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;
56 import org.slf4j.Logger;
57 import org.slf4j.LoggerFactory;
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>
65 * RaftActor has 3 states and each state has a certain behavior associated
66 * with it. A Raft actor can behave as,
69 * <li> A Follower (or) </li>
70 * <li> A Candidate </li>
74 * A RaftActor MUST be a Leader in order to accept requests from clients to
75 * change the state of it's encapsulated state machine. Once a RaftActor becomes
76 * a Leader it is also responsible for ensuring that all followers ultimately
77 * have the same log and therefore the same state machine as itself.
80 * The current behavior of a RaftActor determines how election for leadership
81 * is initiated and how peer RaftActors react to request for votes.
84 * Each RaftActor also needs to know the current election term. It uses this
85 * information for a couple of things. One is to simply figure out who it
86 * voted for in the last election. Another is to figure out if the message
87 * it received to update it's state is stale.
90 * The RaftActor uses akka-persistence to store it's replicated log.
91 * 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
103 protected final Logger LOG = LoggerFactory.getLogger(getClass());
106 * This context should NOT be passed directly to any other actor it is
107 * only to be consumed by the RaftActorBehaviors
109 private final RaftActorContextImpl context;
111 private final DelegatingPersistentDataProvider delegatingPersistenceProvider;
113 private final PersistentDataProvider persistentProvider;
115 private final BehaviorStateTracker behaviorStateTracker = new BehaviorStateTracker();
117 private RaftActorRecoverySupport raftRecovery;
119 private RaftActorSnapshotMessageSupport snapshotSupport;
121 private RaftActorServerConfigurationSupport serverConfigurationSupport;
123 private RaftActorLeadershipTransferCohort leadershipTransferInProgress;
125 private boolean shuttingDown;
127 public RaftActor(String id, Map<String, String> peerAddresses,
128 Optional<ConfigParams> configParams, short payloadVersion) {
130 persistentProvider = new PersistentDataProvider(this);
131 delegatingPersistenceProvider = new RaftActorDelegatingPersistentDataProvider(null, persistentProvider);
133 context = new RaftActorContextImpl(this.getSelf(),
134 this.getContext(), id, new ElectionTermImpl(persistentProvider, id, LOG),
135 -1, -1, peerAddresses,
136 configParams.isPresent() ? configParams.get(): new DefaultConfigParamsImpl(),
137 delegatingPersistenceProvider, LOG);
139 context.setPayloadVersion(payloadVersion);
140 context.setReplicatedLog(ReplicatedLogImpl.newInstance(context));
144 public void preStart() throws Exception {
145 LOG.info("Starting recovery for {} with journal batch size {}", persistenceId(),
146 context.getConfigParams().getJournalRecoveryLogBatchSize());
150 snapshotSupport = newRaftActorSnapshotMessageSupport();
151 serverConfigurationSupport = new RaftActorServerConfigurationSupport(this);
155 public void postStop() {
161 protected void handleRecover(Object message) {
162 if(raftRecovery == null) {
163 raftRecovery = newRaftActorRecoverySupport();
166 boolean recoveryComplete = raftRecovery.handleRecoveryMessage(message, persistentProvider);
167 if(recoveryComplete) {
168 onRecoveryComplete();
170 initializeBehavior();
176 protected RaftActorRecoverySupport newRaftActorRecoverySupport() {
177 return new RaftActorRecoverySupport(context, getRaftActorRecoveryCohort());
181 void initializeBehavior(){
182 changeCurrentBehavior(new Follower(context));
186 protected void changeCurrentBehavior(RaftActorBehavior newBehavior) {
187 final RaftActorBehavior currentBehavior = getCurrentBehavior();
188 if (currentBehavior != null) {
190 currentBehavior.close();
191 } catch (Exception e) {
192 LOG.warn("{}: Error closing behavior {}", persistence(), currentBehavior, e);
196 final BehaviorState state = behaviorStateTracker.capture(currentBehavior);
197 setCurrentBehavior(newBehavior);
198 handleBehaviorChange(state, newBehavior);
202 * Method exposed for subclasses to plug-in their logic. This method is invoked by {@link #handleCommand(Object)}
203 * for messages which are not handled by this class. Subclasses overriding this class should fall back to this
204 * implementation for messages which they do not handle
206 * @param message Incoming command message
208 protected void handleNonRaftCommand(final Object message) {
213 * @deprecated This method is not final for testing purposes. DO NOT OVERRIDE IT, override
214 * {@link #handleNonRaftCommand(Object)} instead.
