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.
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
10 package org.opendaylight.controller.cluster.raft;
12 import akka.actor.ActorRef;
13 import akka.actor.ActorSelection;
14 import akka.actor.PoisonPill;
15 import com.google.common.annotations.VisibleForTesting;
16 import com.google.common.base.Optional;
17 import com.google.common.base.Preconditions;
18 import com.google.common.base.Verify;
19 import com.google.common.collect.Lists;
20 import java.util.Collection;
21 import java.util.HashMap;
22 import java.util.List;
24 import java.util.Objects;
25 import java.util.concurrent.TimeUnit;
26 import javax.annotation.Nonnull;
27 import javax.annotation.Nullable;
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.ApplyState;
37 import org.opendaylight.controller.cluster.raft.base.messages.CheckConsensusReached;
38 import org.opendaylight.controller.cluster.raft.base.messages.InitiateCaptureSnapshot;
39 import org.opendaylight.controller.cluster.raft.base.messages.LeaderTransitioning;
40 import org.opendaylight.controller.cluster.raft.base.messages.Replicate;
41 import org.opendaylight.controller.cluster.raft.base.messages.SwitchBehavior;
42 import org.opendaylight.controller.cluster.raft.behaviors.AbstractLeader;
43 import org.opendaylight.controller.cluster.raft.behaviors.AbstractRaftActorBehavior;
44 import org.opendaylight.controller.cluster.raft.behaviors.Follower;
45 import org.opendaylight.controller.cluster.raft.behaviors.RaftActorBehavior;
46 import org.opendaylight.controller.cluster.raft.client.messages.FindLeader;
47 import org.opendaylight.controller.cluster.raft.client.messages.FindLeaderReply;
48 import org.opendaylight.controller.cluster.raft.client.messages.FollowerInfo;
49 import org.opendaylight.controller.cluster.raft.client.messages.GetOnDemandRaftState;
50 import org.opendaylight.controller.cluster.raft.client.messages.OnDemandRaftState;
51 import org.opendaylight.controller.cluster.raft.client.messages.Shutdown;
52 import org.opendaylight.controller.cluster.raft.persisted.ApplyJournalEntries;
53 import org.opendaylight.controller.cluster.raft.persisted.NoopPayload;
54 import org.opendaylight.controller.cluster.raft.persisted.SimpleReplicatedLogEntry;
55 import org.opendaylight.controller.cluster.raft.protobuff.client.messages.Payload;
56 import org.opendaylight.yangtools.concepts.Identifier;
57 import org.opendaylight.yangtools.concepts.Immutable;
60 * RaftActor encapsulates a state machine that needs to be kept synchronized
61 * in a cluster. It implements the RAFT algorithm as described in the paper
62 * <a href='https://ramcloud.stanford.edu/wiki/download/attachments/11370504/raft.pdf'>
63 * In Search of an Understandable Consensus Algorithm</a>
66 * RaftActor has 3 states and each state has a certain behavior associated
67 * with it. A Raft actor can behave as,
70 * <li> A Follower (or) </li>
71 * <li> A Candidate </li>
75 * A RaftActor MUST be a Leader in order to accept requests from clients to
76 * change the state of it's encapsulated state machine. Once a RaftActor becomes
77 * a Leader it is also responsible for ensuring that all followers ultimately
78 * have the same log and therefore the same state machine as itself.
81 * The current behavior of a RaftActor determines how election for leadership
82 * is initiated and how peer RaftActors react to request for votes.
85 * Each RaftActor also needs to know the current election term. It uses this
86 * information for a couple of things. One is to simply figure out who it
87 * voted for in the last election. Another is to figure out if the message
88 * it received to update it's state is stale.
91 * The RaftActor uses akka-persistence to store it's replicated log.
92 * Furthermore through it's behaviors a Raft Actor determines
94 * <li> when a log entry should be persisted </li>
95 * <li> when a log entry should be applied to the state machine (and) </li>
96 * <li> when a snapshot should be saved </li>
99 public abstract class RaftActor extends AbstractUntypedPersistentActor {
101 private static final long APPLY_STATE_DELAY_THRESHOLD_IN_NANOS = TimeUnit.MILLISECONDS.toNanos(50L); // 50 millis
104 * This context should NOT be passed directly to any other actor it is
105 * only to be consumed by the RaftActorBehaviors.
