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.InitiateCaptureSnapshot;
38 import org.opendaylight.controller.cluster.raft.base.messages.LeaderTransitioning;
39 import org.opendaylight.controller.cluster.raft.base.messages.Replicate;
40 import org.opendaylight.controller.cluster.raft.base.messages.SwitchBehavior;
41 import org.opendaylight.controller.cluster.raft.behaviors.AbstractLeader;
42 import org.opendaylight.controller.cluster.raft.behaviors.AbstractRaftActorBehavior;
43 import org.opendaylight.controller.cluster.raft.behaviors.Follower;
44 import org.opendaylight.controller.cluster.raft.behaviors.RaftActorBehavior;
45 import org.opendaylight.controller.cluster.raft.client.messages.FindLeader;
46 import org.opendaylight.controller.cluster.raft.client.messages.FindLeaderReply;
47 import org.opendaylight.controller.cluster.raft.client.messages.FollowerInfo;
48 import org.opendaylight.controller.cluster.raft.client.messages.GetOnDemandRaftState;
49 import org.opendaylight.controller.cluster.raft.client.messages.OnDemandRaftState;
50 import org.opendaylight.controller.cluster.raft.client.messages.Shutdown;
51 import org.opendaylight.controller.cluster.raft.persisted.ApplyJournalEntries;
52 import org.opendaylight.controller.cluster.raft.persisted.NoopPayload;
53 import org.opendaylight.controller.cluster.raft.protobuff.client.messages.Payload;
54 import org.opendaylight.yangtools.concepts.Identifier;
55 import org.opendaylight.yangtools.concepts.Immutable;
58 * RaftActor encapsulates a state machine that needs to be kept synchronized
59 * in a cluster. It implements the RAFT algorithm as described in the paper
60 * <a href='https://ramcloud.stanford.edu/wiki/download/attachments/11370504/raft.pdf'>
61 * In Search of an Understandable Consensus Algorithm</a>
63 * RaftActor has 3 states and each state has a certain behavior associated
64 * with it. A Raft actor can behave as,
67 * <li> A Follower (or) </li>
68 * <li> A Candidate </li>
72 * A RaftActor MUST be a Leader in order to accept requests from clients to
73 * change the state of it's encapsulated state machine. Once a RaftActor becomes
74 * a Leader it is also responsible for ensuring that all followers ultimately
75 * have the same log and therefore the same state machine as itself.
78 * The current behavior of a RaftActor determines how election for leadership
79 * is initiated and how peer RaftActors react to request for votes.
82 * Each RaftActor also needs to know the current election term. It uses this
83 * information for a couple of things. One is to simply figure out who it
84 * voted for in the last election. Another is to figure out if the message
85 * it received to update it's state is stale.
88 * The RaftActor uses akka-persistence to store it's replicated log.
89 * Furthermore through it's behaviors a Raft Actor determines
92 * <li> when a log entry should be persisted </li>
93 * <li> when a log entry should be applied to the state machine (and) </li>
94 * <li> when a snapshot should be saved </li>
97 public abstract class RaftActor extends AbstractUntypedPersistentActor {
99 private static final long APPLY_STATE_DELAY_THRESHOLD_IN_NANOS = TimeUnit.MILLISECONDS.toNanos(50L); // 50 millis
102 * This context should NOT be passed directly to any other actor it is
103 * only to be consumed by the RaftActorBehaviors.
