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 startTime = System.nanoTime();
 221
 222             if(LOG.isDebugEnabled()) {
 223                 LOG.debug("{}: Applying state for log index {} data {}",
 224                     persistenceId(), applyState.getReplicatedLogEntry().getIndex(),
 225                     applyState.getReplicatedLogEntry().getData());
 226             }
 227
 228             applyState(applyState.getClientActor(), applyState.getIdentifier(),
 229                 applyState.getReplicatedLogEntry().getData());
 230
 231             long elapsedTime = System.nanoTime() - startTime;
 232             if(elapsedTime >= APPLY_STATE_DELAY_THRESHOLD_IN_NANOS){
 233                 LOG.debug("ApplyState took more time than expected. Elapsed Time = {} ms ApplyState = {}",
 234                         TimeUnit.NANOSECONDS.toMillis(elapsedTime), applyState);
 235             }
 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());
 245             }
 246
 247         } else if (message instanceof ApplyJournalEntries) {
 248             ApplyJournalEntries applyEntries = (ApplyJournalEntries) message;
 249             if(LOG.isDebugEnabled()) {
 250                 LOG.debug("{}: Persisting ApplyJournalEntries 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             // Processing the message may affect the state, hence we need to capture it
 274             final RaftActorBehavior currentBehavior = getCurrentBehavior();
 275             final BehaviorState state = behaviorStateTracker.capture(currentBehavior);
 276             final RaftActorBehavior nextBehavior = currentBehavior.handleMessage(getSender(), message);
 277             switchBehavior(state, nextBehavior);
 278         }
 279     }
 280
 281     private void initiateLeadershipTransfer(final RaftActorLeadershipTransferCohort.OnComplete onComplete) {
 282         LOG.debug("{}: Initiating leader transfer", persistenceId());
 283
 284         if(leadershipTransferInProgress == null) {
 285             leadershipTransferInProgress = new RaftActorLeadershipTransferCohort(this);
 286             leadershipTransferInProgress.addOnComplete(new RaftActorLeadershipTransferCohort.OnComplete() {
 287                 @Override
 288                 public void onSuccess(ActorRef raftActorRef) {
 289                     leadershipTransferInProgress = null;
 290                 }
 291
 292                 @Override
 293                 public void onFailure(ActorRef raftActorRef) {
 294                     leadershipTransferInProgress = null;
 295                 }
 296             });
 297
 298             leadershipTransferInProgress.addOnComplete(onComplete);
 299             leadershipTransferInProgress.init();
 300         } else {
 301             LOG.debug("{}: prior leader transfer in progress - adding callback", persistenceId());
 302             leadershipTransferInProgress.addOnComplete(onComplete);
 303         }
 304     }
 305
 306     private void onShutDown() {
 307         LOG.debug("{}: onShutDown", persistenceId());
 308
 309         if(shuttingDown) {
 310             return;
 311         }
 312
 313         shuttingDown = true;
 314
 315         final RaftActorBehavior currentBehavior = context.getCurrentBehavior();
 316         if (currentBehavior.state() != RaftState.Leader) {
 317             // For non-leaders shutdown is a no-op
 318             self().tell(PoisonPill.getInstance(), self());
 319             return;
 320         }
 321
 322         if (context.hasFollowers()) {
 323             initiateLeadershipTransfer(new RaftActorLeadershipTransferCohort.OnComplete() {
 324                 @Override
 325                 public void onSuccess(ActorRef raftActorRef) {
 326                     LOG.debug("{}: leader transfer succeeded - sending PoisonPill", persistenceId());
 327                     raftActorRef.tell(PoisonPill.getInstance(), raftActorRef);
 328                 }
 329
 330                 @Override
 331                 public void onFailure(ActorRef raftActorRef) {
 332                     LOG.debug("{}: leader transfer failed - sending PoisonPill", persistenceId());
 333                     raftActorRef.tell(PoisonPill.getInstance(), raftActorRef);
 334                 }
 335             });
 336         } else {
 337             pauseLeader(new TimedRunnable(context.getConfigParams().getElectionTimeOutInterval(), this) {
 338                 @Override
 339                 protected void doRun() {
 340                     self().tell(PoisonPill.getInstance(), self());
 341                 }
 342
 343                 @Override
 344                 protected void doCancel() {
 345                     self().tell(PoisonPill.getInstance(), self());
 346                 }