218 // FIXME: make this method final once our unit tests do not need to override it
219 protected void handleCommand(final Object message) {
220 if (serverConfigurationSupport.handleMessage(message, getSender())) {
223 if (snapshotSupport.handleSnapshotMessage(message, getSender())) {
227 if (message instanceof ApplyState) {
228 ApplyState applyState = (ApplyState) message;
230 long startTime = System.nanoTime();
232 if(LOG.isDebugEnabled()) {
233 LOG.debug("{}: Applying state for log index {} data {}",
234 persistenceId(), applyState.getReplicatedLogEntry().getIndex(),
235 applyState.getReplicatedLogEntry().getData());
238 if (!(applyState.getReplicatedLogEntry().getData() instanceof NoopPayload)) {
239 applyState(applyState.getClientActor(), applyState.getIdentifier(),
240 applyState.getReplicatedLogEntry().getData());
243 long elapsedTime = System.nanoTime() - startTime;
244 if(elapsedTime >= APPLY_STATE_DELAY_THRESHOLD_IN_NANOS){
245 LOG.debug("ApplyState took more time than expected. Elapsed Time = {} ms ApplyState = {}",
246 TimeUnit.NANOSECONDS.toMillis(elapsedTime), applyState);
249 if (!hasFollowers()) {
250 // for single node, the capture should happen after the apply state
251 // as we delete messages from the persistent journal which have made it to the snapshot
252 // capturing the snapshot before applying makes the persistent journal and snapshot out of sync
253 // and recovery shows data missing
254 context.getReplicatedLog().captureSnapshotIfReady(applyState.getReplicatedLogEntry());
256 context.getSnapshotManager().trimLog(context.getLastApplied());
259 // Send it to the current behavior - some behaviors like PreLeader need to be notified of ApplyState.
260 possiblyHandleBehaviorMessage(message);
262 } else if (message instanceof ApplyJournalEntries) {
263 ApplyJournalEntries applyEntries = (ApplyJournalEntries) message;
264 if(LOG.isDebugEnabled()) {
265 LOG.debug("{}: Persisting ApplyJournalEntries with index={}", persistenceId(), applyEntries.getToIndex());
268 persistence().persist(applyEntries, NoopProcedure.instance());
270 } else if (message instanceof FindLeader) {
272 new FindLeaderReply(getLeaderAddress()),
275 } else if(message instanceof GetOnDemandRaftState) {
276 onGetOnDemandRaftStats();
277 } else if(message instanceof InitiateCaptureSnapshot) {
279 } else if(message instanceof SwitchBehavior) {
280 switchBehavior((SwitchBehavior) message);
281 } else if(message instanceof LeaderTransitioning) {
282 onLeaderTransitioning();
283 } else if(message instanceof Shutdown) {
285 } else if(message instanceof Runnable) {
286 ((Runnable)message).run();
287 } else if(message instanceof NoopPayload) {
288 persistData(null, null, (NoopPayload)message);
289 } else if (!possiblyHandleBehaviorMessage(message)) {
290 handleNonRaftCommand(message);
294 private boolean possiblyHandleBehaviorMessage(final Object message) {
295 final RaftActorBehavior currentBehavior = getCurrentBehavior();
296 final BehaviorState state = behaviorStateTracker.capture(currentBehavior);
298 // A behavior indicates that it processed the change by returning a reference to the next behavior
299 // to be used. A null return indicates it has not processed the message and we should be passing it to
300 // the subclass for handling.