107 private final RaftActorContextImpl context;
109 private final DelegatingPersistentDataProvider delegatingPersistenceProvider;
111 private final PersistentDataProvider persistentProvider;
113 private final BehaviorStateTracker behaviorStateTracker = new BehaviorStateTracker();
115 private RaftActorRecoverySupport raftRecovery;
117 private RaftActorSnapshotMessageSupport snapshotSupport;
119 private RaftActorServerConfigurationSupport serverConfigurationSupport;
121 private RaftActorLeadershipTransferCohort leadershipTransferInProgress;
123 private boolean shuttingDown;
125 protected RaftActor(String id, Map<String, String> peerAddresses,
126 Optional<ConfigParams> configParams, short payloadVersion) {
128 persistentProvider = new PersistentDataProvider(this);
129 delegatingPersistenceProvider = new RaftActorDelegatingPersistentDataProvider(null, persistentProvider);
131 context = new RaftActorContextImpl(this.getSelf(),
132 this.getContext(), id, new ElectionTermImpl(persistentProvider, id, LOG),
133 -1, -1, peerAddresses,
134 configParams.isPresent() ? configParams.get() : new DefaultConfigParamsImpl(),
135 delegatingPersistenceProvider, LOG);
137 context.setPayloadVersion(payloadVersion);
138 context.setReplicatedLog(ReplicatedLogImpl.newInstance(context));
142 public void preStart() throws Exception {
143 LOG.info("Starting recovery for {} with journal batch size {}", persistenceId(),
144 context.getConfigParams().getJournalRecoveryLogBatchSize());
148 snapshotSupport = newRaftActorSnapshotMessageSupport();
149 serverConfigurationSupport = new RaftActorServerConfigurationSupport(this);
153 public void postStop() {
159 protected void handleRecover(Object message) {
160 if (raftRecovery == null) {
161 raftRecovery = newRaftActorRecoverySupport();
164 boolean recoveryComplete = raftRecovery.handleRecoveryMessage(message, persistentProvider);
165 if (recoveryComplete) {
166 onRecoveryComplete();
168 initializeBehavior();
174 protected RaftActorRecoverySupport newRaftActorRecoverySupport() {
175 return new RaftActorRecoverySupport(context, getRaftActorRecoveryCohort());
179 void initializeBehavior() {
180 changeCurrentBehavior(new Follower(context));
184 @SuppressWarnings("checkstyle:IllegalCatch")
185 protected void changeCurrentBehavior(RaftActorBehavior newBehavior) {
186 final RaftActorBehavior currentBehavior = getCurrentBehavior();
187 if (currentBehavior != null) {
189 currentBehavior.close();
190 } catch (Exception e) {
191 LOG.warn("{}: Error closing behavior {}", persistence(), currentBehavior, e);
195 final BehaviorState state = behaviorStateTracker.capture(currentBehavior);
196 setCurrentBehavior(newBehavior);
197 handleBehaviorChange(state, newBehavior);
201 * Method exposed for subclasses to plug-in their logic. This method is invoked by {@link #handleCommand(Object)}
202 * for messages which are not handled by this class. Subclasses overriding this class should fall back to this
203 * implementation for messages which they do not handle
205 * @param message Incoming command message
207 protected void handleNonRaftCommand(final Object message) {
214 * @deprecated This method is not final for testing purposes. DO NOT OVERRIDE IT, override
215 * {@link #handleNonRaftCommand(Object)} instead.
219 // FIXME: make this method final once our unit tests do not need to override it
220 protected void handleCommand(final Object message) {
221 if (serverConfigurationSupport.handleMessage(message, getSender())) {
224 if (snapshotSupport.handleSnapshotMessage(message, getSender())) {
228 if (message instanceof ApplyState) {
229 ApplyState applyState = (ApplyState) message;
231 long startTime = System.nanoTime();
233 if (LOG.isDebugEnabled()) {
234 LOG.debug("{}: Applying state for log index {} data {}",
235 persistenceId(), applyState.getReplicatedLogEntry().getIndex(),
236 applyState.getReplicatedLogEntry().getData());
239 if (!(applyState.getReplicatedLogEntry().getData() instanceof NoopPayload)) {
240 applyState(applyState.getClientActor(), applyState.getIdentifier(),
241 applyState.getReplicatedLogEntry().getData());
244 long elapsedTime = System.nanoTime() - startTime;
245 if (elapsedTime >= APPLY_STATE_DELAY_THRESHOLD_IN_NANOS) {
246 LOG.debug("ApplyState took more time than expected. Elapsed Time = {} ms ApplyState = {}",
247 TimeUnit.NANOSECONDS.toMillis(elapsedTime), applyState);
250 if (!hasFollowers()) {
251 // for single node, the capture should happen after the apply state
252 // as we delete messages from the persistent journal which have made it to the snapshot
253 // capturing the snapshot before applying makes the persistent journal and snapshot out of sync
254 // and recovery shows data missing
255 context.getReplicatedLog().captureSnapshotIfReady(applyState.getReplicatedLogEntry());
257 context.getSnapshotManager().trimLog(context.getLastApplied());
260 // Send it to the current behavior - some behaviors like PreLeader need to be notified of ApplyState.
