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         reusableBehaviorStateHolder.init(getCurrentBehavior());
 206         setCurrentBehavior(newBehavior);
 207         handleBehaviorChange(reusableBehaviorStateHolder, getCurrentBehavior());
 208     }
 209
 210     @Override
 211     protected void handleCommand(final Object message) {
 212         if (serverConfigurationSupport.handleMessage(message, getSender())) {
 213             return;
 214         }
 215         if (snapshotSupport.handleSnapshotMessage(message, getSender())) {
 216             return;
 217         }
 218
 219         if (message instanceof ApplyState) {
 220             ApplyState applyState = (ApplyState) message;
 221
 222             long elapsedTime = (System.nanoTime() - applyState.getStartTime());
 223             if(elapsedTime >= APPLY_STATE_DELAY_THRESHOLD_IN_NANOS){
 224                 LOG.warn("ApplyState took more time than expected. Elapsed Time = {} ms ApplyState = {}",
 225                         TimeUnit.NANOSECONDS.toMillis(elapsedTime), applyState);
 226             }
 227
 228             if(LOG.isDebugEnabled()) {
 229                 LOG.debug("{}: Applying state for log index {} data {}",
 230                     persistenceId(), applyState.getReplicatedLogEntry().getIndex(),
 231                     applyState.getReplicatedLogEntry().getData());
 232             }
 233
 234             applyState(applyState.getClientActor(), applyState.getIdentifier(),
 235                 applyState.getReplicatedLogEntry().getData());
 236
 237             if (!hasFollowers()) {
 238                 // for single node, the capture should happen after the apply state
 239                 // as we delete messages from the persistent journal which have made it to the snapshot
 240                 // capturing the snapshot before applying makes the persistent journal and snapshot out of sync
 241                 // and recovery shows data missing
 242                 context.getReplicatedLog().captureSnapshotIfReady(applyState.getReplicatedLogEntry());
 243
 244                 context.getSnapshotManager().trimLog(context.getLastApplied(), currentBehavior);
 245             }
 246
 247         } else if (message instanceof ApplyJournalEntries) {
 248             ApplyJournalEntries applyEntries = (ApplyJournalEntries) message;
 249             if(LOG.isDebugEnabled()) {
 250                 LOG.debug("{}: Persisting ApplyLogEntries with index={}", persistenceId(), applyEntries.getToIndex());
 251             }
 252
 253             persistence().persist(applyEntries, NoopProcedure.instance());
 254
 255         } else if (message instanceof FindLeader) {
 256             getSender().tell(
 257                 new FindLeaderReply(getLeaderAddress()),
 258                 getSelf()
 259             );
 260         } else if(message instanceof GetOnDemandRaftState) {
 261             onGetOnDemandRaftStats();
 262         } else if(message instanceof InitiateCaptureSnapshot) {
 263             captureSnapshot();
 264         } else if(message instanceof SwitchBehavior) {
 265             switchBehavior(((SwitchBehavior) message));
 266         } else if(message instanceof LeaderTransitioning) {
 267             onLeaderTransitioning();
 268         } else if(message instanceof Shutdown) {
 269             onShutDown();
 270         } else if(message instanceof Runnable) {
 271             ((Runnable)message).run();
 272         } else {
 273             switchBehavior(reusableSwitchBehaviorSupplier.handleMessage(getSender(), message));
 274         }
 275     }
 276
 277     void initiateLeadershipTransfer(final RaftActorLeadershipTransferCohort.OnComplete onComplete) {
 278         LOG.debug("{}: Initiating leader transfer", persistenceId());
 279
 280         if(leadershipTransferInProgress == null) {
 281             leadershipTransferInProgress = new RaftActorLeadershipTransferCohort(this, getSender());
 282             leadershipTransferInProgress.addOnComplete(new RaftActorLeadershipTransferCohort.OnComplete() {
 283                 @Override
 284                 public void onSuccess(ActorRef raftActorRef, ActorRef replyTo) {
