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

   1 /*
   2  * Copyright (c) 2014 Cisco Systems, Inc. and others.  All rights reserved.
   3  * Copyright (c) 2015 Brocade Communications Systems, Inc. and others.  All rights reserved.
   4  *
   5  * This program and the accompanying materials are made available under the
   6  * terms of the Eclipse Public License v1.0 which accompanies this distribution,
   7  * and is available at http://www.eclipse.org/legal/epl-v10.html
   8  */
   9
  10 package org.opendaylight.controller.cluster.raft;
  11
  12 import akka.actor.ActorRef;
  13 import akka.actor.ActorSelection;
  14 import akka.actor.PoisonPill;
  15 import akka.japi.Procedure;
  16 import com.google.common.annotations.VisibleForTesting;
  17 import com.google.common.base.Objects;
  18 import com.google.common.base.Optional;
  19 import com.google.common.base.Supplier;
  20 import com.google.common.collect.Lists;
  21 import java.io.Serializable;
  22 import java.util.Collection;
  23 import java.util.HashMap;
  24 import java.util.List;
  25 import java.util.Map;
  26 import java.util.concurrent.TimeUnit;
  27 import javax.annotation.Nonnull;
  28 import org.apache.commons.lang3.time.DurationFormatUtils;
  29 import org.opendaylight.controller.cluster.DataPersistenceProvider;
  30 import org.opendaylight.controller.cluster.DelegatingPersistentDataProvider;
  31 import org.opendaylight.controller.cluster.NonPersistentDataProvider;
  32 import org.opendaylight.controller.cluster.PersistentDataProvider;
  33 import org.opendaylight.controller.cluster.common.actor.AbstractUntypedPersistentActor;
  34 import org.opendaylight.controller.cluster.notifications.LeaderStateChanged;
  35 import org.opendaylight.controller.cluster.notifications.RoleChanged;
  36 import org.opendaylight.controller.cluster.raft.base.messages.ApplyJournalEntries;
  37 import org.opendaylight.controller.cluster.raft.base.messages.ApplyState;
  38 import org.opendaylight.controller.cluster.raft.base.messages.InitiateCaptureSnapshot;
  39 import org.opendaylight.controller.cluster.raft.base.messages.LeaderTransitioning;
  40 import org.opendaylight.controller.cluster.raft.base.messages.Replicate;
  41 import org.opendaylight.controller.cluster.raft.base.messages.SwitchBehavior;
  42 import org.opendaylight.controller.cluster.raft.behaviors.AbstractLeader;
  43 import org.opendaylight.controller.cluster.raft.behaviors.AbstractRaftActorBehavior;
  44 import org.opendaylight.controller.cluster.raft.behaviors.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     void initiateLeadershipTransfer(final RaftActorLeadershipTransferCohort.OnComplete onComplete) {
 274         LOG.debug("{}: Initiating leader transfer", persistenceId());
 275
 276         if(leadershipTransferInProgress == null) {
 277             leadershipTransferInProgress = new RaftActorLeadershipTransferCohort(this, getSender());
 278             leadershipTransferInProgress.addOnComplete(new RaftActorLeadershipTransferCohort.OnComplete() {
 279                 @Override
 280                 public void onSuccess(ActorRef raftActorRef, ActorRef replyTo) {
 281                     leadershipTransferInProgress = null;
 282                 }
 283
 284                 @Override
 285                 public void onFailure(ActorRef raftActorRef, ActorRef replyTo) {