301 final RaftActorBehavior nextBehavior = currentBehavior.handleMessage(getSender(), message);
302 if (nextBehavior != null) {
303 switchBehavior(state, nextBehavior);
310 private void initiateLeadershipTransfer(final RaftActorLeadershipTransferCohort.OnComplete onComplete) {
311 LOG.debug("{}: Initiating leader transfer", persistenceId());
313 if(leadershipTransferInProgress == null) {
314 leadershipTransferInProgress = new RaftActorLeadershipTransferCohort(this);
315 leadershipTransferInProgress.addOnComplete(new RaftActorLeadershipTransferCohort.OnComplete() {
317 public void onSuccess(ActorRef raftActorRef) {
318 leadershipTransferInProgress = null;
322 public void onFailure(ActorRef raftActorRef) {
323 leadershipTransferInProgress = null;
327 leadershipTransferInProgress.addOnComplete(onComplete);
328 leadershipTransferInProgress.init();
330 LOG.debug("{}: prior leader transfer in progress - adding callback", persistenceId());
331 leadershipTransferInProgress.addOnComplete(onComplete);
335 private void onShutDown() {
336 LOG.debug("{}: onShutDown", persistenceId());
344 final RaftActorBehavior currentBehavior = context.getCurrentBehavior();
345 if (currentBehavior.state() != RaftState.Leader) {
346 // For non-leaders shutdown is a no-op
347 self().tell(PoisonPill.getInstance(), self());
351 if (context.hasFollowers()) {
352 initiateLeadershipTransfer(new RaftActorLeadershipTransferCohort.OnComplete() {
354 public void onSuccess(ActorRef raftActorRef) {
355 LOG.debug("{}: leader transfer succeeded - sending PoisonPill", persistenceId());
356 raftActorRef.tell(PoisonPill.getInstance(), raftActorRef);
360 public void onFailure(ActorRef raftActorRef) {
361 LOG.debug("{}: leader transfer failed - sending PoisonPill", persistenceId());
362 raftActorRef.tell(PoisonPill.getInstance(), raftActorRef);
366 pauseLeader(new TimedRunnable(context.getConfigParams().getElectionTimeOutInterval(), this) {
368 protected void doRun() {
369 self().tell(PoisonPill.getInstance(), self());
373 protected void doCancel() {
374 self().tell(PoisonPill.getInstance(), self());
380 private void onLeaderTransitioning() {
381 LOG.debug("{}: onLeaderTransitioning", persistenceId());
382 Optional<ActorRef> roleChangeNotifier = getRoleChangeNotifier();
383 if(getRaftState() == RaftState.Follower && roleChangeNotifier.isPresent()) {
384 roleChangeNotifier.get().tell(newLeaderStateChanged(getId(), null,
385 getCurrentBehavior().getLeaderPayloadVersion()), getSelf());
389 private void switchBehavior(SwitchBehavior message) {
390 if(!getRaftActorContext().getRaftPolicy().automaticElectionsEnabled()) {
391 RaftState newState = message.getNewState();
392 if( newState == RaftState.Leader || newState == RaftState.Follower) {
393 switchBehavior(behaviorStateTracker.capture(getCurrentBehavior()),
394 AbstractRaftActorBehavior.createBehavior(context, message.getNewState()));
395 getRaftActorContext().getTermInformation().updateAndPersist(message.getNewTerm(), "");
397 LOG.warn("Switching to behavior : {} - not supported", newState);
402 private void switchBehavior(final BehaviorState oldBehaviorState, final RaftActorBehavior nextBehavior) {
403 setCurrentBehavior(nextBehavior);
404 handleBehaviorChange(oldBehaviorState, nextBehavior);
408 RaftActorSnapshotMessageSupport newRaftActorSnapshotMessageSupport() {
409 return new RaftActorSnapshotMessageSupport(context, getRaftActorSnapshotCohort());
412 private void onGetOnDemandRaftStats() {
413 // Debugging message to retrieve raft stats.