 285                     leadershipTransferInProgress = null;
 286                 }
 287
 288                 @Override
 289                 public void onFailure(ActorRef raftActorRef, ActorRef replyTo) {
 290                     leadershipTransferInProgress = null;
 291                 }
 292             });
 293
 294             leadershipTransferInProgress.addOnComplete(onComplete);
 295             leadershipTransferInProgress.init();
 296         } else {
 297             LOG.debug("{}: prior leader transfer in progress - adding callback", persistenceId());
 298             leadershipTransferInProgress.addOnComplete(onComplete);
 299         }
 300     }
 301
 302     private void onShutDown() {
 303         LOG.debug("{}: onShutDown", persistenceId());
 304
 305         if(shuttingDown) {
 306             return;
 307         }
 308
 309         shuttingDown = true;
 310         if(currentBehavior.state() == RaftState.Leader && context.hasFollowers()) {
 311             initiateLeadershipTransfer(new RaftActorLeadershipTransferCohort.OnComplete() {
 312                 @Override
 313                 public void onSuccess(ActorRef raftActorRef, ActorRef replyTo) {
 314                     LOG.debug("{}: leader transfer succeeded - sending PoisonPill", persistenceId());
 315                     raftActorRef.tell(PoisonPill.getInstance(), raftActorRef);
 316                 }
 317
 318                 @Override
 319                 public void onFailure(ActorRef raftActorRef, ActorRef replyTo) {
 320                     LOG.debug("{}: leader transfer failed - sending PoisonPill", persistenceId());
 321                     raftActorRef.tell(PoisonPill.getInstance(), raftActorRef);
 322                 }
 323             });
 324         } else if(currentBehavior.state() == RaftState.Leader) {
 325             pauseLeader(new TimedRunnable(context.getConfigParams().getElectionTimeOutInterval(), this) {
 326                 @Override
 327                 protected void doRun() {
 328                     self().tell(PoisonPill.getInstance(), self());
 329                 }
 330
 331                 @Override
 332                 protected void doCancel() {
 333                     self().tell(PoisonPill.getInstance(), self());
 334                 }
 335             });
 336         } else {
 337             self().tell(PoisonPill.getInstance(), self());
 338         }
 339     }
 340
 341     private void onLeaderTransitioning() {
 342         LOG.debug("{}: onLeaderTransitioning", persistenceId());
 343         Optional<ActorRef> roleChangeNotifier = getRoleChangeNotifier();
 344         if(currentBehavior.state() == RaftState.Follower && roleChangeNotifier.isPresent()) {
 345             roleChangeNotifier.get().tell(newLeaderStateChanged(getId(), null,
 346                     currentBehavior.getLeaderPayloadVersion()), getSelf());
 347         }
 348     }
 349
 350     private void switchBehavior(SwitchBehavior message) {
 351         if(!getRaftActorContext().getRaftPolicy().automaticElectionsEnabled()) {
 352             RaftState newState = message.getNewState();
 353             if( newState == RaftState.Leader || newState == RaftState.Follower) {
 354                 switchBehavior(reusableSwitchBehaviorSupplier.handleMessage(getSender(), message));
 355                 getRaftActorContext().getTermInformation().updateAndPersist(message.getNewTerm(), "");
 356             } else {
 357                 LOG.warn("Switching to behavior : {} - not supported", newState);
 358             }
 359         }
 360     }
 361
 362     private void switchBehavior(Supplier<RaftActorBehavior> supplier){
 363         reusableBehaviorStateHolder.init(getCurrentBehavior());
 364
 365         setCurrentBehavior(supplier.get());
 366
 367         handleBehaviorChange(reusableBehaviorStateHolder, getCurrentBehavior());
 368     }
 369
 370     protected RaftActorSnapshotMessageSupport newRaftActorSnapshotMessageSupport() {
 371         return new RaftActorSnapshotMessageSupport(context, currentBehavior,
 372                 getRaftActorSnapshotCohort());
 373     }
 374
 375     private void onGetOnDemandRaftStats() {
 376         // Debugging message to retrieve raft stats.
