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.japi.Procedure;
  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.io.Serializable;
  22 import java.util.Collection;
  23 import java.util.HashMap;
  24 import java.util.List;
  25 import java.util.Map;
  26 import java.util.Objects;
  27 import java.util.concurrent.TimeUnit;
  28 import javax.annotation.Nonnull;
  29 import javax.annotation.Nullable;
  30 import org.apache.commons.lang3.time.DurationFormatUtils;
  31 import org.opendaylight.controller.cluster.DataPersistenceProvider;
  32 import org.opendaylight.controller.cluster.DelegatingPersistentDataProvider;
  33 import org.opendaylight.controller.cluster.NonPersistentDataProvider;
  34 import org.opendaylight.controller.cluster.PersistentDataProvider;
  35 import org.opendaylight.controller.cluster.common.actor.AbstractUntypedPersistentActor;
  36 import org.opendaylight.controller.cluster.notifications.LeaderStateChanged;
  37 import org.opendaylight.controller.cluster.notifications.RoleChanged;
  38 import org.opendaylight.controller.cluster.raft.base.messages.ApplyJournalEntries;
  39 import org.opendaylight.controller.cluster.raft.base.messages.ApplyState;
  40 import org.opendaylight.controller.cluster.raft.base.messages.InitiateCaptureSnapshot;
  41 import org.opendaylight.controller.cluster.raft.base.messages.LeaderTransitioning;
  42 import org.opendaylight.controller.cluster.raft.base.messages.Replicate;
  43 import org.opendaylight.controller.cluster.raft.base.messages.SwitchBehavior;
  44 import org.opendaylight.controller.cluster.raft.behaviors.AbstractLeader;
  45 import org.opendaylight.controller.cluster.raft.behaviors.AbstractRaftActorBehavior;
  46 import org.opendaylight.controller.cluster.raft.behaviors.Follower;
  47 import org.opendaylight.controller.cluster.raft.behaviors.RaftActorBehavior;
  48 import org.opendaylight.controller.cluster.raft.client.messages.FindLeader;
  49 import org.opendaylight.controller.cluster.raft.client.messages.FindLeaderReply;
  50 import org.opendaylight.controller.cluster.raft.client.messages.FollowerInfo;
  51 import org.opendaylight.controller.cluster.raft.client.messages.GetOnDemandRaftState;
  52 import org.opendaylight.controller.cluster.raft.client.messages.OnDemandRaftState;
  53 import org.opendaylight.controller.cluster.raft.client.messages.Shutdown;
  54 import org.opendaylight.controller.cluster.raft.protobuff.client.messages.Payload;
  55 import org.opendaylight.yangtools.concepts.Immutable;
  56 import org.slf4j.Logger;
  57 import org.slf4j.LoggerFactory;
  58
  59 /**
  60  * RaftActor encapsulates a state machine that needs to be kept synchronized
  61  * in a cluster. It implements the RAFT algorithm as described in the paper
  62  * <a href='https://ramcloud.stanford.edu/wiki/download/attachments/11370504/raft.pdf'>
  63  * In Search of an Understandable Consensus Algorithm</a>
  64  * <p/>
  65  * RaftActor has 3 states and each state has a certain behavior associated
  66  * with it. A Raft actor can behave as,
  67  * <ul>
  68  * <li> A Leader </li>
  69  * <li> A Follower (or) </li>
  70  * <li> A Candidate </li>
  71  * </ul>
  72  * <p/>
  73  * <p/>
  74  * A RaftActor MUST be a Leader in order to accept requests from clients to
  75  * change the state of it's encapsulated state machine. Once a RaftActor becomes
  76  * a Leader it is also responsible for ensuring that all followers ultimately
  77  * have the same log and therefore the same state machine as itself.
  78  * <p/>
  79  * <p/>
  80  * The current behavior of a RaftActor determines how election for leadership
  81  * is initiated and how peer RaftActors react to request for votes.
  82  * <p/>
  83  * <p/>
  84  * Each RaftActor also needs to know the current election term. It uses this
  85  * information for a couple of things. One is to simply figure out who it
  86  * voted for in the last election. Another is to figure out if the message
  87  * it received to update it's state is stale.
  88  * <p/>
  89  * <p/>
  90  * The RaftActor uses akka-persistence to store it's replicated log.