105 private final RaftActorContextImpl context;
107 private final DelegatingPersistentDataProvider delegatingPersistenceProvider;
109 private final PersistentDataProvider persistentProvider;
111 private final BehaviorStateTracker behaviorStateTracker = new BehaviorStateTracker();
113 private RaftActorRecoverySupport raftRecovery;
115 private RaftActorSnapshotMessageSupport snapshotSupport;
117 private RaftActorServerConfigurationSupport serverConfigurationSupport;
119 private RaftActorLeadershipTransferCohort leadershipTransferInProgress;
121 private boolean shuttingDown;
123 protected RaftActor(String id, Map<String, String> peerAddresses,
124 Optional<ConfigParams> configParams, short payloadVersion) {
126 persistentProvider = new PersistentDataProvider(this);
127 delegatingPersistenceProvider = new RaftActorDelegatingPersistentDataProvider(null, persistentProvider);
129 context = new RaftActorContextImpl(this.getSelf(),
130 this.getContext(), id, new ElectionTermImpl(persistentProvider, id, LOG),
131 -1, -1, peerAddresses,
132 configParams.isPresent() ? configParams.get() : new DefaultConfigParamsImpl(),
133 delegatingPersistenceProvider, LOG);
135 context.setPayloadVersion(payloadVersion);
136 context.setReplicatedLog(ReplicatedLogImpl.newInstance(context));
140 public void preStart() throws Exception {
141 LOG.info("Starting recovery for {} with journal batch size {}", persistenceId(),
142 context.getConfigParams().getJournalRecoveryLogBatchSize());
146 snapshotSupport = newRaftActorSnapshotMessageSupport();
147 serverConfigurationSupport = new RaftActorServerConfigurationSupport(this);
151 public void postStop() {
157 protected void handleRecover(Object message) {
158 if (raftRecovery == null) {
159 raftRecovery = newRaftActorRecoverySupport();
162 boolean recoveryComplete = raftRecovery.handleRecoveryMessage(message, persistentProvider);
163 if (recoveryComplete) {
164 onRecoveryComplete();
166 initializeBehavior();
172 protected RaftActorRecoverySupport newRaftActorRecoverySupport() {
173 return new RaftActorRecoverySupport(context, getRaftActorRecoveryCohort());
177 void initializeBehavior() {
178 changeCurrentBehavior(new Follower(context));
182 protected void changeCurrentBehavior(RaftActorBehavior newBehavior) {
183 final RaftActorBehavior currentBehavior = getCurrentBehavior();
184 if (currentBehavior != null) {
186 currentBehavior.close();
187 } catch (Exception e) {
188 LOG.warn("{}: Error closing behavior {}", persistence(), currentBehavior, e);
192 final BehaviorState state = behaviorStateTracker.capture(currentBehavior);
193 setCurrentBehavior(newBehavior);
194 handleBehaviorChange(state, newBehavior);
198 * Method exposed for subclasses to plug-in their logic. This method is invoked by {@link #handleCommand(Object)}
199 * for messages which are not handled by this class. Subclasses overriding this class should fall back to this
200 * implementation for messages which they do not handle
202 * @param message Incoming command message
204 protected void handleNonRaftCommand(final Object message) {
209 * @deprecated This method is not final for testing purposes. DO NOT OVERRIDE IT, override
210 * {@link #handleNonRaftCommand(Object)} instead.
214 // FIXME: make this method final once our unit tests do not need to override it
215 protected void handleCommand(final Object message) {
216 if (serverConfigurationSupport.handleMessage(message, getSender())) {
219 if (snapshotSupport.handleSnapshotMessage(message, getSender())) {
223 if (message instanceof ApplyState) {
224 ApplyState applyState = (ApplyState) message;
226 long startTime = System.nanoTime();
228 if (LOG.isDebugEnabled()) {
229 LOG.debug("{}: Applying state for log index {} data {}",
230 persistenceId(), applyState.getReplicatedLogEntry().getIndex(),
231 applyState.getReplicatedLogEntry().getData());
234 if (!(applyState.getReplicatedLogEntry().getData() instanceof NoopPayload)) {
235 applyState(applyState.getClientActor(), applyState.getIdentifier(),
236 applyState.getReplicatedLogEntry().getData());
239 long elapsedTime = System.nanoTime() - startTime;
240 if (elapsedTime >= APPLY_STATE_DELAY_THRESHOLD_IN_NANOS) {
241 LOG.debug("ApplyState took more time than expected. Elapsed Time = {} ms ApplyState = {}",
242 TimeUnit.NANOSECONDS.toMillis(elapsedTime), applyState);
245 if (!hasFollowers()) {
246 // for single node, the capture should happen after the apply state
247 // as we delete messages from the persistent journal which have made it to the snapshot
248 // capturing the snapshot before applying makes the persistent journal and snapshot out of sync
249 // and recovery shows data missing
250 context.getReplicatedLog().captureSnapshotIfReady(applyState.getReplicatedLogEntry());
252 context.getSnapshotManager().trimLog(context.getLastApplied());
255 // Send it to the current behavior - some behaviors like PreLeader need to be notified of ApplyState.
