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     protected 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     protected void handleCommand(final Object message) {
 211         if (serverConfigurationSupport.handleMessage(message, getSender())) {
 212             return;
 213         }
 214         if (snapshotSupport.handleSnapshotMessage(message, getSender())) {
 215             return;
 216         }
 217
 218         if (message instanceof ApplyState) {
 219             ApplyState applyState = (ApplyState) message;
 220
 221             long elapsedTime = (System.nanoTime() - applyState.getStartTime());
 222             if(elapsedTime >= APPLY_STATE_DELAY_THRESHOLD_IN_NANOS){
 223                 LOG.warn("ApplyState took more time than expected. Elapsed Time = {} ms ApplyState = {}",
 224                         TimeUnit.NANOSECONDS.toMillis(elapsedTime), applyState);
 225             }
 226
 227             if(LOG.isDebugEnabled()) {
 228                 LOG.debug("{}: Applying state for log index {} data {}",
 229                     persistenceId(), applyState.getReplicatedLogEntry().getIndex(),
 230                     applyState.getReplicatedLogEntry().getData());
 231             }
 232
 233             applyState(applyState.getClientActor(), applyState.getIdentifier(),
 234                 applyState.getReplicatedLogEntry().getData());
 235
 236             if (!hasFollowers()) {
 237                 // for single node, the capture should happen after the apply state
 238                 // as we delete messages from the persistent journal which have made it to the snapshot
 239                 // capturing the snapshot before applying makes the persistent journal and snapshot out of sync
 240                 // and recovery shows data missing
 241                 context.getReplicatedLog().captureSnapshotIfReady(applyState.getReplicatedLogEntry());
 242
 243                 context.getSnapshotManager().trimLog(context.getLastApplied(), currentBehavior);
 244             }
 245
 246         } else if (message instanceof ApplyJournalEntries) {
 247             ApplyJournalEntries applyEntries = (ApplyJournalEntries) message;
 248             if(LOG.isDebugEnabled()) {
 249                 LOG.debug("{}: Persisting ApplyLogEntries with index={}", persistenceId(), applyEntries.getToIndex());
 250             }
 251
 252             persistence().persist(applyEntries, NoopProcedure.instance());
 253
 254         } else if (message instanceof FindLeader) {
 255             getSender().tell(
 256                 new FindLeaderReply(getLeaderAddress()),
 257                 getSelf()
 258             );
 259         } else if(message instanceof GetOnDemandRaftState) {
 260             onGetOnDemandRaftStats();
 261         } else if(message instanceof InitiateCaptureSnapshot) {
 262             captureSnapshot();
 263         } else if(message instanceof SwitchBehavior) {
 264             switchBehavior(((SwitchBehavior) message));
 265         } else if(message instanceof LeaderTransitioning) {
 266             onLeaderTransitioning();
 267         } else if(message instanceof Shutdown) {
 268             onShutDown();
 269         } else if(message instanceof Runnable) {
 270             ((Runnable)message).run();
 271         } else {
 272             switchBehavior(reusableSwitchBehaviorSupplier.handleMessage(getSender(), message));
 273         }
 274     }
 275
 276     void initiateLeadershipTransfer(final RaftActorLeadershipTransferCohort.OnComplete onComplete) {
 277         LOG.debug("{}: Initiating leader transfer", persistenceId());
 278
 279         if(leadershipTransferInProgress == null) {
 280             leadershipTransferInProgress = new RaftActorLeadershipTransferCohort(this, getSender());
 281             leadershipTransferInProgress.addOnComplete(new RaftActorLeadershipTransferCohort.OnComplete() {
 282                 @Override
 283                 public void onSuccess(ActorRef raftActorRef, ActorRef replyTo) {
 284                     leadershipTransferInProgress = null;
 285                 }
 286
 287                 @Override