  91  * Furthermore through it's behaviors a Raft Actor determines
  92  * <p/>
  93  * <ul>
  94  * <li> when a log entry should be persisted </li>
  95  * <li> when a log entry should be applied to the state machine (and) </li>
  96  * <li> when a snapshot should be saved </li>
  97  * </ul>
  98  */
  99 public abstract class RaftActor extends AbstractUntypedPersistentActor {
 100
 101     private static final long APPLY_STATE_DELAY_THRESHOLD_IN_NANOS = TimeUnit.MILLISECONDS.toNanos(50L); // 50 millis
 102
 103     protected final Logger LOG = LoggerFactory.getLogger(getClass());
 104
 105     /**
 106      * This context should NOT be passed directly to any other actor it is
 107      * only to be consumed by the RaftActorBehaviors
 108      */
 109     private final RaftActorContextImpl context;
 110
 111     private final DelegatingPersistentDataProvider delegatingPersistenceProvider;
 112
 113     private final PersistentDataProvider persistentProvider;
 114
 115     private final BehaviorStateTracker behaviorStateTracker = new BehaviorStateTracker();
 116
 117     private RaftActorRecoverySupport raftRecovery;
 118
 119     private RaftActorSnapshotMessageSupport snapshotSupport;
 120
 121     private RaftActorServerConfigurationSupport serverConfigurationSupport;
 122
 123     private RaftActorLeadershipTransferCohort leadershipTransferInProgress;
 124
 125     private boolean shuttingDown;
 126
 127     public RaftActor(String id, Map<String, String> peerAddresses,
 128          Optional<ConfigParams> configParams, short payloadVersion) {
 129
 130         persistentProvider = new PersistentDataProvider(this);
 131         delegatingPersistenceProvider = new RaftActorDelegatingPersistentDataProvider(null, persistentProvider);
 132
 133         context = new RaftActorContextImpl(this.getSelf(),
 134             this.getContext(), id, new ElectionTermImpl(persistentProvider, id, LOG),
 135             -1, -1, peerAddresses,
 136             (configParams.isPresent() ? configParams.get(): new DefaultConfigParamsImpl()),
 137             delegatingPersistenceProvider, LOG);
 138
 139         context.setPayloadVersion(payloadVersion);
 140         context.setReplicatedLog(ReplicatedLogImpl.newInstance(context));
 141     }
 142
 143     @Override
 144     public void preStart() throws Exception {
 145         LOG.info("Starting recovery for {} with journal batch size {}", persistenceId(),
 146                 context.getConfigParams().getJournalRecoveryLogBatchSize());
 147
 148         super.preStart();
 149
 150         snapshotSupport = newRaftActorSnapshotMessageSupport();
 151         serverConfigurationSupport = new RaftActorServerConfigurationSupport(this);
 152     }
 153
 154     @Override
 155     public void postStop() {
 156         context.close();
 157         super.postStop();
 158     }
 159
 160     @Override
 161     protected void handleRecover(Object message) {
 162         if(raftRecovery == null) {
 163             raftRecovery = newRaftActorRecoverySupport();
 164         }
 165
 166         boolean recoveryComplete = raftRecovery.handleRecoveryMessage(message, persistentProvider);
 167         if(recoveryComplete) {
 168             onRecoveryComplete();
 169
 170             initializeBehavior();
 171
 172             raftRecovery = null;
 173
 174             if (context.getReplicatedLog().size() > 0) {
 175                 self().tell(new InitiateCaptureSnapshot(), self());
 176                 LOG.info("{}: Snapshot capture initiated after recovery", persistenceId());
 177             } else {
 178                 LOG.info("{}: Snapshot capture NOT initiated after recovery, journal empty", persistenceId());
 179             }
 180         }
 181     }
 182
 183     protected RaftActorRecoverySupport newRaftActorRecoverySupport() {
 184         return new RaftActorRecoverySupport(context, getRaftActorRecoveryCohort());
 185     }
 186
 187     @VisibleForTesting
 188     void initializeBehavior(){
 189         changeCurrentBehavior(new Follower(context));
 190     }
 191
 192     @VisibleForTesting
 193     protected void changeCurrentBehavior(RaftActorBehavior newBehavior) {
 194         final RaftActorBehavior currentBehavior = getCurrentBehavior();
 195         if (currentBehavior != null) {
 196             try {
 197                 currentBehavior.close();
 198             } catch (Exception e) {
 199                 LOG.warn("{}: Error closing behavior {}", persistence(), currentBehavior, e);
 200             }
 201         }
 202
 203         final BehaviorState state = behaviorStateTracker.capture(currentBehavior);
 204         setCurrentBehavior(newBehavior);
 205         handleBehaviorChange(state, newBehavior);
 206     }
 207
 208     @Override
 209     protected void handleCommand(final Object message) {
 210         if (serverConfigurationSupport.handleMessage(message, getSender())) {
 211             return;
 212         }
 213         if (snapshotSupport.handleSnapshotMessage(message, getSender())) {
 214             return;
 215         }
 216
 217         if (message instanceof ApplyState) {
 218             ApplyState applyState = (ApplyState) message;
 219
 220             long elapsedTime = (System.nanoTime() - applyState.getStartTime());
 221             if(elapsedTime >= APPLY_STATE_DELAY_THRESHOLD_IN_NANOS){
 222                 LOG.warn("ApplyState took more time than expected. Elapsed Time = {} ms ApplyState = {}",
 223                         TimeUnit.NANOSECONDS.toMillis(elapsedTime), applyState);
