opendaylight/md-sal/sal-akka-raft/src/main/java/org/opendaylight/controller/cluster/raft/RaftActor.java

   1 /*
   2  * Copyright (c) 2014 Cisco Systems, Inc. and others.  All rights reserved.
   3  * Copyright (c) 2015 Brocade Communications Systems, Inc. and others.  All rights reserved.
   4  *
   5  * This program and the accompanying materials are made available under the
   6  * terms of the Eclipse Public License v1.0 which accompanies this distribution,
   7  * and is available at http://www.eclipse.org/legal/epl-v10.html
   8  */
   9
  10 package org.opendaylight.controller.cluster.raft;
  11
  12 import akka.actor.ActorRef;
  13 import akka.actor.ActorSelection;
  14 import akka.actor.PoisonPill;
  15 import akka.japi.Procedure;
  16 import com.google.common.annotations.VisibleForTesting;
  17 import com.google.common.base.Optional;
  18 import com.google.common.collect.Lists;
  19 import java.io.Serializable;
  20 import java.util.Collection;
  21 import java.util.HashMap;
  22 import java.util.List;
  23 import java.util.Map;
  24 import java.util.Objects;
  25 import java.util.concurrent.TimeUnit;
  26 import java.util.function.Supplier;
  27 import javax.annotation.Nonnull;
  28 import org.apache.commons.lang3.time.DurationFormatUtils;
  29 import org.opendaylight.controller.cluster.DataPersistenceProvider;
  30 import org.opendaylight.controller.cluster.DelegatingPersistentDataProvider;
  31 import org.opendaylight.controller.cluster.NonPersistentDataProvider;
  32 import org.opendaylight.controller.cluster.PersistentDataProvider;
  33 import org.opendaylight.controller.cluster.common.actor.AbstractUntypedPersistentActor;
  34 import org.opendaylight.controller.cluster.notifications.LeaderStateChanged;
  35 import org.opendaylight.controller.cluster.notifications.RoleChanged;
  36 import org.opendaylight.controller.cluster.raft.base.messages.ApplyJournalEntries;
  37 import org.opendaylight.controller.cluster.raft.base.messages.ApplyState;
  38 import org.opendaylight.controller.cluster.raft.base.messages.InitiateCaptureSnapshot;
  39 import org.opendaylight.controller.cluster.raft.base.messages.LeaderTransitioning;
  40 import org.opendaylight.controller.cluster.raft.base.messages.Replicate;
  41 import org.opendaylight.controller.cluster.raft.base.messages.SwitchBehavior;
  42 import org.opendaylight.controller.cluster.raft.behaviors.AbstractLeader;
  43 import org.opendaylight.controller.cluster.raft.behaviors.AbstractRaftActorBehavior;
  44 import org.opendaylight.controller.cluster.raft.behaviors.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.protobuff.client.messages.Payload;
  53 import org.slf4j.Logger;
  54 import org.slf4j.LoggerFactory;
  55
  56 /**
  57  * RaftActor encapsulates a state machine that needs to be kept synchronized
  58  * in a cluster. It implements the RAFT algorithm as described in the paper
  59  * <a href='https://ramcloud.stanford.edu/wiki/download/attachments/11370504/raft.pdf'>
  60  * In Search of an Understandable Consensus Algorithm</a>
  61  * <p/>
  62  * RaftActor has 3 states and each state has a certain behavior associated
  63  * with it. A Raft actor can behave as,
  64  * <ul>
  65  * <li> A Leader </li>
  66  * <li> A Follower (or) </li>
  67  * <li> A Candidate </li>
  68  * </ul>
  69  * <p/>
  70  * <p/>
  71  * A RaftActor MUST be a Leader in order to accept requests from clients to
  72  * change the state of it's encapsulated state machine. Once a RaftActor becomes
  73  * a Leader it is also responsible for ensuring that all followers ultimately
  74  * have the same log and therefore the same state machine as itself.
  75  * <p/>
  76  * <p/>
  77  * The current behavior of a RaftActor determines how election for leadership
  78  * is initiated and how peer RaftActors react to request for votes.
  79  * <p/>
  80  * <p/>
  81  * Each RaftActor also needs to know the current election term. It uses this
  82  * information for a couple of things. One is to simply figure out who it
  83  * voted for in the last election. Another is to figure out if the message
  84  * it received to update it's state is stale.
  85  * <p/>
  86  * <p/>
  87  * The RaftActor uses akka-persistence to store it's replicated log.