256 possiblyHandleBehaviorMessage(message);
258 } else if (message instanceof ApplyJournalEntries) {
259 ApplyJournalEntries applyEntries = (ApplyJournalEntries) message;
260 LOG.debug("{}: Persisting ApplyJournalEntries with index={}", persistenceId(), applyEntries.getToIndex());
262 persistence().persist(applyEntries, NoopProcedure.instance());
264 } else if (message instanceof FindLeader) {
266 new FindLeaderReply(getLeaderAddress()),
269 } else if (message instanceof GetOnDemandRaftState) {
270 onGetOnDemandRaftStats();
271 } else if (message instanceof InitiateCaptureSnapshot) {
273 } else if (message instanceof SwitchBehavior) {
274 switchBehavior((SwitchBehavior) message);
275 } else if (message instanceof LeaderTransitioning) {
276 onLeaderTransitioning();
277 } else if (message instanceof Shutdown) {
279 } else if (message instanceof Runnable) {
280 ((Runnable)message).run();
281 } else if (message instanceof NoopPayload) {
282 persistData(null, null, (NoopPayload)message);
283 } else if (!possiblyHandleBehaviorMessage(message)) {
284 handleNonRaftCommand(message);
288 private boolean possiblyHandleBehaviorMessage(final Object message) {
289 final RaftActorBehavior currentBehavior = getCurrentBehavior();
290 final BehaviorState state = behaviorStateTracker.capture(currentBehavior);
292 // A behavior indicates that it processed the change by returning a reference to the next behavior
293 // to be used. A null return indicates it has not processed the message and we should be passing it to
294 // the subclass for handling.
295 final RaftActorBehavior nextBehavior = currentBehavior.handleMessage(getSender(), message);
296 if (nextBehavior != null) {
297 switchBehavior(state, nextBehavior);
304 private void initiateLeadershipTransfer(final RaftActorLeadershipTransferCohort.OnComplete onComplete) {
305 LOG.debug("{}: Initiating leader transfer", persistenceId());
307 if (leadershipTransferInProgress == null) {
308 leadershipTransferInProgress = new RaftActorLeadershipTransferCohort(this);
309 leadershipTransferInProgress.addOnComplete(new RaftActorLeadershipTransferCohort.OnComplete() {
311 public void onSuccess(ActorRef raftActorRef) {
312 leadershipTransferInProgress = null;
316 public void onFailure(ActorRef raftActorRef) {
317 leadershipTransferInProgress = null;
321 leadershipTransferInProgress.addOnComplete(onComplete);
322 leadershipTransferInProgress.init();
324 LOG.debug("{}: prior leader transfer in progress - adding callback", persistenceId());
325 leadershipTransferInProgress.addOnComplete(onComplete);
329 private void onShutDown() {
330 LOG.debug("{}: onShutDown", persistenceId());
338 final RaftActorBehavior currentBehavior = context.getCurrentBehavior();
339 if (currentBehavior.state() != RaftState.Leader) {
340 // For non-leaders shutdown is a no-op
341 self().tell(PoisonPill.getInstance(), self());
345 if (context.hasFollowers()) {
346 initiateLeadershipTransfer(new RaftActorLeadershipTransferCohort.OnComplete() {
348 public void onSuccess(ActorRef raftActorRef) {
349 LOG.debug("{}: leader transfer succeeded - sending PoisonPill", persistenceId());
350 raftActorRef.tell(PoisonPill.getInstance(), raftActorRef);
354 public void onFailure(ActorRef raftActorRef) {
355 LOG.debug("{}: leader transfer failed - sending PoisonPill", persistenceId());
356 raftActorRef.tell(PoisonPill.getInstance(), raftActorRef);
360 pauseLeader(new TimedRunnable(context.getConfigParams().getElectionTimeOutInterval(), this) {
362 protected void doRun() {
363 self().tell(PoisonPill.getInstance(), self());
367 protected void doCancel() {
368 self().tell(PoisonPill.getInstance(), self());
374 private void onLeaderTransitioning() {
375 LOG.debug("{}: onLeaderTransitioning", persistenceId());
376 Optional<ActorRef> roleChangeNotifier = getRoleChangeNotifier();
377 if (getRaftState() == RaftState.Follower && roleChangeNotifier.isPresent()) {
378 roleChangeNotifier.get().tell(newLeaderStateChanged(getId(), null,