261 possiblyHandleBehaviorMessage(message);
263 } else if (message instanceof ApplyJournalEntries) {
264 ApplyJournalEntries applyEntries = (ApplyJournalEntries) message;
265 LOG.debug("{}: Persisting ApplyJournalEntries with index={}", persistenceId(), applyEntries.getToIndex());
267 persistence().persistAsync(applyEntries, NoopProcedure.instance());
269 } else if (message instanceof FindLeader) {
271 new FindLeaderReply(getLeaderAddress()),
274 } else if (message instanceof GetOnDemandRaftState) {
275 onGetOnDemandRaftStats();
276 } else if (message instanceof InitiateCaptureSnapshot) {
278 } else if (message instanceof SwitchBehavior) {
279 switchBehavior((SwitchBehavior) message);
280 } else if (message instanceof LeaderTransitioning) {
281 onLeaderTransitioning();
282 } else if (message instanceof Shutdown) {
284 } else if (message instanceof Runnable) {
285 ((Runnable)message).run();
286 } else if (message instanceof NoopPayload) {
287 persistData(null, null, (NoopPayload)message, false);
288 } else if (!possiblyHandleBehaviorMessage(message)) {
289 handleNonRaftCommand(message);
293 private boolean possiblyHandleBehaviorMessage(final Object message) {
294 final RaftActorBehavior currentBehavior = getCurrentBehavior();
295 final BehaviorState state = behaviorStateTracker.capture(currentBehavior);
297 // A behavior indicates that it processed the change by returning a reference to the next behavior
298 // to be used. A null return indicates it has not processed the message and we should be passing it to
299 // the subclass for handling.
300 final RaftActorBehavior nextBehavior = currentBehavior.handleMessage(getSender(), message);
301 if (nextBehavior != null) {
302 switchBehavior(state, nextBehavior);
309 private void initiateLeadershipTransfer(final RaftActorLeadershipTransferCohort.OnComplete onComplete) {
310 LOG.debug("{}: Initiating leader transfer", persistenceId());
312 if (leadershipTransferInProgress == null) {
313 leadershipTransferInProgress = new RaftActorLeadershipTransferCohort(this);
314 leadershipTransferInProgress.addOnComplete(new RaftActorLeadershipTransferCohort.OnComplete() {
316 public void onSuccess(ActorRef raftActorRef) {
317 leadershipTransferInProgress = null;
321 public void onFailure(ActorRef raftActorRef) {
322 leadershipTransferInProgress = null;
326 leadershipTransferInProgress.addOnComplete(onComplete);
327 leadershipTransferInProgress.init();
329 LOG.debug("{}: prior leader transfer in progress - adding callback", persistenceId());
330 leadershipTransferInProgress.addOnComplete(onComplete);
334 private void onShutDown() {
335 LOG.debug("{}: onShutDown", persistenceId());
343 final RaftActorBehavior currentBehavior = context.getCurrentBehavior();
344 if (currentBehavior.state() != RaftState.Leader) {
345 // For non-leaders shutdown is a no-op
346 self().tell(PoisonPill.getInstance(), self());
350 if (context.hasFollowers()) {
351 initiateLeadershipTransfer(new RaftActorLeadershipTransferCohort.OnComplete() {
353 public void onSuccess(ActorRef raftActorRef) {
354 LOG.debug("{}: leader transfer succeeded - sending PoisonPill", persistenceId());
355 raftActorRef.tell(PoisonPill.getInstance(), raftActorRef);
359 public void onFailure(ActorRef raftActorRef) {
360 LOG.debug("{}: leader transfer failed - sending PoisonPill", persistenceId());
361 raftActorRef.tell(PoisonPill.getInstance(), raftActorRef);
365 pauseLeader(new TimedRunnable(context.getConfigParams().getElectionTimeOutInterval(), this) {
367 protected void doRun() {
368 self().tell(PoisonPill.getInstance(), self());
372 protected void doCancel() {
373 self().tell(PoisonPill.getInstance(), self());
379 private void onLeaderTransitioning() {
380 LOG.debug("{}: onLeaderTransitioning", persistenceId());
381 Optional<ActorRef> roleChangeNotifier = getRoleChangeNotifier();
382 if (getRaftState() == RaftState.Follower && roleChangeNotifier.isPresent()) {
383 roleChangeNotifier.get().tell(newLeaderStateChanged(getId(), null,