415 Map<String, String> peerAddresses = new HashMap<>();
416 Map<String, Boolean> peerVotingStates = new HashMap<>();
417 for(PeerInfo info: context.getPeers()) {
418 peerVotingStates.put(info.getId(), info.isVoting());
419 peerAddresses.put(info.getId(), info.getAddress() != null ? info.getAddress() : "");
422 final RaftActorBehavior currentBehavior = context.getCurrentBehavior();
423 OnDemandRaftState.Builder builder = OnDemandRaftState.builder()
424 .commitIndex(context.getCommitIndex())
425 .currentTerm(context.getTermInformation().getCurrentTerm())
426 .inMemoryJournalDataSize(replicatedLog().dataSize())
427 .inMemoryJournalLogSize(replicatedLog().size())
428 .isSnapshotCaptureInitiated(context.getSnapshotManager().isCapturing())
429 .lastApplied(context.getLastApplied())
430 .lastIndex(replicatedLog().lastIndex())
431 .lastTerm(replicatedLog().lastTerm())
432 .leader(getLeaderId())
433 .raftState(currentBehavior.state().toString())
434 .replicatedToAllIndex(currentBehavior.getReplicatedToAllIndex())
435 .snapshotIndex(replicatedLog().getSnapshotIndex())
436 .snapshotTerm(replicatedLog().getSnapshotTerm())
437 .votedFor(context.getTermInformation().getVotedFor())
438 .isVoting(context.isVotingMember())
439 .peerAddresses(peerAddresses)
440 .peerVotingStates(peerVotingStates)
441 .customRaftPolicyClassName(context.getConfigParams().getCustomRaftPolicyImplementationClass());
443 ReplicatedLogEntry lastLogEntry = replicatedLog().last();
444 if (lastLogEntry != null) {
445 builder.lastLogIndex(lastLogEntry.getIndex());
446 builder.lastLogTerm(lastLogEntry.getTerm());
449 if(getCurrentBehavior() instanceof AbstractLeader) {
450 AbstractLeader leader = (AbstractLeader)getCurrentBehavior();
451 Collection<String> followerIds = leader.getFollowerIds();
452 List<FollowerInfo> followerInfoList = Lists.newArrayListWithCapacity(followerIds.size());
453 for(String id: followerIds) {
454 final FollowerLogInformation info = leader.getFollower(id);
455 followerInfoList.add(new FollowerInfo(id, info.getNextIndex(), info.getMatchIndex(),
456 info.isFollowerActive(), DurationFormatUtils.formatDurationHMS(info.timeSinceLastActivity()),
457 context.getPeerInfo(info.getId()).isVoting()));
460 builder.followerInfoList(followerInfoList);
463 sender().tell(builder.build(), self());
467 private void handleBehaviorChange(BehaviorState oldBehaviorState, RaftActorBehavior currentBehavior) {
468 RaftActorBehavior oldBehavior = oldBehaviorState.getBehavior();
470 if (oldBehavior != currentBehavior){
474 String lastLeaderId = oldBehavior == null ? null : oldBehaviorState.getLastLeaderId();
475 String lastValidLeaderId = oldBehavior == null ? null : oldBehaviorState.getLastValidLeaderId();
476 String oldBehaviorStateName = oldBehavior == null ? null : oldBehavior.state().name();
478 // it can happen that the state has not changed but the leader has changed.
479 Optional<ActorRef> roleChangeNotifier = getRoleChangeNotifier();
480 if(!Objects.equals(lastLeaderId, currentBehavior.getLeaderId()) ||
481 oldBehaviorState.getLeaderPayloadVersion() != currentBehavior.getLeaderPayloadVersion()) {
482 if(roleChangeNotifier.isPresent()) {
483 roleChangeNotifier.get().tell(newLeaderStateChanged(getId(), currentBehavior.getLeaderId(),
484 currentBehavior.getLeaderPayloadVersion()), getSelf());
487 onLeaderChanged(lastValidLeaderId, currentBehavior.getLeaderId());
489 if(leadershipTransferInProgress != null) {
490 leadershipTransferInProgress.onNewLeader(currentBehavior.getLeaderId());
493 serverConfigurationSupport.onNewLeader(currentBehavior.getLeaderId());
496 if (roleChangeNotifier.isPresent() &&
497 (oldBehavior == null || oldBehavior.state() != currentBehavior.state())) {
498 roleChangeNotifier.get().tell(new RoleChanged(getId(), oldBehaviorStateName ,
499 currentBehavior.state().name()), getSelf());
503 protected LeaderStateChanged newLeaderStateChanged(String memberId, String leaderId, short leaderPayloadVersion) {
504 return new LeaderStateChanged(memberId, leaderId, leaderPayloadVersion);
508 public long snapshotSequenceNr() {
509 // When we do a snapshot capture, we also capture and save the sequence-number of the persistent journal,
510 // so that we can delete the persistent journal based on the saved sequence-number
511 // However , when akka replays the journal during recovery, it replays it from the sequence number when the snapshot
512 // was saved and not the number we saved.
513 // We would want to override it , by asking akka to use the last-sequence number known to us.