 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 && context.hasFollowers()) {
 309             initiateLeadershipTransfer(new RaftActorLeadershipTransferCohort.OnComplete() {
 310                 @Override
 311                 public void onSuccess(ActorRef raftActorRef, ActorRef replyTo) {
 312                     LOG.debug("{}: leader transfer succeeded - sending PoisonPill", persistenceId());
 313                     raftActorRef.tell(PoisonPill.getInstance(), raftActorRef);
 314                 }
 315
 316                 @Override
 317                 public void onFailure(ActorRef raftActorRef, ActorRef replyTo) {
 318                     LOG.debug("{}: leader transfer failed - sending PoisonPill", persistenceId());
 319                     raftActorRef.tell(PoisonPill.getInstance(), raftActorRef);
 320                 }
 321             });
 322         } else if(currentBehavior.state() == RaftState.Leader) {
 323             pauseLeader(new TimedRunnable(context.getConfigParams().getElectionTimeOutInterval(), this) {
 324                 @Override
 325                 protected void doRun() {
 326                     self().tell(PoisonPill.getInstance(), self());
 327                 }
 328
 329                 @Override
 330                 protected void doCancel() {
 331                     self().tell(PoisonPill.getInstance(), self());
 332                 }
 333             });
 334         } else {
 335             self().tell(PoisonPill.getInstance(), self());
 336         }
 337     }
 338
 339     private void onLeaderTransitioning() {
 340         LOG.debug("{}: onLeaderTransitioning", persistenceId());
 341         Optional<ActorRef> roleChangeNotifier = getRoleChangeNotifier();
 342         if(getRaftState() == RaftState.Follower && roleChangeNotifier.isPresent()) {
 343             roleChangeNotifier.get().tell(newLeaderStateChanged(getId(), null,
 344                 getCurrentBehavior().getLeaderPayloadVersion()), getSelf());
 345         }
 346     }
 347
 348     private void switchBehavior(SwitchBehavior message) {
 349         if(!getRaftActorContext().getRaftPolicy().automaticElectionsEnabled()) {
 350             RaftState newState = message.getNewState();
 351             if( newState == RaftState.Leader || newState == RaftState.Follower) {
 352                 switchBehavior(reusableSwitchBehaviorSupplier.handleMessage(getSender(), message));
 353                 getRaftActorContext().getTermInformation().updateAndPersist(message.getNewTerm(), "");
 354             } else {
 355                 LOG.warn("Switching to behavior : {} - not supported", newState);
 356             }
 357         }
 358     }
 359
 360     private void switchBehavior(Supplier<RaftActorBehavior> supplier){
 361         reusableBehaviorStateHolder.init(getCurrentBehavior());
 362
 363         setCurrentBehavior(supplier.get());
 364
 365         handleBehaviorChange(reusableBehaviorStateHolder, getCurrentBehavior());
 366     }
 367
 368     @VisibleForTesting
 369     RaftActorSnapshotMessageSupport newRaftActorSnapshotMessageSupport() {
 370         return new RaftActorSnapshotMessageSupport(context, getRaftActorSnapshotCohort());
 371     }
 372
 373     private void onGetOnDemandRaftStats() {
 374         // Debugging message to retrieve raft stats.