  88  * Furthermore through it's behaviors a Raft Actor determines
  89  * <p/>
  90  * <ul>
  91  * <li> when a log entry should be persisted </li>
  92  * <li> when a log entry should be applied to the state machine (and) </li>
  93  * <li> when a snapshot should be saved </li>
  94  * </ul>
  95  */
  96 public abstract class RaftActor extends AbstractUntypedPersistentActor {
  97
  98     private static final long APPLY_STATE_DELAY_THRESHOLD_IN_NANOS = TimeUnit.MILLISECONDS.toNanos(50L); // 50 millis
  99
 100     protected final Logger LOG = LoggerFactory.getLogger(getClass());
 101
 102     /**
 103      * This context should NOT be passed directly to any other actor it is
 104      * only to be consumed by the RaftActorBehaviors
 105      */
 106     private final RaftActorContextImpl context;
 107
 108     private final DelegatingPersistentDataProvider delegatingPersistenceProvider;
 109
 110     private final PersistentDataProvider persistentProvider;
 111
 112     private RaftActorRecoverySupport raftRecovery;
 113
 114     private RaftActorSnapshotMessageSupport snapshotSupport;
 115
 116     private final BehaviorStateHolder reusableBehaviorStateHolder = new BehaviorStateHolder();
 117
 118     private final SwitchBehaviorSupplier reusableSwitchBehaviorSupplier = new SwitchBehaviorSupplier();
 119
 120     private RaftActorServerConfigurationSupport serverConfigurationSupport;
 121
 122     private RaftActorLeadershipTransferCohort leadershipTransferInProgress;
 123
 124     private boolean shuttingDown;
 125
 126     public RaftActor(String id, Map<String, String> peerAddresses,
 127          Optional<ConfigParams> configParams, short payloadVersion) {
 128
 129         persistentProvider = new PersistentDataProvider(this);
 130         delegatingPersistenceProvider = new RaftActorDelegatingPersistentDataProvider(null, persistentProvider);
 131
 132         context = new RaftActorContextImpl(this.getSelf(),
 133             this.getContext(), id, new ElectionTermImpl(persistentProvider, id, LOG),
 134             -1, -1, peerAddresses,
 135             (configParams.isPresent() ? configParams.get(): new DefaultConfigParamsImpl()),
 136             delegatingPersistenceProvider, LOG);
 137
 138         context.setPayloadVersion(payloadVersion);
 139         context.setReplicatedLog(ReplicatedLogImpl.newInstance(context));
 140     }
 141
 142     @Override
 143     public void preStart() throws Exception {
 144         LOG.info("Starting recovery for {} with journal batch size {}", persistenceId(),
 145                 context.getConfigParams().getJournalRecoveryLogBatchSize());
 146
 147         super.preStart();
 148
 149         snapshotSupport = newRaftActorSnapshotMessageSupport();
 150         serverConfigurationSupport = new RaftActorServerConfigurationSupport(this);
 151     }
 152
 153     @Override
 154     public void postStop() {
 155         context.close();
 156         super.postStop();
 157     }
 158
 159     @Override
 160     protected void handleRecover(Object message) {
 161         if(raftRecovery == null) {
 162             raftRecovery = newRaftActorRecoverySupport();
 163         }
 164
 165         boolean recoveryComplete = raftRecovery.handleRecoveryMessage(message, persistentProvider);
 166         if(recoveryComplete) {
 167             onRecoveryComplete();
 168
 169             initializeBehavior();
 170
 171             raftRecovery = null;
 172
 173             if (context.getReplicatedLog().size() > 0) {
 174                 self().tell(new InitiateCaptureSnapshot(), self());
 175                 LOG.info("{}: Snapshot capture initiated after recovery", persistenceId());
 176             } else {
 177                 LOG.info("{}: Snapshot capture NOT initiated after recovery, journal empty", persistenceId());
 178             }
 179         }
 180     }
 181
 182     protected RaftActorRecoverySupport newRaftActorRecoverySupport() {
 183         return new RaftActorRecoverySupport(context, getRaftActorRecoveryCohort());
 184     }
 185
 186     @VisibleForTesting
 187     void initializeBehavior(){
 188         changeCurrentBehavior(new Follower(context));
 189     }
 190
 191     @VisibleForTesting
 192     protected void changeCurrentBehavior(RaftActorBehavior newBehavior){
 193         if(getCurrentBehavior() != null) {
 194             try {
 195                 getCurrentBehavior().close();
 196             } catch(Exception e) {
 197                 LOG.warn("{}: Error closing behavior {}", persistence(), getCurrentBehavior(), e);
 198             }
 199         }
 200
 201         reusableBehaviorStateHolder.init(getCurrentBehavior());
 202         setCurrentBehavior(newBehavior);
 203         handleBehaviorChange(reusableBehaviorStateHolder, getCurrentBehavior());
 204     }
 205
 206     @Override
 207     protected void handleCommand(final Object message) {
 208         if (serverConfigurationSupport.handleMessage(message, getSender())) {
 209             return;
 210         }
 211         if (snapshotSupport.handleSnapshotMessage(message, getSender())) {
 212             return;
 213         }
 214
 215         if (message instanceof ApplyState) {
 216             ApplyState applyState = (ApplyState) message;
 217
 218             long elapsedTime = (System.nanoTime() - applyState.getStartTime());
 219             if(elapsedTime >= APPLY_STATE_DELAY_THRESHOLD_IN_NANOS){