379 getCurrentBehavior().getLeaderPayloadVersion()), getSelf());
383 private void switchBehavior(SwitchBehavior message) {
384 if (!getRaftActorContext().getRaftPolicy().automaticElectionsEnabled()) {
385 RaftState newState = message.getNewState();
386 if ( newState == RaftState.Leader || newState == RaftState.Follower) {
387 switchBehavior(behaviorStateTracker.capture(getCurrentBehavior()),
388 AbstractRaftActorBehavior.createBehavior(context, message.getNewState()));
389 getRaftActorContext().getTermInformation().updateAndPersist(message.getNewTerm(), "");
391 LOG.warn("Switching to behavior : {} - not supported", newState);
396 private void switchBehavior(final BehaviorState oldBehaviorState, final RaftActorBehavior nextBehavior) {
397 setCurrentBehavior(nextBehavior);
398 handleBehaviorChange(oldBehaviorState, nextBehavior);
402 RaftActorSnapshotMessageSupport newRaftActorSnapshotMessageSupport() {
403 return new RaftActorSnapshotMessageSupport(context, getRaftActorSnapshotCohort());
406 private void onGetOnDemandRaftStats() {
407 // Debugging message to retrieve raft stats.
409 Map<String, String> peerAddresses = new HashMap<>();
410 Map<String, Boolean> peerVotingStates = new HashMap<>();
411 for (PeerInfo info: context.getPeers()) {
412 peerVotingStates.put(info.getId(), info.isVoting());
413 peerAddresses.put(info.getId(), info.getAddress() != null ? info.getAddress() : "");
416 final RaftActorBehavior currentBehavior = context.getCurrentBehavior();
417 OnDemandRaftState.Builder builder = OnDemandRaftState.builder()
418 .commitIndex(context.getCommitIndex())
419 .currentTerm(context.getTermInformation().getCurrentTerm())
420 .inMemoryJournalDataSize(replicatedLog().dataSize())
421 .inMemoryJournalLogSize(replicatedLog().size())
422 .isSnapshotCaptureInitiated(context.getSnapshotManager().isCapturing())
423 .lastApplied(context.getLastApplied())
424 .lastIndex(replicatedLog().lastIndex())
425 .lastTerm(replicatedLog().lastTerm())
426 .leader(getLeaderId())
427 .raftState(currentBehavior.state().toString())
428 .replicatedToAllIndex(currentBehavior.getReplicatedToAllIndex())
429 .snapshotIndex(replicatedLog().getSnapshotIndex())
430 .snapshotTerm(replicatedLog().getSnapshotTerm())
431 .votedFor(context.getTermInformation().getVotedFor())
432 .isVoting(context.isVotingMember())
433 .peerAddresses(peerAddresses)
434 .peerVotingStates(peerVotingStates)
435 .customRaftPolicyClassName(context.getConfigParams().getCustomRaftPolicyImplementationClass());
437 ReplicatedLogEntry lastLogEntry = replicatedLog().last();
438 if (lastLogEntry != null) {
439 builder.lastLogIndex(lastLogEntry.getIndex());
440 builder.lastLogTerm(lastLogEntry.getTerm());
443 if (getCurrentBehavior() instanceof AbstractLeader) {
444 AbstractLeader leader = (AbstractLeader)getCurrentBehavior();
445 Collection<String> followerIds = leader.getFollowerIds();
446 List<FollowerInfo> followerInfoList = Lists.newArrayListWithCapacity(followerIds.size());
447 for (String id: followerIds) {
448 final FollowerLogInformation info = leader.getFollower(id);
449 followerInfoList.add(new FollowerInfo(id, info.getNextIndex(), info.getMatchIndex(),
450 info.isFollowerActive(), DurationFormatUtils.formatDurationHMS(info.timeSinceLastActivity()),
451 context.getPeerInfo(info.getId()).isVoting()));
454 builder.followerInfoList(followerInfoList);
457 sender().tell(builder.build(), self());
461 private void handleBehaviorChange(BehaviorState oldBehaviorState, RaftActorBehavior currentBehavior) {
462 RaftActorBehavior oldBehavior = oldBehaviorState.getBehavior();
464 if (oldBehavior != currentBehavior){
468 String lastLeaderId = oldBehavior == null ? null : oldBehaviorState.getLastLeaderId();
469 String lastValidLeaderId = oldBehavior == null ? null : oldBehaviorState.getLastValidLeaderId();
470 String oldBehaviorStateName = oldBehavior == null ? null : oldBehavior.state().name();
472 // it can happen that the state has not changed but the leader has changed.
