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         } else if (message instanceof ApplyJournalEntries) {
 261             ApplyJournalEntries applyEntries = (ApplyJournalEntries) message;
 262             if(LOG.isDebugEnabled()) {
 263                 LOG.debug("{}: Persisting ApplyJournalEntries with index={}", persistenceId(), applyEntries.getToIndex());
 264             }
 265
 266             persistence().persist(applyEntries, NoopProcedure.instance());
 267
 268         } else if (message instanceof FindLeader) {
 269             getSender().tell(
 270                 new FindLeaderReply(getLeaderAddress()),
 271                 getSelf()
 272             );
 273         } else if(message instanceof GetOnDemandRaftState) {
 274             onGetOnDemandRaftStats();
 275         } else if(message instanceof InitiateCaptureSnapshot) {
 276             captureSnapshot();
 277         } else if(message instanceof SwitchBehavior) {
 278             switchBehavior(((SwitchBehavior) message));
 279         } else if(message instanceof LeaderTransitioning) {
 280             onLeaderTransitioning();
 281         } else if(message instanceof Shutdown) {
 282             onShutDown();
 283         } else if(message instanceof Runnable) {
 284             ((Runnable)message).run();
 285         } else if(message instanceof NoopPayload) {
 286             persistData(null, null, (NoopPayload)message);
 287         } else {
 288             // Processing the message may affect the state, hence we need to capture it
 289             final RaftActorBehavior currentBehavior = getCurrentBehavior();
 290             final BehaviorState state = behaviorStateTracker.capture(currentBehavior);
 291
 292             // A behavior indicates that it processed the change by returning a reference to the next behavior
 293             // to be used. A null return indicates it has not processed the message and we should be passing it to
 294             // the subclass for handling.
 295             final RaftActorBehavior nextBehavior = currentBehavior.handleMessage(getSender(), message);
 296             if (nextBehavior != null) {
 297                 switchBehavior(state, nextBehavior);
 298             } else {
 299                 handleNonRaftCommand(message);
 300             }
 301         }
 302     }
 303
 304     private void initiateLeadershipTransfer(final RaftActorLeadershipTransferCohort.OnComplete onComplete) {
 305         LOG.debug("{}: Initiating leader transfer", persistenceId());
 306
 307         if(leadershipTransferInProgress == null) {
 308             leadershipTransferInProgress = new RaftActorLeadershipTransferCohort(this);
 309             leadershipTransferInProgress.addOnComplete(new RaftActorLeadershipTransferCohort.OnComplete() {
 310                 @Override
 311                 public void onSuccess(ActorRef raftActorRef) {
 312                     leadershipTransferInProgress = null;
 313                 }
 314
 315                 @Override
 316                 public void onFailure(ActorRef raftActorRef) {
 317                     leadershipTransferInProgress = null;
 318                 }
 319             });
 320
 321             leadershipTransferInProgress.addOnComplete(onComplete);
 322             leadershipTransferInProgress.init();
 323         } else {
 324             LOG.debug("{}: prior leader transfer in progress - adding callback", persistenceId());
 325             leadershipTransferInProgress.addOnComplete(onComplete);
 326         }
 327     }
 328
 329     private void onShutDown() {
