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 com.google.common.annotations.VisibleForTesting;
  16 import com.google.common.base.Optional;
  17 import com.google.common.base.Preconditions;
  18 import com.google.common.base.Verify;
  19 import com.google.common.collect.Lists;
  20 import java.io.Serializable;
  21 import java.util.Collection;
  22 import java.util.HashMap;
  23 import java.util.List;
  24 import java.util.Map;
  25 import java.util.Objects;
  26 import java.util.concurrent.TimeUnit;
  27 import javax.annotation.Nonnull;
  28 import javax.annotation.Nullable;
  29 import org.apache.commons.lang3.time.DurationFormatUtils;
  30 import org.opendaylight.controller.cluster.DataPersistenceProvider;
  31 import org.opendaylight.controller.cluster.DelegatingPersistentDataProvider;
  32 import org.opendaylight.controller.cluster.NonPersistentDataProvider;
  33 import org.opendaylight.controller.cluster.PersistentDataProvider;
  34 import org.opendaylight.controller.cluster.common.actor.AbstractUntypedPersistentActor;
  35 import org.opendaylight.controller.cluster.notifications.LeaderStateChanged;
  36 import org.opendaylight.controller.cluster.notifications.RoleChanged;
  37 import org.opendaylight.controller.cluster.raft.base.messages.ApplyState;
  38 import org.opendaylight.controller.cluster.raft.base.messages.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.Follower;
  45 import org.opendaylight.controller.cluster.raft.behaviors.RaftActorBehavior;
  46 import org.opendaylight.controller.cluster.raft.client.messages.FindLeader;
  47 import org.opendaylight.controller.cluster.raft.client.messages.FindLeaderReply;
  48 import org.opendaylight.controller.cluster.raft.client.messages.FollowerInfo;
  49 import org.opendaylight.controller.cluster.raft.client.messages.GetOnDemandRaftState;
  50 import org.opendaylight.controller.cluster.raft.client.messages.OnDemandRaftState;
  51 import org.opendaylight.controller.cluster.raft.client.messages.Shutdown;
  52 import org.opendaylight.controller.cluster.raft.persisted.ApplyJournalEntries;
  53 import org.opendaylight.controller.cluster.raft.persisted.NoopPayload;
  54 import org.opendaylight.controller.cluster.raft.protobuff.client.messages.Payload;
  55 import org.opendaylight.yangtools.concepts.Identifier;
  56 import org.opendaylight.yangtools.concepts.Immutable;
  57 import org.slf4j.Logger;
  58 import org.slf4j.LoggerFactory;
  59
  60 /**
  61  * RaftActor encapsulates a state machine that needs to be kept synchronized
  62  * in a cluster. It implements the RAFT algorithm as described in the paper
  63  * <a href='https://ramcloud.stanford.edu/wiki/download/attachments/11370504/raft.pdf'>
  64  * In Search of an Understandable Consensus Algorithm</a>
  65  * <p/>
  66  * RaftActor has 3 states and each state has a certain behavior associated
  67  * with it. A Raft actor can behave as,
  68  * <ul>
  69  * <li> A Leader </li>
  70  * <li> A Follower (or) </li>
  71  * <li> A Candidate </li>
  72  * </ul>
  73  * <p/>
  74  * <p/>
  75  * A RaftActor MUST be a Leader in order to accept requests from clients to
  76  * change the state of it's encapsulated state machine. Once a RaftActor becomes
  77  * a Leader it is also responsible for ensuring that all followers ultimately
  78  * have the same log and therefore the same state machine as itself.
  79  * <p/>
  80  * <p/>
  81  * The current behavior of a RaftActor determines how election for leadership
  82  * is initiated and how peer RaftActors react to request for votes.
  83  * <p/>
  84  * <p/>
  85  * Each RaftActor also needs to know the current election term. It uses this
  86  * information for a couple of things. One is to simply figure out who it
  87  * voted for in the last election. Another is to figure out if the message
  88  * it received to update it's state is stale.
  89  * <p/>
  90  * <p/>
  91  * The RaftActor uses akka-persistence to store it's replicated log.