 224             }
 225
 226             if(LOG.isDebugEnabled()) {
 227                 LOG.debug("{}: Applying state for log index {} data {}",
 228                     persistenceId(), applyState.getReplicatedLogEntry().getIndex(),
 229                     applyState.getReplicatedLogEntry().getData());
 230             }
 231
 232             applyState(applyState.getClientActor(), applyState.getIdentifier(),
 233                 applyState.getReplicatedLogEntry().getData());
 234
 235             if (!hasFollowers()) {
 236                 // for single node, the capture should happen after the apply state
 237                 // as we delete messages from the persistent journal which have made it to the snapshot
 238                 // capturing the snapshot before applying makes the persistent journal and snapshot out of sync
 239                 // and recovery shows data missing
 240                 context.getReplicatedLog().captureSnapshotIfReady(applyState.getReplicatedLogEntry());
 241
 242                 context.getSnapshotManager().trimLog(context.getLastApplied());
 243             }
 244
 245         } else if (message instanceof ApplyJournalEntries) {
 246             ApplyJournalEntries applyEntries = (ApplyJournalEntries) message;
 247             if(LOG.isDebugEnabled()) {
 248                 LOG.debug("{}: Persisting ApplyJournalEntries with index={}", persistenceId(), applyEntries.getToIndex());
 249             }
 250
 251             persistence().persist(applyEntries, NoopProcedure.instance());
 252
 253         } else if (message instanceof FindLeader) {
 254             getSender().tell(
 255                 new FindLeaderReply(getLeaderAddress()),
 256                 getSelf()
 257             );
 258         } else if(message instanceof GetOnDemandRaftState) {
 259             onGetOnDemandRaftStats();
 260         } else if(message instanceof InitiateCaptureSnapshot) {
 261             captureSnapshot();
 262         } else if(message instanceof SwitchBehavior) {
 263             switchBehavior(((SwitchBehavior) message));
 264         } else if(message instanceof LeaderTransitioning) {
 265             onLeaderTransitioning();
 266         } else if(message instanceof Shutdown) {
 267             onShutDown();
 268         } else if(message instanceof Runnable) {
 269             ((Runnable)message).run();
 270         } else {
 271             // Processing the message may affect the state, hence we need to capture it
 272             final RaftActorBehavior currentBehavior = getCurrentBehavior();
 273             final BehaviorState state = behaviorStateTracker.capture(currentBehavior);
 274             final RaftActorBehavior nextBehavior = currentBehavior.handleMessage(getSender(), message);
 275             switchBehavior(state, nextBehavior);
 276         }
 277     }
 278
 279     private void initiateLeadershipTransfer(final RaftActorLeadershipTransferCohort.OnComplete onComplete) {
 280         LOG.debug("{}: Initiating leader transfer", persistenceId());
 281
 282         if(leadershipTransferInProgress == null) {
 283             leadershipTransferInProgress = new RaftActorLeadershipTransferCohort(this);
 284             leadershipTransferInProgress.addOnComplete(new RaftActorLeadershipTransferCohort.OnComplete() {
 285                 @Override
 286                 public void onSuccess(ActorRef raftActorRef) {
 287                     leadershipTransferInProgress = null;
 288                 }
 289
 290                 @Override
 291                 public void onFailure(ActorRef raftActorRef) {
 292                     leadershipTransferInProgress = null;
 293                 }
 294             });
 295
 296             leadershipTransferInProgress.addOnComplete(onComplete);
 297             leadershipTransferInProgress.init();
 298         } else {
 299             LOG.debug("{}: prior leader transfer in progress - adding callback", persistenceId());
 300             leadershipTransferInProgress.addOnComplete(onComplete);
 301         }
 302     }
 303
 304     private void onShutDown() {
 305         LOG.debug("{}: onShutDown", persistenceId());
 306
 307         if(shuttingDown) {
 308             return;
 309         }
 310
 311         shuttingDown = true;
 312
 313         final RaftActorBehavior currentBehavior = context.getCurrentBehavior();
 314         if (currentBehavior.state() != RaftState.Leader) {
 315             // For non-leaders shutdown is a no-op
 316             self().tell(PoisonPill.getInstance(), self());
 317             return;
 318         }
 319
 320         if (context.hasFollowers()) {
 321             initiateLeadershipTransfer(new RaftActorLeadershipTransferCohort.OnComplete() {
 322                 @Override
 323                 public void onSuccess(ActorRef raftActorRef) {
 324                     LOG.debug("{}: leader transfer succeeded - sending PoisonPill", persistenceId());
 325                     raftActorRef.tell(PoisonPill.getInstance(), raftActorRef);
 326                 }
 327
 328                 @Override
 329                 public void onFailure(ActorRef raftActorRef) {
 330                     LOG.debug("{}: leader transfer failed - sending PoisonPill", persistenceId());
 331                     raftActorRef.tell(PoisonPill.getInstance(), raftActorRef);
 332                 }
 333             });
 334         } else {
 335             pauseLeader(new TimedRunnable(context.getConfigParams().getElectionTimeOutInterval(), this) {