 220                 LOG.warn("ApplyState took more time than expected. Elapsed Time = {} ms ApplyState = {}",
 221                         TimeUnit.NANOSECONDS.toMillis(elapsedTime), applyState);
 222             }
 223
 224             if(LOG.isDebugEnabled()) {
 225                 LOG.debug("{}: Applying state for log index {} data {}",
 226                     persistenceId(), applyState.getReplicatedLogEntry().getIndex(),
 227                     applyState.getReplicatedLogEntry().getData());
 228             }
 229
 230             applyState(applyState.getClientActor(), applyState.getIdentifier(),
 231                 applyState.getReplicatedLogEntry().getData());
 232
 233             if (!hasFollowers()) {
 234                 // for single node, the capture should happen after the apply state
 235                 // as we delete messages from the persistent journal which have made it to the snapshot
 236                 // capturing the snapshot before applying makes the persistent journal and snapshot out of sync
 237                 // and recovery shows data missing
 238                 context.getReplicatedLog().captureSnapshotIfReady(applyState.getReplicatedLogEntry());
 239
 240                 context.getSnapshotManager().trimLog(context.getLastApplied());
 241             }
 242
 243         } else if (message instanceof ApplyJournalEntries) {
 244             ApplyJournalEntries applyEntries = (ApplyJournalEntries) message;
 245             if(LOG.isDebugEnabled()) {
 246                 LOG.debug("{}: Persisting ApplyJournalEntries with index={}", persistenceId(), applyEntries.getToIndex());
 247             }
 248
 249             persistence().persist(applyEntries, NoopProcedure.instance());
 250
 251         } else if (message instanceof FindLeader) {
 252             getSender().tell(
 253                 new FindLeaderReply(getLeaderAddress()),
 254                 getSelf()
 255             );
 256         } else if(message instanceof GetOnDemandRaftState) {
 257             onGetOnDemandRaftStats();
 258         } else if(message instanceof InitiateCaptureSnapshot) {
 259             captureSnapshot();
 260         } else if(message instanceof SwitchBehavior) {
 261             switchBehavior(((SwitchBehavior) message));
 262         } else if(message instanceof LeaderTransitioning) {
 263             onLeaderTransitioning();
 264         } else if(message instanceof Shutdown) {
 265             onShutDown();
 266         } else if(message instanceof Runnable) {
 267             ((Runnable)message).run();
 268         } else {
 269             switchBehavior(reusableSwitchBehaviorSupplier.handleMessage(getSender(), message));
 270         }
 271     }
 272
 273     private void initiateLeadershipTransfer(final RaftActorLeadershipTransferCohort.OnComplete onComplete) {
 274         LOG.debug("{}: Initiating leader transfer", persistenceId());
 275
 276         if(leadershipTransferInProgress == null) {
 277             leadershipTransferInProgress = new RaftActorLeadershipTransferCohort(this);
 278             leadershipTransferInProgress.addOnComplete(new RaftActorLeadershipTransferCohort.OnComplete() {
 279                 @Override
 280                 public void onSuccess(ActorRef raftActorRef) {
 281                     leadershipTransferInProgress = null;
 282                 }
 283
 284                 @Override
 285                 public void onFailure(ActorRef raftActorRef) {
 286                     leadershipTransferInProgress = null;
 287                 }
 288             });
 289
 290             leadershipTransferInProgress.addOnComplete(onComplete);
 291             leadershipTransferInProgress.init();
 292         } else {
 293             LOG.debug("{}: prior leader transfer in progress - adding callback", persistenceId());
 294             leadershipTransferInProgress.addOnComplete(onComplete);
 295         }
 296     }
 297
 298     private void onShutDown() {
 299         LOG.debug("{}: onShutDown", persistenceId());
 300
 301         if(shuttingDown) {
 302             return;
 303         }
 304
 305         shuttingDown = true;
 306
 307         final RaftActorBehavior currentBehavior = context.getCurrentBehavior();
 308         if (currentBehavior.state() != RaftState.Leader) {
 309             // For non-leaders shutdown is a no-op
 310             self().tell(PoisonPill.getInstance(), self());
 311             return;
 312         }
 313
 314         if (context.hasFollowers()) {
 315             initiateLeadershipTransfer(new RaftActorLeadershipTransferCohort.OnComplete() {
 316                 @Override
 317                 public void onSuccess(ActorRef raftActorRef) {
 318                     LOG.debug("{}: leader transfer succeeded - sending PoisonPill", persistenceId());
 319                     raftActorRef.tell(PoisonPill.getInstance(), raftActorRef);
 320                 }
 321
 322                 @Override
 323                 public void onFailure(ActorRef raftActorRef) {
 324                     LOG.debug("{}: leader transfer failed - sending PoisonPill", persistenceId());
 325                     raftActorRef.tell(PoisonPill.getInstance(), raftActorRef);
 326                 }
 327             });
 328         } else {
 329             pauseLeader(new TimedRunnable(context.getConfigParams().getElectionTimeOutInterval(), this) {
 330                 @Override