473 Optional<ActorRef> roleChangeNotifier = getRoleChangeNotifier();
474 if (!Objects.equals(lastLeaderId, currentBehavior.getLeaderId())
475 || oldBehaviorState.getLeaderPayloadVersion() != currentBehavior.getLeaderPayloadVersion()) {
476 if (roleChangeNotifier.isPresent()) {
477 roleChangeNotifier.get().tell(newLeaderStateChanged(getId(), currentBehavior.getLeaderId(),
478 currentBehavior.getLeaderPayloadVersion()), getSelf());
481 onLeaderChanged(lastValidLeaderId, currentBehavior.getLeaderId());
483 if (leadershipTransferInProgress != null) {
484 leadershipTransferInProgress.onNewLeader(currentBehavior.getLeaderId());
487 serverConfigurationSupport.onNewLeader(currentBehavior.getLeaderId());
490 if (roleChangeNotifier.isPresent()
491 && (oldBehavior == null || oldBehavior.state() != currentBehavior.state())) {
492 roleChangeNotifier.get().tell(new RoleChanged(getId(), oldBehaviorStateName ,
493 currentBehavior.state().name()), getSelf());
497 protected LeaderStateChanged newLeaderStateChanged(String memberId, String leaderId, short leaderPayloadVersion) {
498 return new LeaderStateChanged(memberId, leaderId, leaderPayloadVersion);
502 public long snapshotSequenceNr() {
503 // When we do a snapshot capture, we also capture and save the sequence-number of the persistent journal,
504 // so that we can delete the persistent journal based on the saved sequence-number
505 // However , when akka replays the journal during recovery, it replays it from the sequence number when the
506 // snapshot was saved and not the number we saved. We would want to override it , by asking akka to use the
507 // last-sequence number known to us.
508 return context.getSnapshotManager().getLastSequenceNumber();
512 * When a derived RaftActor needs to persist something it must call
515 protected final void persistData(final ActorRef clientActor, final Identifier identifier, final Payload data) {
517 ReplicatedLogEntry replicatedLogEntry = new ReplicatedLogImplEntry(
518 context.getReplicatedLog().lastIndex() + 1,
519 context.getTermInformation().getCurrentTerm(), data);
521 LOG.debug("{}: Persist data {}", persistenceId(), replicatedLogEntry);
523 final RaftActorContext raftContext = getRaftActorContext();
525 replicatedLog().appendAndPersist(replicatedLogEntry, replicatedLogEntry1 -> {
526 if (!hasFollowers()) {
527 // Increment the Commit Index and the Last Applied values
528 raftContext.setCommitIndex(replicatedLogEntry1.getIndex());
529 raftContext.setLastApplied(replicatedLogEntry1.getIndex());
531 // Apply the state immediately.
