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