 330         LOG.debug("{}: onShutDown", persistenceId());
 331
 332         if(shuttingDown) {
 333             return;
 334         }
 335
 336         shuttingDown = true;
 337
 338         final RaftActorBehavior currentBehavior = context.getCurrentBehavior();
 339         if (currentBehavior.state() != RaftState.Leader) {
 340             // For non-leaders shutdown is a no-op
 341             self().tell(PoisonPill.getInstance(), self());
 342             return;
 343         }
 344
 345         if (context.hasFollowers()) {
 346             initiateLeadershipTransfer(new RaftActorLeadershipTransferCohort.OnComplete() {
 347                 @Override
 348                 public void onSuccess(ActorRef raftActorRef) {
 349                     LOG.debug("{}: leader transfer succeeded - sending PoisonPill", persistenceId());
 350                     raftActorRef.tell(PoisonPill.getInstance(), raftActorRef);
 351                 }
 352
 353                 @Override
 354                 public void onFailure(ActorRef raftActorRef) {
 355                     LOG.debug("{}: leader transfer failed - sending PoisonPill", persistenceId());
 356                     raftActorRef.tell(PoisonPill.getInstance(), raftActorRef);
 357                 }
 358             });
 359         } else {
 360             pauseLeader(new TimedRunnable(context.getConfigParams().getElectionTimeOutInterval(), this) {
 361                 @Override
 362                 protected void doRun() {
 363                     self().tell(PoisonPill.getInstance(), self());
 364                 }
 365
 366                 @Override
 367                 protected void doCancel() {
 368                     self().tell(PoisonPill.getInstance(), self());
 369                 }
 370             });
 371         }
 372     }
 373
 374     private void onLeaderTransitioning() {
 375         LOG.debug("{}: onLeaderTransitioning", persistenceId());
 376         Optional<ActorRef> roleChangeNotifier = getRoleChangeNotifier();
 377         if(getRaftState() == RaftState.Follower && roleChangeNotifier.isPresent()) {
 378             roleChangeNotifier.get().tell(newLeaderStateChanged(getId(), null,
 379                 getCurrentBehavior().getLeaderPayloadVersion()), getSelf());
 380         }
 381     }
 382
 383     private void switchBehavior(SwitchBehavior message) {
 384         if(!getRaftActorContext().getRaftPolicy().automaticElectionsEnabled()) {
 385             RaftState newState = message.getNewState();
 386             if( newState == RaftState.Leader || newState == RaftState.Follower) {
 387                 switchBehavior(behaviorStateTracker.capture(getCurrentBehavior()),
 388                     AbstractRaftActorBehavior.createBehavior(context, message.getNewState()));
 389                 getRaftActorContext().getTermInformation().updateAndPersist(message.getNewTerm(), "");
 390             } else {
 391                 LOG.warn("Switching to behavior : {} - not supported", newState);
 392             }
 393         }
 394     }
 395
 396     private void switchBehavior(final BehaviorState oldBehaviorState, final RaftActorBehavior nextBehavior) {
 397         setCurrentBehavior(nextBehavior);
 398         handleBehaviorChange(oldBehaviorState, nextBehavior);
 399     }
 400
 401     @VisibleForTesting
 402     RaftActorSnapshotMessageSupport newRaftActorSnapshotMessageSupport() {
 403         return new RaftActorSnapshotMessageSupport(context, getRaftActorSnapshotCohort());
 404     }
 405
 406     private void onGetOnDemandRaftStats() {
 407         // Debugging message to retrieve raft stats.