 331                 protected void doRun() {
 332                     self().tell(PoisonPill.getInstance(), self());
 333                 }
 334
 335                 @Override
 336                 protected void doCancel() {
 337                     self().tell(PoisonPill.getInstance(), self());
 338                 }
 339             });
 340         }
 341     }
 342
 343     private void onLeaderTransitioning() {
 344         LOG.debug("{}: onLeaderTransitioning", persistenceId());
 345         Optional<ActorRef> roleChangeNotifier = getRoleChangeNotifier();
 346         if(getRaftState() == RaftState.Follower && roleChangeNotifier.isPresent()) {
 347             roleChangeNotifier.get().tell(newLeaderStateChanged(getId(), null,
 348                 getCurrentBehavior().getLeaderPayloadVersion()), getSelf());
 349         }
 350     }
 351
 352     private void switchBehavior(SwitchBehavior message) {
 353         if(!getRaftActorContext().getRaftPolicy().automaticElectionsEnabled()) {
 354             RaftState newState = message.getNewState();
 355             if( newState == RaftState.Leader || newState == RaftState.Follower) {
 356                 switchBehavior(reusableSwitchBehaviorSupplier.handleMessage(getSender(), message));
 357                 getRaftActorContext().getTermInformation().updateAndPersist(message.getNewTerm(), "");
 358             } else {
 359                 LOG.warn("Switching to behavior : {} - not supported", newState);
 360             }
 361         }
 362     }
 363
 364     private void switchBehavior(Supplier<RaftActorBehavior> supplier){
 365         reusableBehaviorStateHolder.init(getCurrentBehavior());
 366
 367         setCurrentBehavior(supplier.get());
 368
 369         handleBehaviorChange(reusableBehaviorStateHolder, getCurrentBehavior());
 370     }
 371
 372     @VisibleForTesting
 373     RaftActorSnapshotMessageSupport newRaftActorSnapshotMessageSupport() {
 374         return new RaftActorSnapshotMessageSupport(context, getRaftActorSnapshotCohort());
 375     }
 376
 377     private void onGetOnDemandRaftStats() {
 378         // Debugging message to retrieve raft stats.
 379
 380         Map<String, String> peerAddresses = new HashMap<>();
 381         for(String peerId: context.getPeerIds()) {
 382             peerAddresses.put(peerId, context.getPeerAddress(peerId));
 383         }
 384
 385         final RaftActorBehavior currentBehavior = context.getCurrentBehavior();
 386         OnDemandRaftState.Builder builder = OnDemandRaftState.builder()
 387                 .commitIndex(context.getCommitIndex())
 388                 .currentTerm(context.getTermInformation().getCurrentTerm())
 389                 .inMemoryJournalDataSize(replicatedLog().dataSize())
 390                 .inMemoryJournalLogSize(replicatedLog().size())
 391                 .isSnapshotCaptureInitiated(context.getSnapshotManager().isCapturing())
 392                 .lastApplied(context.getLastApplied())
 393                 .lastIndex(replicatedLog().lastIndex())
 394                 .lastTerm(replicatedLog().lastTerm())
 395                 .leader(getLeaderId())
 396                 .raftState(currentBehavior.state().toString())
 397                 .replicatedToAllIndex(currentBehavior.getReplicatedToAllIndex())
 398                 .snapshotIndex(replicatedLog().getSnapshotIndex())
 399                 .snapshotTerm(replicatedLog().getSnapshotTerm())
 400                 .votedFor(context.getTermInformation().getVotedFor())
 401                 .peerAddresses(peerAddresses)
 402                 .customRaftPolicyClassName(context.getConfigParams().getCustomRaftPolicyImplementationClass());
 403
 404         ReplicatedLogEntry lastLogEntry = replicatedLog().last();
 405         if (lastLogEntry != null) {
 406             builder.lastLogIndex(lastLogEntry.getIndex());
 407             builder.lastLogTerm(lastLogEntry.getTerm());
 408         }
 409
 410         if(getCurrentBehavior() instanceof AbstractLeader) {
 411             AbstractLeader leader = (AbstractLeader)getCurrentBehavior();
 412             Collection<String> followerIds = leader.getFollowerIds();
 413             List<FollowerInfo> followerInfoList = Lists.newArrayListWithCapacity(followerIds.size());
 414             for(String id: followerIds) {
 415                 final FollowerLogInformation info = leader.getFollower(id);
 416                 followerInfoList.add(new FollowerInfo(id, info.getNextIndex(), info.getMatchIndex(),
 417                         info.isFollowerActive(), DurationFormatUtils.formatDurationHMS(info.timeSinceLastActivity())));
 418             }
 419
 420             builder.followerInfoList(followerInfoList);
 421         }
 422
 423         sender().tell(builder.build(), self());
 424
 425     }
 426
 427     private void handleBehaviorChange(BehaviorStateHolder oldBehaviorState, RaftActorBehavior currentBehavior) {
 428         RaftActorBehavior oldBehavior = oldBehaviorState.getBehavior();
 429
 430         if (oldBehavior != currentBehavior){
 431             onStateChanged();
 432         }
 433
 434         String lastValidLeaderId = oldBehavior == null ? null : oldBehaviorState.getLastValidLeaderId();
 435         String oldBehaviorStateName = oldBehavior == null ? null : oldBehavior.state().name();
 436
 437         // it can happen that the state has not changed but the leader has changed.