  92  * Furthermore through it's behaviors a Raft Actor determines
  93  * <p/>
  94  * <ul>
  95  * <li> when a log entry should be persisted </li>
  96  * <li> when a log entry should be applied to the state machine (and) </li>
  97  * <li> when a snapshot should be saved </li>
  98  * </ul>
  99  */
 100 public abstract class RaftActor extends AbstractUntypedPersistentActor {
 101
 102     private static final long APPLY_STATE_DELAY_THRESHOLD_IN_NANOS = TimeUnit.MILLISECONDS.toNanos(50L); // 50 millis
 103
 104     protected final Logger LOG = LoggerFactory.getLogger(getClass());
 105
 106     /**
 107      * This context should NOT be passed directly to any other actor it is
 108      * only to be consumed by the RaftActorBehaviors
 109      */
 110     private final RaftActorContextImpl context;
 111
 112     private final DelegatingPersistentDataProvider delegatingPersistenceProvider;
 113
 114     private final PersistentDataProvider persistentProvider;
 115
 116     private final BehaviorStateTracker behaviorStateTracker = new BehaviorStateTracker();
 117
 118     private RaftActorRecoverySupport raftRecovery;
 119
 120     private RaftActorSnapshotMessageSupport snapshotSupport;
 121
 122     private RaftActorServerConfigurationSupport serverConfigurationSupport;
 123
 124     private RaftActorLeadershipTransferCohort leadershipTransferInProgress;
 125
 126     private boolean shuttingDown;
 127
 128     public RaftActor(String id, Map<String, String> peerAddresses,
 129          Optional<ConfigParams> configParams, short payloadVersion) {
 130
 131         persistentProvider = new PersistentDataProvider(this);
 132         delegatingPersistenceProvider = new RaftActorDelegatingPersistentDataProvider(null, persistentProvider);
 133
 134         context = new RaftActorContextImpl(this.getSelf(),
 135             this.getContext(), id, new ElectionTermImpl(persistentProvider, id, LOG),
 136             -1, -1, peerAddresses,
 137             configParams.isPresent() ? configParams.get(): new DefaultConfigParamsImpl(),
 138             delegatingPersistenceProvider, LOG);
 139
 140         context.setPayloadVersion(payloadVersion);
 141         context.setReplicatedLog(ReplicatedLogImpl.newInstance(context));
 142     }
 143
 144     @Override
 145     public void preStart() throws Exception {
 146         LOG.info("Starting recovery for {} with journal batch size {}", persistenceId(),
 147                 context.getConfigParams().getJournalRecoveryLogBatchSize());
 148
 149         super.preStart();
 150
 151         snapshotSupport = newRaftActorSnapshotMessageSupport();
 152         serverConfigurationSupport = new RaftActorServerConfigurationSupport(this);
 153     }
 154
 155     @Override
 156     public void postStop() {
 157         context.close();
 158         super.postStop();
 159     }
 160
 161     @Override
 162     protected void handleRecover(Object message) {
 163         if(raftRecovery == null) {
 164             raftRecovery = newRaftActorRecoverySupport();
 165         }
 166
 167         boolean recoveryComplete = raftRecovery.handleRecoveryMessage(message, persistentProvider);
 168         if(recoveryComplete) {
 169             onRecoveryComplete();
 170
 171             initializeBehavior();
 172
 173             raftRecovery = null;
 174         }
 175     }
 176
 177     protected RaftActorRecoverySupport newRaftActorRecoverySupport() {
 178         return new RaftActorRecoverySupport(context, getRaftActorRecoveryCohort());
 179     }
 180
 181     @VisibleForTesting
 182     void initializeBehavior(){
 183         changeCurrentBehavior(new Follower(context));
 184     }
 185
 186     @VisibleForTesting
 187     protected void changeCurrentBehavior(RaftActorBehavior newBehavior) {
 188         final RaftActorBehavior currentBehavior = getCurrentBehavior();
 189         if (currentBehavior != null) {
 190             try {
 191                 currentBehavior.close();
 192             } catch (Exception e) {
 193                 LOG.warn("{}: Error closing behavior {}", persistence(), currentBehavior, e);
 194             }
 195         }
 196
 197         final BehaviorState state = behaviorStateTracker.capture(currentBehavior);
 198         setCurrentBehavior(newBehavior);
 199         handleBehaviorChange(state, newBehavior);
 200     }
 201
 202     /**
 203      * Method exposed for subclasses to plug-in their logic. This method is invoked by {@link #handleCommand(Object)}
 204      * for messages which are not handled by this class. Subclasses overriding this class should fall back to this
 205      * implementation for messages which they do not handle
 206      *
 207      * @param message Incoming command message
 208      */
 209     protected void handleNonRaftCommand(final Object message) {
 210         unhandled(message);
 211     }
 212
 213     /**
 214      * @deprecated This method is not final for testing purposes. DO NOT OVERRIDE IT, override
 215      * {@link #handleNonRaftCommand(Object)} instead.
 216      */
 217     @Deprecated
 218     @Override
 219     // FIXME: make this method final once our unit tests do not need to override it
 220     protected void handleCommand(final Object message) {
 221         if (serverConfigurationSupport.handleMessage(message, getSender())) {
 222             return;
 223         }
 224         if (snapshotSupport.handleSnapshotMessage(message, getSender())) {
 225             return;
 226         }
 227
 228         if (message instanceof ApplyState) {
 229             ApplyState applyState = (ApplyState) message;
 230
 231             long startTime = System.nanoTime();
 232
 233             if(LOG.isDebugEnabled()) {
 234                 LOG.debug("{}: Applying state for log index {} data {}",
 235                     persistenceId(), applyState.getReplicatedLogEntry().getIndex(),
 236                     applyState.getReplicatedLogEntry().getData());
 237             }
 238
 239             if (!(applyState.getReplicatedLogEntry().getData() instanceof NoopPayload)) {
 240                 applyState(applyState.getClientActor(), applyState.getIdentifier(),
 241                     applyState.getReplicatedLogEntry().getData());
 242             }
 243
 244             long elapsedTime = System.nanoTime() - startTime;
 245             if(elapsedTime >= APPLY_STATE_DELAY_THRESHOLD_IN_NANOS){
 246                 LOG.debug("ApplyState took more time than expected. Elapsed Time = {} ms ApplyState = {}",
 247                         TimeUnit.NANOSECONDS.toMillis(elapsedTime), applyState);
 248             }
 249
 250             if (!hasFollowers()) {
 251                 // for single node, the capture should happen after the apply state
 252                 // as we delete messages from the persistent journal which have made it to the snapshot
 253                 // capturing the snapshot before applying makes the persistent journal and snapshot out of sync
 254                 // and recovery shows data missing
 255                 context.getReplicatedLog().captureSnapshotIfReady(applyState.getReplicatedLogEntry());
 256
 257                 context.getSnapshotManager().trimLog(context.getLastApplied());
 258             }
 259
 260             // Send it to the current behavior - some behaviors like PreLeader need to be notified of ApplyState.