 408
 409         Map<String, String> peerAddresses = new HashMap<>();
 410         Map<String, Boolean> peerVotingStates = new HashMap<>();
 411         for(PeerInfo info: context.getPeers()) {
 412             peerVotingStates.put(info.getId(), info.isVoting());
 413             peerAddresses.put(info.getId(), info.getAddress() != null ? info.getAddress() : "");
 414         }
 415
 416         final RaftActorBehavior currentBehavior = context.getCurrentBehavior();
 417         OnDemandRaftState.Builder builder = OnDemandRaftState.builder()
 418                 .commitIndex(context.getCommitIndex())
 419                 .currentTerm(context.getTermInformation().getCurrentTerm())
 420                 .inMemoryJournalDataSize(replicatedLog().dataSize())
 421                 .inMemoryJournalLogSize(replicatedLog().size())
 422                 .isSnapshotCaptureInitiated(context.getSnapshotManager().isCapturing())
 423                 .lastApplied(context.getLastApplied())
 424                 .lastIndex(replicatedLog().lastIndex())
 425                 .lastTerm(replicatedLog().lastTerm())
 426                 .leader(getLeaderId())
 427                 .raftState(currentBehavior.state().toString())
 428                 .replicatedToAllIndex(currentBehavior.getReplicatedToAllIndex())
 429                 .snapshotIndex(replicatedLog().getSnapshotIndex())
 430                 .snapshotTerm(replicatedLog().getSnapshotTerm())
 431                 .votedFor(context.getTermInformation().getVotedFor())
 432                 .isVoting(context.isVotingMember())
 433                 .peerAddresses(peerAddresses)
 434                 .peerVotingStates(peerVotingStates)
 435                 .customRaftPolicyClassName(context.getConfigParams().getCustomRaftPolicyImplementationClass());
 436
 437         ReplicatedLogEntry lastLogEntry = replicatedLog().last();
 438         if (lastLogEntry != null) {
 439             builder.lastLogIndex(lastLogEntry.getIndex());
 440             builder.lastLogTerm(lastLogEntry.getTerm());
 441         }
 442
 443         if(getCurrentBehavior() instanceof AbstractLeader) {
 444             AbstractLeader leader = (AbstractLeader)getCurrentBehavior();
 445             Collection<String> followerIds = leader.getFollowerIds();
 446             List<FollowerInfo> followerInfoList = Lists.newArrayListWithCapacity(followerIds.size());
 447             for(String id: followerIds) {
 448                 final FollowerLogInformation info = leader.getFollower(id);
 449                 followerInfoList.add(new FollowerInfo(id, info.getNextIndex(), info.getMatchIndex(),
 450                         info.isFollowerActive(), DurationFormatUtils.formatDurationHMS(info.timeSinceLastActivity()),
 451                         context.getPeerInfo(info.getId()).isVoting()));
 452             }
 453
 454             builder.followerInfoList(followerInfoList);
 455         }
 456
 457         sender().tell(builder.build(), self());
 458
 459     }
 460
 461     private void handleBehaviorChange(BehaviorState oldBehaviorState, RaftActorBehavior currentBehavior) {
 462         RaftActorBehavior oldBehavior = oldBehaviorState.getBehavior();
 463
 464         if (oldBehavior != currentBehavior){
 465             onStateChanged();
 466         }
 467
 468         String lastLeaderId = oldBehavior == null ? null : oldBehaviorState.getLastLeaderId();
 469         String lastValidLeaderId = oldBehavior == null ? null : oldBehaviorState.getLastValidLeaderId();
 470         String oldBehaviorStateName = oldBehavior == null ? null : oldBehavior.state().name();
 471
 472         // it can happen that the state has not changed but the leader has changed.
 473         Optional<ActorRef> roleChangeNotifier = getRoleChangeNotifier();
 474         if(!Objects.equals(lastLeaderId, currentBehavior.getLeaderId()) ||
 475            oldBehaviorState.getLeaderPayloadVersion() != currentBehavior.getLeaderPayloadVersion()) {
 476             if(roleChangeNotifier.isPresent()) {
 477                 roleChangeNotifier.get().tell(newLeaderStateChanged(getId(), currentBehavior.getLeaderId(),
 478                         currentBehavior.getLeaderPayloadVersion()), getSelf());
 479             }
 480
 481             onLeaderChanged(lastValidLeaderId, currentBehavior.getLeaderId());
 482
 483             if(leadershipTransferInProgress != null) {
 484                 leadershipTransferInProgress.onNewLeader(currentBehavior.getLeaderId());
 485             }
 486
 487             serverConfigurationSupport.onNewLeader(currentBehavior.getLeaderId());
 488         }
 489
 490         if (roleChangeNotifier.isPresent() &&
 491                 (oldBehavior == null || (oldBehavior.state() != currentBehavior.state()))) {
 492             roleChangeNotifier.get().tell(new RoleChanged(getId(), oldBehaviorStateName ,
 493                     currentBehavior.state().name()), getSelf());
 494         }
 495     }
 496
 497     protected LeaderStateChanged newLeaderStateChanged(String memberId, String leaderId, short leaderPayloadVersion) {
 498         return new LeaderStateChanged(memberId, leaderId, leaderPayloadVersion);
 499     }
 500
 501     @Override
 502     public long snapshotSequenceNr() {
 503         // When we do a snapshot capture, we also capture and save the sequence-number of the persistent journal,
 504         // so that we can delete the persistent journal based on the saved sequence-number
 505         // However , when akka replays the journal during recovery, it replays it from the sequence number when the snapshot
 506         // was saved and not the number we saved.