 288                 public void onFailure(ActorRef raftActorRef, ActorRef replyTo) {
 289                     leadershipTransferInProgress = null;
 290                 }
 291             });
 292
 293             leadershipTransferInProgress.addOnComplete(onComplete);
 294             leadershipTransferInProgress.init();
 295         } else {
 296             LOG.debug("{}: prior leader transfer in progress - adding callback", persistenceId());
 297             leadershipTransferInProgress.addOnComplete(onComplete);
 298         }
 299     }
 300
 301     private void onShutDown() {
 302         LOG.debug("{}: onShutDown", persistenceId());
 303
 304         if(shuttingDown) {
 305             return;
 306         }
 307
 308         shuttingDown = true;
 309         if(currentBehavior.state() == RaftState.Leader && context.hasFollowers()) {
 310             initiateLeadershipTransfer(new RaftActorLeadershipTransferCohort.OnComplete() {
 311                 @Override
 312                 public void onSuccess(ActorRef raftActorRef, ActorRef replyTo) {
 313                     LOG.debug("{}: leader transfer succeeded - sending PoisonPill", persistenceId());
 314                     raftActorRef.tell(PoisonPill.getInstance(), raftActorRef);
 315                 }
 316
 317                 @Override
 318                 public void onFailure(ActorRef raftActorRef, ActorRef replyTo) {
 319                     LOG.debug("{}: leader transfer failed - sending PoisonPill", persistenceId());
 320                     raftActorRef.tell(PoisonPill.getInstance(), raftActorRef);
 321                 }
 322             });
 323         } else if(currentBehavior.state() == RaftState.Leader) {
 324             pauseLeader(new TimedRunnable(context.getConfigParams().getElectionTimeOutInterval(), this) {
 325                 @Override
 326                 protected void doRun() {
 327                     self().tell(PoisonPill.getInstance(), self());
 328                 }
 329
 330                 @Override
 331                 protected void doCancel() {
 332                     self().tell(PoisonPill.getInstance(), self());
 333                 }
 334             });
 335         } else {
 336             self().tell(PoisonPill.getInstance(), self());
 337         }
 338     }
 339
 340     private void onLeaderTransitioning() {
 341         LOG.debug("{}: onLeaderTransitioning", persistenceId());
 342         Optional<ActorRef> roleChangeNotifier = getRoleChangeNotifier();
 343         if(currentBehavior.state() == RaftState.Follower && roleChangeNotifier.isPresent()) {
 344             roleChangeNotifier.get().tell(newLeaderStateChanged(getId(), null,
 345                     currentBehavior.getLeaderPayloadVersion()), getSelf());
 346         }
 347     }
 348
 349     private void switchBehavior(SwitchBehavior message) {
 350         if(!getRaftActorContext().getRaftPolicy().automaticElectionsEnabled()) {
 351             RaftState newState = message.getNewState();
 352             if( newState == RaftState.Leader || newState == RaftState.Follower) {
 353                 switchBehavior(reusableSwitchBehaviorSupplier.handleMessage(getSender(), message));
 354                 getRaftActorContext().getTermInformation().updateAndPersist(message.getNewTerm(), "");
 355             } else {
 356                 LOG.warn("Switching to behavior : {} - not supported", newState);
 357             }
 358         }
 359     }
 360
 361     private void switchBehavior(Supplier<RaftActorBehavior> supplier){
 362         reusableBehaviorStateHolder.init(getCurrentBehavior());
 363
 364         setCurrentBehavior(supplier.get());
 365
 366         handleBehaviorChange(reusableBehaviorStateHolder, getCurrentBehavior());
 367     }
 368
 369     protected RaftActorSnapshotMessageSupport newRaftActorSnapshotMessageSupport() {
 370         return new RaftActorSnapshotMessageSupport(context, currentBehavior,
 371                 getRaftActorSnapshotCohort());
 372     }
 373
 374     private void onGetOnDemandRaftStats() {
 375         // Debugging message to retrieve raft stats.