 261             possiblyHandleBehaviorMessage(message);
 262
 263         } else if (message instanceof ApplyJournalEntries) {
 264             ApplyJournalEntries applyEntries = (ApplyJournalEntries) message;
 265             if(LOG.isDebugEnabled()) {
 266                 LOG.debug("{}: Persisting ApplyJournalEntries with index={}", persistenceId(), applyEntries.getToIndex());
 267             }
 268
 269             persistence().persist(applyEntries, NoopProcedure.instance());
 270
 271         } else if (message instanceof FindLeader) {
 272             getSender().tell(
 273                 new FindLeaderReply(getLeaderAddress()),
 274                 getSelf()
 275             );
 276         } else if(message instanceof GetOnDemandRaftState) {
 277             onGetOnDemandRaftStats();
 278         } else if(message instanceof InitiateCaptureSnapshot) {
 279             captureSnapshot();
 280         } else if(message instanceof SwitchBehavior) {
 281             switchBehavior((SwitchBehavior) message);
 282         } else if(message instanceof LeaderTransitioning) {
 283             onLeaderTransitioning((LeaderTransitioning)message);
 284         } else if(message instanceof Shutdown) {
 285             onShutDown();
 286         } else if(message instanceof Runnable) {
 287             ((Runnable)message).run();
 288         } else if(message instanceof NoopPayload) {
 289             persistData(null, null, (NoopPayload)message);
 290         } else if (!possiblyHandleBehaviorMessage(message)) {
 291             handleNonRaftCommand(message);
 292         }
 293     }
 294
 295     private boolean possiblyHandleBehaviorMessage(final Object message) {
 296         final RaftActorBehavior currentBehavior = getCurrentBehavior();
 297         final BehaviorState state = behaviorStateTracker.capture(currentBehavior);
 298
 299         // A behavior indicates that it processed the change by returning a reference to the next behavior
 300         // to be used. A null return indicates it has not processed the message and we should be passing it to
 301         // the subclass for handling.
 302         final RaftActorBehavior nextBehavior = currentBehavior.handleMessage(getSender(), message);
 303         if (nextBehavior != null) {
 304             switchBehavior(state, nextBehavior);
 305             return true;
 306         }
 307
 308         return false;
 309     }
 310
 311     private void initiateLeadershipTransfer(final RaftActorLeadershipTransferCohort.OnComplete onComplete) {
 312         LOG.debug("{}: Initiating leader transfer", persistenceId());
 313
 314         if(leadershipTransferInProgress == null) {
 315             leadershipTransferInProgress = new RaftActorLeadershipTransferCohort(this);
 316             leadershipTransferInProgress.addOnComplete(new RaftActorLeadershipTransferCohort.OnComplete() {
 317                 @Override
 318                 public void onSuccess(ActorRef raftActorRef) {
 319                     leadershipTransferInProgress = null;
 320                 }
 321
 322                 @Override
 323                 public void onFailure(ActorRef raftActorRef) {
 324                     leadershipTransferInProgress = null;
 325                 }
 326             });
 327
 328             leadershipTransferInProgress.addOnComplete(onComplete);
 329             leadershipTransferInProgress.init();
 330         } else {
 331             LOG.debug("{}: prior leader transfer in progress - adding callback", persistenceId());
 332             leadershipTransferInProgress.addOnComplete(onComplete);
 333         }
 334     }
 335
 336     private void onShutDown() {
 337         LOG.debug("{}: onShutDown", persistenceId());
 338
 339         if(shuttingDown) {
 340             return;
 341         }
 342
 343         shuttingDown = true;
 344
 345         final RaftActorBehavior currentBehavior = context.getCurrentBehavior();
 346         if (currentBehavior.state() != RaftState.Leader) {
 347             // For non-leaders shutdown is a no-op
 348             self().tell(PoisonPill.getInstance(), self());
 349             return;
 350         }
 351
 352         if (context.hasFollowers()) {
 353             initiateLeadershipTransfer(new RaftActorLeadershipTransferCohort.OnComplete() {
 354                 @Override
 355                 public void onSuccess(ActorRef raftActorRef) {
 356                     LOG.debug("{}: leader transfer succeeded - sending PoisonPill", persistenceId());
 357                     raftActorRef.tell(PoisonPill.getInstance(), raftActorRef);
 358                 }
 359
 360                 @Override
 361                 public void onFailure(ActorRef raftActorRef) {
 362                     LOG.debug("{}: leader transfer failed - sending PoisonPill", persistenceId());
 363                     raftActorRef.tell(PoisonPill.getInstance(), raftActorRef);
 364                 }
 365             });
 366         } else {
 367             pauseLeader(new TimedRunnable(context.getConfigParams().getElectionTimeOutInterval(), this) {
 368                 @Override
 369                 protected void doRun() {
 370                     self().tell(PoisonPill.getInstance(), self());
 371                 }
 372
 373                 @Override
 374                 protected void doCancel() {
 375                     self().tell(PoisonPill.getInstance(), self());
 376                 }
 377             });
 378         }
 379     }
 380
 381     private void onLeaderTransitioning(final LeaderTransitioning leaderTransitioning) {
