation().getCurrentTerm(), data);
 586         replicatedLogEntry.setPersistencePending(true);
 587
 588         LOG.debug("{}: Persist data {}", persistenceId(), replicatedLogEntry);
 589
 590         final RaftActorContext raftContext = getRaftActorContext();
 591
 592         boolean wasAppended = replicatedLog().appendAndPersist(replicatedLogEntry, persistedLogEntry -> {
 593             // Clear the persistence pending flag in the log entry.
 594             persistedLogEntry.setPersistencePending(false);
 595
 596             if (!hasFollowers()) {
 597                 // Increment the Commit Index and the Last Applied values
 598                 raftContext.setCommitIndex(persistedLogEntry.getIndex());
 599                 raftContext.setLastApplied(persistedLogEntry.getIndex());
 600
 601                 // Apply the state immediately.
 602                 handleApplyState(new ApplyState(clientActor, identifier, persistedLogEntry));
 603
 604                 // Send a ApplyJournalEntries message so that we write the fact that we applied
 605                 // the state to durable storage
 606                 self().tell(new ApplyJournalEntries(persistedLogEntry.getIndex()), self());
 607
 608             } else {
 609                 context.getReplicatedLog().captureSnapshotIfReady(replicatedLogEntry);
 610
 611                 // Local persistence is complete so send the CheckConsensusReached message to the behavior (which
 612                 // normally should still be the leader) to check if consensus has now been reached in conjunction with
 613                 // follower replication.
 614                 getCurrentBehavior().handleMessage(getSelf(), CheckConsensusReached.INSTANCE);
 615             }
 616         }, true);
 617
 618         if (wasAppended && hasFollowers()) {
 619             // Send log entry for replication.
 620             getCurrentBehavior().handleMessage(getSelf(), new Replicate(clientActor, identifier, replicatedLogEntry,
 621                     !batchHint));
 622         }
 623     }
 624
 625     private ReplicatedLog replicatedLog() {
 626         return context.getReplicatedLog();
 627     }
 628
 629     protected String getId() {
 630         return context.getId();
 631     }
 632
 633     @VisibleForTesting
 634     void setCurrentBehavior(RaftActorBehavior behavior) {
 635         context.setCurrentBehavior(behavior);
 636     }
 637
 638     protected RaftActorBehavior getCurrentBehavior() {
 639         return context.getCurrentBehavior();
 640     }
 641
 642     /**
 643      * Derived actors can call the isLeader method to check if the current
 644      * RaftActor is the Leader or not.
 645      *
 646      * @return true it this RaftActor is a Leader false otherwise
 647      */
 648     protected boolean isLeader() {
 649         return context.getId().equals(getCurrentBehavior().getLeaderId());
 650     }
 651
 652     protected final boolean isLeaderActive() {
 653         return getRaftState() != RaftState.IsolatedLeader && getRaftState() != RaftState.PreLeader
 654                 && !shuttingDown && !isLeadershipTransferInProgress();
 655     }
 656
 657     private boolean isLeadershipTransferInProgress() {
 658         return leadershipTransferInProgress != null && leadershipTransferInProgress.isTransferring();
 659     }
 660
 661     /**
 662      * Derived actor can call getLeader if they need a reference to the Leader.
 663      * This would be useful for example in forwarding a request to an actor
 664      * which is the leader
 665      *
 666      * @return A reference to the leader if known, null otherwise
 667      */
 668     public ActorSelection getLeader() {
 669         String leaderAddress = getLeaderAddress();
 670
 671         if (leaderAddress == null) {
 672             return null;
 673         }
 674
 675         return context.actorSelection(leaderAddress);
 676     }
 677
 678     /**
 679      * Returns the id of the current leader.
 680      *
 681      * @return the current leader's id
 682      */
 683     protected final String getLeaderId() {
 684         return getCurrentBehavior().getLeaderId();
 685     }
 686
 687     @VisibleForTesting
 688     protected final RaftState getRaftState() {
 689         return getCurrentBehavior().state();
 690     }
 691
 692     protected Long getCurrentTerm() {
 693         return context.getTermInformation().getCurrentTerm();
 694     }
 695
 696     protected RaftActorContext getRaftActorContext() {
 697         return context;
 698     }
 699
 700     protected void updateConfigParams(ConfigParams configParams) {
 701
 702         // obtain the RaftPolicy for oldConfigParams and the updated one.