 376
 377         Map<String, String> peerAddresses = new HashMap<>();
 378         for(String peerId: context.getPeerIds()) {
 379             peerAddresses.put(peerId, context.getPeerAddress(peerId));
 380         }
 381
 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 = getLastLogEntry();
 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
 449         if (roleChangeNotifier.isPresent() &&
 450                 (oldBehavior == null || (oldBehavior.state() != currentBehavior.state()))) {
 451             roleChangeNotifier.get().tell(new RoleChanged(getId(), oldBehaviorStateName ,
 452                     currentBehavior.state().name()), getSelf());
 453         }
 454     }
 455
 456     protected LeaderStateChanged newLeaderStateChanged(String memberId, String leaderId, short leaderPayloadVersion) {
 457         return new LeaderStateChanged(memberId, leaderId, leaderPayloadVersion);
 458     }
 459
 460     @Override
 461     public long snapshotSequenceNr() {
 462         // When we do a snapshot capture, we also capture and save the sequence-number of the persistent journal,
 463         // so that we can delete the persistent journal based on the saved sequence-number
 464         // However , when akka replays the journal during recovery, it replays it from the sequence number when the snapshot
 465         // was saved and not the number we saved.
 466         // We would want to override it , by asking akka to use the last-sequence number known to us.
 467         return context.getSnapshotManager().getLastSequenceNumber();
 468     }
 469
 470     /**
 471      * When a derived RaftActor needs to persist something it must call
 472      * persistData.
 473      *
 474      * @param clientActor
 475      * @param identifier
 476      * @param data
 477      */
 478     protected void persistData(final ActorRef clientActor, final String identifier,
 479         final Payload data) {
 480
 481         ReplicatedLogEntry replicatedLogEntry = new ReplicatedLogImplEntry(
 482             context.getReplicatedLog().lastIndex() + 1,
 483             context.getTermInformation().getCurrentTerm(), data);
 484
 485         if(LOG.isDebugEnabled()) {
 486             LOG.debug("{}: Persist data {}", persistenceId(), replicatedLogEntry);
 487         }
 488
 489         final RaftActorContext raftContext = getRaftActorContext();
 490
 491         replicatedLog().appendAndPersist(replicatedLogEntry, new Procedure<ReplicatedLogEntry>() {
 492             @Override
 493             public void apply(ReplicatedLogEntry replicatedLogEntry) {
 494                 if (!hasFollowers()){
 495                     // Increment the Commit Index and the Last Applied values
 496                     raftContext.setCommitIndex(replicatedLogEntry.getIndex());
 497                     raftContext.setLastApplied(replicatedLogEntry.getIndex());
 498
 499                     // Apply the state immediately.
 500                     self().tell(new ApplyState(clientActor, identifier, replicatedLogEntry), self());
 501
 502                     // Send a ApplyJournalEntries message so that we write the fact that we applied
 503                     // the state to durable storage
 504                     self().tell(new ApplyJournalEntries(replicatedLogEntry.getIndex()), self());
 505
 506                 } else if (clientActor != null) {
 507                     context.getReplicatedLog().captureSnapshotIfReady(replicatedLogEntry);
 508
 509                     // Send message for replication
 510                     currentBehavior.handleMessage(getSelf(),
 511                             new Replicate(clientActor, identifier, replicatedLogEntry));
 512                 }
 513             }
 514         });
 515     }
 516
 517     private ReplicatedLog replicatedLog() {
 518         return context.getReplicatedLog();
 519     }
 520
 521     protected String getId() {
 522         return context.getId();
 523     }
 524
 525     @VisibleForTesting
 526     void setCurrentBehavior(RaftActorBehavior behavior) {
 527         currentBehavior.setDelegate(behavior);
 528     }
 529
 530     protected RaftActorBehavior getCurrentBehavior() {
 531         return currentBehavior.getDelegate();
 532     }
 533
 534     /**
 535      * Derived actors can call the isLeader method to check if the current
 536      * RaftActor is the Leader or not
 537      *
 538      * @return true it this RaftActor is a Leader false otherwise
 539      */
 540     protected boolean isLeader() {
 541         return context.getId().equals(currentBehavior.getLeaderId());
 542     }
 543
 544     protected boolean isLeaderActive() {
 545         return currentBehavior.state() != RaftState.IsolatedLeader && !shuttingDown &&
 546                 !isLeadershipTransferInProgress();
 547     }
 548
 549     private boolean isLeadershipTransferInProgress() {
 550         return leadershipTransferInProgress != null && leadershipTransferInProgress.isTransferring();
 551     }
 552
 553     /**
 554      * Derived actor can call getLeader if they need a reference to the Leader.