 382         LOG.debug("{}: onLeaderTransitioning: {}", persistenceId(), leaderTransitioning);
 383         Optional<ActorRef> roleChangeNotifier = getRoleChangeNotifier();
 384         if (getRaftState() == RaftState.Follower && roleChangeNotifier.isPresent()
 385                 && leaderTransitioning.getLeaderId().equals(getCurrentBehavior().getLeaderId())) {
 386             roleChangeNotifier.get().tell(newLeaderStateChanged(getId(), null,
 387                 getCurrentBehavior().getLeaderPayloadVersion()), getSelf());
 388         }
 389     }
 390
 391     private void switchBehavior(SwitchBehavior message) {
 392         if(!getRaftActorContext().getRaftPolicy().automaticElectionsEnabled()) {
 393             RaftState newState = message.getNewState();
 394             if( newState == RaftState.Leader || newState == RaftState.Follower) {
 395                 switchBehavior(behaviorStateTracker.capture(getCurrentBehavior()),
 396                     AbstractRaftActorBehavior.createBehavior(context, message.getNewState()));
 397                 getRaftActorContext().getTermInformation().updateAndPersist(message.getNewTerm(), "");
 398             } else {
 399                 LOG.warn("Switching to behavior : {} - not supported", newState);
 400             }
 401         }
 402     }
 403
 404     private void switchBehavior(final BehaviorState oldBehaviorState, final RaftActorBehavior nextBehavior) {
 405         setCurrentBehavior(nextBehavior);
 406         handleBehaviorChange(oldBehaviorState, nextBehavior);
 407     }
 408
 409     @VisibleForTesting
 410     RaftActorSnapshotMessageSupport newRaftActorSnapshotMessageSupport() {
 411         return new RaftActorSnapshotMessageSupport(context, getRaftActorSnapshotCohort());
 412     }
 413
 414     private void onGetOnDemandRaftStats() {
 415         // Debugging message to retrieve raft stats.
 416
 417         Map<String, String> peerAddresses = new HashMap<>();
 418         Map<String, Boolean> peerVotingStates = new HashMap<>();
 419         for(PeerInfo info: context.getPeers()) {
 420             peerVotingStates.put(info.getId(), info.isVoting());
 421             peerAddresses.put(info.getId(), info.getAddress() != null ? info.getAddress() : "");
 422         }
 423
 424         final RaftActorBehavior currentBehavior = context.getCurrentBehavior();
 425         OnDemandRaftState.Builder builder = OnDemandRaftState.builder()
 426                 .commitIndex(context.getCommitIndex())
 427                 .currentTerm(context.getTermInformation().getCurrentTerm())
 428                 .inMemoryJournalDataSize(replicatedLog().dataSize())
 429                 .inMemoryJournalLogSize(replicatedLog().size())
 430                 .isSnapshotCaptureInitiated(context.getSnapshotManager().isCapturing())
 431                 .lastApplied(context.getLastApplied())
 432                 .lastIndex(replicatedLog().lastIndex())
 433                 .lastTerm(replicatedLog().lastTerm())
 434                 .leader(getLeaderId())
 435                 .raftState(currentBehavior.state().toString())
 436                 .replicatedToAllIndex(currentBehavior.getReplicatedToAllIndex())
 437                 .snapshotIndex(replicatedLog().getSnapshotIndex())
 438                 .snapshotTerm(replicatedLog().getSnapshotTerm())
 439                 .votedFor(context.getTermInformation().getVotedFor())
 440                 .isVoting(context.isVotingMember())
 441                 .peerAddresses(peerAddresses)
 442                 .peerVotingStates(peerVotingStates)
 443                 .customRaftPolicyClassName(context.getConfigParams().getCustomRaftPolicyImplementationClass());
 444
 445         ReplicatedLogEntry lastLogEntry = replicatedLog().last();
 446         if (lastLogEntry != null) {
 447             builder.lastLogIndex(lastLogEntry.getIndex());
 448             builder.lastLogTerm(lastLogEntry.getTerm());
 449         }
 450
 451         if(getCurrentBehavior() instanceof AbstractLeader) {
 452             AbstractLeader leader = (AbstractLeader)getCurrentBehavior();
 453             Collection<String> followerIds = leader.getFollowerIds();
 454             List<FollowerInfo> followerInfoList = Lists.newArrayListWithCapacity(followerIds.size());
 455             for(String id: followerIds) {
 456                 final FollowerLogInformation info = leader.getFollower(id);
 457                 followerInfoList.add(new FollowerInfo(id, info.getNextIndex(), info.getMatchIndex(),
 458                         info.isFollowerActive(), DurationFormatUtils.formatDurationHMS(info.timeSinceLastActivity()),
 459                         context.getPeerInfo(info.getId()).isVoting()));
 460             }
 461
 462             builder.followerInfoList(followerInfoList);
 463         }
 464
 465         sender().tell(builder.build(), self());
 466
 467     }
 468
 469     private void handleBehaviorChange(BehaviorState oldBehaviorState, RaftActorBehavior currentBehavior) {
 470         RaftActorBehavior oldBehavior = oldBehaviorState.getBehavior();
 471
 472         if (oldBehavior != currentBehavior){
 473             onStateChanged();
 474         }
 475
 476         String lastLeaderId = oldBehavior == null ? null : oldBehaviorState.getLastLeaderId();
 477         String lastValidLeaderId = oldBehavior == null ? null : oldBehaviorState.getLastValidLeaderId();
 478         String oldBehaviorStateName = oldBehavior == null ? null : oldBehavior.state().name();
 479
 480         // it can happen that the state has not changed but the leader has changed.