514 return context.getSnapshotManager().getLastSequenceNumber();
518 * When a derived RaftActor needs to persist something it must call
525 protected final void persistData(final ActorRef clientActor, final Identifier identifier, final Payload data) {
527 ReplicatedLogEntry replicatedLogEntry = new ReplicatedLogImplEntry(
528 context.getReplicatedLog().lastIndex() + 1,
529 context.getTermInformation().getCurrentTerm(), data);
531 if(LOG.isDebugEnabled()) {
532 LOG.debug("{}: Persist data {}", persistenceId(), replicatedLogEntry);
535 final RaftActorContext raftContext = getRaftActorContext();
537 replicatedLog().appendAndPersist(replicatedLogEntry, replicatedLogEntry1 -> {
538 if (!hasFollowers()){
539 // Increment the Commit Index and the Last Applied values
540 raftContext.setCommitIndex(replicatedLogEntry1.getIndex());
541 raftContext.setLastApplied(replicatedLogEntry1.getIndex());
543 // Apply the state immediately.
544 self().tell(new ApplyState(clientActor, identifier, replicatedLogEntry1), self());
546 // Send a ApplyJournalEntries message so that we write the fact that we applied
547 // the state to durable storage
548 self().tell(new ApplyJournalEntries(replicatedLogEntry1.getIndex()), self());
551 context.getReplicatedLog().captureSnapshotIfReady(replicatedLogEntry1);
553 // Send message for replication
554 getCurrentBehavior().handleMessage(getSelf(),
555 new Replicate(clientActor, identifier, replicatedLogEntry1));
560 private ReplicatedLog replicatedLog() {
561 return context.getReplicatedLog();
564 protected String getId() {
565 return context.getId();
569 void setCurrentBehavior(RaftActorBehavior behavior) {
570 context.setCurrentBehavior(behavior);
573 protected RaftActorBehavior getCurrentBehavior() {
574 return context.getCurrentBehavior();
578 * Derived actors can call the isLeader method to check if the current
579 * RaftActor is the Leader or not
581 * @return true it this RaftActor is a Leader false otherwise
583 protected boolean isLeader() {
584 return context.getId().equals(getCurrentBehavior().getLeaderId());
587 protected final boolean isLeaderActive() {
588 return getRaftState() != RaftState.IsolatedLeader && getRaftState() != RaftState.PreLeader &&
589 !shuttingDown && !isLeadershipTransferInProgress();
592 private boolean isLeadershipTransferInProgress() {
593 return leadershipTransferInProgress != null && leadershipTransferInProgress.isTransferring();
597 * Derived actor can call getLeader if they need a reference to the Leader.
598 * This would be useful for example in forwarding a request to an actor
599 * which is the leader
601 * @return A reference to the leader if known, null otherwise
603 public ActorSelection getLeader(){
604 String leaderAddress = getLeaderAddress();
606 if(leaderAddress == null){
610 return context.actorSelection(leaderAddress);
615 * @return the current leader's id
617 protected final String getLeaderId(){
618 return getCurrentBehavior().getLeaderId();
622 protected final RaftState getRaftState() {
623 return getCurrentBehavior().state();
626 protected Long getCurrentTerm(){
627 return context.getTermInformation().getCurrentTerm();
630 protected RaftActorContext getRaftActorContext() {
634 protected void updateConfigParams(ConfigParams configParams) {
636 // obtain the RaftPolicy for oldConfigParams and the updated one.
637 String oldRaftPolicy = context.getConfigParams().
638 getCustomRaftPolicyImplementationClass();
639 String newRaftPolicy = configParams.
640 getCustomRaftPolicyImplementationClass();
642 LOG.debug("{}: RaftPolicy used with prev.config {}, RaftPolicy used with newConfig {}", persistenceId(),
643 oldRaftPolicy, newRaftPolicy);
644 context.setConfigParams(configParams);
645 if (!Objects.equals(oldRaftPolicy, newRaftPolicy)) {
646 // The RaftPolicy was modified. If the current behavior is Follower then re-initialize to Follower
647 // but transfer the previous leaderId so it doesn't immediately try to schedule an election. This
648 // avoids potential disruption. Otherwise, switch to Follower normally.