532 self().tell(new ApplyState(clientActor, identifier, replicatedLogEntry1), self());
534 // Send a ApplyJournalEntries message so that we write the fact that we applied
535 // the state to durable storage
536 self().tell(new ApplyJournalEntries(replicatedLogEntry1.getIndex()), self());
539 context.getReplicatedLog().captureSnapshotIfReady(replicatedLogEntry1);
541 // Send message for replication
542 getCurrentBehavior().handleMessage(getSelf(),
543 new Replicate(clientActor, identifier, replicatedLogEntry1));
548 private ReplicatedLog replicatedLog() {
549 return context.getReplicatedLog();
552 protected String getId() {
553 return context.getId();
557 void setCurrentBehavior(RaftActorBehavior behavior) {
558 context.setCurrentBehavior(behavior);
561 protected RaftActorBehavior getCurrentBehavior() {
562 return context.getCurrentBehavior();
566 * Derived actors can call the isLeader method to check if the current
567 * RaftActor is the Leader or not.
569 * @return true it this RaftActor is a Leader false otherwise
571 protected boolean isLeader() {
572 return context.getId().equals(getCurrentBehavior().getLeaderId());
575 protected final boolean isLeaderActive() {
576 return getRaftState() != RaftState.IsolatedLeader && getRaftState() != RaftState.PreLeader
577 && !shuttingDown && !isLeadershipTransferInProgress();
580 private boolean isLeadershipTransferInProgress() {
581 return leadershipTransferInProgress != null && leadershipTransferInProgress.isTransferring();
585 * Derived actor can call getLeader if they need a reference to the Leader.
586 * This would be useful for example in forwarding a request to an actor
587 * which is the leader
589 * @return A reference to the leader if known, null otherwise
591 public ActorSelection getLeader() {
592 String leaderAddress = getLeaderAddress();
594 if (leaderAddress == null) {
598 return context.actorSelection(leaderAddress);
602 * Returns the id of the current leader.
604 * @return the current leader's id
606 protected final String getLeaderId() {
607 return getCurrentBehavior().getLeaderId();
611 protected final RaftState getRaftState() {
612 return getCurrentBehavior().state();
615 protected Long getCurrentTerm() {
616 return context.getTermInformation().getCurrentTerm();
619 protected RaftActorContext getRaftActorContext() {
623 protected void updateConfigParams(ConfigParams configParams) {
625 // obtain the RaftPolicy for oldConfigParams and the updated one.
626 String oldRaftPolicy = context.getConfigParams().getCustomRaftPolicyImplementationClass();
627 String newRaftPolicy = configParams.getCustomRaftPolicyImplementationClass();
629 LOG.debug("{}: RaftPolicy used with prev.config {}, RaftPolicy used with newConfig {}", persistenceId(),
630 oldRaftPolicy, newRaftPolicy);
631 context.setConfigParams(configParams);
632 if (!Objects.equals(oldRaftPolicy, newRaftPolicy)) {
633 // The RaftPolicy was modified. If the current behavior is Follower then re-initialize to Follower
634 // but transfer the previous leaderId so it doesn't immediately try to schedule an election. This
635 // avoids potential disruption. Otherwise, switch to Follower normally.
636 RaftActorBehavior behavior = getCurrentBehavior();
637 if (behavior != null && behavior.state() == RaftState.Follower) {
638 String previousLeaderId = behavior.getLeaderId();
639 short previousLeaderPayloadVersion = behavior.getLeaderPayloadVersion();
641 LOG.debug("{}: Re-initializing to Follower with previous leaderId {}", persistenceId(),
644 changeCurrentBehavior(new Follower(context, previousLeaderId, previousLeaderPayloadVersion));
646 initializeBehavior();
651 public final DataPersistenceProvider persistence() {
652 return delegatingPersistenceProvider.getDelegate();
655 public void setPersistence(DataPersistenceProvider provider) {
656 delegatingPersistenceProvider.setDelegate(provider);
659 protected void setPersistence(boolean persistent) {
660 DataPersistenceProvider currentPersistence = persistence();
661 if (persistent && (currentPersistence == null || !currentPersistence.isRecoveryApplicable())) {
662 setPersistence(new PersistentDataProvider(this));
664 if (getCurrentBehavior() != null) {
665 LOG.info("{}: Persistence has been enabled - capturing snapshot", persistenceId());
668 } else if (!persistent && (currentPersistence == null || currentPersistence.isRecoveryApplicable())) {
669 setPersistence(new NonPersistentDataProvider() {
671 * The way snapshotting works is,
673 * <li> RaftActor calls createSnapshot on the Shard
674 * <li> Shard sends a CaptureSnapshotReply and RaftActor then calls saveSnapshot
675 * <li> When saveSnapshot is invoked on the akka-persistence API it uses the SnapshotStore to save
676 * the snapshot. The SnapshotStore sends SaveSnapshotSuccess or SaveSnapshotFailure. When the
677 * RaftActor gets SaveSnapshot success it commits the snapshot to the in-memory journal. This
678 * commitSnapshot is mimicking what is done in SaveSnapshotSuccess.
