Bug-2397:Provide a mechanism for stakeholders to get notifications on Raft state...
[controller.git] / opendaylight / md-sal / sal-akka-raft / src / main / java / org / opendaylight / controller / cluster / raft / RaftActor.java
1 /*
2  * Copyright (c) 2014 Cisco Systems, Inc. and others.  All rights reserved.
3  *
4  * This program and the accompanying materials are made available under the
5  * terms of the Eclipse Public License v1.0 which accompanies this distribution,
6  * and is available at http://www.eclipse.org/legal/epl-v10.html
7  */
8
9 package org.opendaylight.controller.cluster.raft;
10
11 import akka.actor.ActorRef;
12 import akka.actor.ActorSelection;
13 import akka.event.Logging;
14 import akka.event.LoggingAdapter;
15 import akka.japi.Procedure;
16 import akka.persistence.RecoveryCompleted;
17 import akka.persistence.SaveSnapshotFailure;
18 import akka.persistence.SaveSnapshotSuccess;
19 import akka.persistence.SnapshotOffer;
20 import akka.persistence.SnapshotSelectionCriteria;
21 import com.google.common.annotations.VisibleForTesting;
22 import com.google.common.base.Optional;
23 import com.google.common.base.Stopwatch;
24 import com.google.protobuf.ByteString;
25 import java.io.Serializable;
26 import java.util.Map;
27 import org.opendaylight.controller.cluster.DataPersistenceProvider;
28 import org.opendaylight.controller.cluster.common.actor.AbstractUntypedPersistentActor;
29 import org.opendaylight.controller.cluster.notifications.RoleChanged;
30 import org.opendaylight.controller.cluster.raft.base.messages.ApplyLogEntries;
31 import org.opendaylight.controller.cluster.raft.base.messages.ApplySnapshot;
32 import org.opendaylight.controller.cluster.raft.base.messages.ApplyState;
33 import org.opendaylight.controller.cluster.raft.base.messages.CaptureSnapshot;
34 import org.opendaylight.controller.cluster.raft.base.messages.CaptureSnapshotReply;
35 import org.opendaylight.controller.cluster.raft.base.messages.Replicate;
36 import org.opendaylight.controller.cluster.raft.base.messages.SendHeartBeat;
37 import org.opendaylight.controller.cluster.raft.base.messages.SendInstallSnapshot;
38 import org.opendaylight.controller.cluster.raft.behaviors.AbstractRaftActorBehavior;
39 import org.opendaylight.controller.cluster.raft.behaviors.Follower;
40 import org.opendaylight.controller.cluster.raft.behaviors.RaftActorBehavior;
41 import org.opendaylight.controller.cluster.raft.client.messages.FindLeader;
42 import org.opendaylight.controller.cluster.raft.client.messages.FindLeaderReply;
43 import org.opendaylight.controller.cluster.raft.messages.AppendEntriesReply;
44 import org.opendaylight.controller.cluster.raft.protobuff.client.messages.Payload;
45 import org.opendaylight.controller.protobuff.messages.cluster.raft.AppendEntriesMessages;
46
47 /**
48  * RaftActor encapsulates a state machine that needs to be kept synchronized
49  * in a cluster. It implements the RAFT algorithm as described in the paper
50  * <a href='https://ramcloud.stanford.edu/wiki/download/attachments/11370504/raft.pdf'>
51  * In Search of an Understandable Consensus Algorithm</a>
52  * <p/>
53  * RaftActor has 3 states and each state has a certain behavior associated
54  * with it. A Raft actor can behave as,
55  * <ul>
56  * <li> A Leader </li>
57  * <li> A Follower (or) </li>
58  * <li> A Candidate </li>
59  * </ul>
60  * <p/>
61  * <p/>
62  * A RaftActor MUST be a Leader in order to accept requests from clients to
63  * change the state of it's encapsulated state machine. Once a RaftActor becomes
64  * a Leader it is also responsible for ensuring that all followers ultimately
65  * have the same log and therefore the same state machine as itself.
66  * <p/>
67  * <p/>
68  * The current behavior of a RaftActor determines how election for leadership
69  * is initiated and how peer RaftActors react to request for votes.
70  * <p/>
71  * <p/>
72  * Each RaftActor also needs to know the current election term. It uses this
73  * information for a couple of things. One is to simply figure out who it
74  * voted for in the last election. Another is to figure out if the message
75  * it received to update it's state is stale.
76  * <p/>
77  * <p/>
78  * The RaftActor uses akka-persistence to store it's replicated log.