 347             });
 348         }
 349     }
 350
 351     private void onLeaderTransitioning() {
 352         LOG.debug("{}: onLeaderTransitioning", persistenceId());
 353         Optional<ActorRef> roleChangeNotifier = getRoleChangeNotifier();
 354         if(getRaftState() == RaftState.Follower && roleChangeNotifier.isPresent()) {
 355             roleChangeNotifier.get().tell(newLeaderStateChanged(getId(), null,
 356                 getCurrentBehavior().getLeaderPayloadVersion()), getSelf());
 357         }
 358     }
 359
 360     private void switchBehavior(SwitchBehavior message) {
 361         if(!getRaftActorContext().getRaftPolicy().automaticElectionsEnabled()) {
 362             RaftState newState = message.getNewState();
 363             if( newState == RaftState.Leader || newState == RaftState.Follower) {
 364                 switchBehavior(behaviorStateTracker.capture(getCurrentBehavior()),
 365                     AbstractRaftActorBehavior.createBehavior(context, message.getNewState()));
 366                 getRaftActorContext().getTermInformation().updateAndPersist(message.getNewTerm(), "");
 367             } else {
 368                 LOG.warn("Switching to behavior : {} - not supported", newState);
 369             }
 370         }
 371     }
 372
 373     private void switchBehavior(final BehaviorState oldBehaviorState, final RaftActorBehavior nextBehavior) {
 374         setCurrentBehavior(nextBehavior);
 375         handleBehaviorChange(oldBehaviorState, nextBehavior);
 376     }
 377
 378     @VisibleForTesting
 379     RaftActorSnapshotMessageSupport newRaftActorSnapshotMessageSupport() {
 380         return new RaftActorSnapshotMessageSupport(context, 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         final RaftActorBehavior currentBehavior = context.getCurrentBehavior();
 392         OnDemandRaftState.Builder builder = OnDemandRaftState.builder()
 393                 .commitIndex(context.getCommitIndex())
 394                 .currentTerm(context.getTermInformation().getCurrentTerm())
 395                 .inMemoryJournalDataSize(replicatedLog().dataSize())
 396                 .inMemoryJournalLogSize(replicatedLog().size())
 397                 .isSnapshotCaptureInitiated(context.getSnapshotManager().isCapturing())
 398                 .lastApplied(context.getLastApplied())
 399                 .lastIndex(replicatedLog().lastIndex())
 400                 .lastTerm(replicatedLog().lastTerm())
 401                 .leader(getLeaderId())
 402                 .raftState(currentBehavior.state().toString())
 403                 .replicatedToAllIndex(currentBehavior.getReplicatedToAllIndex())
 404                 .snapshotIndex(replicatedLog().getSnapshotIndex())
 405                 .snapshotTerm(replicatedLog().getSnapshotTerm())
 406                 .votedFor(context.getTermInformation().getVotedFor())
 407                 .peerAddresses(peerAddresses)
 408                 .customRaftPolicyClassName(context.getConfigParams().getCustomRaftPolicyImplementationClass());
 409
 410         ReplicatedLogEntry lastLogEntry = replicatedLog().last();
 411         if (lastLogEntry != null) {
 412             builder.lastLogIndex(lastLogEntry.getIndex());
 413             builder.lastLogTerm(lastLogEntry.getTerm());
 414         }
 415
 416         if(getCurrentBehavior() instanceof AbstractLeader) {
 417             AbstractLeader leader = (AbstractLeader)getCurrentBehavior();
 418             Collection<String> followerIds = leader.getFollowerIds();
 419             List<FollowerInfo> followerInfoList = Lists.newArrayListWithCapacity(followerIds.size());
 420             for(String id: followerIds) {
 421                 final FollowerLogInformation info = leader.getFollower(id);
 422                 followerInfoList.add(new FollowerInfo(id, info.getNextIndex(), info.getMatchIndex(),
 423                         info.isFollowerActive(), DurationFormatUtils.formatDurationHMS(info.timeSinceLastActivity())));
 424             }
 425
 426             builder.followerInfoList(followerInfoList);
 427         }
 428
 429         sender().tell(builder.build(), self());
 430
 431     }
 432
 433     private void handleBehaviorChange(BehaviorState oldBehaviorState, RaftActorBehavior currentBehavior) {
 434         RaftActorBehavior oldBehavior = oldBehaviorState.getBehavior();
 435
 436         if (oldBehavior != currentBehavior){
 437             onStateChanged();
 438         }
 439
 440         String lastValidLeaderId = oldBehavior == null ? null : oldBehaviorState.getLastValidLeaderId();
 441         String oldBehaviorStateName = oldBehavior == null ? null : oldBehavior.state().name();
 442
 443         // it can happen that the state has not changed but the leader has changed.