 481         Optional<ActorRef> roleChangeNotifier = getRoleChangeNotifier();
 482         if(!Objects.equals(lastLeaderId, currentBehavior.getLeaderId()) ||
 483            oldBehaviorState.getLeaderPayloadVersion() != currentBehavior.getLeaderPayloadVersion()) {
 484             if(roleChangeNotifier.isPresent()) {
 485                 roleChangeNotifier.get().tell(newLeaderStateChanged(getId(), currentBehavior.getLeaderId(),
 486                         currentBehavior.getLeaderPayloadVersion()), getSelf());
 487             }
 488
 489             onLeaderChanged(lastValidLeaderId, currentBehavior.getLeaderId());
 490
 491             if(leadershipTransferInProgress != null) {
 492                 leadershipTransferInProgress.onNewLeader(currentBehavior.getLeaderId());
 493             }
 494
 495             serverConfigurationSupport.onNewLeader(currentBehavior.getLeaderId());
 496         }
 497
 498         if (roleChangeNotifier.isPresent() &&
 499                 (oldBehavior == null || oldBehavior.state() != currentBehavior.state())) {
 500             roleChangeNotifier.get().tell(new RoleChanged(getId(), oldBehaviorStateName ,
 501                     currentBehavior.state().name()), getSelf());
 502         }
 503     }
 504
 505     protected LeaderStateChanged newLeaderStateChanged(String memberId, String leaderId, short leaderPayloadVersion) {
 506         return new LeaderStateChanged(memberId, leaderId, leaderPayloadVersion);
 507     }
 508
 509     @Override
 510     public long snapshotSequenceNr() {
 511         // When we do a snapshot capture, we also capture and save the sequence-number of the persistent journal,
 512         // so that we can delete the persistent journal based on the saved sequence-number
 513         // However , when akka replays the journal during recovery, it replays it from the sequence number when the snapshot
 514         // was saved and not the number we saved.
 515         // We would want to override it , by asking akka to use the last-sequence number known to us.
 516         return context.getSnapshotManager().getLastSequenceNumber();
 517     }
 518
 519     /**
 520      * When a derived RaftActor needs to persist something it must call
 521      * persistData.
 522      *
 523      * @param clientActor
 524      * @param identifier
 525      * @param data
 526      */
 527     protected final void persistData(final ActorRef clientActor, final Identifier identifier, final Payload data) {
 528
 529         ReplicatedLogEntry replicatedLogEntry = new ReplicatedLogImplEntry(
 530             context.getReplicatedLog().lastIndex() + 1,
 531             context.getTermInformation().getCurrentTerm(), data);
 532
 533         if(LOG.isDebugEnabled()) {
 534             LOG.debug("{}: Persist data {}", persistenceId(), replicatedLogEntry);
 535         }
 536
 537         final RaftActorContext raftContext = getRaftActorContext();
 538
 539         replicatedLog().appendAndPersist(replicatedLogEntry, replicatedLogEntry1 -> {
 540             if (!hasFollowers()){
 541                 // Increment the Commit Index and the Last Applied values
 542                 raftContext.setCommitIndex(replicatedLogEntry1.getIndex());
 543                 raftContext.setLastApplied(replicatedLogEntry1.getIndex());
 544
 545                 // Apply the state immediately.
 546                 self().tell(new ApplyState(clientActor, identifier, replicatedLogEntry1), self());
 547
 548                 // Send a ApplyJournalEntries message so that we write the fact that we applied
 549                 // the state to durable storage
 550                 self().tell(new ApplyJournalEntries(replicatedLogEntry1.getIndex()), self());
 551
 552             } else {
 553                 context.getReplicatedLog().captureSnapshotIfReady(replicatedLogEntry1);
 554
 555                 // Send message for replication
 556                 getCurrentBehavior().handleMessage(getSelf(),
 557                         new Replicate(clientActor, identifier, replicatedLogEntry1));
 558             }
 559         });
 560     }
 561
 562     private ReplicatedLog replicatedLog() {
 563         return context.getReplicatedLog();
 564     }
 565
 566     protected String getId() {
 567         return context.getId();
 568     }
 569
 570     @VisibleForTesting
 571     void setCurrentBehavior(RaftActorBehavior behavior) {
 572         context.setCurrentBehavior(behavior);
 573     }
 574
 575     protected RaftActorBehavior getCurrentBehavior() {
 576         return context.getCurrentBehavior();
 577     }
 578
 579     /**
 580      * Derived actors can call the isLeader method to check if the current
 581      * RaftActor is the Leader or not
 582      *
 583      * @return true it this RaftActor is a Leader false otherwise
 584      */
 585     protected boolean isLeader() {
 586         return context.getId().equals(getCurrentBehavior().getLeaderId());
 587     }
 588
 589     protected final boolean isLeaderActive() {
 590         return getRaftState() != RaftState.IsolatedLeader && getRaftState() != RaftState.PreLeader &&
 591                 !shuttingDown && !isLeadershipTransferInProgress();
 592     }
 593
 594     private boolean isLeadershipTransferInProgress() {
 595         return leadershipTransferInProgress != null && leadershipTransferInProgress.isTransferring();
 596     }
 597
 598     /**
 599      * Derived actor can call getLeader if they need a reference to the Leader.