79  * Furthermore through it's behaviors a Raft Actor determines
80  * <p/>
81  * <ul>
82  * <li> when a log entry should be persisted </li>
83  * <li> when a log entry should be applied to the state machine (and) </li>
84  * <li> when a snapshot should be saved </li>
85  * </ul>
86  */
87 public abstract class RaftActor extends AbstractUntypedPersistentActor {
88     protected final LoggingAdapter LOG =
89         Logging.getLogger(getContext().system(), this);
90
91     /**
92      * The current state determines the current behavior of a RaftActor
93      * A Raft Actor always starts off in the Follower State
94      */
95     private RaftActorBehavior currentBehavior;
96
97     /**
98      * This context should NOT be passed directly to any other actor it is
99      * only to be consumed by the RaftActorBehaviors
100      */
101     private final RaftActorContext context;
102
103     /**
104      * The in-memory journal
105      */
106     private ReplicatedLogImpl replicatedLog = new ReplicatedLogImpl();
107
108     private CaptureSnapshot captureSnapshot = null;
109
110     private volatile boolean hasSnapshotCaptureInitiated = false;
111
112     private Stopwatch recoveryTimer;
113
114     private int currentRecoveryBatchCount;
115
116     public RaftActor(String id, Map<String, String> peerAddresses) {
117         this(id, peerAddresses, Optional.<ConfigParams>absent());
118     }
119
120     public RaftActor(String id, Map<String, String> peerAddresses,
121          Optional<ConfigParams> configParams) {
122
123         context = new RaftActorContextImpl(this.getSelf(),
124             this.getContext(), id, new ElectionTermImpl(),
125             -1, -1, replicatedLog, peerAddresses,
126             (configParams.isPresent() ? configParams.get(): new DefaultConfigParamsImpl()),
127             LOG);
128     }
129
130     private void initRecoveryTimer() {
131         if(recoveryTimer == null) {
132             recoveryTimer = new Stopwatch();
133             recoveryTimer.start();
134         }
135     }
136
137     @Override
138     public void preStart() throws Exception {
139         LOG.info("Starting recovery for {} with journal batch size {}", persistenceId(),
140                 context.getConfigParams().getJournalRecoveryLogBatchSize());
141
142         super.preStart();
143     }
144
145     @Override
146     public void handleRecover(Object message) {
147         if(persistence().isRecoveryApplicable()) {
148             if (message instanceof SnapshotOffer) {
149                 onRecoveredSnapshot((SnapshotOffer) message);
150             } else if (message instanceof ReplicatedLogEntry) {
151                 onRecoveredJournalLogEntry((ReplicatedLogEntry) message);
152             } else if (message instanceof ApplyLogEntries) {
153                 onRecoveredApplyLogEntries((ApplyLogEntries) message);
154             } else if (message instanceof DeleteEntries) {
155                 replicatedLog.removeFrom(((DeleteEntries) message).getFromIndex());
156             } else if (message instanceof UpdateElectionTerm) {
157                 context.getTermInformation().update(((UpdateElectionTerm) message).getCurrentTerm(),
158                         ((UpdateElectionTerm) message).getVotedFor());
159             } else if (message instanceof RecoveryCompleted) {
160                 onRecoveryCompletedMessage();
161             }
162         } else {
163             if (message instanceof RecoveryCompleted) {
164                 // Delete all the messages from the akka journal so that we do not end up with consistency issues
165                 // Note I am not using the dataPersistenceProvider and directly using the akka api here
166                 deleteMessages(lastSequenceNr());
167
168                 // Delete all the akka snapshots as they will not be needed
169                 deleteSnapshots(new SnapshotSelectionCriteria(scala.Long.MaxValue(), scala.Long.MaxValue()));
170
171                 onRecoveryComplete();
172
173                 RaftActorBehavior oldBehavior = currentBehavior;
174                 currentBehavior = new Follower(context);
175                 handleBehaviorChange(oldBehavior, currentBehavior);
176             }
177         }
178     }
179
180     private void onRecoveredSnapshot(SnapshotOffer offer) {
181         if(LOG.isDebugEnabled()) {
182             LOG.debug("SnapshotOffer called..");
183         }
184
185         initRecoveryTimer();
186
187         Snapshot snapshot = (Snapshot) offer.snapshot();
188
189         // Create a replicated log with the snapshot information
190         // The replicated log can be used later on to retrieve this snapshot
191         // when we need to install it on a peer
192         replicatedLog = new ReplicatedLogImpl(snapshot);
193
194         context.setReplicatedLog(replicatedLog);
195         context.setLastApplied(snapshot.getLastAppliedIndex());