 438         Optional<ActorRef> roleChangeNotifier = getRoleChangeNotifier();
 439         if(!Objects.equals(lastValidLeaderId, currentBehavior.getLeaderId()) ||
 440            oldBehaviorState.getLeaderPayloadVersion() != currentBehavior.getLeaderPayloadVersion()) {
 441             if(roleChangeNotifier.isPresent()) {
 442                 roleChangeNotifier.get().tell(newLeaderStateChanged(getId(), currentBehavior.getLeaderId(),
 443                         currentBehavior.getLeaderPayloadVersion()), getSelf());
 444             }
 445
 446             onLeaderChanged(lastValidLeaderId, currentBehavior.getLeaderId());
 447
 448             if(leadershipTransferInProgress != null) {
 449                 leadershipTransferInProgress.onNewLeader(currentBehavior.getLeaderId());
 450             }
 451
 452             serverConfigurationSupport.onNewLeader(currentBehavior.getLeaderId());
 453         }
 454
 455         if (roleChangeNotifier.isPresent() &&
 456                 (oldBehavior == null || (oldBehavior.state() != currentBehavior.state()))) {
 457             roleChangeNotifier.get().tell(new RoleChanged(getId(), oldBehaviorStateName ,
 458                     currentBehavior.state().name()), getSelf());
 459         }
 460     }
 461
 462     protected LeaderStateChanged newLeaderStateChanged(String memberId, String leaderId, short leaderPayloadVersion) {
 463         return new LeaderStateChanged(memberId, leaderId, leaderPayloadVersion);
 464     }
 465
 466     @Override
 467     public long snapshotSequenceNr() {
 468         // When we do a snapshot capture, we also capture and save the sequence-number of the persistent journal,
 469         // so that we can delete the persistent journal based on the saved sequence-number
 470         // However , when akka replays the journal during recovery, it replays it from the sequence number when the snapshot
 471         // was saved and not the number we saved.
 472         // We would want to override it , by asking akka to use the last-sequence number known to us.
 473         return context.getSnapshotManager().getLastSequenceNumber();
 474     }
 475
 476     /**
 477      * When a derived RaftActor needs to persist something it must call
 478      * persistData.
 479      *
 480      * @param clientActor
 481      * @param identifier
 482      * @param data
 483      */
 484     protected void persistData(final ActorRef clientActor, final String identifier,
 485         final Payload data) {
 486
 487         ReplicatedLogEntry replicatedLogEntry = new ReplicatedLogImplEntry(
 488             context.getReplicatedLog().lastIndex() + 1,
 489             context.getTermInformation().getCurrentTerm(), data);
 490
 491         if(LOG.isDebugEnabled()) {
 492             LOG.debug("{}: Persist data {}", persistenceId(), replicatedLogEntry);
 493         }
 494
 495         final RaftActorContext raftContext = getRaftActorContext();
 496
 497         replicatedLog().appendAndPersist(replicatedLogEntry, new Procedure<ReplicatedLogEntry>() {
 498             @Override
 499             public void apply(ReplicatedLogEntry replicatedLogEntry) {
 500                 if (!hasFollowers()){
 501                     // Increment the Commit Index and the Last Applied values
 502                     raftContext.setCommitIndex(replicatedLogEntry.getIndex());
 503                     raftContext.setLastApplied(replicatedLogEntry.getIndex());
 504
 505                     // Apply the state immediately.