 375
 376         Map<String, String> peerAddresses = new HashMap<>();
 377         for(String peerId: context.getPeerIds()) {
 378             peerAddresses.put(peerId, context.getPeerAddress(peerId));
 379         }
 380
 381         final RaftActorBehavior currentBehavior = context.getCurrentBehavior();
 382         OnDemandRaftState.Builder builder = OnDemandRaftState.builder()
 383                 .commitIndex(context.getCommitIndex())
 384                 .currentTerm(context.getTermInformation().getCurrentTerm())
 385                 .inMemoryJournalDataSize(replicatedLog().dataSize())
 386                 .inMemoryJournalLogSize(replicatedLog().size())
 387                 .isSnapshotCaptureInitiated(context.getSnapshotManager().isCapturing())
 388                 .lastApplied(context.getLastApplied())
 389                 .lastIndex(replicatedLog().lastIndex())
 390                 .lastTerm(replicatedLog().lastTerm())
 391                 .leader(getLeaderId())
 392                 .raftState(currentBehavior.state().toString())
 393                 .replicatedToAllIndex(currentBehavior.getReplicatedToAllIndex())
 394                 .snapshotIndex(replicatedLog().getSnapshotIndex())
 395                 .snapshotTerm(replicatedLog().getSnapshotTerm())
 396                 .votedFor(context.getTermInformation().getVotedFor())
 397                 .peerAddresses(peerAddresses)
 398                 .customRaftPolicyClassName(context.getConfigParams().getCustomRaftPolicyImplementationClass());
 399
 400         ReplicatedLogEntry lastLogEntry = replicatedLog().last();
 401         if (lastLogEntry != null) {
 402             builder.lastLogIndex(lastLogEntry.getIndex());
 403             builder.lastLogTerm(lastLogEntry.getTerm());
 404         }
 405
 406         if(getCurrentBehavior() instanceof AbstractLeader) {
 407             AbstractLeader leader = (AbstractLeader)getCurrentBehavior();
 408             Collection<String> followerIds = leader.getFollowerIds();
 409             List<FollowerInfo> followerInfoList = Lists.newArrayListWithCapacity(followerIds.size());
 410             for(String id: followerIds) {
 411                 final FollowerLogInformation info = leader.getFollower(id);
 412                 followerInfoList.add(new FollowerInfo(id, info.getNextIndex(), info.getMatchIndex(),
 413                         info.isFollowerActive(), DurationFormatUtils.formatDurationHMS(info.timeSinceLastActivity())));
 414             }
 415
 416             builder.followerInfoList(followerInfoList);
 417         }
 418
 419         sender().tell(builder.build(), self());
 420
 421     }
 422
 423     private void handleBehaviorChange(BehaviorStateHolder oldBehaviorState, RaftActorBehavior currentBehavior) {
 424         RaftActorBehavior oldBehavior = oldBehaviorState.getBehavior();
 425
 426         if (oldBehavior != currentBehavior){
 427             onStateChanged();
 428         }
 429
 430         String lastValidLeaderId = oldBehavior == null ? null : oldBehaviorState.getLastValidLeaderId();
 431         String oldBehaviorStateName = oldBehavior == null ? null : oldBehavior.state().name();
 432
 433         // it can happen that the state has not changed but the leader has changed.
 434         Optional<ActorRef> roleChangeNotifier = getRoleChangeNotifier();
 435         if(!Objects.equal(lastValidLeaderId, currentBehavior.getLeaderId()) ||
 436            oldBehaviorState.getLeaderPayloadVersion() != currentBehavior.getLeaderPayloadVersion()) {
 437             if(roleChangeNotifier.isPresent()) {
 438                 roleChangeNotifier.get().tell(newLeaderStateChanged(getId(), currentBehavior.getLeaderId(),
 439                         currentBehavior.getLeaderPayloadVersion()), getSelf());
 440             }
 441
 442             onLeaderChanged(lastValidLeaderId, currentBehavior.getLeaderId());
 443
 444             if(leadershipTransferInProgress != null) {
 445                 leadershipTransferInProgress.onNewLeader(currentBehavior.getLeaderId());
 446             }
 447
 448             serverConfigurationSupport.onNewLeader(currentBehavior.getLeaderId());
 449         }
 450
 451         if (roleChangeNotifier.isPresent() &&
 452                 (oldBehavior == null || (oldBehavior.state() != currentBehavior.state()))) {
 453             roleChangeNotifier.get().tell(new RoleChanged(getId(), oldBehaviorStateName ,
 454                     currentBehavior.state().name()), getSelf());
 455         }
 456     }
 457
 458     protected LeaderStateChanged newLeaderStateChanged(String memberId, String leaderId, short leaderPayloadVersion) {
 459         return new LeaderStateChanged(memberId, leaderId, leaderPayloadVersion);
 460     }
 461
 462     @Override
 463     public long snapshotSequenceNr() {
 464         // When we do a snapshot capture, we also capture and save the sequence-number of the persistent journal,
 465         // so that we can delete the persistent journal based on the saved sequence-number
 466         // However , when akka replays the journal during recovery, it replays it from the sequence number when the snapshot
 467         // was saved and not the number we saved.