 377
 378         Map<String, String> peerAddresses = new HashMap<>();
 379         for(String peerId: context.getPeerIds()) {
 380             peerAddresses.put(peerId, context.getPeerAddress(peerId));
 381         }
 382
 383         OnDemandRaftState.Builder builder = OnDemandRaftState.builder()
 384                 .commitIndex(context.getCommitIndex())
 385                 .currentTerm(context.getTermInformation().getCurrentTerm())
 386                 .inMemoryJournalDataSize(replicatedLog().dataSize())
 387                 .inMemoryJournalLogSize(replicatedLog().size())
 388                 .isSnapshotCaptureInitiated(context.getSnapshotManager().isCapturing())
 389                 .lastApplied(context.getLastApplied())
 390                 .lastIndex(replicatedLog().lastIndex())
 391                 .lastTerm(replicatedLog().lastTerm())
 392                 .leader(getLeaderId())
 393                 .raftState(currentBehavior.state().toString())
 394                 .replicatedToAllIndex(currentBehavior.getReplicatedToAllIndex())
 395                 .snapshotIndex(replicatedLog().getSnapshotIndex())
 396                 .snapshotTerm(replicatedLog().getSnapshotTerm())
 397                 .votedFor(context.getTermInformation().getVotedFor())
 398                 .peerAddresses(peerAddresses)
 399                 .customRaftPolicyClassName(context.getConfigParams().getCustomRaftPolicyImplementationClass());
 400
 401         ReplicatedLogEntry lastLogEntry = getLastLogEntry();
 402         if (lastLogEntry != null) {
 403             builder.lastLogIndex(lastLogEntry.getIndex());
 404             builder.lastLogTerm(lastLogEntry.getTerm());
 405         }
 406
 407         if(getCurrentBehavior() instanceof AbstractLeader) {
 408             AbstractLeader leader = (AbstractLeader)getCurrentBehavior();
 409             Collection<String> followerIds = leader.getFollowerIds();
 410             List<FollowerInfo> followerInfoList = Lists.newArrayListWithCapacity(followerIds.size());
 411             for(String id: followerIds) {
 412                 final FollowerLogInformation info = leader.getFollower(id);
 413                 followerInfoList.add(new FollowerInfo(id, info.getNextIndex(), info.getMatchIndex(),
 414                         info.isFollowerActive(), DurationFormatUtils.formatDurationHMS(info.timeSinceLastActivity())));
 415             }
 416
 417             builder.followerInfoList(followerInfoList);
 418         }
 419
 420         sender().tell(builder.build(), self());
 421
 422     }
 423
 424     private void handleBehaviorChange(BehaviorStateHolder oldBehaviorState, RaftActorBehavior currentBehavior) {
 425         RaftActorBehavior oldBehavior = oldBehaviorState.getBehavior();
 426
 427         if (oldBehavior != currentBehavior){
 428             onStateChanged();
 429         }
 430
 431         String lastValidLeaderId = oldBehavior == null ? null : oldBehaviorState.getLastValidLeaderId();
 432         String oldBehaviorStateName = oldBehavior == null ? null : oldBehavior.state().name();
 433
 434         // it can happen that the state has not changed but the leader has changed.