 507         // We would want to override it , by asking akka to use the last-sequence number known to us.
 508         return context.getSnapshotManager().getLastSequenceNumber();
 509     }
 510
 511     /**
 512      * When a derived RaftActor needs to persist something it must call
 513      * persistData.
 514      *
 515      * @param clientActor
 516      * @param identifier
 517      * @param data
 518      */
 519     protected final void persistData(final ActorRef clientActor, final Identifier identifier, final Payload data) {
 520
 521         ReplicatedLogEntry replicatedLogEntry = new ReplicatedLogImplEntry(
 522             context.getReplicatedLog().lastIndex() + 1,
 523             context.getTermInformation().getCurrentTerm(), data);
 524
 525         if(LOG.isDebugEnabled()) {
 526             LOG.debug("{}: Persist data {}", persistenceId(), replicatedLogEntry);
 527         }
 528
 529         final RaftActorContext raftContext = getRaftActorContext();
 530
 531         replicatedLog().appendAndPersist(replicatedLogEntry, replicatedLogEntry1 -> {
 532             if (!hasFollowers()){
 533                 // Increment the Commit Index and the Last Applied values
 534                 raftContext.setCommitIndex(replicatedLogEntry1.getIndex());
 535                 raftContext.setLastApplied(replicatedLogEntry1.getIndex());
 536
 537                 // Apply the state immediately.
 538                 self().tell(new ApplyState(clientActor, identifier, replicatedLogEntry1), self());
 539
 540                 // Send a ApplyJournalEntries message so that we write the fact that we applied
 541                 // the state to durable storage
 542                 self().tell(new ApplyJournalEntries(replicatedLogEntry1.getIndex()), self());
 543
 544             } else {
 545                 context.getReplicatedLog().captureSnapshotIfReady(replicatedLogEntry1);
 546
 547                 // Send message for replication
 548                 getCurrentBehavior().handleMessage(getSelf(),
 549                         new Replicate(clientActor, identifier, replicatedLogEntry1));
 550             }
 551         });
 552     }
 553
 554     private ReplicatedLog replicatedLog() {
 555         return context.getReplicatedLog();
 556     }
 557
 558     protected String getId() {
 559         return context.getId();
 560     }
 561
 562     @VisibleForTesting
 563     void setCurrentBehavior(RaftActorBehavior behavior) {
 564         context.setCurrentBehavior(behavior);
 565     }
 566
 567     protected RaftActorBehavior getCurrentBehavior() {
 568         return context.getCurrentBehavior();
 569     }
 570
 571     /**
 572      * Derived actors can call the isLeader method to check if the current
 573      * RaftActor is the Leader or not
 574      *
 575      * @return true it this RaftActor is a Leader false otherwise
 576      */
 577     protected boolean isLeader() {
 578         return context.getId().equals(getCurrentBehavior().getLeaderId());
 579     }
 580
 581     protected final boolean isLeaderActive() {
 582         return getRaftState() != RaftState.IsolatedLeader && getRaftState() != RaftState.PreLeader &&
 583                 !shuttingDown && !isLeadershipTransferInProgress();
 584     }
 585
 586     private boolean isLeadershipTransferInProgress() {
 587         return leadershipTransferInProgress != null && leadershipTransferInProgress.isTransferring();
 588     }
 589
 590     /**
 591      * Derived actor can call getLeader if they need a reference to the Leader.