 468         // We would want to override it , by asking akka to use the last-sequence number known to us.
 469         return context.getSnapshotManager().getLastSequenceNumber();
 470     }
 471
 472     /**
 473      * When a derived RaftActor needs to persist something it must call
 474      * persistData.
 475      *
 476      * @param clientActor
 477      * @param identifier
 478      * @param data
 479      */
 480     protected void persistData(final ActorRef clientActor, final String identifier,
 481         final Payload data) {
 482
 483         ReplicatedLogEntry replicatedLogEntry = new ReplicatedLogImplEntry(
 484             context.getReplicatedLog().lastIndex() + 1,
 485             context.getTermInformation().getCurrentTerm(), data);
 486
 487         if(LOG.isDebugEnabled()) {
 488             LOG.debug("{}: Persist data {}", persistenceId(), replicatedLogEntry);
 489         }
 490
 491         final RaftActorContext raftContext = getRaftActorContext();
 492
 493         replicatedLog().appendAndPersist(replicatedLogEntry, new Procedure<ReplicatedLogEntry>() {
 494             @Override
 495             public void apply(ReplicatedLogEntry replicatedLogEntry) {
 496                 if (!hasFollowers()){
 497                     // Increment the Commit Index and the Last Applied values
 498                     raftContext.setCommitIndex(replicatedLogEntry.getIndex());
 499                     raftContext.setLastApplied(replicatedLogEntry.getIndex());
 500
 501                     // Apply the state immediately.
 502                     self().tell(new ApplyState(clientActor, identifier, replicatedLogEntry), self());
 503
 504                     // Send a ApplyJournalEntries message so that we write the fact that we applied
 505                     // the state to durable storage
 506                     self().tell(new ApplyJournalEntries(replicatedLogEntry.getIndex()), self());
 507
 508                 } else if (clientActor != null) {
 509                     context.getReplicatedLog().captureSnapshotIfReady(replicatedLogEntry);
 510
 511                     // Send message for replication
 512                     getCurrentBehavior().handleMessage(getSelf(),
 513                             new Replicate(clientActor, identifier, replicatedLogEntry));
 514                 }
 515             }
 516         });
 517     }
 518
 519     private ReplicatedLog replicatedLog() {
 520         return context.getReplicatedLog();
 521     }
 522
 523     protected String getId() {
 524         return context.getId();
 525     }
 526
 527     @VisibleForTesting
 528     void setCurrentBehavior(RaftActorBehavior behavior) {
 529         context.setCurrentBehavior(behavior);
 530     }
 531
 532     protected RaftActorBehavior getCurrentBehavior() {
 533         return context.getCurrentBehavior();
 534     }
 535
 536     /**
 537      * Derived actors can call the isLeader method to check if the current
 538      * RaftActor is the Leader or not
 539      *
 540      * @return true it this RaftActor is a Leader false otherwise
 541      */
 542     protected boolean isLeader() {
 543         return context.getId().equals(getCurrentBehavior().getLeaderId());
 544     }
 545
 546     protected final boolean isLeaderActive() {
 547         return getRaftState() != RaftState.IsolatedLeader && !shuttingDown &&
 548                 !isLeadershipTransferInProgress();
 549     }
 550
 551     private boolean isLeadershipTransferInProgress() {
 552         return leadershipTransferInProgress != null && leadershipTransferInProgress.isTransferring();
 553     }
 554
 555     /**
 556      * Derived actor can call getLeader if they need a reference to the Leader.