 336                 @Override
 337                 protected void doRun() {
 338                     self().tell(PoisonPill.getInstance(), self());
 339                 }
 340
 341                 @Override
 342                 protected void doCancel() {
 343                     self().tell(PoisonPill.getInstance(), self());
 344                 }
 345             });
 346         }
 347     }
 348
 349     private void onLeaderTransitioning() {
 350         LOG.debug("{}: onLeaderTransitioning", persistenceId());
 351         Optional<ActorRef> roleChangeNotifier = getRoleChangeNotifier();
 352         if(getRaftState() == RaftState.Follower && roleChangeNotifier.isPresent()) {
 353             roleChangeNotifier.get().tell(newLeaderStateChanged(getId(), null,
 354                 getCurrentBehavior().getLeaderPayloadVersion()), getSelf());
 355         }
 356     }
 357
 358     private void switchBehavior(SwitchBehavior message) {
 359         if(!getRaftActorContext().getRaftPolicy().automaticElectionsEnabled()) {
 360             RaftState newState = message.getNewState();
 361             if( newState == RaftState.Leader || newState == RaftState.Follower) {
 362                 switchBehavior(behaviorStateTracker.capture(getCurrentBehavior()),
 363                     AbstractRaftActorBehavior.createBehavior(context, message.getNewState()));
 364                 getRaftActorContext().getTermInformation().updateAndPersist(message.getNewTerm(), "");
 365             } else {
 366                 LOG.warn("Switching to behavior : {} - not supported", newState);
 367             }
 368         }
 369     }
 370
 371     private void switchBehavior(final BehaviorState oldBehaviorState, final RaftActorBehavior nextBehavior) {
 372         setCurrentBehavior(nextBehavior);
 373         handleBehaviorChange(oldBehaviorState, nextBehavior);
 374     }
 375
 376     @VisibleForTesting
 377     RaftActorSnapshotMessageSupport newRaftActorSnapshotMessageSupport() {
 378         return new RaftActorSnapshotMessageSupport(context, getRaftActorSnapshotCohort());
 379     }
 380
 381     private void onGetOnDemandRaftStats() {
 382         // Debugging message to retrieve raft stats.
 383
 384         Map<String, String> peerAddresses = new HashMap<>();
 385         for(String peerId: context.getPeerIds()) {
 386             peerAddresses.put(peerId, context.getPeerAddress(peerId));
 387         }
 388
 389         final RaftActorBehavior currentBehavior = context.getCurrentBehavior();
 390         OnDemandRaftState.Builder builder = OnDemandRaftState.builder()
 391                 .commitIndex(context.getCommitIndex())
 392                 .currentTerm(context.getTermInformation().getCurrentTerm())
 393                 .inMemoryJournalDataSize(replicatedLog().dataSize())
 394                 .inMemoryJournalLogSize(replicatedLog().size())
 395                 .isSnapshotCaptureInitiated(context.getSnapshotManager().isCapturing())
 396                 .lastApplied(context.getLastApplied())
 397                 .lastIndex(replicatedLog().lastIndex())
 398                 .lastTerm(replicatedLog().lastTerm())
 399                 .leader(getLeaderId())
 400                 .raftState(currentBehavior.state().toString())
 401                 .replicatedToAllIndex(currentBehavior.getReplicatedToAllIndex())
 402                 .snapshotIndex(replicatedLog().getSnapshotIndex())
 403                 .snapshotTerm(replicatedLog().getSnapshotTerm())
 404                 .votedFor(context.getTermInformation().getVotedFor())
 405                 .peerAddresses(peerAddresses)
 406                 .customRaftPolicyClassName(context.getConfigParams().getCustomRaftPolicyImplementationClass());
 407
 408         ReplicatedLogEntry lastLogEntry = replicatedLog().last();
 409         if (lastLogEntry != null) {
 410             builder.lastLogIndex(lastLogEntry.getIndex());
 411             builder.lastLogTerm(lastLogEntry.getTerm());
 412         }
 413
 414         if(getCurrentBehavior() instanceof AbstractLeader) {
 415             AbstractLeader leader = (AbstractLeader)getCurrentBehavior();
 416             Collection<String> followerIds = leader.getFollowerIds();
 417             List<FollowerInfo> followerInfoList = Lists.newArrayListWithCapacity(followerIds.size());
 418             for(String id: followerIds) {
 419                 final FollowerLogInformation info = leader.getFollower(id);
 420                 followerInfoList.add(new FollowerInfo(id, info.getNextIndex(), info.getMatchIndex(),
 421                         info.isFollowerActive(), DurationFormatUtils.formatDurationHMS(info.timeSinceLastActivity())));
 422             }
 423
 424             builder.followerInfoList(followerInfoList);
 425         }
 426
 427         sender().tell(builder.build(), self());
 428
 429     }
 430
 431     private void handleBehaviorChange(BehaviorState oldBehaviorState, RaftActorBehavior currentBehavior) {
 432         RaftActorBehavior oldBehavior = oldBehaviorState.getBehavior();
 433
 434         if (oldBehavior != currentBehavior){
 435             onStateChanged();
 436         }
 437
 438         String lastValidLeaderId = oldBehavior == null ? null : oldBehaviorState.getLastValidLeaderId();
 439         String oldBehaviorStateName = oldBehavior == null ? null : oldBehavior.state().name();
 440
 441         // it can happen that the state has not changed but the leader has changed.