 555      * This would be useful for example in forwarding a request to an actor
 556      * which is the leader
 557      *
 558      * @return A reference to the leader if known, null otherwise
 559      */
 560     protected ActorSelection getLeader(){
 561         String leaderAddress = getLeaderAddress();
 562
 563         if(leaderAddress == null){
 564             return null;
 565         }
 566
 567         return context.actorSelection(leaderAddress);
 568     }
 569
 570     /**
 571      *
 572      * @return the current leader's id
 573      */
 574     protected String getLeaderId(){
 575         return currentBehavior.getLeaderId();
 576     }
 577
 578     protected RaftState getRaftState() {
 579         return currentBehavior.state();
 580     }
 581
 582     protected ReplicatedLogEntry getLastLogEntry() {
 583         return replicatedLog().last();
 584     }
 585
 586     protected Long getCurrentTerm(){
 587         return context.getTermInformation().getCurrentTerm();
 588     }
 589
 590     protected Long getCommitIndex(){
 591         return context.getCommitIndex();
 592     }
 593
 594     protected Long getLastApplied(){
 595         return context.getLastApplied();
 596     }
 597
 598     protected RaftActorContext getRaftActorContext() {
 599         return context;
 600     }
 601
 602     protected void updateConfigParams(ConfigParams configParams) {
 603
 604         // obtain the RaftPolicy for oldConfigParams and the updated one.
 605         String oldRaftPolicy = context.getConfigParams().
 606             getCustomRaftPolicyImplementationClass();
 607         String newRaftPolicy = configParams.
 608             getCustomRaftPolicyImplementationClass();
 609
 610         LOG.debug("{}: RaftPolicy used with prev.config {}, RaftPolicy used with newConfig {}", persistenceId(),
 611             oldRaftPolicy, newRaftPolicy);
 612         context.setConfigParams(configParams);
 613         if (!Objects.equal(oldRaftPolicy, newRaftPolicy)) {
 614             // The RaftPolicy was modified. If the current behavior is Follower then re-initialize to Follower
 615             // but transfer the previous leaderId so it doesn't immediately try to schedule an election. This
 616             // avoids potential disruption. Otherwise, switch to Follower normally.
 617             RaftActorBehavior behavior = currentBehavior.getDelegate();
 618             if(behavior instanceof Follower) {
 619                 String previousLeaderId = ((Follower)behavior).getLeaderId();
 620                 short previousLeaderPayloadVersion = behavior.getLeaderPayloadVersion();
 621
 622                 LOG.debug("{}: Re-initializing to Follower with previous leaderId {}", persistenceId(), previousLeaderId);
 623
 624                 changeCurrentBehavior(new Follower(context, previousLeaderId, previousLeaderPayloadVersion));
 625             } else {
 626                 initializeBehavior();
 627             }
 628         }
 629     }
 630
 631     public final DataPersistenceProvider persistence() {
 632         return delegatingPersistenceProvider.getDelegate();
 633     }
 634
 635     public void setPersistence(DataPersistenceProvider provider) {
 636         delegatingPersistenceProvider.setDelegate(provider);
 637     }
 638
 639     protected void setPersistence(boolean persistent) {
 640         if(persistent) {
 641             setPersistence(new PersistentDataProvider(this));
 642         } else {
 643             setPersistence(new NonPersistentDataProvider() {
 644                 /**
 645                  * The way snapshotting works is,
 646                  * <ol>
 647                  * <li> RaftActor calls createSnapshot on the Shard
 648                  * <li> Shard sends a CaptureSnapshotReply and RaftActor then calls saveSnapshot
 649                  * <li> When saveSnapshot is invoked on the akka-persistence API it uses the SnapshotStore to save
 650                  * the snapshot. The SnapshotStore sends SaveSnapshotSuccess or SaveSnapshotFailure. When the
 651                  * RaftActor gets SaveSnapshot success it commits the snapshot to the in-memory journal. This
 652                  * commitSnapshot is mimicking what is done in SaveSnapshotSuccess.