 506                     self().tell(new ApplyState(clientActor, identifier, replicatedLogEntry), self());
 507
 508                     // Send a ApplyJournalEntries message so that we write the fact that we applied
 509                     // the state to durable storage
 510                     self().tell(new ApplyJournalEntries(replicatedLogEntry.getIndex()), self());
 511
 512                 } else if (clientActor != null) {
 513                     context.getReplicatedLog().captureSnapshotIfReady(replicatedLogEntry);
 514
 515                     // Send message for replication
 516                     getCurrentBehavior().handleMessage(getSelf(),
 517                             new Replicate(clientActor, identifier, replicatedLogEntry));
 518                 }
 519             }
 520         });
 521     }
 522
 523     private ReplicatedLog replicatedLog() {
 524         return context.getReplicatedLog();
 525     }
 526
 527     protected String getId() {
 528         return context.getId();
 529     }
 530
 531     @VisibleForTesting
 532     void setCurrentBehavior(RaftActorBehavior behavior) {
 533         context.setCurrentBehavior(behavior);
 534     }
 535
 536     protected RaftActorBehavior getCurrentBehavior() {
 537         return context.getCurrentBehavior();
 538     }
 539
 540     /**
 541      * Derived actors can call the isLeader method to check if the current
 542      * RaftActor is the Leader or not
 543      *
 544      * @return true it this RaftActor is a Leader false otherwise
 545      */
 546     protected boolean isLeader() {
 547         return context.getId().equals(getCurrentBehavior().getLeaderId());
 548     }
 549
 550     protected final boolean isLeaderActive() {
 551         return getRaftState() != RaftState.IsolatedLeader && !shuttingDown &&
 552                 !isLeadershipTransferInProgress();
 553     }
 554
 555     private boolean isLeadershipTransferInProgress() {
 556         return leadershipTransferInProgress != null && leadershipTransferInProgress.isTransferring();
 557     }
 558
 559     /**
 560      * Derived actor can call getLeader if they need a reference to the Leader.
 561      * This would be useful for example in forwarding a request to an actor
 562      * which is the leader
 563      *
 564      * @return A reference to the leader if known, null otherwise
 565      */
 566     protected ActorSelection getLeader(){
 567         String leaderAddress = getLeaderAddress();
 568
 569         if(leaderAddress == null){
 570             return null;
 571         }
 572
 573         return context.actorSelection(leaderAddress);
 574     }
 575
 576     /**
 577      *
 578      * @return the current leader's id
 579      */
 580     protected final String getLeaderId(){
 581         return getCurrentBehavior().getLeaderId();
 582     }
 583
 584     @VisibleForTesting
 585     protected final RaftState getRaftState() {
 586         return getCurrentBehavior().state();
 587     }
 588
 589     protected Long getCurrentTerm(){
 590         return context.getTermInformation().getCurrentTerm();
 591     }
 592
 593     protected RaftActorContext getRaftActorContext() {
 594         return context;
 595     }
 596
 597     protected void updateConfigParams(ConfigParams configParams) {
 598
 599         // obtain the RaftPolicy for oldConfigParams and the updated one.
 600         String oldRaftPolicy = context.getConfigParams().
 601             getCustomRaftPolicyImplementationClass();
 602         String newRaftPolicy = configParams.
 603             getCustomRaftPolicyImplementationClass();
 604
 605         LOG.debug("{}: RaftPolicy used with prev.config {}, RaftPolicy used with newConfig {}", persistenceId(),
 606             oldRaftPolicy, newRaftPolicy);
 607         context.setConfigParams(configParams);
 608         if (!Objects.equals(oldRaftPolicy, newRaftPolicy)) {
 609             // The RaftPolicy was modified. If the current behavior is Follower then re-initialize to Follower
 610             // but transfer the previous leaderId so it doesn't immediately try to schedule an election. This
 611             // avoids potential disruption. Otherwise, switch to Follower normally.
 612             RaftActorBehavior behavior = getCurrentBehavior();
 613             if(behavior instanceof Follower) {
 614                 String previousLeaderId = ((Follower)behavior).getLeaderId();
 615                 short previousLeaderPayloadVersion = behavior.getLeaderPayloadVersion();
 616
 617                 LOG.debug("{}: Re-initializing to Follower with previous leaderId {}", persistenceId(), previousLeaderId);
 618
 619                 changeCurrentBehavior(new Follower(context, previousLeaderId, previousLeaderPayloadVersion));
 620             } else {
 621                 initializeBehavior();
 622             }
 623         }
 624     }
 625
 626     public final DataPersistenceProvider persistence() {
 627         return delegatingPersistenceProvider.getDelegate();
 628     }
 629
 630     public void setPersistence(DataPersistenceProvider provider) {
 631         delegatingPersistenceProvider.setDelegate(provider);
 632     }
 633
 634     protected void setPersistence(boolean persistent) {
 635         if(persistent) {
 636             setPersistence(new PersistentDataProvider(this));
 637         } else {
 638             setPersistence(new NonPersistentDataProvider() {
 639                 /**
 640                  * The way snapshotting works is,
 641                  * <ol>
 642                  * <li> RaftActor calls createSnapshot on the Shard
 643                  * <li> Shard sends a CaptureSnapshotReply and RaftActor then calls saveSnapshot
 644                  * <li> When saveSnapshot is invoked on the akka-persistence API it uses the SnapshotStore to save
 645                  * the snapshot. The SnapshotStore sends SaveSnapshotSuccess or SaveSnapshotFailure. When the
 646                  * RaftActor gets SaveSnapshot success it commits the snapshot to the in-memory journal. This
 647                  * commitSnapshot is mimicking what is done in SaveSnapshotSuccess.