 435         Optional<ActorRef> roleChangeNotifier = getRoleChangeNotifier();
 436         if(!Objects.equal(lastValidLeaderId, currentBehavior.getLeaderId()) ||
 437            oldBehaviorState.getLeaderPayloadVersion() != currentBehavior.getLeaderPayloadVersion()) {
 438             if(roleChangeNotifier.isPresent()) {
 439                 roleChangeNotifier.get().tell(newLeaderStateChanged(getId(), currentBehavior.getLeaderId(),
 440                         currentBehavior.getLeaderPayloadVersion()), getSelf());
 441             }
 442
 443             onLeaderChanged(lastValidLeaderId, currentBehavior.getLeaderId());
 444
 445             if(leadershipTransferInProgress != null) {
 446                 leadershipTransferInProgress.onNewLeader(currentBehavior.getLeaderId());
 447             }
 448         }
 449
 450         if (roleChangeNotifier.isPresent() &&
 451                 (oldBehavior == null || (oldBehavior.state() != currentBehavior.state()))) {
 452             roleChangeNotifier.get().tell(new RoleChanged(getId(), oldBehaviorStateName ,
 453                     currentBehavior.state().name()), getSelf());
 454         }
 455     }
 456
 457     protected LeaderStateChanged newLeaderStateChanged(String memberId, String leaderId, short leaderPayloadVersion) {
 458         return new LeaderStateChanged(memberId, leaderId, leaderPayloadVersion);
 459     }
 460
 461     @Override
 462     public long snapshotSequenceNr() {
 463         // When we do a snapshot capture, we also capture and save the sequence-number of the persistent journal,
 464         // so that we can delete the persistent journal based on the saved sequence-number
 465         // However , when akka replays the journal during recovery, it replays it from the sequence number when the snapshot
 466         // was saved and not the number we saved.
 467         // We would want to override it , by asking akka to use the last-sequence number known to us.
 468         return context.getSnapshotManager().getLastSequenceNumber();
 469     }
 470
 471     /**
 472      * When a derived RaftActor needs to persist something it must call
 473      * persistData.
 474      *
 475      * @param clientActor
 476      * @param identifier
 477      * @param data
 478      */
 479     protected void persistData(final ActorRef clientActor, final String identifier,
 480         final Payload data) {
 481
 482         ReplicatedLogEntry replicatedLogEntry = new ReplicatedLogImplEntry(
 483             context.getReplicatedLog().lastIndex() + 1,
 484             context.getTermInformation().getCurrentTerm(), data);
 485
 486         if(LOG.isDebugEnabled()) {
 487             LOG.debug("{}: Persist data {}", persistenceId(), replicatedLogEntry);
 488         }
 489
 490         final RaftActorContext raftContext = getRaftActorContext();
 491
 492         replicatedLog().appendAndPersist(replicatedLogEntry, new Procedure<ReplicatedLogEntry>() {
 493             @Override
 494             public void apply(ReplicatedLogEntry replicatedLogEntry) {
 495                 if (!hasFollowers()){
 496                     // Increment the Commit Index and the Last Applied values
 497                     raftContext.setCommitIndex(replicatedLogEntry.getIndex());
 498                     raftContext.setLastApplied(replicatedLogEntry.getIndex());
 499
 500                     // Apply the state immediately.
 501                     self().tell(new ApplyState(clientActor, identifier, replicatedLogEntry), self());
 502
 503                     // Send a ApplyJournalEntries message so that we write the fact that we applied
 504                     // the state to durable storage
 505                     self().tell(new ApplyJournalEntries(replicatedLogEntry.getIndex()), self());
 506
 507                 } else if (clientActor != null) {
 508                     context.getReplicatedLog().captureSnapshotIfReady(replicatedLogEntry);
 509
 510                     // Send message for replication
 511                     currentBehavior.handleMessage(getSelf(),
 512                             new Replicate(clientActor, identifier, replicatedLogEntry));
 513                 }
 514             }
 515         });
 516     }
 517
 518     private ReplicatedLog replicatedLog() {
 519         return context.getReplicatedLog();
 520     }
 521
 522     protected String getId() {
 523         return context.getId();
 524     }
 525
 526     @VisibleForTesting
 527     void setCurrentBehavior(RaftActorBehavior behavior) {
 528         currentBehavior.setDelegate(behavior);
 529     }
 530
 531     protected RaftActorBehavior getCurrentBehavior() {
 532         return currentBehavior.getDelegate();
 533     }
 534
 535     /**
 536      * Derived actors can call the isLeader method to check if the current
 537      * RaftActor is the Leader or not
 538      *
 539      * @return true it this RaftActor is a Leader false otherwise
 540      */
 541     protected boolean isLeader() {
 542         return context.getId().equals(currentBehavior.getLeaderId());
 543     }
 544
 545     protected boolean isLeaderActive() {
 546         return currentBehavior.state() != RaftState.IsolatedLeader && !shuttingDown &&
 547                 !isLeadershipTransferInProgress();
 548     }
 549
 550     private boolean isLeadershipTransferInProgress() {
 551         return leadershipTransferInProgress != null && leadershipTransferInProgress.isTransferring();
 552     }
 553
 554     /**
 555      * Derived actor can call getLeader if they need a reference to the Leader.