384 getCurrentBehavior().getLeaderPayloadVersion()), getSelf());
388 private void switchBehavior(SwitchBehavior message) {
389 if (!getRaftActorContext().getRaftPolicy().automaticElectionsEnabled()) {
390 RaftState newState = message.getNewState();
391 if ( newState == RaftState.Leader || newState == RaftState.Follower) {
392 switchBehavior(behaviorStateTracker.capture(getCurrentBehavior()),
393 AbstractRaftActorBehavior.createBehavior(context, message.getNewState()));
394 getRaftActorContext().getTermInformation().updateAndPersist(message.getNewTerm(), "");
396 LOG.warn("Switching to behavior : {} - not supported", newState);
401 private void switchBehavior(final BehaviorState oldBehaviorState, final RaftActorBehavior nextBehavior) {
402 setCurrentBehavior(nextBehavior);
403 handleBehaviorChange(oldBehaviorState, nextBehavior);
407 RaftActorSnapshotMessageSupport newRaftActorSnapshotMessageSupport() {
408 return new RaftActorSnapshotMessageSupport(context, getRaftActorSnapshotCohort());
411 private void onGetOnDemandRaftStats() {
412 // Debugging message to retrieve raft stats.
414 Map<String, String> peerAddresses = new HashMap<>();
415 Map<String, Boolean> peerVotingStates = new HashMap<>();
416 for (PeerInfo info: context.getPeers()) {
417 peerVotingStates.put(info.getId(), info.isVoting());
418 peerAddresses.put(info.getId(), info.getAddress() != null ? info.getAddress() : "");
421 final RaftActorBehavior currentBehavior = context.getCurrentBehavior();
422 OnDemandRaftState.Builder builder = OnDemandRaftState.builder()
423 .commitIndex(context.getCommitIndex())
424 .currentTerm(context.getTermInformation().getCurrentTerm())
425 .inMemoryJournalDataSize(replicatedLog().dataSize())
426 .inMemoryJournalLogSize(replicatedLog().size())
427 .isSnapshotCaptureInitiated(context.getSnapshotManager().isCapturing())
428 .lastApplied(context.getLastApplied())
429 .lastIndex(replicatedLog().lastIndex())
430 .lastTerm(replicatedLog().lastTerm())
431 .leader(getLeaderId())
432 .raftState(currentBehavior.state().toString())
433 .replicatedToAllIndex(currentBehavior.getReplicatedToAllIndex())
434 .snapshotIndex(replicatedLog().getSnapshotIndex())
435 .snapshotTerm(replicatedLog().getSnapshotTerm())
436 .votedFor(context.getTermInformation().getVotedFor())
437 .isVoting(context.isVotingMember())
438 .peerAddresses(peerAddresses)
439 .peerVotingStates(peerVotingStates)
440 .customRaftPolicyClassName(context.getConfigParams().getCustomRaftPolicyImplementationClass());
442 ReplicatedLogEntry lastLogEntry = replicatedLog().last();
443 if (lastLogEntry != null) {
444 builder.lastLogIndex(lastLogEntry.getIndex());
445 builder.lastLogTerm(lastLogEntry.getTerm());
448 if (getCurrentBehavior() instanceof AbstractLeader) {
449 AbstractLeader leader = (AbstractLeader)getCurrentBehavior();
450 Collection<String> followerIds = leader.getFollowerIds();
451 List<FollowerInfo> followerInfoList = Lists.newArrayListWithCapacity(followerIds.size());
452 for (String id: followerIds) {
453 final FollowerLogInformation info = leader.getFollower(id);
454 followerInfoList.add(new FollowerInfo(id, info.getNextIndex(), info.getMatchIndex(),
455 info.isFollowerActive(), DurationFormatUtils.formatDurationHMS(info.timeSinceLastActivity()),
456 context.getPeerInfo(info.getId()).isVoting()));
459 builder.followerInfoList(followerInfoList);
462 sender().tell(builder.build(), self());
466 private void handleBehaviorChange(BehaviorState oldBehaviorState, RaftActorBehavior currentBehavior) {
467 RaftActorBehavior oldBehavior = oldBehaviorState.getBehavior();
469 if (oldBehavior != currentBehavior) {
473 String lastLeaderId = oldBehavior == null ? null : oldBehaviorState.getLastLeaderId();
474 String lastValidLeaderId = oldBehavior == null ? null : oldBehaviorState.getLastValidLeaderId();
475 String oldBehaviorStateName = oldBehavior == null ? null : oldBehavior.state().name();
477 // it can happen that the state has not changed but the leader has changed.