 557      * This would be useful for example in forwarding a request to an actor
 558      * which is the leader
 559      *
 560      * @return A reference to the leader if known, null otherwise
 561      */
 562     protected ActorSelection getLeader(){
 563         String leaderAddress = getLeaderAddress();
 564
 565         if(leaderAddress == null){
 566             return null;
 567         }
 568
 569         return context.actorSelection(leaderAddress);
 570     }
 571
 572     /**
 573      *
 574      * @return the current leader's id
 575      */
 576     protected final String getLeaderId(){
 577         return getCurrentBehavior().getLeaderId();
 578     }
 579
 580     @VisibleForTesting
 581     protected final RaftState getRaftState() {
 582         return getCurrentBehavior().state();
 583     }
 584
 585     protected Long getCurrentTerm(){
 586         return context.getTermInformation().getCurrentTerm();
 587     }
 588
 589     protected RaftActorContext getRaftActorContext() {
 590         return context;
 591     }
 592
 593     protected void updateConfigParams(ConfigParams configParams) {
 594
 595         // obtain the RaftPolicy for oldConfigParams and the updated one.
 596         String oldRaftPolicy = context.getConfigParams().
 597             getCustomRaftPolicyImplementationClass();
 598         String newRaftPolicy = configParams.
 599             getCustomRaftPolicyImplementationClass();
 600
 601         LOG.debug("{}: RaftPolicy used with prev.config {}, RaftPolicy used with newConfig {}", persistenceId(),
 602             oldRaftPolicy, newRaftPolicy);
 603         context.setConfigParams(configParams);
 604         if (!Objects.equal(oldRaftPolicy, newRaftPolicy)) {
 605             // The RaftPolicy was modified. If the current behavior is Follower then re-initialize to Follower
 606             // but transfer the previous leaderId so it doesn't immediately try to schedule an election. This
 607             // avoids potential disruption. Otherwise, switch to Follower normally.
 608             RaftActorBehavior behavior = getCurrentBehavior();
 609             if(behavior instanceof Follower) {
 610                 String previousLeaderId = ((Follower)behavior).getLeaderId();
 611                 short previousLeaderPayloadVersion = behavior.getLeaderPayloadVersion();
 612
 613                 LOG.debug("{}: Re-initializing to Follower with previous leaderId {}", persistenceId(), previousLeaderId);
 614
 615                 changeCurrentBehavior(new Follower(context, previousLeaderId, previousLeaderPayloadVersion));
 616             } else {
 617                 initializeBehavior();
 618             }
 619         }
 620     }
 621
 622     public final DataPersistenceProvider persistence() {
 623         return delegatingPersistenceProvider.getDelegate();
 624     }
 625
 626     public void setPersistence(DataPersistenceProvider provider) {
 627         delegatingPersistenceProvider.setDelegate(provider);
 628     }
 629
 630     protected void setPersistence(boolean persistent) {
 631         if(persistent) {
 632             setPersistence(new PersistentDataProvider(this));
 633         } else {
 634             setPersistence(new NonPersistentDataProvider() {
 635                 /**
 636                  * The way snapshotting works is,
 637                  * <ol>
 638                  * <li> RaftActor calls createSnapshot on the Shard
 639                  * <li> Shard sends a CaptureSnapshotReply and RaftActor then calls saveSnapshot
 640                  * <li> When saveSnapshot is invoked on the akka-persistence API it uses the SnapshotStore to save
 641                  * the snapshot. The SnapshotStore sends SaveSnapshotSuccess or SaveSnapshotFailure. When the
 642                  * RaftActor gets SaveSnapshot success it commits the snapshot to the in-memory journal. This
 643                  * commitSnapshot is mimicking what is done in SaveSnapshotSuccess.
 644                  * </ol>
 645                  */
 646                 @Override
 647                 public void saveSnapshot(Object o) {
 648                     // Make saving Snapshot successful
 649                     // Committing the snapshot here would end up calling commit in the creating state which would
 650                     // be a state violation. That's why now we send a message to commit the snapshot.
 651                     self().tell(RaftActorSnapshotMessageSupport.COMMIT_SNAPSHOT, self());
 652                 }
 653             });
 654         }
 655     }
 656
 657     /**
 658      * setPeerAddress sets the address of a known peer at a later time.