 442         Optional<ActorRef> roleChangeNotifier = getRoleChangeNotifier();
 443         if(!Objects.equals(lastValidLeaderId, currentBehavior.getLeaderId()) ||
 444            oldBehaviorState.getLeaderPayloadVersion() != currentBehavior.getLeaderPayloadVersion()) {
 445             if(roleChangeNotifier.isPresent()) {
 446                 roleChangeNotifier.get().tell(newLeaderStateChanged(getId(), currentBehavior.getLeaderId(),
 447                         currentBehavior.getLeaderPayloadVersion()), getSelf());
 448             }
 449
 450             onLeaderChanged(lastValidLeaderId, currentBehavior.getLeaderId());
 451
 452             if(leadershipTransferInProgress != null) {
 453                 leadershipTransferInProgress.onNewLeader(currentBehavior.getLeaderId());
 454             }
 455
 456             serverConfigurationSupport.onNewLeader(currentBehavior.getLeaderId());
 457         }
 458
 459         if (roleChangeNotifier.isPresent() &&
 460                 (oldBehavior == null || (oldBehavior.state() != currentBehavior.state()))) {
 461             roleChangeNotifier.get().tell(new RoleChanged(getId(), oldBehaviorStateName ,
 462                     currentBehavior.state().name()), getSelf());
 463         }
 464     }
 465
 466     protected LeaderStateChanged newLeaderStateChanged(String memberId, String leaderId, short leaderPayloadVersion) {
 467         return new LeaderStateChanged(memberId, leaderId, leaderPayloadVersion);
 468     }
 469
 470     @Override
 471     public long snapshotSequenceNr() {
 472         // When we do a snapshot capture, we also capture and save the sequence-number of the persistent journal,
 473         // so that we can delete the persistent journal based on the saved sequence-number
 474         // However , when akka replays the journal during recovery, it replays it from the sequence number when the snapshot
 475         // was saved and not the number we saved.
 476         // We would want to override it , by asking akka to use the last-sequence number known to us.
 477         return context.getSnapshotManager().getLastSequenceNumber();
 478     }
 479
 480     /**
 481      * When a derived RaftActor needs to persist something it must call
 482      * persistData.
 483      *
 484      * @param clientActor
 485      * @param identifier
 486      * @param data
 487      */
 488     protected void persistData(final ActorRef clientActor, final String identifier,
 489         final Payload data) {
 490
 491         ReplicatedLogEntry replicatedLogEntry = new ReplicatedLogImplEntry(
 492             context.getReplicatedLog().lastIndex() + 1,
 493             context.getTermInformation().getCurrentTerm(), data);
 494
 495         if(LOG.isDebugEnabled()) {
 496             LOG.debug("{}: Persist data {}", persistenceId(), replicatedLogEntry);
 497         }
 498
 499         final RaftActorContext raftContext = getRaftActorContext();
 500
 501         replicatedLog().appendAndPersist(replicatedLogEntry, new Procedure<ReplicatedLogEntry>() {
 502             @Override
 503             public void apply(ReplicatedLogEntry replicatedLogEntry) {
 504                 if (!hasFollowers()){
 505                     // Increment the Commit Index and the Last Applied values
 506                     raftContext.setCommitIndex(replicatedLogEntry.getIndex());
 507                     raftContext.setLastApplied(replicatedLogEntry.getIndex());
 508
 509                     // Apply the state immediately.
 510                     self().tell(new ApplyState(clientActor, identifier, replicatedLogEntry), self());
 511
 512                     // Send a ApplyJournalEntries message so that we write the fact that we applied
 513                     // the state to durable storage
 514                     self().tell(new ApplyJournalEntries(replicatedLogEntry.getIndex()), self());
 515
 516                 } else if (clientActor != null) {
 517                     context.getReplicatedLog().captureSnapshotIfReady(replicatedLogEntry);
 518
 519                     // Send message for replication
 520                     getCurrentBehavior().handleMessage(getSelf(),
 521                             new Replicate(clientActor, identifier, replicatedLogEntry));
 522                 }
 523             }
 524         });
 525     }
 526
 527     private ReplicatedLog replicatedLog() {
 528         return context.getReplicatedLog();
 529     }
 530
 531     protected String getId() {
 532         return context.getId();
 533     }
 534
 535     @VisibleForTesting
 536     void setCurrentBehavior(RaftActorBehavior behavior) {
 537         context.setCurrentBehavior(behavior);
 538     }
 539
 540     protected RaftActorBehavior getCurrentBehavior() {
 541         return context.getCurrentBehavior();
 542     }
 543
 544     /**
 545      * Derived actors can call the isLeader method to check if the current
 546      * RaftActor is the Leader or not
 547      *
 548      * @return true it this RaftActor is a Leader false otherwise
 549      */
 550     protected boolean isLeader() {
 551         return context.getId().equals(getCurrentBehavior().getLeaderId());
 552     }
 553
 554     protected final boolean isLeaderActive() {
 555         return getRaftState() != RaftState.IsolatedLeader && !shuttingDown &&
 556                 !isLeadershipTransferInProgress();
 557     }
 558
 559     private boolean isLeadershipTransferInProgress() {
 560         return leadershipTransferInProgress != null && leadershipTransferInProgress.isTransferring();
 561     }
 562
 563     /**
 564      * Derived actor can call getLeader if they need a reference to the Leader.