478 Optional<ActorRef> roleChangeNotifier = getRoleChangeNotifier();
479 if (!Objects.equals(lastLeaderId, currentBehavior.getLeaderId())
480 || oldBehaviorState.getLeaderPayloadVersion() != currentBehavior.getLeaderPayloadVersion()) {
481 if (roleChangeNotifier.isPresent()) {
482 roleChangeNotifier.get().tell(newLeaderStateChanged(getId(), currentBehavior.getLeaderId(),
483 currentBehavior.getLeaderPayloadVersion()), getSelf());
486 onLeaderChanged(lastValidLeaderId, currentBehavior.getLeaderId());
488 if (leadershipTransferInProgress != null) {
489 leadershipTransferInProgress.onNewLeader(currentBehavior.getLeaderId());
492 serverConfigurationSupport.onNewLeader(currentBehavior.getLeaderId());
495 if (roleChangeNotifier.isPresent()
496 && (oldBehavior == null || oldBehavior.state() != currentBehavior.state())) {
497 roleChangeNotifier.get().tell(new RoleChanged(getId(), oldBehaviorStateName ,
498 currentBehavior.state().name()), getSelf());
502 protected LeaderStateChanged newLeaderStateChanged(String memberId, String leaderId, short leaderPayloadVersion) {
503 return new LeaderStateChanged(memberId, leaderId, leaderPayloadVersion);
507 public long snapshotSequenceNr() {
508 // When we do a snapshot capture, we also capture and save the sequence-number of the persistent journal,
509 // so that we can delete the persistent journal based on the saved sequence-number
510 // However , when akka replays the journal during recovery, it replays it from the sequence number when the
511 // snapshot was saved and not the number we saved. We would want to override it , by asking akka to use the
512 // last-sequence number known to us.
513 return context.getSnapshotManager().getLastSequenceNumber();
517 * Persists the given Payload in the journal and replicates to any followers. After successful completion,
518 * {@link #applyState(ActorRef, Identifier, Object)} is notified.
520 * @param clientActor optional ActorRef that is provided via the applyState callback
521 * @param identifier the payload identifier
522 * @param data the payload data to persist
523 * @param batchHint if true, an attempt is made to delay immediate replication and batch the payload with
524 * subsequent payloads for efficiency. Otherwise the payload is immediately replicated.
526 protected final void persistData(final ActorRef clientActor, final Identifier identifier, final Payload data,
527 final boolean batchHint) {
528 ReplicatedLogEntry replicatedLogEntry = new SimpleReplicatedLogEntry(
529 context.getReplicatedLog().lastIndex() + 1,
530 context.getTermInformation().getCurrentTerm(), data);
531 replicatedLogEntry.setPersistencePending(true);
533 LOG.debug("{}: Persist data {}", persistenceId(), replicatedLogEntry);
535 final RaftActorContext raftContext = getRaftActorContext();
537 boolean wasAppended = replicatedLog().appendAndPersist(replicatedLogEntry, persistedLogEntry -> {
538 // Clear the persistence pending flag in the log entry.