 600      * This would be useful for example in forwarding a request to an actor
 601      * which is the leader
 602      *
 603      * @return A reference to the leader if known, null otherwise
 604      */
 605     public ActorSelection getLeader(){
 606         String leaderAddress = getLeaderAddress();
 607
 608         if(leaderAddress == null){
 609             return null;
 610         }
 611
 612         return context.actorSelection(leaderAddress);
 613     }
 614
 615     /**
 616      *
 617      * @return the current leader's id
 618      */
 619     protected final String getLeaderId(){
 620         return getCurrentBehavior().getLeaderId();
 621     }
 622
 623     @VisibleForTesting
 624     protected final RaftState getRaftState() {
 625         return getCurrentBehavior().state();
 626     }
 627
 628     protected Long getCurrentTerm(){
 629         return context.getTermInformation().getCurrentTerm();
 630     }
 631
 632     protected RaftActorContext getRaftActorContext() {
 633         return context;
 634     }
 635
 636     protected void updateConfigParams(ConfigParams configParams) {
 637
 638         // obtain the RaftPolicy for oldConfigParams and the updated one.
 639         String oldRaftPolicy = context.getConfigParams().
 640             getCustomRaftPolicyImplementationClass();
 641         String newRaftPolicy = configParams.
 642             getCustomRaftPolicyImplementationClass();
 643
 644         LOG.debug("{}: RaftPolicy used with prev.config {}, RaftPolicy used with newConfig {}", persistenceId(),
 645             oldRaftPolicy, newRaftPolicy);
 646         context.setConfigParams(configParams);
 647         if (!Objects.equals(oldRaftPolicy, newRaftPolicy)) {
 648             // The RaftPolicy was modified. If the current behavior is Follower then re-initialize to Follower
 649             // but transfer the previous leaderId so it doesn't immediately try to schedule an election. This
 650             // avoids potential disruption. Otherwise, switch to Follower normally.
 651             RaftActorBehavior behavior = getCurrentBehavior();
 652             if (behavior != null && behavior.state() == RaftState.Follower) {
 653                 String previousLeaderId = behavior.getLeaderId();
 654                 short previousLeaderPayloadVersion = behavior.getLeaderPayloadVersion();
 655
 656                 LOG.debug("{}: Re-initializing to Follower with previous leaderId {}", persistenceId(), previousLeaderId);
 657
 658                 changeCurrentBehavior(new Follower(context, previousLeaderId, previousLeaderPayloadVersion));
 659             } else {
 660                 initializeBehavior();
 661             }
 662         }
 663     }
 664
 665     public final DataPersistenceProvider persistence() {
 666         return delegatingPersistenceProvider.getDelegate();
 667     }
 668
 669     public void setPersistence(DataPersistenceProvider provider) {
 670         delegatingPersistenceProvider.setDelegate(provider);
 671     }
 672
 673     protected void setPersistence(boolean persistent) {
 674         DataPersistenceProvider currentPersistence = persistence();
 675         if(persistent && (currentPersistence == null || !currentPersistence.isRecoveryApplicable())) {
 676             setPersistence(new PersistentDataProvider(this));
 677
 678             if(getCurrentBehavior() != null) {
 679                 LOG.info("{}: Persistence has been enabled - capturing snapshot", persistenceId());
 680                 captureSnapshot();
 681             }
 682         } else if(!persistent && (currentPersistence == null || currentPersistence.isRecoveryApplicable())) {
 683             setPersistence(new NonPersistentDataProvider() {
 684                 /**
 685                  * The way snapshotting works is,
 686                  * <ol>
 687                  * <li> RaftActor calls createSnapshot on the Shard
 688                  * <li> Shard sends a CaptureSnapshotReply and RaftActor then calls saveSnapshot
 689                  * <li> When saveSnapshot is invoked on the akka-persistence API it uses the SnapshotStore to save
 690                  * the snapshot. The SnapshotStore sends SaveSnapshotSuccess or SaveSnapshotFailure. When the
 691                  * RaftActor gets SaveSnapshot success it commits the snapshot to the in-memory journal. This
 692                  * commitSnapshot is mimicking what is done in SaveSnapshotSuccess.
 693                  * </ol>
 694                  */
 695                 @Override
 696                 public void saveSnapshot(Object o) {
 697                     // Make saving Snapshot successful
 698                     // Committing the snapshot here would end up calling commit in the creating state which would
 699                     // be a state violation. That's why now we send a message to commit the snapshot.
 700                     self().tell(RaftActorSnapshotMessageSupport.COMMIT_SNAPSHOT, self());
 701                 }
 702             });
 703         }
 704     }
 705
 706     /**
 707      * setPeerAddress sets the address of a known peer at a later time.
 708      * <p>
 709      * This is to account for situations where a we know that a peer
 710      * exists but we do not know an address up-front. This may also be used in
 711      * situations where a known peer starts off in a different location and we
 712      * need to change it's address
 713      * <p>
 714      * Note that if the peerId does not match the list of peers passed to
 715      * this actor during construction an IllegalStateException will be thrown.