 565      * This would be useful for example in forwarding a request to an actor
 566      * which is the leader
 567      *
 568      * @return A reference to the leader if known, null otherwise
 569      */
 570     protected ActorSelection getLeader(){
 571         String leaderAddress = getLeaderAddress();
 572
 573         if(leaderAddress == null){
 574             return null;
 575         }
 576
 577         return context.actorSelection(leaderAddress);
 578     }
 579
 580     /**
 581      *
 582      * @return the current leader's id
 583      */
 584     protected final String getLeaderId(){
 585         return getCurrentBehavior().getLeaderId();
 586     }
 587
 588     @VisibleForTesting
 589     protected final RaftState getRaftState() {
 590         return getCurrentBehavior().state();
 591     }
 592
 593     protected Long getCurrentTerm(){
 594         return context.getTermInformation().getCurrentTerm();
 595     }
 596
 597     protected RaftActorContext getRaftActorContext() {
 598         return context;
 599     }
 600
 601     protected void updateConfigParams(ConfigParams configParams) {
 602
 603         // obtain the RaftPolicy for oldConfigParams and the updated one.
 604         String oldRaftPolicy = context.getConfigParams().
 605             getCustomRaftPolicyImplementationClass();
 606         String newRaftPolicy = configParams.
 607             getCustomRaftPolicyImplementationClass();
 608
 609         LOG.debug("{}: RaftPolicy used with prev.config {}, RaftPolicy used with newConfig {}", persistenceId(),
 610             oldRaftPolicy, newRaftPolicy);
 611         context.setConfigParams(configParams);
 612         if (!Objects.equals(oldRaftPolicy, newRaftPolicy)) {
 613             // The RaftPolicy was modified. If the current behavior is Follower then re-initialize to Follower
 614             // but transfer the previous leaderId so it doesn't immediately try to schedule an election. This
 615             // avoids potential disruption. Otherwise, switch to Follower normally.
 616             RaftActorBehavior behavior = getCurrentBehavior();
 617             if (behavior != null && behavior.state() == RaftState.Follower) {
 618                 String previousLeaderId = behavior.getLeaderId();
 619                 short previousLeaderPayloadVersion = behavior.getLeaderPayloadVersion();
 620
 621                 LOG.debug("{}: Re-initializing to Follower with previous leaderId {}", persistenceId(), previousLeaderId);
 622
 623                 changeCurrentBehavior(new Follower(context, previousLeaderId, previousLeaderPayloadVersion));
 624             } else {
 625                 initializeBehavior();
 626             }
 627         }
 628     }
 629
 630     public final DataPersistenceProvider persistence() {
 631         return delegatingPersistenceProvider.getDelegate();
 632     }
 633
 634     public void setPersistence(DataPersistenceProvider provider) {
 635         delegatingPersistenceProvider.setDelegate(provider);
 636     }
 637
 638     protected void setPersistence(boolean persistent) {
 639         if(persistent) {
 640             setPersistence(new PersistentDataProvider(this));
 641         } else {
 642             setPersistence(new NonPersistentDataProvider() {
 643                 /**
 644                  * The way snapshotting works is,
 645                  * <ol>
 646                  * <li> RaftActor calls createSnapshot on the Shard
 647                  * <li> Shard sends a CaptureSnapshotReply and RaftActor then calls saveSnapshot
 648                  * <li> When saveSnapshot is invoked on the akka-persistence API it uses the SnapshotStore to save
 649                  * the snapshot. The SnapshotStore sends SaveSnapshotSuccess or SaveSnapshotFailure. When the
 650                  * RaftActor gets SaveSnapshot success it commits the snapshot to the in-memory journal. This
 651                  * commitSnapshot is mimicking what is done in SaveSnapshotSuccess.
 652                  * </ol>
 653                  */
 654                 @Override
 655                 public void saveSnapshot(Object o) {
 656                     // Make saving Snapshot successful
 657                     // Committing the snapshot here would end up calling commit in the creating state which would
 658                     // be a state violation. That's why now we send a message to commit the snapshot.
 659                     self().tell(RaftActorSnapshotMessageSupport.COMMIT_SNAPSHOT, self());
 660                 }
 661             });
 662         }
 663     }
 664
 665     /**
 666      * setPeerAddress sets the address of a known peer at a later time.
 667      * <p>
 668      * This is to account for situations where a we know that a peer
 669      * exists but we do not know an address up-front. This may also be used in
 670      * situations where a known peer starts off in a different location and we
 671      * need to change it's address
 672      * <p>
 673      * Note that if the peerId does not match the list of peers passed to
 674      * this actor during construction an IllegalStateException will be thrown.