 648                  * </ol>
 649                  */
 650                 @Override
 651                 public void saveSnapshot(Object o) {
 652                     // Make saving Snapshot successful
 653                     // Committing the snapshot here would end up calling commit in the creating state which would
 654                     // be a state violation. That's why now we send a message to commit the snapshot.
 655                     self().tell(RaftActorSnapshotMessageSupport.COMMIT_SNAPSHOT, self());
 656                 }
 657             });
 658         }
 659     }
 660
 661     /**
 662      * setPeerAddress sets the address of a known peer at a later time.
 663      * <p>
 664      * This is to account for situations where a we know that a peer
 665      * exists but we do not know an address up-front. This may also be used in
 666      * situations where a known peer starts off in a different location and we
 667      * need to change it's address
 668      * <p>
 669      * Note that if the peerId does not match the list of peers passed to
 670      * this actor during construction an IllegalStateException will be thrown.
 671      *
 672      * @param peerId
 673      * @param peerAddress
 674      */
 675     protected void setPeerAddress(String peerId, String peerAddress){
 676         context.setPeerAddress(peerId, peerAddress);
 677     }
 678
 679     /**
 680      * The applyState method will be called by the RaftActor when some data
 681      * needs to be applied to the actor's state
 682      *
 683      * @param clientActor A reference to the client who sent this message. This
 684      *                    is the same reference that was passed to persistData
 685      *                    by the derived actor. clientActor may be null when
 686      *                    the RaftActor is behaving as a follower or during
 687      *                    recovery.
 688      * @param identifier  The identifier of the persisted data. This is also
 689      *                    the same identifier that was passed to persistData by
 690      *                    the derived actor. identifier may be null when
 691      *                    the RaftActor is behaving as a follower or during
 692      *                    recovery
 693      * @param data        A piece of data that was persisted by the persistData call.
 694      *                    This should NEVER be null.
 695      */
 696     protected abstract void applyState(ActorRef clientActor, String identifier,
 697         Object data);
 698
 699     /**
 700      * Returns the RaftActorRecoveryCohort to participate in persistence recovery.
 701      */
 702     @Nonnull
 703     protected abstract RaftActorRecoveryCohort getRaftActorRecoveryCohort();
 704
 705     /**
 706      * This method is called when recovery is complete.
 707      */
 708     protected abstract void onRecoveryComplete();
 709
 710     /**
 711      * Returns the RaftActorSnapshotCohort to participate in persistence recovery.
 712      */
 713     @Nonnull
 714     protected abstract RaftActorSnapshotCohort getRaftActorSnapshotCohort();
 715
 716     /**
 717      * This method will be called by the RaftActor when the state of the
 718      * RaftActor changes. The derived actor can then use methods like
 719      * isLeader or getLeader to do something useful
 720      */
 721     protected abstract void onStateChanged();
 722
 723     /**
 724      * Notifier Actor for this RaftActor to notify when a role change happens
 725      * @return ActorRef - ActorRef of the notifier or Optional.absent if none.
 726      */
 727     protected abstract Optional<ActorRef> getRoleChangeNotifier();
 728
 729     /**
 730      * This method is called prior to operations such as leadership transfer and actor shutdown when the leader
 731      * must pause or stop its duties. This method allows derived classes to gracefully pause or finish current
 732      * work prior to performing the operation. On completion of any work, the run method must be called on the
 733      * given Runnable to proceed with the given operation. <b>Important:</b> the run method must be called on
 734      * this actor's thread dispatcher as as it modifies internal state.
 735      * <p>
 736      * The default implementation immediately runs the operation.
 737      *
 738      * @param operation the operation to run
 739      */
 740     protected void pauseLeader(Runnable operation) {
 741         operation.run();
 742     }
 743
 744     protected void onLeaderChanged(String oldLeader, String newLeader) {
 745
 746     };
 747
 748     private String getLeaderAddress(){
 749         if(isLeader()){
 750             return getSelf().path().toString();
 751         }
 752         String leaderId = getLeaderId();
 753         if (leaderId == null) {
 754             return null;
 755         }
 756         String peerAddress = context.getPeerAddress(leaderId);
 757         if(LOG.isDebugEnabled()) {
 758             LOG.debug("{}: getLeaderAddress leaderId = {} peerAddress = {}",
 759                     persistenceId(), leaderId, peerAddress);
 760         }
 761
 762         return peerAddress;
 763     }
 764
 765     protected boolean hasFollowers(){
 766         return getRaftActorContext().hasFollowers();
 767     }
 768
 769     private void captureSnapshot() {
 770         SnapshotManager snapshotManager = context.getSnapshotManager();
 771
 772         if (!snapshotManager.isCapturing()) {
 773             final long idx = getCurrentBehavior().getReplicatedToAllIndex();
 774             LOG.debug("Take a snapshot of current state. lastReplicatedLog is {} and replicatedToAllIndex is {}",
 775                 replicatedLog().last(), idx);
 776
 777             snapshotManager.capture(replicatedLog().last(), idx);
 778         }
 779     }
 780
 781     /**
 782      * Switch this member to non-voting status. This is a no-op for all behaviors except when we are the leader,
 783      * in which case we need to step down.