 659      * <p>
 660      * This is to account for situations where a we know that a peer
 661      * exists but we do not know an address up-front. This may also be used in
 662      * situations where a known peer starts off in a different location and we
 663      * need to change it's address
 664      * <p>
 665      * Note that if the peerId does not match the list of peers passed to
 666      * this actor during construction an IllegalStateException will be thrown.
 667      *
 668      * @param peerId
 669      * @param peerAddress
 670      */
 671     protected void setPeerAddress(String peerId, String peerAddress){
 672         context.setPeerAddress(peerId, peerAddress);
 673     }
 674
 675     /**
 676      * The applyState method will be called by the RaftActor when some data
 677      * needs to be applied to the actor's state
 678      *
 679      * @param clientActor A reference to the client who sent this message. This
 680      *                    is the same reference that was passed to persistData
 681      *                    by the derived actor. clientActor may be null when
 682      *                    the RaftActor is behaving as a follower or during
 683      *                    recovery.
 684      * @param identifier  The identifier of the persisted data. This is also
 685      *                    the same identifier that was passed to persistData by
 686      *                    the derived actor. identifier may be null when
 687      *                    the RaftActor is behaving as a follower or during
 688      *                    recovery
 689      * @param data        A piece of data that was persisted by the persistData call.
 690      *                    This should NEVER be null.
 691      */
 692     protected abstract void applyState(ActorRef clientActor, String identifier,
 693         Object data);
 694
 695     /**
 696      * Returns the RaftActorRecoveryCohort to participate in persistence recovery.
 697      */
 698     @Nonnull
 699     protected abstract RaftActorRecoveryCohort getRaftActorRecoveryCohort();
 700
 701     /**
 702      * This method is called when recovery is complete.
 703      */
 704     protected abstract void onRecoveryComplete();
 705
 706     /**
 707      * Returns the RaftActorSnapshotCohort to participate in persistence recovery.
 708      */
 709     @Nonnull
 710     protected abstract RaftActorSnapshotCohort getRaftActorSnapshotCohort();
 711
 712     /**
 713      * This method will be called by the RaftActor when the state of the
 714      * RaftActor changes. The derived actor can then use methods like
 715      * isLeader or getLeader to do something useful
 716      */
 717     protected abstract void onStateChanged();
 718
 719     /**
 720      * Notifier Actor for this RaftActor to notify when a role change happens
 721      * @return ActorRef - ActorRef of the notifier or Optional.absent if none.
 722      */
 723     protected abstract Optional<ActorRef> getRoleChangeNotifier();
 724
 725     /**
 726      * This method is called prior to operations such as leadership transfer and actor shutdown when the leader
 727      * must pause or stop its duties. This method allows derived classes to gracefully pause or finish current
 728      * work prior to performing the operation. On completion of any work, the run method must be called on the
 729      * given Runnable to proceed with the given operation. <b>Important:</b> the run method must be called on
 730      * this actor's thread dispatcher as as it modifies internal state.
 731      * <p>
 732      * The default implementation immediately runs the operation.