 716      *
 717      * @param peerId
 718      * @param peerAddress
 719      */
 720     protected void setPeerAddress(String peerId, String peerAddress){
 721         context.setPeerAddress(peerId, peerAddress);
 722     }
 723
 724     /**
 725      * The applyState method will be called by the RaftActor when some data
 726      * needs to be applied to the actor's state
 727      *
 728      * @param clientActor A reference to the client who sent this message. This
 729      *                    is the same reference that was passed to persistData
 730      *                    by the derived actor. clientActor may be null when
 731      *                    the RaftActor is behaving as a follower or during
 732      *                    recovery.
 733      * @param identifier  The identifier of the persisted data. This is also
 734      *                    the same identifier that was passed to persistData by
 735      *                    the derived actor. identifier may be null when
 736      *                    the RaftActor is behaving as a follower or during
 737      *                    recovery
 738      * @param data        A piece of data that was persisted by the persistData call.
 739      *                    This should NEVER be null.
 740      */
 741     protected abstract void applyState(ActorRef clientActor, Identifier identifier, Object data);
 742
 743     /**
 744      * Returns the RaftActorRecoveryCohort to participate in persistence recovery.
 745      */
 746     @Nonnull
 747     protected abstract RaftActorRecoveryCohort getRaftActorRecoveryCohort();
 748
 749     /**
 750      * This method is called when recovery is complete.
 751      */
 752     protected abstract void onRecoveryComplete();
 753
 754     /**
 755      * Returns the RaftActorSnapshotCohort to participate in persistence recovery.
 756      */
 757     @Nonnull
 758     protected abstract RaftActorSnapshotCohort getRaftActorSnapshotCohort();
 759
 760     /**
 761      * This method will be called by the RaftActor when the state of the
 762      * RaftActor changes. The derived actor can then use methods like
 763      * isLeader or getLeader to do something useful
 764      */
 765     protected abstract void onStateChanged();
 766
 767     /**
 768      * Notifier Actor for this RaftActor to notify when a role change happens
 769      * @return ActorRef - ActorRef of the notifier or Optional.absent if none.
 770      */
 771     protected abstract Optional<ActorRef> getRoleChangeNotifier();
 772
 773     /**
 774      * This method is called prior to operations such as leadership transfer and actor shutdown when the leader
 775      * must pause or stop its duties. This method allows derived classes to gracefully pause or finish current
 776      * work prior to performing the operation. On completion of any work, the run method must be called on the
 777      * given Runnable to proceed with the given operation. <b>Important:</b> the run method must be called on
 778      * this actor's thread dispatcher as as it modifies internal state.
 779      * <p>
 780      * The default implementation immediately runs the operation.
 781      *
 782      * @param operation the operation to run
 783      */
 784     protected void pauseLeader(Runnable operation) {
 785         operation.run();
 786     }
 787
 788     protected void onLeaderChanged(String oldLeader, String newLeader) {
 789
 790     };
 791
 792     private String getLeaderAddress(){
 793         if(isLeader()){
 794             return getSelf().path().toString();
 795         }
 796         String leaderId = getLeaderId();
 797         if (leaderId == null) {
 798             return null;
 799         }
 800         String peerAddress = context.getPeerAddress(leaderId);
 801         if(LOG.isDebugEnabled()) {
 802             LOG.debug("{}: getLeaderAddress leaderId = {} peerAddress = {}",
 803                     persistenceId(), leaderId, peerAddress);
 804         }
 805
 806         return peerAddress;
 807     }
 808
 809     protected boolean hasFollowers(){
 810         return getRaftActorContext().hasFollowers();
 811     }
 812
 813     private void captureSnapshot() {
 814         SnapshotManager snapshotManager = context.getSnapshotManager();
 815
 816         if (!snapshotManager.isCapturing()) {
 817             final long idx = getCurrentBehavior().getReplicatedToAllIndex();
 818             LOG.debug("Take a snapshot of current state. lastReplicatedLog is {} and replicatedToAllIndex is {}",
 819                 replicatedLog().last(), idx);
 820
 821             snapshotManager.capture(replicatedLog().last(), idx);
 822         }
 823     }
 824
 825     /**
 826      * Switch this member to non-voting status. This is a no-op for all behaviors except when we are the leader,
 827      * in which case we need to step down.
 828      */
 829     void becomeNonVoting() {
 830         if (isLeader()) {
 831             initiateLeadershipTransfer(new RaftActorLeadershipTransferCohort.OnComplete() {
 832                 @Override
 833                 public void onSuccess(ActorRef raftActorRef) {
 834                     LOG.debug("{}: leader transfer succeeded after change to non-voting", persistenceId());
 835                     ensureFollowerState();
 836                 }
 837
 838                 @Override
 839                 public void onFailure(ActorRef raftActorRef) {
 840                     LOG.debug("{}: leader transfer failed after change to non-voting", persistenceId());
 841                     ensureFollowerState();
 842                 }
 843
 844                 private void ensureFollowerState() {
 845                     // Whether or not leadership transfer succeeded, we have to step down as leader and
 846                     // switch to Follower so ensure that.
 847                     if (getRaftState() != RaftState.Follower) {
 848                         initializeBehavior();
 849                     }
 850                 }
 851             });
 852         }
 853     }
 854
 855     /**
 856      * @deprecated Deprecated in favor of {@link org.opendaylight.controller.cluster.raft.persisted.DeleteEntries}
 857      *             whose type for fromIndex is long instead of int. This class was kept for backwards
 858      *             compatibility with Helium.