 592      * This would be useful for example in forwarding a request to an actor
 593      * which is the leader
 594      *
 595      * @return A reference to the leader if known, null otherwise
 596      */
 597     protected ActorSelection getLeader(){
 598         String leaderAddress = getLeaderAddress();
 599
 600         if(leaderAddress == null){
 601             return null;
 602         }
 603
 604         return context.actorSelection(leaderAddress);
 605     }
 606
 607     /**
 608      *
 609      * @return the current leader's id
 610      */
 611     protected final String getLeaderId(){
 612         return getCurrentBehavior().getLeaderId();
 613     }
 614
 615     @VisibleForTesting
 616     protected final RaftState getRaftState() {
 617         return getCurrentBehavior().state();
 618     }
 619
 620     protected Long getCurrentTerm(){
 621         return context.getTermInformation().getCurrentTerm();
 622     }
 623
 624     protected RaftActorContext getRaftActorContext() {
 625         return context;
 626     }
 627
 628     protected void updateConfigParams(ConfigParams configParams) {
 629
 630         // obtain the RaftPolicy for oldConfigParams and the updated one.
 631         String oldRaftPolicy = context.getConfigParams().
 632             getCustomRaftPolicyImplementationClass();
 633         String newRaftPolicy = configParams.
 634             getCustomRaftPolicyImplementationClass();
 635
 636         LOG.debug("{}: RaftPolicy used with prev.config {}, RaftPolicy used with newConfig {}", persistenceId(),
 637             oldRaftPolicy, newRaftPolicy);
 638         context.setConfigParams(configParams);
 639         if (!Objects.equals(oldRaftPolicy, newRaftPolicy)) {
 640             // The RaftPolicy was modified. If the current behavior is Follower then re-initialize to Follower
 641             // but transfer the previous leaderId so it doesn't immediately try to schedule an election. This
 642             // avoids potential disruption. Otherwise, switch to Follower normally.
 643             RaftActorBehavior behavior = getCurrentBehavior();
 644             if (behavior != null && behavior.state() == RaftState.Follower) {
 645                 String previousLeaderId = behavior.getLeaderId();
 646                 short previousLeaderPayloadVersion = behavior.getLeaderPayloadVersion();
 647
 648                 LOG.debug("{}: Re-initializing to Follower with previous leaderId {}", persistenceId(), previousLeaderId);
 649
 650                 changeCurrentBehavior(new Follower(context, previousLeaderId, previousLeaderPayloadVersion));
 651             } else {
 652                 initializeBehavior();
 653             }
 654         }
 655     }
 656
 657     public final DataPersistenceProvider persistence() {
 658         return delegatingPersistenceProvider.getDelegate();
 659     }
 660
 661     public void setPersistence(DataPersistenceProvider provider) {
 662         delegatingPersistenceProvider.setDelegate(provider);
 663     }
 664
 665     protected void setPersistence(boolean persistent) {
 666         if(persistent) {
 667             setPersistence(new PersistentDataProvider(this));
 668         } else {
 669             setPersistence(new NonPersistentDataProvider() {
 670                 /**
 671                  * The way snapshotting works is,
 672                  * <ol>
 673                  * <li> RaftActor calls createSnapshot on the Shard
 674                  * <li> Shard sends a CaptureSnapshotReply and RaftActor then calls saveSnapshot
 675                  * <li> When saveSnapshot is invoked on the akka-persistence API it uses the SnapshotStore to save
 676                  * the snapshot. The SnapshotStore sends SaveSnapshotSuccess or SaveSnapshotFailure. When the
 677                  * RaftActor gets SaveSnapshot success it commits the snapshot to the in-memory journal. This
 678                  * commitSnapshot is mimicking what is done in SaveSnapshotSuccess.