 444         Optional<ActorRef> roleChangeNotifier = getRoleChangeNotifier();
 445         if(!Objects.equals(lastValidLeaderId, currentBehavior.getLeaderId()) ||
 446            oldBehaviorState.getLeaderPayloadVersion() != currentBehavior.getLeaderPayloadVersion()) {
 447             if(roleChangeNotifier.isPresent()) {
 448                 roleChangeNotifier.get().tell(newLeaderStateChanged(getId(), currentBehavior.getLeaderId(),
 449                         currentBehavior.getLeaderPayloadVersion()), getSelf());
 450             }
 451
 452             onLeaderChanged(lastValidLeaderId, currentBehavior.getLeaderId());
 453
 454             if(leadershipTransferInProgress != null) {
 455                 leadershipTransferInProgress.onNewLeader(currentBehavior.getLeaderId());
 456             }
 457
 458             serverConfigurationSupport.onNewLeader(currentBehavior.getLeaderId());
 459         }
 460
 461         if (roleChangeNotifier.isPresent() &&
 462                 (oldBehavior == null || (oldBehavior.state() != currentBehavior.state()))) {
 463             roleChangeNotifier.get().tell(new RoleChanged(getId(), oldBehaviorStateName ,
 464                     currentBehavior.state().name()), getSelf());
 465         }
 466     }
 467
 468     protected LeaderStateChanged newLeaderStateChanged(String memberId, String leaderId, short leaderPayloadVersion) {
 469         return new LeaderStateChanged(memberId, leaderId, leaderPayloadVersion);
 470     }
 471
 472     @Override
 473     public long snapshotSequenceNr() {
 474         // When we do a snapshot capture, we also capture and save the sequence-number of the persistent journal,
 475         // so that we can delete the persistent journal based on the saved sequence-number
 476         // However , when akka replays the journal during recovery, it replays it from the sequence number when the snapshot
 477         // was saved and not the number we saved.
 478         // We would want to override it , by asking akka to use the last-sequence number known to us.
 479         return context.getSnapshotManager().getLastSequenceNumber();
 480     }
 481
 482     /**
 483      * When a derived RaftActor needs to persist something it must call
 484      * persistData.
 485      *
 486      * @param clientActor
 487      * @param identifier
 488      * @param data
 489      */
 490     protected void persistData(final ActorRef clientActor, final String identifier,
 491         final Payload data) {
 492
 493         ReplicatedLogEntry replicatedLogEntry = new ReplicatedLogImplEntry(
 494             context.getReplicatedLog().lastIndex() + 1,
 495             context.getTermInformation().getCurrentTerm(), data);
 496
 497         if(LOG.isDebugEnabled()) {
 498             LOG.debug("{}: Persist data {}", persistenceId(), replicatedLogEntry);
 499         }
 500
 501         final RaftActorContext raftContext = getRaftActorContext();
 502
 503         replicatedLog().appendAndPersist(replicatedLogEntry, new Procedure<ReplicatedLogEntry>() {
 504             @Override
 505             public void apply(ReplicatedLogEntry replicatedLogEntry) {
 506                 if (!hasFollowers()){
 507                     // Increment the Commit Index and the Last Applied values
 508                     raftContext.setCommitIndex(replicatedLogEntry.getIndex());
 509                     raftContext.setLastApplied(replicatedLogEntry.getIndex());
 510
 511                     // Apply the state immediately.
 512                     self().tell(new ApplyState(clientActor, identifier, replicatedLogEntry), self());
 513
 514                     // Send a ApplyJournalEntries message so that we write the fact that we applied
 515                     // the state to durable storage
 516                     self().tell(new ApplyJournalEntries(replicatedLogEntry.getIndex()), self());
 517
 518                 } else if (clientActor != null) {
 519                     context.getReplicatedLog().captureSnapshotIfReady(replicatedLogEntry);
 520
 521                     // Send message for replication
 522                     getCurrentBehavior().handleMessage(getSelf(),
 523                             new Replicate(clientActor, identifier, replicatedLogEntry));
 524                 }
 525             }
 526         });
 527     }
 528
 529     private ReplicatedLog replicatedLog() {
 530         return context.getReplicatedLog();
 531     }
 532
 533     protected String getId() {
 534         return context.getId();
 535     }
 536
 537     @VisibleForTesting
 538     void setCurrentBehavior(RaftActorBehavior behavior) {
 539         context.setCurrentBehavior(behavior);
 540     }
 541
 542     protected RaftActorBehavior getCurrentBehavior() {
 543         return context.getCurrentBehavior();
 544     }
 545
 546     /**
 547      * Derived actors can call the isLeader method to check if the current
 548      * RaftActor is the Leader or not
 549      *
 550      * @return true it this RaftActor is a Leader false otherwise
 551      */
 552     protected boolean isLeader() {
 553         return context.getId().equals(getCurrentBehavior().getLeaderId());
 554     }
 555
 556     protected final boolean isLeaderActive() {
 557         return getRaftState() != RaftState.IsolatedLeader && !shuttingDown &&
 558                 !isLeadershipTransferInProgress();
 559     }
 560
 561     private boolean isLeadershipTransferInProgress() {
 562         return leadershipTransferInProgress != null && leadershipTransferInProgress.isTransferring();
 563     }
 564
 565     /**
 566      * Derived actor can call getLeader if they need a reference to the Leader.