 703         String oldRaftPolicy = context.getConfigParams().getCustomRaftPolicyImplementationClass();
 704         String newRaftPolicy = configParams.getCustomRaftPolicyImplementationClass();
 705
 706         LOG.debug("{}: RaftPolicy used with prev.config {}, RaftPolicy used with newConfig {}", persistenceId(),
 707             oldRaftPolicy, newRaftPolicy);
 708         context.setConfigParams(configParams);
 709         if (!Objects.equals(oldRaftPolicy, newRaftPolicy)) {
 710             // The RaftPolicy was modified. If the current behavior is Follower then re-initialize to Follower
 711             // but transfer the previous leaderId so it doesn't immediately try to schedule an election. This
 712             // avoids potential disruption. Otherwise, switch to Follower normally.
 713             RaftActorBehavior behavior = getCurrentBehavior();
 714             if (behavior != null && behavior.state() == RaftState.Follower) {
 715                 String previousLeaderId = behavior.getLeaderId();
 716                 short previousLeaderPayloadVersion = behavior.getLeaderPayloadVersion();
 717
 718                 LOG.debug("{}: Re-initializing to Follower with previous leaderId {}", persistenceId(),
 719                         previousLeaderId);
 720
 721                 changeCurrentBehavior(new Follower(context, previousLeaderId, previousLeaderPayloadVersion));
 722             } else {
 723                 initializeBehavior();
 724             }
 725         }
 726     }
 727
 728     public final DataPersistenceProvider persistence() {
 729         return delegatingPersistenceProvider.getDelegate();
 730     }
 731
 732     public void setPersistence(DataPersistenceProvider provider) {
 733         delegatingPersistenceProvider.setDelegate(provider);
 734     }
 735
 736     protected void setPersistence(boolean persistent) {
 737         DataPersistenceProvider currentPersistence = persistence();
 738         if (persistent && (currentPersistence == null || !currentPersistence.isRecoveryApplicable())) {
 739             setPersistence(new PersistentDataProvider(this));
 740
 741             if (getCurrentBehavior() != null) {
 742                 LOG.info("{}: Persistence has been enabled - capturing snapshot", persistenceId());
 743                 captureSnapshot();
 744             }
 745         } else if (!persistent && (currentPersistence == null || currentPersistence.isRecoveryApplicable())) {
 746             setPersistence(new NonPersistentDataProvider() {
 747                 /**
 748                  * The way snapshotting works is,
 749                  * <ol>
 750                  * <li> RaftActor calls createSnapshot on the Shard
 751                  * <li> Shard sends a CaptureSnapshotReply and RaftActor then calls saveSnapshot
 752                  * <li> When saveSnapshot is invoked on the akka-persistence API it uses the SnapshotStore to save
 753                  * the snapshot. The SnapshotStore sends SaveSnapshotSuccess or SaveSnapshotFailure. When the
 754                  * RaftActor gets SaveSnapshot success it commits the snapshot to the in-memory journal. This
 755                  * commitSnapshot is mimicking what is done in SaveSnapshotSuccess.
 756                  * </ol>
 757                  */
 758                 @Override
 759                 public void saveSnapshot(Object object) {
 760                     // Make saving Snapshot successful
 761                     // Committing the snapshot here would end up calling commit in the creating state which would
 762                     // be a state violation. That's why now we send a message to commit the snapshot.
 763                     self().tell(RaftActorSnapshotMessageSupport.COMMIT_SNAPSHOT, self());
 764                 }
 765             });
 766         }
 767     }
 768
 769     /**
 770      * setPeerAddress sets the address of a known peer at a later time.
 771      *
 772      * <p>
 773      * This is to account for situations where a we know that a peer
 774      * exists but we do not know an address up-front. This may also be used in
 775      * situations where a known peer starts off in a different location and we
 776      * need to change it's address
 777      *
 778      * <p>
 779      * Note that if the peerId does not match the list of peers passed to
 780      * this actor during construction an IllegalStateException will be thrown.
 781      */
 782     protected void setPeerAddress(String peerId, String peerAddress) {
 783         context.setPeerAddress(peerId, peerAddress);
 784     }
 785
 786     /**
 787      * The applyState method will be called by the RaftActor when some data
 788      * needs to be applied to the actor's state.