539 persistedLogEntry.setPersistencePending(false);
541 if (!hasFollowers()) {
542 // Increment the Commit Index and the Last Applied values
543 raftContext.setCommitIndex(persistedLogEntry.getIndex());
544 raftContext.setLastApplied(persistedLogEntry.getIndex());
546 // Apply the state immediately.
547 self().tell(new ApplyState(clientActor, identifier, persistedLogEntry), self());
549 // Send a ApplyJournalEntries message so that we write the fact that we applied
550 // the state to durable storage
551 self().tell(new ApplyJournalEntries(persistedLogEntry.getIndex()), self());
554 context.getReplicatedLog().captureSnapshotIfReady(replicatedLogEntry);
556 // Local persistence is complete so send the CheckConsensusReached message to the behavior (which
557 // normally should still be the leader) to check if consensus has now been reached in conjunction with
558 // follower replication.
559 getCurrentBehavior().handleMessage(getSelf(), CheckConsensusReached.INSTANCE);
563 if (wasAppended && hasFollowers()) {
564 // Send log entry for replication.
565 getCurrentBehavior().handleMessage(getSelf(), new Replicate(clientActor, identifier, replicatedLogEntry,
570 private ReplicatedLog replicatedLog() {
571 return context.getReplicatedLog();
574 protected String getId() {
575 return context.getId();
579 void setCurrentBehavior(RaftActorBehavior behavior) {
580 context.setCurrentBehavior(behavior);
583 protected RaftActorBehavior getCurrentBehavior() {
584 return context.getCurrentBehavior();
588 * Derived actors can call the isLeader method to check if the current
589 * RaftActor is the Leader or not.
591 * @return true it this RaftActor is a Leader false otherwise
593 protected boolean isLeader() {
594 return context.getId().equals(getCurrentBehavior().getLeaderId());
597 protected final boolean isLeaderActive() {
598 return getRaftState() != RaftState.IsolatedLeader && getRaftState() != RaftState.PreLeader
599 && !shuttingDown && !isLeadershipTransferInProgress();
602 private boolean isLeadershipTransferInProgress() {
603 return leadershipTransferInProgress != null && leadershipTransferInProgress.isTransferring();
607 * Derived actor can call getLeader if they need a reference to the Leader.
608 * This would be useful for example in forwarding a request to an actor
609 * which is the leader
611 * @return A reference to the leader if known, null otherwise
613 public ActorSelection getLeader() {
614 String leaderAddress = getLeaderAddress();
616 if (leaderAddress == null) {
620 return context.actorSelection(leaderAddress);
624 * Returns the id of the current leader.
626 * @return the current leader's id
628 protected final String getLeaderId() {
629 return getCurrentBehavior().getLeaderId();
633 protected final RaftState getRaftState() {
634 return getCurrentBehavior().state();
637 protected Long getCurrentTerm() {
638 return context.getTermInformation().getCurrentTerm();
641 protected RaftActorContext getRaftActorContext() {
645 protected void updateConfigParams(ConfigParams configParams) {
647 // obtain the RaftPolicy for oldConfigParams and the updated one.
648 String oldRaftPolicy = context.getConfigParams().getCustomRaftPolicyImplementationClass();
649 String newRaftPolicy = configParams.getCustomRaftPolicyImplementationClass();
651 LOG.debug("{}: RaftPolicy used with prev.config {}, RaftPolicy used with newConfig {}", persistenceId(),
652 oldRaftPolicy, newRaftPolicy);
653 context.setConfigParams(configParams);
654 if (!Objects.equals(oldRaftPolicy, newRaftPolicy)) {
655 // The RaftPolicy was modified. If the current behavior is Follower then re-initialize to Follower
656 // but transfer the previous leaderId so it doesn't immediately try to schedule an election. This
657 // avoids potential disruption. Otherwise, switch to Follower normally.