 784      */
 785     void becomeNonVoting() {
 786         if (isLeader()) {
 787             initiateLeadershipTransfer(new RaftActorLeadershipTransferCohort.OnComplete() {
 788                 @Override
 789                 public void onSuccess(ActorRef raftActorRef) {
 790                     LOG.debug("{}: leader transfer succeeded after change to non-voting", persistenceId());
 791                     ensureFollowerState();
 792                 }
 793
 794                 @Override
 795                 public void onFailure(ActorRef raftActorRef) {
 796                     LOG.debug("{}: leader transfer failed after change to non-voting", persistenceId());
 797                     ensureFollowerState();
 798                 }
 799
 800                 private void ensureFollowerState() {
 801                     // Whether or not leadership transfer succeeded, we have to step down as leader and
 802                     // switch to Follower so ensure that.
 803                     if (getRaftState() != RaftState.Follower) {
 804                         initializeBehavior();
 805                     }
 806                 }
 807             });
 808         }
 809     }
 810
 811     /**
 812      * @deprecated Deprecated in favor of {@link org.opendaylight.controller.cluster.raft.base.messages.DeleteEntries}
 813      *             whose type for fromIndex is long instead of int. This class was kept for backwards
 814      *             compatibility with Helium.
 815      */
 816     // Suppressing this warning as we can't set serialVersionUID to maintain backwards compatibility.
 817     @SuppressWarnings("serial")
 818     @Deprecated
 819     static class DeleteEntries implements Serializable {
 820         private final int fromIndex;
 821
 822         public DeleteEntries(int fromIndex) {
 823             this.fromIndex = fromIndex;
 824         }
 825
 826         public int getFromIndex() {
 827             return fromIndex;
 828         }
 829     }
 830
 831     /**
 832      * @deprecated Deprecated in favor of non-inner class {@link org.opendaylight.controller.cluster.raft.base.messages.UpdateElectionTerm}
 833      *             which has serialVersionUID set. This class was kept for backwards compatibility with Helium.
 834      */
 835     // Suppressing this warning as we can't set serialVersionUID to maintain backwards compatibility.
 836     @SuppressWarnings("serial")
 837     @Deprecated
 838     static class UpdateElectionTerm implements Serializable {
 839         private final long currentTerm;
 840         private final String votedFor;
 841
 842         public UpdateElectionTerm(long currentTerm, String votedFor) {
 843             this.currentTerm = currentTerm;
 844             this.votedFor = votedFor;
 845         }
 846
 847         public long getCurrentTerm() {
 848             return currentTerm;
 849         }
 850
 851         public String getVotedFor() {
 852             return votedFor;
 853         }
 854     }
 855
 856     private static class BehaviorStateHolder {
 857         private RaftActorBehavior behavior;
 858         private String lastValidLeaderId;
 859         private short leaderPayloadVersion;
 860
 861         void init(RaftActorBehavior behavior) {
 862             this.behavior = behavior;
 863             this.leaderPayloadVersion = behavior != null ? behavior.getLeaderPayloadVersion() : -1;
 864
 865             String behaviorLeaderId = behavior != null ? behavior.getLeaderId() : null;
 866             if(behaviorLeaderId != null) {
 867                 this.lastValidLeaderId = behaviorLeaderId;
 868             }
 869         }
 870
 871         RaftActorBehavior getBehavior() {
 872             return behavior;
 873         }
 874
 875         String getLastValidLeaderId() {
 876             return lastValidLeaderId;
 877         }
 878
 879         short getLeaderPayloadVersion() {
 880             return leaderPayloadVersion;
 881         }
 882     }
 883
 884     private class SwitchBehaviorSupplier implements Supplier<RaftActorBehavior> {
 885         private Object message;
 886         private ActorRef sender;
 887
 888         public SwitchBehaviorSupplier handleMessage(ActorRef sender, Object message){
 889             this.sender = sender;
 890             this.message = message;
 891             return this;
 892         }
 893
 894         @Override
 895         public RaftActorBehavior get() {
 896             if(this.message instanceof SwitchBehavior){
 897                 return AbstractRaftActorBehavior.createBehavior(context, ((SwitchBehavior) message).getNewState());
 898             }
 899             return getCurrentBehavior().handleMessage(sender, message);
 900         }
 901     }
 902 }