 859      */
 860     // Suppressing this warning as we can't set serialVersionUID to maintain backwards compatibility.
 861     @SuppressWarnings("serial")
 862     @Deprecated
 863     static class DeleteEntries implements Serializable {
 864         private final int fromIndex;
 865
 866         public DeleteEntries(int fromIndex) {
 867             this.fromIndex = fromIndex;
 868         }
 869
 870         public int getFromIndex() {
 871             return fromIndex;
 872         }
 873
 874         private Object readResolve() {
 875             return org.opendaylight.controller.cluster.raft.persisted.DeleteEntries.createMigrated(fromIndex);
 876         }
 877     }
 878
 879     /**
 880      * @deprecated Deprecated in favor of non-inner class {@link org.opendaylight.controller.cluster.raft.persisted.UpdateElectionTerm}
 881      *             which has serialVersionUID set. This class was kept for backwards compatibility with Helium.
 882      */
 883     // Suppressing this warning as we can't set serialVersionUID to maintain backwards compatibility.
 884     @SuppressWarnings("serial")
 885     @Deprecated
 886     static class UpdateElectionTerm implements Serializable {
 887         private final long currentTerm;
 888         private final String votedFor;
 889
 890         public UpdateElectionTerm(long currentTerm, String votedFor) {
 891             this.currentTerm = currentTerm;
 892             this.votedFor = votedFor;
 893         }
 894
 895         public long getCurrentTerm() {
 896             return currentTerm;
 897         }
 898
 899         public String getVotedFor() {
 900             return votedFor;
 901         }
 902
 903         private Object readResolve() {
 904             return org.opendaylight.controller.cluster.raft.persisted.UpdateElectionTerm.createMigrated(
 905                     currentTerm, votedFor);
 906         }
 907     }
 908
 909     /**
 910      * A point-in-time capture of {@link RaftActorBehavior} state critical for transitioning between behaviors.
 911      */
 912     private static abstract class BehaviorState implements Immutable {
 913         @Nullable abstract RaftActorBehavior getBehavior();
 914         @Nullable abstract String getLastValidLeaderId();
 915         @Nullable abstract String getLastLeaderId();
 916         @Nullable abstract short getLeaderPayloadVersion();
 917     }
 918
 919     /**
 920      * A {@link BehaviorState} corresponding to non-null {@link RaftActorBehavior} state.
 921      */
 922     private static final class SimpleBehaviorState extends BehaviorState {
 923         private final RaftActorBehavior behavior;
 924         private final String lastValidLeaderId;
 925         private final String lastLeaderId;
 926         private final short leaderPayloadVersion;
 927
 928         SimpleBehaviorState(final String lastValidLeaderId, final String lastLeaderId,
 929                 final RaftActorBehavior behavior) {
 930             this.lastValidLeaderId = lastValidLeaderId;
 931             this.lastLeaderId = lastLeaderId;
 932             this.behavior = Preconditions.checkNotNull(behavior);
 933             this.leaderPayloadVersion = behavior.getLeaderPayloadVersion();
 934         }
 935
 936         @Override
 937         RaftActorBehavior getBehavior() {
 938             return behavior;
 939         }
 940
 941         @Override
 942         String getLastValidLeaderId() {
 943             return lastValidLeaderId;
 944         }
 945
 946         @Override
 947         short getLeaderPayloadVersion() {
 948             return leaderPayloadVersion;
 949         }
 950
 951         @Override
 952         String getLastLeaderId() {
 953             return lastLeaderId;
 954         }
 955     }
 956
 957     /**
 958      * Class tracking behavior-related information, which we need to keep around and pass across behavior switches.
 959      * An instance is created for each RaftActor. It has two functions:
 960      * - it keeps track of the last leader ID we have encountered since we have been created
 961      * - it creates state capture needed to transition from one behavior to the next
 962      */
 963     private static final class BehaviorStateTracker {
 964         /**
 965          * A {@link BehaviorState} corresponding to null {@link RaftActorBehavior} state. Since null behavior is only
 966          * allowed before we receive the first message, we know the leader ID to be null.
 967          */
 968         private static final BehaviorState NULL_BEHAVIOR_STATE = new BehaviorState() {
 969             @Override
 970             RaftActorBehavior getBehavior() {
 971                 return null;
 972             }
 973
 974             @Override
 975             String getLastValidLeaderId() {
 976                 return null;
 977             }
 978
 979             @Override
 980             short getLeaderPayloadVersion() {
 981                 return -1;
 982             }
 983
 984             @Override
 985             String getLastLeaderId() {
 986                 return null;
 987             }
 988         };
 989
 990         private String lastValidLeaderId;
 991         private String lastLeaderId;
 992
 993         BehaviorState capture(final RaftActorBehavior behavior) {
 994             if (behavior == null) {
 995                 Verify.verify(lastValidLeaderId == null, "Null behavior with non-null last leader");
 996                 return NULL_BEHAVIOR_STATE;
 997             }
 998
 999             lastLeaderId = behavior.getLeaderId();
1000             if (lastLeaderId != null) {
1001                 lastValidLeaderId = lastLeaderId;
1002             }
1003
1004             return new SimpleBehaviorState(lastValidLeaderId, lastLeaderId, behavior);
1005         }
1006     }
1007
1008 }