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