 675      *
 676      * @param peerId
 677      * @param peerAddress
 678      */
 679     protected void setPeerAddress(String peerId, String peerAddress){
 680         context.setPeerAddress(peerId, peerAddress);
 681     }
 682
 683     /**
 684      * The applyState method will be called by the RaftActor when some data
 685      * needs to be applied to the actor's state
 686      *
 687      * @param clientActor A reference to the client who sent this message. This
 688      *                    is the same reference that was passed to persistData
 689      *                    by the derived actor. clientActor may be null when
 690      *                    the RaftActor is behaving as a follower or during
 691      *                    recovery.
 692      * @param identifier  The identifier of the persisted data. This is also
 693      *                    the same identifier that was passed to persistData by
 694      *                    the derived actor. identifier may be null when
 695      *                    the RaftActor is behaving as a follower or during
 696      *                    recovery
 697      * @param data        A piece of data that was persisted by the persistData call.
 698      *                    This should NEVER be null.
 699      */
 700     protected abstract void applyState(ActorRef clientActor, String identifier,
 701         Object data);
 702
 703     /**
 704      * Returns the RaftActorRecoveryCohort to participate in persistence recovery.
 705      */
 706     @Nonnull
 707     protected abstract RaftActorRecoveryCohort getRaftActorRecoveryCohort();
 708
 709     /**
 710      * This method is called when recovery is complete.
 711      */
 712     protected abstract void onRecoveryComplete();
 713
 714     /**
 715      * Returns the RaftActorSnapshotCohort to participate in persistence recovery.
 716      */
 717     @Nonnull
 718     protected abstract RaftActorSnapshotCohort getRaftActorSnapshotCohort();
 719
 720     /**
 721      * This method will be called by the RaftActor when the state of the
 722      * RaftActor changes. The derived actor can then use methods like
 723      * isLeader or getLeader to do something useful
 724      */
 725     protected abstract void onStateChanged();
 726
 727     /**
 728      * Notifier Actor for this RaftActor to notify when a role change happens
 729      * @return ActorRef - ActorRef of the notifier or Optional.absent if none.
 730      */
 731     protected abstract Optional<ActorRef> getRoleChangeNotifier();
 732
 733     /**
 734      * This method is called prior to operations such as leadership transfer and actor shutdown when the leader
 735      * must pause or stop its duties. This method allows derived classes to gracefully pause or finish current
 736      * work prior to performing the operation. On completion of any work, the run method must be called on the
 737      * given Runnable to proceed with the given operation. <b>Important:</b> the run method must be called on
 738      * this actor's thread dispatcher as as it modifies internal state.
 739      * <p>
 740      * The default implementation immediately runs the operation.
 741      *
 742      * @param operation the operation to run
 743      */
 744     protected void pauseLeader(Runnable operation) {
 745         operation.run();
 746     }
 747
 748     protected void onLeaderChanged(String oldLeader, String newLeader) {
 749
 750     };
 751
 752     private String getLeaderAddress(){
 753         if(isLeader()){
 754             return getSelf().path().toString();
 755         }
 756         String leaderId = getLeaderId();
 757         if (leaderId == null) {
 758             return null;
 759         }
 760         String peerAddress = context.getPeerAddress(leaderId);
 761         if(LOG.isDebugEnabled()) {
 762             LOG.debug("{}: getLeaderAddress leaderId = {} peerAddress = {}",
 763                     persistenceId(), leaderId, peerAddress);
 764         }
 765
 766         return peerAddress;
 767     }
 768
 769     protected boolean hasFollowers(){
 770         return getRaftActorContext().hasFollowers();
 771     }
 772
 773     private void captureSnapshot() {
 774         SnapshotManager snapshotManager = context.getSnapshotManager();
 775
 776         if (!snapshotManager.isCapturing()) {
 777             final long idx = getCurrentBehavior().getReplicatedToAllIndex();
 778             LOG.debug("Take a snapshot of current state. lastReplicatedLog is {} and replicatedToAllIndex is {}",
 779                 replicatedLog().last(), idx);
 780
 781             snapshotManager.capture(replicatedLog().last(), idx);
 782         }
 783     }
 784
 785     /**
 786      * Switch this member to non-voting status. This is a no-op for all behaviors except when we are the leader,
 787      * in which case we need to step down.
 788      */
 789     void becomeNonVoting() {
 790         if (isLeader()) {
 791             initiateLeadershipTransfer(new RaftActorLeadershipTransferCohort.OnComplete() {
 792                 @Override
 793                 public void onSuccess(ActorRef raftActorRef) {
 794                     LOG.debug("{}: leader transfer succeeded after change to non-voting", persistenceId());
 795                     ensureFollowerState();
 796                 }
 797
 798                 @Override
 799                 public void onFailure(ActorRef raftActorRef) {
 800                     LOG.debug("{}: leader transfer failed after change to non-voting", persistenceId());
 801                     ensureFollowerState();
 802                 }
 803
 804                 private void ensureFollowerState() {
 805                     // Whether or not leadership transfer succeeded, we have to step down as leader and
 806                     // switch to Follower so ensure that.