 556      * This would be useful for example in forwarding a request to an actor
 557      * which is the leader
 558      *
 559      * @return A reference to the leader if known, null otherwise
 560      */
 561     protected ActorSelection getLeader(){
 562         String leaderAddress = getLeaderAddress();
 563
 564         if(leaderAddress == null){
 565             return null;
 566         }
 567
 568         return context.actorSelection(leaderAddress);
 569     }
 570
 571     /**
 572      *
 573      * @return the current leader's id
 574      */
 575     protected String getLeaderId(){
 576         return currentBehavior.getLeaderId();
 577     }
 578
 579     protected RaftState getRaftState() {
 580         return currentBehavior.state();
 581     }
 582
 583     protected ReplicatedLogEntry getLastLogEntry() {
 584         return replicatedLog().last();
 585     }
 586
 587     protected Long getCurrentTerm(){
 588         return context.getTermInformation().getCurrentTerm();
 589     }
 590
 591     protected Long getCommitIndex(){
 592         return context.getCommitIndex();
 593     }
 594
 595     protected Long getLastApplied(){
 596         return context.getLastApplied();
 597     }
 598
 599     protected RaftActorContext getRaftActorContext() {
 600         return context;
 601     }
 602
 603     protected void updateConfigParams(ConfigParams configParams) {
 604
 605         // obtain the RaftPolicy for oldConfigParams and the updated one.
 606         String oldRaftPolicy = context.getConfigParams().
 607             getCustomRaftPolicyImplementationClass();
 608         String newRaftPolicy = configParams.
 609             getCustomRaftPolicyImplementationClass();
 610
 611         LOG.debug("{}: RaftPolicy used with prev.config {}, RaftPolicy used with newConfig {}", persistenceId(),
 612             oldRaftPolicy, newRaftPolicy);
 613         context.setConfigParams(configParams);
 614         if (!Objects.equal(oldRaftPolicy, newRaftPolicy)) {
 615             // The RaftPolicy was modified. If the current behavior is Follower then re-initialize to Follower
 616             // but transfer the previous leaderId so it doesn't immediately try to schedule an election. This
 617             // avoids potential disruption. Otherwise, switch to Follower normally.
 618             RaftActorBehavior behavior = currentBehavior.getDelegate();
 619             if(behavior instanceof Follower) {
 620                 String previousLeaderId = ((Follower)behavior).getLeaderId();
 621                 short previousLeaderPayloadVersion = behavior.getLeaderPayloadVersion();
 622
 623                 LOG.debug("{}: Re-initializing to Follower with previous leaderId {}", persistenceId(), previousLeaderId);
 624
 625                 changeCurrentBehavior(new Follower(context, previousLeaderId, previousLeaderPayloadVersion));
 626             } else {
 627                 initializeBehavior();
 628             }
 629         }
 630     }
 631
 632     public final DataPersistenceProvider persistence() {
 633         return delegatingPersistenceProvider.getDelegate();
 634     }
 635
 636     public void setPersistence(DataPersistenceProvider provider) {
 637         delegatingPersistenceProvider.setDelegate(provider);
 638     }
 639
 640     protected void setPersistence(boolean persistent) {
 641         if(persistent) {
 642             setPersistence(new PersistentDataProvider(this));
 643         } else {
 644             setPersistence(new NonPersistentDataProvider() {
 645                 /**
 646                  * The way snapshotting works is,
 647                  * <ol>
 648                  * <li> RaftActor calls createSnapshot on the Shard
 649                  * <li> Shard sends a CaptureSnapshotReply and RaftActor then calls saveSnapshot
 650                  * <li> When saveSnapshot is invoked on the akka-persistence API it uses the SnapshotStore to save
 651                  * the snapshot. The SnapshotStore sends SaveSnapshotSuccess or SaveSnapshotFailure. When the
 652                  * RaftActor gets SaveSnapshot success it commits the snapshot to the in-memory journal. This
 653                  * commitSnapshot is mimicking what is done in SaveSnapshotSuccess.