 679                  * </ol>
 680                  */
 681                 @Override
 682                 public void saveSnapshot(Object o) {
 683                     // Make saving Snapshot successful
 684                     // Committing the snapshot here would end up calling commit in the creating state which would
 685                     // be a state violation. That's why now we send a message to commit the snapshot.
 686                     self().tell(RaftActorSnapshotMessageSupport.COMMIT_SNAPSHOT, self());
 687                 }
 688             });
 689         }
 690     }
 691
 692     /**
 693      * setPeerAddress sets the address of a known peer at a later time.
 694      * <p>
 695      * This is to account for situations where a we know that a peer
 696      * exists but we do not know an address up-front. This may also be used in
 697      * situations where a known peer starts off in a different location and we
 698      * need to change it's address
 699      * <p>
 700      * Note that if the peerId does not match the list of peers passed to
 701      * this actor during construction an IllegalStateException will be thrown.
 702      *
 703      * @param peerId
 704      * @param peerAddress
 705      */
 706     protected void setPeerAddress(String peerId, String peerAddress){
 707         context.setPeerAddress(peerId, peerAddress);
 708     }
 709
 710     /**
 711      * The applyState method will be called by the RaftActor when some data
 712      * needs to be applied to the actor's state
 713      *
 714      * @param clientActor A reference to the client who sent this message. This
 715      *                    is the same reference that was passed to persistData
 716      *                    by the derived actor. clientActor may be null when
 717      *                    the RaftActor is behaving as a follower or during
 718      *                    recovery.
 719      * @param identifier  The identifier of the persisted data. This is also
 720      *                    the same identifier that was passed to persistData by
 721      *                    the derived actor. identifier may be null when
 722      *                    the RaftActor is behaving as a follower or during
 723      *                    recovery
 724      * @param data        A piece of data that was persisted by the persistData call.
 725      *                    This should NEVER be null.
 726      */
 727     protected abstract void applyState(ActorRef clientActor, Identifier identifier, Object data);
 728
 729     /**
 730      * Returns the RaftActorRecoveryCohort to participate in persistence recovery.
 731      */
 732     @Nonnull
 733     protected abstract RaftActorRecoveryCohort getRaftActorRecoveryCohort();
 734
 735     /**
 736      * This method is called when recovery is complete.
 737      */
 738     protected abstract void onRecoveryComplete();
 739
 740     /**
 741      * Returns the RaftActorSnapshotCohort to participate in persistence recovery.
 742      */
 743     @Nonnull
 744     protected abstract RaftActorSnapshotCohort getRaftActorSnapshotCohort();
 745
 746     /**
 747      * This method will be called by the RaftActor when the state of the
 748      * RaftActor changes. The derived actor can then use methods like
 749      * isLeader or getLeader to do something useful
 750      */
 751     protected abstract void onStateChanged();
 752
 753     /**
 754      * Notifier Actor for this RaftActor to notify when a role change happens
 755      * @return ActorRef - ActorRef of the notifier or Optional.absent if none.
 756      */
 757     protected abstract Optional<ActorRef> getRoleChangeNotifier();
 758
 759     /**
 760      * This method is called prior to operations such as leadership transfer and actor shutdown when the leader
 761      * must pause or stop its duties. This method allows derived classes to gracefully pause or finish current
 762      * work prior to performing the operation. On completion of any work, the run method must be called on the
 763      * given Runnable to proceed with the given operation. <b>Important:</b> the run method must be called on
 764      * this actor's thread dispatcher as as it modifies internal state.
 765      * <p>
 766      * The default implementation immediately runs the operation.