658 RaftActorBehavior behavior = getCurrentBehavior();
659 if (behavior != null && behavior.state() == RaftState.Follower) {
660 String previousLeaderId = behavior.getLeaderId();
661 short previousLeaderPayloadVersion = behavior.getLeaderPayloadVersion();
663 LOG.debug("{}: Re-initializing to Follower with previous leaderId {}", persistenceId(),
666 changeCurrentBehavior(new Follower(context, previousLeaderId, previousLeaderPayloadVersion));
668 initializeBehavior();
673 public final DataPersistenceProvider persistence() {
674 return delegatingPersistenceProvider.getDelegate();
677 public void setPersistence(DataPersistenceProvider provider) {
678 delegatingPersistenceProvider.setDelegate(provider);
681 protected void setPersistence(boolean persistent) {
682 DataPersistenceProvider currentPersistence = persistence();
683 if (persistent && (currentPersistence == null || !currentPersistence.isRecoveryApplicable())) {
684 setPersistence(new PersistentDataProvider(this));
686 if (getCurrentBehavior() != null) {
687 LOG.info("{}: Persistence has been enabled - capturing snapshot", persistenceId());
690 } else if (!persistent && (currentPersistence == null || currentPersistence.isRecoveryApplicable())) {
691 setPersistence(new NonPersistentDataProvider() {
693 * The way snapshotting works is,
695 * <li> RaftActor calls createSnapshot on the Shard
696 * <li> Shard sends a CaptureSnapshotReply and RaftActor then calls saveSnapshot
697 * <li> When saveSnapshot is invoked on the akka-persistence API it uses the SnapshotStore to save
698 * the snapshot. The SnapshotStore sends SaveSnapshotSuccess or SaveSnapshotFailure. When the
699 * RaftActor gets SaveSnapshot success it commits the snapshot to the in-memory journal. This
700 * commitSnapshot is mimicking what is done in SaveSnapshotSuccess.
704 public void saveSnapshot(Object object) {
705 // Make saving Snapshot successful
706 // Committing the snapshot here would end up calling commit in the creating state which would
707 // be a state violation. That's why now we send a message to commit the snapshot.
708 self().tell(RaftActorSnapshotMessageSupport.COMMIT_SNAPSHOT, self());
715 * setPeerAddress sets the address of a known peer at a later time.
718 * This is to account for situations where a we know that a peer
719 * exists but we do not know an address up-front. This may also be used in
720 * situations where a known peer starts off in a different location and we
721 * need to change it's address
724 * Note that if the peerId does not match the list of peers passed to
725 * this actor during construction an IllegalStateException will be thrown.
727 protected void setPeerAddress(String peerId, String peerAddress) {
728 context.setPeerAddress(peerId, peerAddress);
732 * The applyState method will be called by the RaftActor when some data
733 * needs to be applied to the actor's state.
735 * @param clientActor A reference to the client who sent this message. This
736 * is the same reference that was passed to persistData
737 * by the derived actor. clientActor may be null when
738 * the RaftActor is behaving as a follower or during
740 * @param identifier The identifier of the persisted data. This is also
741 * the same identifier that was passed to persistData by
742 * the derived actor. identifier may be null when
743 * the RaftActor is behaving as a follower or during
745 * @param data A piece of data that was persisted by the persistData call.
746 * This should NEVER be null.
748 protected abstract void applyState(ActorRef clientActor, Identifier identifier, Object data);
751 * Returns the RaftActorRecoveryCohort to participate in persistence recovery.
754 protected abstract RaftActorRecoveryCohort getRaftActorRecoveryCohort();
757 * This method is called when recovery is complete.
759 protected abstract void onRecoveryComplete();
762 * Returns the RaftActorSnapshotCohort to participate in persistence recovery.
765 protected abstract RaftActorSnapshotCohort getRaftActorSnapshotCohort();
768 * This method will be called by the RaftActor when the state of the
769 * RaftActor changes. The derived actor can then use methods like
770 * isLeader or getLeader to do something useful
772 protected abstract void onStateChanged();
775 * Notifier Actor for this RaftActor to notify when a role change happens.
777 * @return ActorRef - ActorRef of the notifier or Optional.absent if none.
779 protected abstract Optional<ActorRef> getRoleChangeNotifier();
782 * This method is called prior to operations such as leadership transfer and actor shutdown when the leader
783 * must pause or stop its duties. This method allows derived classes to gracefully pause or finish current
784 * work prior to performing the operation. On completion of any work, the run method must be called on the
785 * given Runnable to proceed with the given operation. <b>Important:</b> the run method must be called on
786 * this actor's thread dispatcher as as it modifies internal state.
789 * The default implementation immediately runs the operation.