682 public void saveSnapshot(Object object) {
683 // Make saving Snapshot successful
684 // Committing the snapshot here would end up calling commit in the creating state which would
685 // be a state violation. That's why now we send a message to commit the snapshot.
686 self().tell(RaftActorSnapshotMessageSupport.COMMIT_SNAPSHOT, self());
693 * setPeerAddress sets the address of a known peer at a later time.
696 * This is to account for situations where a we know that a peer
697 * exists but we do not know an address up-front. This may also be used in
698 * situations where a known peer starts off in a different location and we
699 * need to change it's address
702 * Note that if the peerId does not match the list of peers passed to
703 * this actor during construction an IllegalStateException will be thrown.
705 protected void setPeerAddress(String peerId, String peerAddress) {
706 context.setPeerAddress(peerId, peerAddress);
710 * The applyState method will be called by the RaftActor when some data
711 * needs to be applied to the actor's state.
713 * @param clientActor A reference to the client who sent this message. This
714 * is the same reference that was passed to persistData
715 * by the derived actor. clientActor may be null when
716 * the RaftActor is behaving as a follower or during
718 * @param identifier The identifier of the persisted data. This is also
719 * the same identifier that was passed to persistData by
720 * the derived actor. identifier may be null when
721 * the RaftActor is behaving as a follower or during
723 * @param data A piece of data that was persisted by the persistData call.
724 * This should NEVER be null.
726 protected abstract void applyState(ActorRef clientActor, Identifier identifier, Object data);
729 * Returns the RaftActorRecoveryCohort to participate in persistence recovery.
732 protected abstract RaftActorRecoveryCohort getRaftActorRecoveryCohort();
735 * This method is called when recovery is complete.
737 protected abstract void onRecoveryComplete();
740 * Returns the RaftActorSnapshotCohort to participate in persistence recovery.
743 protected abstract RaftActorSnapshotCohort getRaftActorSnapshotCohort();
746 * This method will be called by the RaftActor when the state of the
747 * RaftActor changes. The derived actor can then use methods like
748 * isLeader or getLeader to do something useful
750 protected abstract void onStateChanged();
753 * Notifier Actor for this RaftActor to notify when a role change happens.
755 * @return ActorRef - ActorRef of the notifier or Optional.absent if none.
757 protected abstract Optional<ActorRef> getRoleChangeNotifier();
760 * This method is called prior to operations such as leadership transfer and actor shutdown when the leader
761 * must pause or stop its duties. This method allows derived classes to gracefully pause or finish current
762 * work prior to performing the operation. On completion of any work, the run method must be called on the
763 * given Runnable to proceed with the given operation. <b>Important:</b> the run method must be called on
764 * this actor's thread dispatcher as as it modifies internal state.
767 * The default implementation immediately runs the operation.