 767      *
 768      * @param operation the operation to run
 769      */
 770     protected void pauseLeader(Runnable operation) {
 771         operation.run();
 772     }
 773
 774     protected void onLeaderChanged(String oldLeader, String newLeader) {
 775
 776     };
 777
 778     private String getLeaderAddress(){
 779         if(isLeader()){
 780             return getSelf().path().toString();
 781         }
 782         String leaderId = getLeaderId();
 783         if (leaderId == null) {
 784             return null;
 785         }
 786         String peerAddress = context.getPeerAddress(leaderId);
 787         if(LOG.isDebugEnabled()) {
 788             LOG.debug("{}: getLeaderAddress leaderId = {} peerAddress = {}",
 789                     persistenceId(), leaderId, peerAddress);
 790         }
 791
 792         return peerAddress;
 793     }
 794
 795     protected boolean hasFollowers(){
 796         return getRaftActorContext().hasFollowers();
 797     }
 798
 799     private void captureSnapshot() {
 800         SnapshotManager snapshotManager = context.getSnapshotManager();
 801
 802         if (!snapshotManager.isCapturing()) {
 803             final long idx = getCurrentBehavior().getReplicatedToAllIndex();
 804             LOG.debug("Take a snapshot of current state. lastReplicatedLog is {} and replicatedToAllIndex is {}",
 805                 replicatedLog().last(), idx);
 806
 807             snapshotManager.capture(replicatedLog().last(), idx);
 808         }
 809     }
 810
 811     /**
 812      * Switch this member to non-voting status. This is a no-op for all behaviors except when we are the leader,
 813      * in which case we need to step down.
 814      */
 815     void becomeNonVoting() {
 816         if (isLeader()) {
 817             initiateLeadershipTransfer(new RaftActorLeadershipTransferCohort.OnComplete() {
 818                 @Override
 819                 public void onSuccess(ActorRef raftActorRef) {
 820                     LOG.debug("{}: leader transfer succeeded after change to non-voting", persistenceId());
 821                     ensureFollowerState();
 822                 }
 823
 824                 @Override
 825                 public void onFailure(ActorRef raftActorRef) {
 826                     LOG.debug("{}: leader transfer failed after change to non-voting", persistenceId());
 827                     ensureFollowerState();
 828                 }
 829
 830                 private void ensureFollowerState() {
 831                     // Whether or not leadership transfer succeeded, we have to step down as leader and
 832                     // switch to Follower so ensure that.
 833                     if (getRaftState() != RaftState.Follower) {
 834                         initializeBehavior();
 835                     }
 836                 }
 837             });
 838         }
 839     }
 840
 841     /**
 842      * @deprecated Deprecated in favor of {@link org.opendaylight.controller.cluster.raft.persisted.DeleteEntries}
 843      *             whose type for fromIndex is long instead of int. This class was kept for backwards
 844      *             compatibility with Helium.
 845      */
 846     // Suppressing this warning as we can't set serialVersionUID to maintain backwards compatibility.
 847     @SuppressWarnings("serial")
 848     @Deprecated
 849     static class DeleteEntries implements Serializable {
 850         private final int fromIndex;
 851
 852         public DeleteEntries(int fromIndex) {
 853             this.fromIndex = fromIndex;
 854         }
 855
 856         public int getFromIndex() {
 857             return fromIndex;
 858         }
 859
 860         private Object readResolve() {
 861             return org.opendaylight.controller.cluster.raft.persisted.DeleteEntries.createMigrated(fromIndex);
 862         }
 863     }
 864
 865     /**
 866      * @deprecated Deprecated in favor of non-inner class {@link org.opendaylight.controller.cluster.raft.persisted.UpdateElectionTerm}
 867      *             which has serialVersionUID set. This class was kept for backwards compatibility with Helium.
 868      */
 869     // Suppressing this warning as we can't set serialVersionUID to maintain backwards compatibility.