791 * @param operation the operation to run
793 protected void pauseLeader(Runnable operation) {
797 protected void onLeaderChanged(String oldLeader, String newLeader) {
800 private String getLeaderAddress() {
802 return getSelf().path().toString();
804 String leaderId = getLeaderId();
805 if (leaderId == null) {
808 String peerAddress = context.getPeerAddress(leaderId);
809 LOG.debug("{}: getLeaderAddress leaderId = {} peerAddress = {}", persistenceId(), leaderId, peerAddress);
814 protected boolean hasFollowers() {
815 return getRaftActorContext().hasFollowers();
818 private void captureSnapshot() {
819 SnapshotManager snapshotManager = context.getSnapshotManager();
821 if (!snapshotManager.isCapturing()) {
822 final long idx = getCurrentBehavior().getReplicatedToAllIndex();
823 LOG.debug("Take a snapshot of current state. lastReplicatedLog is {} and replicatedToAllIndex is {}",
824 replicatedLog().last(), idx);
826 snapshotManager.capture(replicatedLog().last(), idx);
831 * Switch this member to non-voting status. This is a no-op for all behaviors except when we are the leader,
832 * in which case we need to step down.
834 void becomeNonVoting() {
836 initiateLeadershipTransfer(new RaftActorLeadershipTransferCohort.OnComplete() {
838 public void onSuccess(ActorRef raftActorRef) {
839 LOG.debug("{}: leader transfer succeeded after change to non-voting", persistenceId());
840 ensureFollowerState();
844 public void onFailure(ActorRef raftActorRef) {
845 LOG.debug("{}: leader transfer failed after change to non-voting", persistenceId());
846 ensureFollowerState();
849 private void ensureFollowerState() {
850 // Whether or not leadership transfer succeeded, we have to step down as leader and
851 // switch to Follower so ensure that.
852 if (getRaftState() != RaftState.Follower) {
853 initializeBehavior();
861 * A point-in-time capture of {@link RaftActorBehavior} state critical for transitioning between behaviors.
863 private abstract static class BehaviorState implements Immutable {
864 @Nullable abstract RaftActorBehavior getBehavior();
866 @Nullable abstract String getLastValidLeaderId();
868 @Nullable abstract String getLastLeaderId();
870 @Nullable abstract short getLeaderPayloadVersion();
874 * A {@link BehaviorState} corresponding to non-null {@link RaftActorBehavior} state.
876 private static final class SimpleBehaviorState extends BehaviorState {
877 private final RaftActorBehavior behavior;
878 private final String lastValidLeaderId;
879 private final String lastLeaderId;
880 private final short leaderPayloadVersion;
882 SimpleBehaviorState(final String lastValidLeaderId, final String lastLeaderId,
883 final RaftActorBehavior behavior) {
884 this.lastValidLeaderId = lastValidLeaderId;
885 this.lastLeaderId = lastLeaderId;
886 this.behavior = Preconditions.checkNotNull(behavior);
887 this.leaderPayloadVersion = behavior.getLeaderPayloadVersion();
891 RaftActorBehavior getBehavior() {
896 String getLastValidLeaderId() {
897 return lastValidLeaderId;
901 short getLeaderPayloadVersion() {
902 return leaderPayloadVersion;
906 String getLastLeaderId() {
912 * Class tracking behavior-related information, which we need to keep around and pass across behavior switches.
913 * An instance is created for each RaftActor. It has two functions:
914 * - it keeps track of the last leader ID we have encountered since we have been created
915 * - it creates state capture needed to transition from one behavior to the next
917 private static final class BehaviorStateTracker {
919 * A {@link BehaviorState} corresponding to null {@link RaftActorBehavior} state. Since null behavior is only
920 * allowed before we receive the first message, we know the leader ID to be null.
922 private static final BehaviorState NULL_BEHAVIOR_STATE = new BehaviorState() {
924 RaftActorBehavior getBehavior() {
929 String getLastValidLeaderId() {
934 short getLeaderPayloadVersion() {
939 String getLastLeaderId() {
944 private String lastValidLeaderId;
945 private String lastLeaderId;
947 BehaviorState capture(final RaftActorBehavior behavior) {
948 if (behavior == null) {
949 Verify.verify(lastValidLeaderId == null, "Null behavior with non-null last leader");
950 return NULL_BEHAVIOR_STATE;
953 lastLeaderId = behavior.getLeaderId();
954 if (lastLeaderId != null) {
955 lastValidLeaderId = lastLeaderId;
958 return new SimpleBehaviorState(lastValidLeaderId, lastLeaderId, behavior);