769 * @param operation the operation to run
771 protected void pauseLeader(Runnable operation) {
775 protected void onLeaderChanged(String oldLeader, String newLeader) {
778 private String getLeaderAddress() {
780 return getSelf().path().toString();
782 String leaderId = getLeaderId();
783 if (leaderId == null) {
786 String peerAddress = context.getPeerAddress(leaderId);
787 LOG.debug("{}: getLeaderAddress leaderId = {} peerAddress = {}", persistenceId(), leaderId, peerAddress);
792 protected boolean hasFollowers() {
793 return getRaftActorContext().hasFollowers();
796 private void captureSnapshot() {
797 SnapshotManager snapshotManager = context.getSnapshotManager();
799 if (!snapshotManager.isCapturing()) {
800 final long idx = getCurrentBehavior().getReplicatedToAllIndex();
801 LOG.debug("Take a snapshot of current state. lastReplicatedLog is {} and replicatedToAllIndex is {}",
802 replicatedLog().last(), idx);
804 snapshotManager.capture(replicatedLog().last(), idx);
809 * Switch this member to non-voting status. This is a no-op for all behaviors except when we are the leader,
810 * in which case we need to step down.
812 void becomeNonVoting() {
814 initiateLeadershipTransfer(new RaftActorLeadershipTransferCohort.OnComplete() {
816 public void onSuccess(ActorRef raftActorRef) {
817 LOG.debug("{}: leader transfer succeeded after change to non-voting", persistenceId());
818 ensureFollowerState();
822 public void onFailure(ActorRef raftActorRef) {
823 LOG.debug("{}: leader transfer failed after change to non-voting", persistenceId());
824 ensureFollowerState();
827 private void ensureFollowerState() {
828 // Whether or not leadership transfer succeeded, we have to step down as leader and
829 // switch to Follower so ensure that.
830 if (getRaftState() != RaftState.Follower) {
831 initializeBehavior();
839 * A point-in-time capture of {@link RaftActorBehavior} state critical for transitioning between behaviors.
841 private abstract static class BehaviorState implements Immutable {
842 @Nullable abstract RaftActorBehavior getBehavior();
844 @Nullable abstract String getLastValidLeaderId();
846 @Nullable abstract String getLastLeaderId();
848 @Nullable abstract short getLeaderPayloadVersion();
852 * A {@link BehaviorState} corresponding to non-null {@link RaftActorBehavior} state.
854 private static final class SimpleBehaviorState extends BehaviorState {
855 private final RaftActorBehavior behavior;
856 private final String lastValidLeaderId;
857 private final String lastLeaderId;
858 private final short leaderPayloadVersion;
860 SimpleBehaviorState(final String lastValidLeaderId, final String lastLeaderId,
861 final RaftActorBehavior behavior) {
862 this.lastValidLeaderId = lastValidLeaderId;
863 this.lastLeaderId = lastLeaderId;
864 this.behavior = Preconditions.checkNotNull(behavior);
865 this.leaderPayloadVersion = behavior.getLeaderPayloadVersion();
869 RaftActorBehavior getBehavior() {
874 String getLastValidLeaderId() {
875 return lastValidLeaderId;
879 short getLeaderPayloadVersion() {
880 return leaderPayloadVersion;
884 String getLastLeaderId() {
890 * Class tracking behavior-related information, which we need to keep around and pass across behavior switches.
891 * An instance is created for each RaftActor. It has two functions:
892 * - it keeps track of the last leader ID we have encountered since we have been created
893 * - it creates state capture needed to transition from one behavior to the next
895 private static final class BehaviorStateTracker {
897 * A {@link BehaviorState} corresponding to null {@link RaftActorBehavior} state. Since null behavior is only
898 * allowed before we receive the first message, we know the leader ID to be null.
900 private static final BehaviorState NULL_BEHAVIOR_STATE = new BehaviorState() {
902 RaftActorBehavior getBehavior() {
907 String getLastValidLeaderId() {
912 short getLeaderPayloadVersion() {
917 String getLastLeaderId() {
922 private String lastValidLeaderId;
923 private String lastLeaderId;
925 BehaviorState capture(final RaftActorBehavior behavior) {
926 if (behavior == null) {
927 Verify.verify(lastValidLeaderId == null, "Null behavior with non-null last leader");
928 return NULL_BEHAVIOR_STATE;
931 lastLeaderId = behavior.getLeaderId();
932 if (lastLeaderId != null) {
933 lastValidLeaderId = lastLeaderId;
936 return new SimpleBehaviorState(lastValidLeaderId, lastLeaderId, behavior);