 789      *
 790      * @param clientActor A reference to the client who sent this message. This
 791      *                    is the same reference that was passed to persistData
 792      *                    by the derived actor. clientActor may be null when
 793      *                    the RaftActor is behaving as a follower or during
 794      *                    recovery.
 795      * @param identifier  The identifier of the persisted data. This is also
 796      *                    the same identifier that was passed to persistData by
 797      *                    the derived actor. identifier may be null when
 798      *                    the RaftActor is behaving as a follower or during
 799      *                    recovery
 800      * @param data        A piece of data that was persisted by the persistData call.
 801      *                    This should NEVER be null.
 802      */
 803     protected abstract void applyState(ActorRef clientActor, Identifier identifier, Object data);
 804
 805     /**
 806      * Returns the RaftActorRecoveryCohort to participate in persistence recovery.
 807      */
 808     @Nonnull
 809     protected abstract RaftActorRecoveryCohort getRaftActorRecoveryCohort();
 810
 811     /**
 812      * This method is called when recovery is complete.
 813      */
 814     protected abstract void onRecoveryComplete();
 815
 816     /**
 817      * Returns the RaftActorSnapshotCohort to participate in snapshot captures.
 818      */
 819     @Nonnull
 820     protected abstract RaftActorSnapshotCohort getRaftActorSnapshotCohort();
 821
 822     /**
 823      * This method will be called by the RaftActor when the state of the
 824      * RaftActor changes. The derived actor can then use methods like
 825      * isLeader or getLeader to do something useful
 826      */
 827     protected abstract void onStateChanged();
 828
 829     /**
 830      * Notifier Actor for this RaftActor to notify when a role change happens.
 831      *
 832      * @return ActorRef - ActorRef of the notifier or Optional.absent if none.
 833      */
 834     protected abstract Optional<ActorRef> getRoleChangeNotifier();
 835
 836     /**
 837      * This method is called prior to operations such as leadership transfer and actor shutdown when the leader
 838      * must pause or stop its duties. This method allows derived classes to gracefully pause or finish current
 839      * work prior to performing the operation. On completion of any work, the run method must be called on the
 840      * given Runnable to proceed with the given operation. <b>Important:</b> the run method must be called on
 841      * this actor's thread dispatcher as as it modifies internal state.
 842      *
 843      * <p>
 844      * The default implementation immediately runs the operation.
 845      *
 846      * @param operation the operation to run
 847      */
 848     protected void pauseLeader(Runnable operation) {
 849         operation.run();
 850     }
 851
 852     protected void onLeaderChanged(String oldLeader, String newLeader) {
 853     }
 854
 855     private String getLeaderAddress() {
 856         if (isLeader()) {
 857             return getSelf().path().toString();
 858         }
 859         String leaderId = getLeaderId();
 860         if (leaderId == null) {
 861             return null;
 862         }
 863         String peerAddress = context.getPeerAddress(leaderId);
 864         LOG.debug("{}: getLeaderAddress leaderId = {} peerAddress = {}", persistenceId(), leaderId, peerAddress);
 865
 866         return peerAddress;
 867     }
 868
 869     protected boolean hasFollowers() {
 870         return getRaftActorContext().hasFollowers();
 871     }
 872
 873     private void captureSnapshot() {
 874         SnapshotManager snapshotManager = context.getSnapshotManager();
 875
 876         if (!snapshotManager.isCapturing()) {
 877             final long idx = getCurrentBehavior().getReplicatedToAllIndex();
 878             LOG.debug("Take a snapshot of current state. lastReplicatedLog is {} and replicatedToAllIndex is {}",
 879                 replicatedLog().last(), idx);
 880
 881             snapshotManager.capture(replicatedLog().last(), idx);
 882         }
 883     }
 884
 885     /**
 886      * Switch this member to non-voting status. This is a no-op for all behaviors except when we are the leader,
 887      * in which case we need to step down.