 654                  * </ol>
 655                  */
 656                 @Override
 657                 public void saveSnapshot(Object o) {
 658                     // Make saving Snapshot successful
 659                     // Committing the snapshot here would end up calling commit in the creating state which would
 660                     // be a state violation. That's why now we send a message to commit the snapshot.
 661                     self().tell(RaftActorSnapshotMessageSupport.COMMIT_SNAPSHOT, self());
 662                 }
 663             });
 664         }
 665     }
 666
 667     /**
 668      * setPeerAddress sets the address of a known peer at a later time.
 669      * <p>
 670      * This is to account for situations where a we know that a peer
 671      * exists but we do not know an address up-front. This may also be used in
 672      * situations where a known peer starts off in a different location and we
 673      * need to change it's address
 674      * <p>
 675      * Note that if the peerId does not match the list of peers passed to
 676      * this actor during construction an IllegalStateException will be thrown.
 677      *
 678      * @param peerId
 679      * @param peerAddress
 680      */
 681     protected void setPeerAddress(String peerId, String peerAddress){
 682         context.setPeerAddress(peerId, peerAddress);
 683     }
 684
 685     /**
 686      * The applyState method will be called by the RaftActor when some data
 687      * needs to be applied to the actor's state
 688      *
 689      * @param clientActor A reference to the client who sent this message. This
 690      *                    is the same reference that was passed to persistData
 691      *                    by the derived actor. clientActor may be null when
 692      *                    the RaftActor is behaving as a follower or during
 693      *                    recovery.
 694      * @param identifier  The identifier of the persisted data. This is also
 695      *                    the same identifier that was passed to persistData by
 696      *                    the derived actor. identifier may be null when
 697      *                    the RaftActor is behaving as a follower or during
 698      *                    recovery
 699      * @param data        A piece of data that was persisted by the persistData call.
 700      *                    This should NEVER be null.
 701      */
 702     protected abstract void applyState(ActorRef clientActor, String identifier,
 703         Object data);
 704
 705     /**
 706      * Returns the RaftActorRecoveryCohort to participate in persistence recovery.
 707      */
 708     @Nonnull
 709     protected abstract RaftActorRecoveryCohort getRaftActorRecoveryCohort();
 710
 711     /**
 712      * This method is called when recovery is complete.
 713      */
 714     protected abstract void onRecoveryComplete();
 715
 716     /**
 717      * Returns the RaftActorSnapshotCohort to participate in persistence recovery.
 718      */
 719     @Nonnull
 720     protected abstract RaftActorSnapshotCohort getRaftActorSnapshotCohort();
 721
 722     /**
 723      * This method will be called by the RaftActor when the state of the
 724      * RaftActor changes. The derived actor can then use methods like
 725      * isLeader or getLeader to do something useful
 726      */
 727     protected abstract void onStateChanged();
 728
 729     /**
 730      * Notifier Actor for this RaftActor to notify when a role change happens
 731      * @return ActorRef - ActorRef of the notifier or Optional.absent if none.
 732      */
 733     protected abstract Optional<ActorRef> getRoleChangeNotifier();
 734
 735     /**
 736      * This method is called prior to operations such as leadership transfer and actor shutdown when the leader
 737      * must pause or stop its duties. This method allows derived classes to gracefully pause or finish current
 738      * work prior to performing the operation. On completion of any work, the run method must be called on the
 739      * given Runnable to proceed with the given operation. <b>Important:</b> the run method must be called on
 740      * this actor's thread dispatcher as as it modifies internal state.
 741      * <p>
 742      * The default implementation immediately runs the operation.