 733      *
 734      * @param operation the operation to run
 735      */
 736     protected void pauseLeader(Runnable operation) {
 737         operation.run();
 738     }
 739
 740     protected void onLeaderChanged(String oldLeader, String newLeader) {
 741
 742     };
 743
 744     private String getLeaderAddress(){
 745         if(isLeader()){
 746             return getSelf().path().toString();
 747         }
 748         String leaderId = getLeaderId();
 749         if (leaderId == null) {
 750             return null;
 751         }
 752         String peerAddress = context.getPeerAddress(leaderId);
 753         if(LOG.isDebugEnabled()) {
 754             LOG.debug("{}: getLeaderAddress leaderId = {} peerAddress = {}",
 755                     persistenceId(), leaderId, peerAddress);
 756         }
 757
 758         return peerAddress;
 759     }
 760
 761     protected boolean hasFollowers(){
 762         return getRaftActorContext().hasFollowers();
 763     }
 764
 765     private void captureSnapshot() {
 766         SnapshotManager snapshotManager = context.getSnapshotManager();
 767
 768         if (!snapshotManager.isCapturing()) {
 769             final long idx = getCurrentBehavior().getReplicatedToAllIndex();
 770             LOG.debug("Take a snapshot of current state. lastReplicatedLog is {} and replicatedToAllIndex is {}",
 771                 replicatedLog().last(), idx);
 772
 773             snapshotManager.capture(replicatedLog().last(), idx);
 774         }
 775     }
 776
 777     /**
 778      * @deprecated Deprecated in favor of {@link org.opendaylight.controller.cluster.raft.base.messages.DeleteEntries}
 779      *             whose type for fromIndex is long instead of int. This class was kept for backwards
 780      *             compatibility with Helium.
 781      */
 782     // Suppressing this warning as we can't set serialVersionUID to maintain backwards compatibility.
 783     @SuppressWarnings("serial")
 784     @Deprecated
 785     static class DeleteEntries implements Serializable {
 786         private final int fromIndex;
 787
 788         public DeleteEntries(int fromIndex) {
 789             this.fromIndex = fromIndex;
 790         }
 791
 792         public int getFromIndex() {
 793             return fromIndex;
 794         }
 795     }
 796
 797     /**
 798      * @deprecated Deprecated in favor of non-inner class {@link org.opendaylight.controller.cluster.raft.base.messages.UpdateElectionTerm}
 799      *             which has serialVersionUID set. This class was kept for backwards compatibility with Helium.
 800      */
 801     // Suppressing this warning as we can't set serialVersionUID to maintain backwards compatibility.
 802     @SuppressWarnings("serial")
 803     @Deprecated
 804     static class UpdateElectionTerm implements Serializable {
 805         private final long currentTerm;
 806         private final String votedFor;
 807
 808         public UpdateElectionTerm(long currentTerm, String votedFor) {
 809             this.currentTerm = currentTerm;
 810             this.votedFor = votedFor;
 811         }
 812
 813         public long getCurrentTerm() {
 814             return currentTerm;
 815         }
 816
 817         public String getVotedFor() {
 818             return votedFor;
 819         }
 820     }
 821
 822     private static class BehaviorStateHolder {
 823         private RaftActorBehavior behavior;
 824         private String lastValidLeaderId;
 825         private short leaderPayloadVersion;
 826
 827         void init(RaftActorBehavior behavior) {
 828             this.behavior = behavior;
 829             this.leaderPayloadVersion = behavior != null ? behavior.getLeaderPayloadVersion() : -1;
 830
 831             String behaviorLeaderId = behavior != null ? behavior.getLeaderId() : null;
 832             if(behaviorLeaderId != null) {
 833                 this.lastValidLeaderId = behaviorLeaderId;
 834             }
 835         }
 836
 837         RaftActorBehavior getBehavior() {
 838             return behavior;
 839         }
 840
 841         String getLastValidLeaderId() {
 842             return lastValidLeaderId;
 843         }
 844
 845         short getLeaderPayloadVersion() {
 846             return leaderPayloadVersion;
 847         }
 848     }
 849
 850     private class SwitchBehaviorSupplier implements Supplier<RaftActorBehavior> {
 851         private Object message;
 852         private ActorRef sender;
 853
 854         public SwitchBehaviorSupplier handleMessage(ActorRef sender, Object message){
 855             this.sender = sender;
 856             this.message = message;
 857             return this;
 858         }
 859
 860         @Override
 861         public RaftActorBehavior get() {
 862             if(this.message instanceof SwitchBehavior){
 863                 return AbstractRaftActorBehavior.createBehavior(context, ((SwitchBehavior) message).getNewState());
 864             }
 865             return getCurrentBehavior().handleMessage(sender, message);
 866         }
 867     }
 868 }