196         context.setCommitIndex(snapshot.getLastAppliedIndex());
197
198         Stopwatch timer = new Stopwatch();
199         timer.start();
200
201         // Apply the snapshot to the actors state
202         applyRecoverySnapshot(ByteString.copyFrom(snapshot.getState()));
203
204         timer.stop();
205         LOG.info("Recovery snapshot applied for {} in {}: snapshotIndex={}, snapshotTerm={}, journal-size=" +
206                 replicatedLog.size(), persistenceId(), timer.toString(),
207                 replicatedLog.snapshotIndex, replicatedLog.snapshotTerm);
208     }
209
210     private void onRecoveredJournalLogEntry(ReplicatedLogEntry logEntry) {
211         if(LOG.isDebugEnabled()) {
212             LOG.debug("Received ReplicatedLogEntry for recovery: {}", logEntry.getIndex());
213         }
214
215         replicatedLog.append(logEntry);
216     }
217
218     private void onRecoveredApplyLogEntries(ApplyLogEntries ale) {
219         if(LOG.isDebugEnabled()) {
220             LOG.debug("Received ApplyLogEntries for recovery, applying to state: {} to {}",
221                     context.getLastApplied() + 1, ale.getToIndex());
222         }
223
224         for (long i = context.getLastApplied() + 1; i <= ale.getToIndex(); i++) {
225             batchRecoveredLogEntry(replicatedLog.get(i));
226         }
227
228         context.setLastApplied(ale.getToIndex());
229         context.setCommitIndex(ale.getToIndex());
230     }
231
232     private void batchRecoveredLogEntry(ReplicatedLogEntry logEntry) {
233         initRecoveryTimer();
234
235         int batchSize = context.getConfigParams().getJournalRecoveryLogBatchSize();
236         if(currentRecoveryBatchCount == 0) {
237             startLogRecoveryBatch(batchSize);
238         }
239
240         appendRecoveredLogEntry(logEntry.getData());
241
242         if(++currentRecoveryBatchCount >= batchSize) {
243             endCurrentLogRecoveryBatch();
244         }
245     }
246
247     private void endCurrentLogRecoveryBatch() {
248         applyCurrentLogRecoveryBatch();
249         currentRecoveryBatchCount = 0;
250     }
251
252     private void onRecoveryCompletedMessage() {
253         if(currentRecoveryBatchCount > 0) {
254             endCurrentLogRecoveryBatch();
255         }
256
257         onRecoveryComplete();
258
259         String recoveryTime = "";
260         if(recoveryTimer != null) {
261             recoveryTimer.stop();
262             recoveryTime = " in " + recoveryTimer.toString();
263             recoveryTimer = null;
264         }
265
266         LOG.info(
267             "Recovery completed" + recoveryTime + " - Switching actor to Follower - " +
268                 "Persistence Id =  " + persistenceId() +
269                 " Last index in log={}, snapshotIndex={}, snapshotTerm={}, " +
270                 "journal-size={}",
271             replicatedLog.lastIndex(), replicatedLog.snapshotIndex,
272             replicatedLog.snapshotTerm, replicatedLog.size());
273
274         RaftActorBehavior oldBehavior = currentBehavior;
275         currentBehavior = new Follower(context);
276         handleBehaviorChange(oldBehavior, currentBehavior);
277     }
278
279     @Override public void handleCommand(Object message) {
280         if (message instanceof ApplyState){
281             ApplyState applyState = (ApplyState) message;
282
283             if(LOG.isDebugEnabled()) {
284                 LOG.debug("Applying state for log index {} data {}",
285                     applyState.getReplicatedLogEntry().getIndex(),
286                     applyState.getReplicatedLogEntry().getData());
287             }
288
289             applyState(applyState.getClientActor(), applyState.getIdentifier(),
290                 applyState.getReplicatedLogEntry().getData());
291
292         } else if (message instanceof ApplyLogEntries){
293             ApplyLogEntries ale = (ApplyLogEntries) message;
294             if(LOG.isDebugEnabled()) {
295                 LOG.debug("Persisting ApplyLogEntries with index={}", ale.getToIndex());
296             }
297             persistence().persist(new ApplyLogEntries(ale.getToIndex()), new Procedure<ApplyLogEntries>() {
298                 @Override
299                 public void apply(ApplyLogEntries param) throws Exception {
300                 }
301             });
302
303         } else if(message instanceof ApplySnapshot ) {
304             Snapshot snapshot = ((ApplySnapshot) message).getSnapshot();
305
306             if(LOG.isDebugEnabled()) {
307                 LOG.debug("ApplySnapshot called on Follower Actor " +
308                         "snapshotIndex:{}, snapshotTerm:{}", snapshot.getLastAppliedIndex(),
309                     snapshot.getLastAppliedTerm()
310                 );
311             }
312             applySnapshot(ByteString.copyFrom(snapshot.getState()));