 567      * This would be useful for example in forwarding a request to an actor
 568      * which is the leader
 569      *
 570      * @return A reference to the leader if known, null otherwise
 571      */
 572     protected ActorSelection getLeader(){
 573         String leaderAddress = getLeaderAddress();
 574
 575         if(leaderAddress == null){
 576             return null;
 577         }
 578
 579         return context.actorSelection(leaderAddress);
 580     }
 581
 582     /**
 583      *
 584      * @return the current leader's id
 585      */
 586     protected final String getLeaderId(){
 587         return getCurrentBehavior().getLeaderId();
 588     }
 589
 590     @VisibleForTesting
 591     protected final RaftState getRaftState() {
 592         return getCurrentBehavior().state();
 593     }
 594
 595     protected Long getCurrentTerm(){
 596         return context.getTermInformation().getCurrentTerm();
 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.equals(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 = getCurrentBehavior();
 619             if (behavior != null && behavior.state() == RaftState.Follower) {
 620                 String previousLeaderId = 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     };
 753
 754     private String getLeaderAddress(){
 755         if(isLeader()){
 756             return getSelf().path().toString();
 757         }
 758         String leaderId = getLeaderId();
 759         if (leaderId == null) {
 760             return null;
 761         }
 762         String peerAddress = context.getPeerAddress(leaderId);
 763         if(LOG.isDebugEnabled()) {
 764             LOG.debug("{}: getLeaderAddress leaderId = {} peerAddress = {}",
 765                     persistenceId(), leaderId, peerAddress);
 766         }
 767
 768         return peerAddress;
 769     }
 770
 771     protected boolean hasFollowers(){
 772         return getRaftActorContext().hasFollowers();
 773     }
 774
 775     private void captureSnapshot() {
 776         SnapshotManager snapshotManager = context.getSnapshotManager();
 777
 778         if (!snapshotManager.isCapturing()) {
 779             final long idx = getCurrentBehavior().getReplicatedToAllIndex();
 780             LOG.debug("Take a snapshot of current state. lastReplicatedLog is {} and replicatedToAllIndex is {}",
 781                 replicatedLog().last(), idx);
 782
 783             snapshotManager.capture(replicatedLog().last(), idx);
 784         }
 785     }
 786
 787     /**
 788      * Switch this member to non-voting status. This is a no-op for all behaviors except when we are the leader,
 789      * in which case we need to step down.
 790      */
 791     void becomeNonVoting() {
 792         if (isLeader()) {
 793             initiateLeadershipTransfer(new RaftActorLeadershipTransferCohort.OnComplete() {
 794                 @Override
 795                 public void onSuccess(ActorRef raftActorRef) {
 796                     LOG.debug("{}: leader transfer succeeded after change to non-voting", persistenceId());
 797                     ensureFollowerState();
 798                 }
 799
 800                 @Override
 801                 public void onFailure(ActorRef raftActorRef) {
 802                     LOG.debug("{}: leader transfer failed after change to non-voting", persistenceId());
 803                     ensureFollowerState();
 804                 }
 805
 806                 private void ensureFollowerState() {
 807                     // Whether or not leadership transfer succeeded, we have to step down as leader and
 808                     // switch to Follower so ensure that.
 809                     if (getRaftState() != RaftState.Follower) {
 810                         initializeBehavior();
 811                     }
 812                 }
 813             });
 814         }
 815     }
 816
 817     /**
 818      * @deprecated Deprecated in favor of {@link org.opendaylight.controller.cluster.raft.base.messages.DeleteEntries}
 819      *             whose type for fromIndex is long instead of int. This class was kept for backwards
 820      *             compatibility with Helium.