649 RaftActorBehavior behavior = getCurrentBehavior();
650 if (behavior != null && behavior.state() == RaftState.Follower) {
651 String previousLeaderId = behavior.getLeaderId();
652 short previousLeaderPayloadVersion = behavior.getLeaderPayloadVersion();
654 LOG.debug("{}: Re-initializing to Follower with previous leaderId {}", persistenceId(), previousLeaderId);
656 changeCurrentBehavior(new Follower(context, previousLeaderId, previousLeaderPayloadVersion));
658 initializeBehavior();
663 public final DataPersistenceProvider persistence() {
664 return delegatingPersistenceProvider.getDelegate();
667 public void setPersistence(DataPersistenceProvider provider) {
668 delegatingPersistenceProvider.setDelegate(provider);
671 protected void setPersistence(boolean persistent) {
672 DataPersistenceProvider currentPersistence = persistence();
673 if(persistent && (currentPersistence == null || !currentPersistence.isRecoveryApplicable())) {
674 setPersistence(new PersistentDataProvider(this));
676 if(getCurrentBehavior() != null) {
677 LOG.info("{}: Persistence has been enabled - capturing snapshot", persistenceId());
680 } else if(!persistent && (currentPersistence == null || currentPersistence.isRecoveryApplicable())) {
681 setPersistence(new NonPersistentDataProvider() {
683 * The way snapshotting works is,
685 * <li> RaftActor calls createSnapshot on the Shard
686 * <li> Shard sends a CaptureSnapshotReply and RaftActor then calls saveSnapshot
687 * <li> When saveSnapshot is invoked on the akka-persistence API it uses the SnapshotStore to save
688 * the snapshot. The SnapshotStore sends SaveSnapshotSuccess or SaveSnapshotFailure. When the
689 * RaftActor gets SaveSnapshot success it commits the snapshot to the in-memory journal. This
690 * commitSnapshot is mimicking what is done in SaveSnapshotSuccess.
694 public void saveSnapshot(Object o) {
695 // Make saving Snapshot successful
696 // Committing the snapshot here would end up calling commit in the creating state which would
697 // be a state violation. That's why now we send a message to commit the snapshot.
698 self().tell(RaftActorSnapshotMessageSupport.COMMIT_SNAPSHOT, self());
705 * setPeerAddress sets the address of a known peer at a later time.
707 * This is to account for situations where a we know that a peer
708 * exists but we do not know an address up-front. This may also be used in
709 * situations where a known peer starts off in a different location and we
710 * need to change it's address
712 * Note that if the peerId does not match the list of peers passed to
713 * this actor during construction an IllegalStateException will be thrown.
718 protected void setPeerAddress(String peerId, String peerAddress){
719 context.setPeerAddress(peerId, peerAddress);
723 * The applyState method will be called by the RaftActor when some data
724 * needs to be applied to the actor's state
726 * @param clientActor A reference to the client who sent this message. This
727 * is the same reference that was passed to persistData
728 * by the derived actor. clientActor may be null when
729 * the RaftActor is behaving as a follower or during
731 * @param identifier The identifier of the persisted data. This is also
732 * the same identifier that was passed to persistData by
733 * the derived actor. identifier may be null when
734 * the RaftActor is behaving as a follower or during
736 * @param data A piece of data that was persisted by the persistData call.
737 * This should NEVER be null.
739 protected abstract void applyState(ActorRef clientActor, Identifier identifier, Object data);
742 * Returns the RaftActorRecoveryCohort to participate in persistence recovery.
745 protected abstract RaftActorRecoveryCohort getRaftActorRecoveryCohort();
748 * This method is called when recovery is complete.
750 protected abstract void onRecoveryComplete();
753 * Returns the RaftActorSnapshotCohort to participate in persistence recovery.
756 protected abstract RaftActorSnapshotCohort getRaftActorSnapshotCohort();
759 * This method will be called by the RaftActor when the state of the
760 * RaftActor changes. The derived actor can then use methods like
761 * isLeader or getLeader to do something useful
763 protected abstract void onStateChanged();
766 * Notifier Actor for this RaftActor to notify when a role change happens
767 * @return ActorRef - ActorRef of the notifier or Optional.absent if none.
769 protected abstract Optional<ActorRef> getRoleChangeNotifier();
772 * This method is called prior to operations such as leadership transfer and actor shutdown when the leader
773 * must pause or stop its duties. This method allows derived classes to gracefully pause or finish current
774 * work prior to performing the operation. On completion of any work, the run method must be called on the
775 * given Runnable to proceed with the given operation. <b>Important:</b> the run method must be called on
776 * this actor's thread dispatcher as as it modifies internal state.
778 * The default implementation immediately runs the operation.