 888      */
 889     void becomeNonVoting() {
 890         if (isLeader()) {
 891             initiateLeadershipTransfer(new RaftActorLeadershipTransferCohort.OnComplete() {
 892                 @Override
 893                 public void onSuccess(ActorRef raftActorRef) {
 894                     LOG.debug("{}: leader transfer succeeded after change to non-voting", persistenceId());
 895                     ensureFollowerState();
 896                 }
 897
 898                 @Override
 899                 public void onFailure(ActorRef raftActorRef) {
 900                     LOG.debug("{}: leader transfer failed after change to non-voting", persistenceId());
 901                     ensureFollowerState();
 902                 }
 903
 904                 private void ensureFollowerState() {
 905                     // Whether or not leadership transfer succeeded, we have to step down as leader and
 906                     // switch to Follower so ensure that.
 907                     if (getRaftState() != RaftState.Follower) {
 908                         initializeBehavior();
 909                     }
 910                 }
 911             });
 912         }
 913     }
 914
 915     /**
 916      * A point-in-time capture of {@link RaftActorBehavior} state critical for transitioning between behaviors.
 917      */
 918     private abstract static class BehaviorState implements Immutable {
 919         @Nullable abstract RaftActorBehavior getBehavior();
 920
 921         @Nullable abstract String getLastValidLeaderId();
 922
 923         @Nullable abstract String getLastLeaderId();
 924
 925         @Nullable abstract short getLeaderPayloadVersion();
 926     }
 927
 928     /**
 929      * A {@link BehaviorState} corresponding to non-null {@link RaftActorBehavior} state.
 930      */
 931     private static final class SimpleBehaviorState extends BehaviorState {
 932         private final RaftActorBehavior behavior;
 933         private final String lastValidLeaderId;
 934         private final String lastLeaderId;
 935         private final short leaderPayloadVersion;
 936
 937         SimpleBehaviorState(final String lastValidLeaderId, final String lastLeaderId,
 938                 final RaftActorBehavior behavior) {
 939             this.lastValidLeaderId = lastValidLeaderId;
 940             this.lastLeaderId = lastLeaderId;
 941             this.behavior = Preconditions.checkNotNull(behavior);
 942             this.leaderPayloadVersion = behavior.getLeaderPayloadVersion();
 943         }
 944
 945         @Override
 946         RaftActorBehavior getBehavior() {
 947             return behavior;
 948         }
 949
 950         @Override
 951         String getLastValidLeaderId() {
 952             return lastValidLeaderId;
 953         }
 954
 955         @Override
 956         short getLeaderPayloadVersion() {
 957             return leaderPayloadVersion;
 958         }
 959
 960         @Override
 961         String getLastLeaderId() {
 962             return lastLeaderId;
 963         }
 964     }
 965
 966     /**
 967      * Class tracking behavior-related information, which we need to keep around and pass across behavior switches.
 968      * An instance is created for each RaftActor. It has two functions:
 969      * - it keeps track of the last leader ID we have encountered since we have been created
 970      * - it creates state capture needed to transition from one behavior to the next
 971      */
 972     private static final class BehaviorStateTracker {
 973         /**
 974          * A {@link BehaviorState} corresponding to null {@link RaftActorBehavior} state. Since null behavior is only
 975          * allowed before we receive the first message, we know the leader ID to be null.
 976          */
 977         private static final BehaviorState NULL_BEHAVIOR_STATE = new BehaviorState() {
 978             @Override
 979             RaftActorBehavior getBehavior() {
 980                 return null;
 981             }
 982
 983             @Override
 984             String getLastValidLeaderId() {
 985                 return null;
 986             }
 987
 988             @Override
 989             short getLeaderPayloadVersion() {
 990                 return -1;
 991             }
 992
 993             @Override
 994             String getLastLeaderId() {
 995                 return null;
 996             }
 997         };
 998
 999         private String lastValidLeaderId;
1000         private String lastLeaderId;
1001
1002         BehaviorState capture(final RaftActorBehavior behavior) {
1003             if (behavior == null) {
1004                 Verify.verify(lastValidLeaderId == null, "Null behavior with non-null last leader");
1005                 return NULL_BEHAVIOR_STATE;
1006             }
1007
1008             lastLeaderId = behavior.getLeaderId();
1009             if (lastLeaderId != null) {
1010                 lastValidLeaderId = lastLeaderId;
1011             }
1012
1013             return new SimpleBehaviorState(lastValidLeaderId, lastLeaderId, behavior);
1014         }
1015     }
1016
1017 }