 821      */
 822     // Suppressing this warning as we can't set serialVersionUID to maintain backwards compatibility.
 823     @SuppressWarnings("serial")
 824     @Deprecated
 825     static class DeleteEntries implements Serializable {
 826         private final int fromIndex;
 827
 828         public DeleteEntries(int fromIndex) {
 829             this.fromIndex = fromIndex;
 830         }
 831
 832         public int getFromIndex() {
 833             return fromIndex;
 834         }
 835     }
 836
 837     /**
 838      * @deprecated Deprecated in favor of non-inner class {@link org.opendaylight.controller.cluster.raft.base.messages.UpdateElectionTerm}
 839      *             which has serialVersionUID set. This class was kept for backwards compatibility with Helium.
 840      */
 841     // Suppressing this warning as we can't set serialVersionUID to maintain backwards compatibility.
 842     @SuppressWarnings("serial")
 843     @Deprecated
 844     static class UpdateElectionTerm implements Serializable {
 845         private final long currentTerm;
 846         private final String votedFor;
 847
 848         public UpdateElectionTerm(long currentTerm, String votedFor) {
 849             this.currentTerm = currentTerm;
 850             this.votedFor = votedFor;
 851         }
 852
 853         public long getCurrentTerm() {
 854             return currentTerm;
 855         }
 856
 857         public String getVotedFor() {
 858             return votedFor;
 859         }
 860     }
 861
 862     /**
 863      * A point-in-time capture of {@link RaftActorBehavior} state critical for transitioning between behaviors.
 864      */
 865     private static abstract class BehaviorState implements Immutable {
 866         @Nullable abstract RaftActorBehavior getBehavior();
 867         @Nullable abstract String getLastValidLeaderId();
 868         @Nullable abstract short getLeaderPayloadVersion();
 869     }
 870
 871     /**
 872      * A {@link BehaviorState} corresponding to non-null {@link RaftActorBehavior} state.
 873      */
 874     private static final class SimpleBehaviorState extends BehaviorState {
 875         private final RaftActorBehavior behavior;
 876         private final String lastValidLeaderId;
 877         private final short leaderPayloadVersion;
 878
 879         SimpleBehaviorState(final String lastValidLeaderId, final RaftActorBehavior behavior) {
 880             this.lastValidLeaderId = lastValidLeaderId;
 881             this.behavior = Preconditions.checkNotNull(behavior);
 882             this.leaderPayloadVersion = behavior.getLeaderPayloadVersion();
 883         }
 884
 885         @Override
 886         RaftActorBehavior getBehavior() {
 887             return behavior;
 888         }
 889
 890         @Override
 891         String getLastValidLeaderId() {
 892             return lastValidLeaderId;
 893         }
 894
 895         @Override
 896         short getLeaderPayloadVersion() {
 897             return leaderPayloadVersion;
 898         }
 899     }
 900
 901     /**
 902      * Class tracking behavior-related information, which we need to keep around and pass across behavior switches.
 903      * An instance is created for each RaftActor. It has two functions:
 904      * - it keeps track of the last leader ID we have encountered since we have been created
 905      * - it creates state capture needed to transition from one behavior to the next
 906      */
 907     private static final class BehaviorStateTracker {
 908         /**
 909          * A {@link BehaviorState} corresponding to null {@link RaftActorBehavior} state. Since null behavior is only
 910          * allowed before we receive the first message, we know the leader ID to be null.
 911          */
 912         private static final BehaviorState NULL_BEHAVIOR_STATE = new BehaviorState() {
 913             @Override
 914             RaftActorBehavior getBehavior() {
 915                 return null;
 916             }
 917
 918             @Override
 919             String getLastValidLeaderId() {
 920                 return null;
 921             }
 922
 923             @Override
 924             short getLeaderPayloadVersion() {
 925                 return -1;
 926             }
 927         };
 928
 929         private String lastValidLeaderId;
 930
 931         BehaviorState capture(final RaftActorBehavior behavior) {
 932             if (behavior == null) {
 933                 Verify.verify(lastValidLeaderId == null, "Null behavior with non-null last leader");
 934                 return NULL_BEHAVIOR_STATE;
 935             }
 936
 937             final String leaderId = behavior.getLeaderId();
 938             if (leaderId != null) {
 939                 lastValidLeaderId = leaderId;
 940             }
 941
 942             return new SimpleBehaviorState(lastValidLeaderId, behavior);
 943         }
 944     }
 945
 946 }