 807                     if (getRaftState() != RaftState.Follower) {
 808                         initializeBehavior();
 809                     }
 810                 }
 811             });
 812         }
 813     }
 814
 815     /**
 816      * @deprecated Deprecated in favor of {@link org.opendaylight.controller.cluster.raft.base.messages.DeleteEntries}
 817      *             whose type for fromIndex is long instead of int. This class was kept for backwards
 818      *             compatibility with Helium.
 819      */
 820     // Suppressing this warning as we can't set serialVersionUID to maintain backwards compatibility.
 821     @SuppressWarnings("serial")
 822     @Deprecated
 823     static class DeleteEntries implements Serializable {
 824         private final int fromIndex;
 825
 826         public DeleteEntries(int fromIndex) {
 827             this.fromIndex = fromIndex;
 828         }
 829
 830         public int getFromIndex() {
 831             return fromIndex;
 832         }
 833     }
 834
 835     /**
 836      * @deprecated Deprecated in favor of non-inner class {@link org.opendaylight.controller.cluster.raft.base.messages.UpdateElectionTerm}
 837      *             which has serialVersionUID set. This class was kept for backwards compatibility with Helium.
 838      */
 839     // Suppressing this warning as we can't set serialVersionUID to maintain backwards compatibility.
 840     @SuppressWarnings("serial")
 841     @Deprecated
 842     static class UpdateElectionTerm implements Serializable {
 843         private final long currentTerm;
 844         private final String votedFor;
 845
 846         public UpdateElectionTerm(long currentTerm, String votedFor) {
 847             this.currentTerm = currentTerm;
 848             this.votedFor = votedFor;
 849         }
 850
 851         public long getCurrentTerm() {
 852             return currentTerm;
 853         }
 854
 855         public String getVotedFor() {
 856             return votedFor;
 857         }
 858     }
 859
 860     /**
 861      * A point-in-time capture of {@link RaftActorBehavior} state critical for transitioning between behaviors.
 862      */
 863     private static abstract class BehaviorState implements Immutable {
 864         @Nullable abstract RaftActorBehavior getBehavior();
 865         @Nullable abstract String getLastValidLeaderId();
 866         @Nullable abstract short getLeaderPayloadVersion();
 867     }
 868
 869     /**
 870      * A {@link BehaviorState} corresponding to non-null {@link RaftActorBehavior} state.
 871      */
 872     private static final class SimpleBehaviorState extends BehaviorState {
 873         private final RaftActorBehavior behavior;
 874         private final String lastValidLeaderId;
 875         private final short leaderPayloadVersion;
 876
 877         SimpleBehaviorState(final String lastValidLeaderId, final RaftActorBehavior behavior) {
 878             this.lastValidLeaderId = lastValidLeaderId;
 879             this.behavior = Preconditions.checkNotNull(behavior);
 880             this.leaderPayloadVersion = behavior.getLeaderPayloadVersion();
 881         }
 882
 883         @Override
 884         RaftActorBehavior getBehavior() {
 885             return behavior;
 886         }
 887
 888         @Override
 889         String getLastValidLeaderId() {
 890             return lastValidLeaderId;
 891         }
 892
 893         @Override
 894         short getLeaderPayloadVersion() {
 895             return leaderPayloadVersion;
 896         }
 897     }
 898
 899     /**
 900      * Class tracking behavior-related information, which we need to keep around and pass across behavior switches.
 901      * An instance is created for each RaftActor. It has two functions:
 902      * - it keeps track of the last leader ID we have encountered since we have been created
 903      * - it creates state capture needed to transition from one behavior to the next
 904      */
 905     private static final class BehaviorStateTracker {
 906         /**
 907          * A {@link BehaviorState} corresponding to null {@link RaftActorBehavior} state. Since null behavior is only
 908          * allowed before we receive the first message, we know the leader ID to be null.
 909          */
 910         private static final BehaviorState NULL_BEHAVIOR_STATE = new BehaviorState() {
 911             @Override
 912             RaftActorBehavior getBehavior() {
 913                 return null;
 914             }
 915
 916             @Override
 917             String getLastValidLeaderId() {
 918                 return null;
 919             }
 920
 921             @Override
 922             short getLeaderPayloadVersion() {
 923                 return -1;
 924             }
 925         };
 926
 927         private String lastValidLeaderId;
 928
 929         BehaviorState capture(final RaftActorBehavior behavior) {
 930             if (behavior == null) {
 931                 Verify.verify(lastValidLeaderId == null, "Null behavior with non-null last leader");
 932                 return NULL_BEHAVIOR_STATE;
 933             }
 934
 935             final String leaderId = behavior.getLeaderId();
 936             if (leaderId != null) {
 937                 lastValidLeaderId = leaderId;
 938             }
 939
 940             return new SimpleBehaviorState(lastValidLeaderId, behavior);
 941         }
 942     }
 943
 944 }