 653                  * </ol>
 654                  */
 655                 @Override
 656                 public void saveSnapshot(Object o) {
 657                     // Make saving Snapshot successful
 658                     // Committing the snapshot here would end up calling commit in the creating state which would
 659                     // be a state violation. That's why now we send a message to commit the snapshot.
 660                     self().tell(RaftActorSnapshotMessageSupport.COMMIT_SNAPSHOT, self());
 661                 }
 662             });
 663         }
 664     }
 665
 666     /**
 667      * setPeerAddress sets the address of a known peer at a later time.
 668      * <p>
 669      * This is to account for situations where a we know that a peer
 670      * exists but we do not know an address up-front. This may also be used in
 671      * situations where a known peer starts off in a different location and we
 672      * need to change it's address
 673      * <p>
 674      * Note that if the peerId does not match the list of peers passed to
 675      * this actor during construction an IllegalStateException will be thrown.
 676      *
 677      * @param peerId
 678      * @param peerAddress
 679      */
 680     protected void setPeerAddress(String peerId, String peerAddress){
 681         context.setPeerAddress(peerId, peerAddress);
 682     }
 683
 684     /**
 685      * The applyState method will be called by the RaftActor when some data
 686      * needs to be applied to the actor's state
 687      *
 688      * @param clientActor A reference to the client who sent this message. This
 689      *                    is the same reference that was passed to persistData
 690      *                    by the derived actor. clientActor may be null when
 691      *                    the RaftActor is behaving as a follower or during
 692      *                    recovery.
 693      * @param identifier  The identifier of the persisted data. This is also
 694      *                    the same identifier that was passed to persistData by
 695      *                    the derived actor. identifier may be null when
 696      *                    the RaftActor is behaving as a follower or during
 697      *                    recovery
 698      * @param data        A piece of data that was persisted by the persistData call.
 699      *                    This should NEVER be null.
 700      */
 701     protected abstract void applyState(ActorRef clientActor, String identifier,
 702         Object data);
 703
 704     /**
 705      * Returns the RaftActorRecoveryCohort to participate in persistence recovery.
 706      */
 707     @Nonnull
 708     protected abstract RaftActorRecoveryCohort getRaftActorRecoveryCohort();
 709
 710     /**
 711      * This method is called when recovery is complete.
 712      */
 713     protected abstract void onRecoveryComplete();
 714
 715     /**
 716      * Returns the RaftActorSnapshotCohort to participate in persistence recovery.
 717      */
 718     @Nonnull
 719     protected abstract RaftActorSnapshotCohort getRaftActorSnapshotCohort();
 720
 721     /**
 722      * This method will be called by the RaftActor when the state of the
 723      * RaftActor changes. The derived actor can then use methods like
 724      * isLeader or getLeader to do something useful
 725      */
 726     protected abstract void onStateChanged();
 727
 728     /**
 729      * Notifier Actor for this RaftActor to notify when a role change happens
 730      * @return ActorRef - ActorRef of the notifier or Optional.absent if none.
 731      */
 732     protected abstract Optional<ActorRef> getRoleChangeNotifier();
 733
 734     /**
 735      * This method is called prior to operations such as leadership transfer and actor shutdown when the leader
 736      * must pause or stop its duties. This method allows derived classes to gracefully pause or finish current
 737      * work prior to performing the operation. On completion of any work, the run method must be called on the
 738      * given Runnable to proceed with the given operation. <b>Important:</b> the run method must be called on
 739      * this actor's thread dispatcher as as it modifies internal state.
 740      * <p>
 741      * The default implementation immediately runs the operation.