 743      *
 744      * @param operation the operation to run
 745      */
 746     protected void pauseLeader(Runnable operation) {
 747         operation.run();
 748     }
 749
 750     protected void onLeaderChanged(String oldLeader, String newLeader){};
 751
 752     private String getLeaderAddress(){
 753         if(isLeader()){
 754             return getSelf().path().toString();
 755         }
 756         String leaderId = currentBehavior.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             LOG.debug("Take a snapshot of current state. lastReplicatedLog is {} and replicatedToAllIndex is {}",
 778                 replicatedLog().last(), currentBehavior.getReplicatedToAllIndex());
 779
 780             snapshotManager.capture(replicatedLog().last(), currentBehavior.getReplicatedToAllIndex());
 781         }
 782     }
 783
 784     /**
 785      * @deprecated Deprecated in favor of {@link org.opendaylight.controller.cluster.raft.base.messages.DeleteEntries}
 786      *             whose type for fromIndex is long instead of int. This class was kept for backwards
 787      *             compatibility with Helium.
 788      */
 789     // Suppressing this warning as we can't set serialVersionUID to maintain backwards compatibility.
 790     @SuppressWarnings("serial")
 791     @Deprecated
 792     static class DeleteEntries implements Serializable {
 793         private final int fromIndex;
 794
 795         public DeleteEntries(int fromIndex) {
 796             this.fromIndex = fromIndex;
 797         }
 798
 799         public int getFromIndex() {
 800             return fromIndex;
 801         }
 802     }
 803
 804     /**
 805      * @deprecated Deprecated in favor of non-inner class {@link org.opendaylight.controller.cluster.raft.base.messages.UpdateElectionTerm}
 806      *             which has serialVersionUID set. This class was kept for backwards compatibility with Helium.
 807      */
 808     // Suppressing this warning as we can't set serialVersionUID to maintain backwards compatibility.
 809     @SuppressWarnings("serial")
 810     @Deprecated
 811     static class UpdateElectionTerm implements Serializable {
 812         private final long currentTerm;
 813         private final String votedFor;
 814
 815         public UpdateElectionTerm(long currentTerm, String votedFor) {
 816             this.currentTerm = currentTerm;
 817             this.votedFor = votedFor;
 818         }
 819
 820         public long getCurrentTerm() {
 821             return currentTerm;
 822         }
 823
 824         public String getVotedFor() {
 825             return votedFor;
 826         }
 827     }
 828
 829     private static class BehaviorStateHolder {
 830         private RaftActorBehavior behavior;
 831         private String lastValidLeaderId;
 832         private short leaderPayloadVersion;
 833
 834         void init(RaftActorBehavior behavior) {
 835             this.behavior = behavior;
 836             this.leaderPayloadVersion = behavior != null ? behavior.getLeaderPayloadVersion() : -1;
 837
 838             String behaviorLeaderId = behavior != null ? behavior.getLeaderId() : null;
 839             if(behaviorLeaderId != null) {
 840                 this.lastValidLeaderId = behaviorLeaderId;
 841             }
 842         }
 843
 844         RaftActorBehavior getBehavior() {
 845             return behavior;
 846         }
 847
 848         String getLastValidLeaderId() {
 849             return lastValidLeaderId;
 850         }
 851
 852         short getLeaderPayloadVersion() {
 853             return leaderPayloadVersion;
 854         }
 855     }
 856
 857     private class SwitchBehaviorSupplier implements Supplier<RaftActorBehavior> {
 858         private Object message;
 859         private ActorRef sender;
 860
 861         public SwitchBehaviorSupplier handleMessage(ActorRef sender, Object message){
 862             this.sender = sender;
 863             this.message = message;
 864             return this;
 865         }
 866
 867         @Override
 868         public RaftActorBehavior get() {
 869             if(this.message instanceof SwitchBehavior){
 870                 return AbstractRaftActorBehavior.createBehavior(context, ((SwitchBehavior) message).getNewState());
 871             }
 872             return currentBehavior.handleMessage(sender, message);
 873         }
 874     }
 875 }