 870     @SuppressWarnings("serial")
 871     @Deprecated
 872     static class UpdateElectionTerm implements Serializable {
 873         private final long currentTerm;
 874         private final String votedFor;
 875
 876         public UpdateElectionTerm(long currentTerm, String votedFor) {
 877             this.currentTerm = currentTerm;
 878             this.votedFor = votedFor;
 879         }
 880
 881         public long getCurrentTerm() {
 882             return currentTerm;
 883         }
 884
 885         public String getVotedFor() {
 886             return votedFor;
 887         }
 888
 889         private Object readResolve() {
 890             return org.opendaylight.controller.cluster.raft.persisted.UpdateElectionTerm.createMigrated(
 891                     currentTerm, votedFor);
 892         }
 893     }
 894
 895     /**
 896      * A point-in-time capture of {@link RaftActorBehavior} state critical for transitioning between behaviors.
 897      */
 898     private static abstract class BehaviorState implements Immutable {
 899         @Nullable abstract RaftActorBehavior getBehavior();
 900         @Nullable abstract String getLastValidLeaderId();
 901         @Nullable abstract String getLastLeaderId();
 902         @Nullable abstract short getLeaderPayloadVersion();
 903     }
 904
 905     /**
 906      * A {@link BehaviorState} corresponding to non-null {@link RaftActorBehavior} state.
 907      */
 908     private static final class SimpleBehaviorState extends BehaviorState {
 909         private final RaftActorBehavior behavior;
 910         private final String lastValidLeaderId;
 911         private final String lastLeaderId;
 912         private final short leaderPayloadVersion;
 913
 914         SimpleBehaviorState(final String lastValidLeaderId, final String lastLeaderId,
 915                 final RaftActorBehavior behavior) {
 916             this.lastValidLeaderId = lastValidLeaderId;
 917             this.lastLeaderId = lastLeaderId;
 918             this.behavior = Preconditions.checkNotNull(behavior);
 919             this.leaderPayloadVersion = behavior.getLeaderPayloadVersion();
 920         }
 921
 922         @Override
 923         RaftActorBehavior getBehavior() {
 924             return behavior;
 925         }
 926
 927         @Override
 928         String getLastValidLeaderId() {
 929             return lastValidLeaderId;
 930         }
 931
 932         @Override
 933         short getLeaderPayloadVersion() {
 934             return leaderPayloadVersion;
 935         }
 936
 937         @Override
 938         String getLastLeaderId() {
 939             return lastLeaderId;
 940         }
 941     }
 942
 943     /**
 944      * Class tracking behavior-related information, which we need to keep around and pass across behavior switches.
 945      * An instance is created for each RaftActor. It has two functions:
 946      * - it keeps track of the last leader ID we have encountered since we have been created
 947      * - it creates state capture needed to transition from one behavior to the next
 948      */
 949     private static final class BehaviorStateTracker {
 950         /**
 951          * A {@link BehaviorState} corresponding to null {@link RaftActorBehavior} state. Since null behavior is only
 952          * allowed before we receive the first message, we know the leader ID to be null.
 953          */
 954         private static final BehaviorState NULL_BEHAVIOR_STATE = new BehaviorState() {
 955             @Override
 956             RaftActorBehavior getBehavior() {
 957                 return null;
 958             }
 959
 960             @Override
 961             String getLastValidLeaderId() {
 962                 return null;
 963             }
 964
 965             @Override
 966             short getLeaderPayloadVersion() {
 967                 return -1;
 968             }
 969
 970             @Override
 971             String getLastLeaderId() {
 972                 return null;
 973             }
 974         };
 975
 976         private String lastValidLeaderId;
 977         private String lastLeaderId;
 978
 979         BehaviorState capture(final RaftActorBehavior behavior) {
 980             if (behavior == null) {
 981                 Verify.verify(lastValidLeaderId == null, "Null behavior with non-null last leader");
 982                 return NULL_BEHAVIOR_STATE;
 983             }
 984
 985             lastLeaderId = behavior.getLeaderId();
 986             if (lastLeaderId != null) {
 987                 lastValidLeaderId = lastLeaderId;
 988             }
 989
 990             return new SimpleBehaviorState(lastValidLeaderId, lastLeaderId, behavior);
 991         }
 992     }
 993
 994 }