780 * @param operation the operation to run
782 protected void pauseLeader(Runnable operation) {
786 protected void onLeaderChanged(String oldLeader, String newLeader) {
790 private String getLeaderAddress(){
792 return getSelf().path().toString();
794 String leaderId = getLeaderId();
795 if (leaderId == null) {
798 String peerAddress = context.getPeerAddress(leaderId);
799 if(LOG.isDebugEnabled()) {
800 LOG.debug("{}: getLeaderAddress leaderId = {} peerAddress = {}",
801 persistenceId(), leaderId, peerAddress);
807 protected boolean hasFollowers(){
808 return getRaftActorContext().hasFollowers();
811 private void captureSnapshot() {
812 SnapshotManager snapshotManager = context.getSnapshotManager();
814 if (!snapshotManager.isCapturing()) {
815 final long idx = getCurrentBehavior().getReplicatedToAllIndex();
816 LOG.debug("Take a snapshot of current state. lastReplicatedLog is {} and replicatedToAllIndex is {}",
817 replicatedLog().last(), idx);
819 snapshotManager.capture(replicatedLog().last(), idx);
824 * Switch this member to non-voting status. This is a no-op for all behaviors except when we are the leader,
825 * in which case we need to step down.
827 void becomeNonVoting() {
829 initiateLeadershipTransfer(new RaftActorLeadershipTransferCohort.OnComplete() {
831 public void onSuccess(ActorRef raftActorRef) {
832 LOG.debug("{}: leader transfer succeeded after change to non-voting", persistenceId());
833 ensureFollowerState();
837 public void onFailure(ActorRef raftActorRef) {
838 LOG.debug("{}: leader transfer failed after change to non-voting", persistenceId());
839 ensureFollowerState();
842 private void ensureFollowerState() {
843 // Whether or not leadership transfer succeeded, we have to step down as leader and
844 // switch to Follower so ensure that.
845 if (getRaftState() != RaftState.Follower) {
846 initializeBehavior();
854 * A point-in-time capture of {@link RaftActorBehavior} state critical for transitioning between behaviors.
856 private static abstract class BehaviorState implements Immutable {
857 @Nullable abstract RaftActorBehavior getBehavior();
858 @Nullable abstract String getLastValidLeaderId();
859 @Nullable abstract String getLastLeaderId();
860 @Nullable abstract short getLeaderPayloadVersion();
864 * A {@link BehaviorState} corresponding to non-null {@link RaftActorBehavior} state.
866 private static final class SimpleBehaviorState extends BehaviorState {
867 private final RaftActorBehavior behavior;
868 private final String lastValidLeaderId;
869 private final String lastLeaderId;
870 private final short leaderPayloadVersion;
872 SimpleBehaviorState(final String lastValidLeaderId, final String lastLeaderId,
873 final RaftActorBehavior behavior) {
874 this.lastValidLeaderId = lastValidLeaderId;
875 this.lastLeaderId = lastLeaderId;
876 this.behavior = Preconditions.checkNotNull(behavior);
877 this.leaderPayloadVersion = behavior.getLeaderPayloadVersion();
881 RaftActorBehavior getBehavior() {
886 String getLastValidLeaderId() {
887 return lastValidLeaderId;
891 short getLeaderPayloadVersion() {
892 return leaderPayloadVersion;
896 String getLastLeaderId() {
902 * Class tracking behavior-related information, which we need to keep around and pass across behavior switches.
903 * An instance is created for each RaftActor. It has two functions:
904 * - it keeps track of the last leader ID we have encountered since we have been created
905 * - it creates state capture needed to transition from one behavior to the next
907 private static final class BehaviorStateTracker {
909 * A {@link BehaviorState} corresponding to null {@link RaftActorBehavior} state. Since null behavior is only
910 * allowed before we receive the first message, we know the leader ID to be null.
912 private static final BehaviorState NULL_BEHAVIOR_STATE = new BehaviorState() {
914 RaftActorBehavior getBehavior() {
919 String getLastValidLeaderId() {
924 short getLeaderPayloadVersion() {
929 String getLastLeaderId() {
934 private String lastValidLeaderId;
935 private String lastLeaderId;
937 BehaviorState capture(final RaftActorBehavior behavior) {
938 if (behavior == null) {
939 Verify.verify(lastValidLeaderId == null, "Null behavior with non-null last leader");
940 return NULL_BEHAVIOR_STATE;
943 lastLeaderId = behavior.getLeaderId();
944 if (lastLeaderId != null) {
945 lastValidLeaderId = lastLeaderId;
948 return new SimpleBehaviorState(lastValidLeaderId, lastLeaderId, behavior);