 742      *
 743      * @param operation the operation to run
 744      */
 745     protected void pauseLeader(Runnable operation) {
 746         operation.run();
 747     }
 748
 749     protected void onLeaderChanged(String oldLeader, String newLeader){};
 750
 751     private String getLeaderAddress(){
 752         if(isLeader()){
 753             return getSelf().path().toString();
 754         }
 755         String leaderId = currentBehavior.getLeaderId();
 756         if (leaderId == null) {
 757             return null;
 758         }
 759         String peerAddress = context.getPeerAddress(leaderId);
 760         if(LOG.isDebugEnabled()) {
 761             LOG.debug("{}: getLeaderAddress leaderId = {} peerAddress = {}",
 762                     persistenceId(), leaderId, peerAddress);
 763         }
 764
 765         return peerAddress;
 766     }
 767
 768     protected boolean hasFollowers(){
 769         return getRaftActorContext().hasFollowers();
 770     }
 771
 772     private void captureSnapshot() {
 773         SnapshotManager snapshotManager = context.getSnapshotManager();
 774
 775         if(!snapshotManager.isCapturing()) {
 776             LOG.debug("Take a snapshot of current state. lastReplicatedLog is {} and replicatedToAllIndex is {}",
 777                 replicatedLog().last(), currentBehavior.getReplicatedToAllIndex());
 778
 779             snapshotManager.capture(replicatedLog().last(), currentBehavior.getReplicatedToAllIndex());
 780         }
 781     }
 782
 783     /**
 784      * @deprecated Deprecated in favor of {@link org.opendaylight.controller.cluster.raft.base.messages.DeleteEntries}
 785      *             whose type for fromIndex is long instead of int. This class was kept for backwards
 786      *             compatibility with Helium.
 787      */
 788     // Suppressing this warning as we can't set serialVersionUID to maintain backwards compatibility.
 789     @SuppressWarnings("serial")
 790     @Deprecated
 791     static class DeleteEntries implements Serializable {
 792         private final int fromIndex;
 793
 794         public DeleteEntries(int fromIndex) {
 795             this.fromIndex = fromIndex;
 796         }
 797
 798         public int getFromIndex() {
 799             return fromIndex;
 800         }
 801     }
 802
 803     /**
 804      * @deprecated Deprecated in favor of non-inner class {@link org.opendaylight.controller.cluster.raft.base.messages.UpdateElectionTerm}
 805      *             which has serialVersionUID set. This class was kept for backwards compatibility with Helium.
 806      */
 807     // Suppressing this warning as we can't set serialVersionUID to maintain backwards compatibility.
 808     @SuppressWarnings("serial")
 809     @Deprecated
 810     static class UpdateElectionTerm implements Serializable {
 811         private final long currentTerm;
 812         private final String votedFor;
 813
 814         public UpdateElectionTerm(long currentTerm, String votedFor) {
 815             this.currentTerm = currentTerm;
 816             this.votedFor = votedFor;
 817         }
 818
 819         public long getCurrentTerm() {
 820             return currentTerm;
 821         }
 822
 823         public String getVotedFor() {
 824             return votedFor;
 825         }
 826     }
 827
 828     private static class BehaviorStateHolder {
 829         private RaftActorBehavior behavior;
 830         private String lastValidLeaderId;
 831         private short leaderPayloadVersion;
 832
 833         void init(RaftActorBehavior behavior) {
 834             this.behavior = behavior;
 835             this.leaderPayloadVersion = behavior != null ? behavior.getLeaderPayloadVersion() : -1;
 836
 837             String behaviorLeaderId = behavior != null ? behavior.getLeaderId() : null;
 838             if(behaviorLeaderId != null) {
 839                 this.lastValidLeaderId = behaviorLeaderId;
 840             }
 841         }
 842
 843         RaftActorBehavior getBehavior() {
 844             return behavior;
 845         }
 846
 847         String getLastValidLeaderId() {
 848             return lastValidLeaderId;
 849         }
 850
 851         short getLeaderPayloadVersion() {
 852             return leaderPayloadVersion;
 853         }
 854     }
 855
 856     private class SwitchBehaviorSupplier implements Supplier<RaftActorBehavior> {
 857         private Object message;
 858         private ActorRef sender;
 859
 860         public SwitchBehaviorSupplier handleMessage(ActorRef sender, Object message){
 861             this.sender = sender;
 862             this.message = message;
 863             return this;
 864         }
 865
 866         @Override
 867         public RaftActorBehavior get() {
 868             if(this.message instanceof SwitchBehavior){
 869                 return ((SwitchBehavior) message).getNewState().createBehavior(getRaftActorContext());
 870             }
 871             return currentBehavior.handleMessage(sender, message);
 872         }
 873     }
 874 }