313
314             //clears the followers log, sets the snapshot index to ensure adjusted-index works
315             replicatedLog = new ReplicatedLogImpl(snapshot);
316             context.setReplicatedLog(replicatedLog);
317             context.setLastApplied(snapshot.getLastAppliedIndex());
318
319         } else if (message instanceof FindLeader) {
320             getSender().tell(
321                 new FindLeaderReply(getLeaderAddress()),
322                 getSelf()
323             );
324
325         } else if (message instanceof SaveSnapshotSuccess) {
326             SaveSnapshotSuccess success = (SaveSnapshotSuccess) message;
327             LOG.info("SaveSnapshotSuccess received for snapshot");
328
329             long sequenceNumber = success.metadata().sequenceNr();
330
331             commitSnapshot(sequenceNumber);
332
333         } else if (message instanceof SaveSnapshotFailure) {
334             SaveSnapshotFailure saveSnapshotFailure = (SaveSnapshotFailure) message;
335
336             LOG.info("saveSnapshotFailure.metadata():{}", saveSnapshotFailure.metadata().toString());
337             LOG.error(saveSnapshotFailure.cause(), "SaveSnapshotFailure received for snapshot Cause:");
338
339             context.getReplicatedLog().snapshotRollback();
340
341             LOG.info("Replicated Log rollbacked. Snapshot will be attempted in the next cycle." +
342                 "snapshotIndex:{}, snapshotTerm:{}, log-size:{}",
343                 context.getReplicatedLog().getSnapshotIndex(),
344                 context.getReplicatedLog().getSnapshotTerm(),
345                 context.getReplicatedLog().size());
346
347         } else if (message instanceof CaptureSnapshot) {
348             LOG.info("CaptureSnapshot received by actor");
349             CaptureSnapshot cs = (CaptureSnapshot)message;
350             captureSnapshot = cs;
351             createSnapshot();
352
353         } else if (message instanceof CaptureSnapshotReply){
354             LOG.info("CaptureSnapshotReply received by actor");
355             CaptureSnapshotReply csr = (CaptureSnapshotReply) message;
356
357             ByteString stateInBytes = csr.getSnapshot();
358             LOG.info("CaptureSnapshotReply stateInBytes size:{}", stateInBytes.size());
359             handleCaptureSnapshotReply(stateInBytes);
360
361         } else {
362             if (!(message instanceof AppendEntriesMessages.AppendEntries)
363                 && !(message instanceof AppendEntriesReply) && !(message instanceof SendHeartBeat)) {
364                 if(LOG.isDebugEnabled()) {
365                     LOG.debug("onReceiveCommand: message: {}", message.getClass());
366                 }
367             }
368
369             RaftActorBehavior oldBehavior = currentBehavior;
370             currentBehavior = currentBehavior.handleMessage(getSender(), message);
371
372             handleBehaviorChange(oldBehavior, currentBehavior);
373         }
374     }
375
376     private void handleBehaviorChange(RaftActorBehavior oldBehavior, RaftActorBehavior currentBehavior) {
377         if (oldBehavior != currentBehavior){
378             onStateChanged();
379         }
380         if (oldBehavior != null) {
381             // it can happen that the state has not changed but the leader has changed.
382             onLeaderChanged(oldBehavior.getLeaderId(), currentBehavior.getLeaderId());
383
384             if (getRoleChangeNotifier().isPresent() && oldBehavior.state() != currentBehavior.state()) {
385                 // we do not want to notify when the behavior/role is set for the first time (i.e follower)
386                 getRoleChangeNotifier().get().tell(new RoleChanged(getId(), oldBehavior.state().name(),
387                     currentBehavior.state().name()), getSelf());
388             }
389         }
390     }
391
392     /**
393      * When a derived RaftActor needs to persist something it must call
394      * persistData.
395      *
396      * @param clientActor
397      * @param identifier
398      * @param data
399      */
400     protected void persistData(ActorRef clientActor, String identifier,
401         Payload data) {
402
403         ReplicatedLogEntry replicatedLogEntry = new ReplicatedLogImplEntry(
404             context.getReplicatedLog().lastIndex() + 1,
405             context.getTermInformation().getCurrentTerm(), data);
406
407         if(LOG.isDebugEnabled()) {
408             LOG.debug("Persist data {}", replicatedLogEntry);
409         }
410
411         replicatedLog
412             .appendAndPersist(clientActor, identifier, replicatedLogEntry);
413     }
414
415     protected String getId() {
416         return context.getId();
417     }
418
419     /**
420      * Derived actors can call the isLeader method to check if the current
421      * RaftActor is the Leader or not
422      *
423      * @return true it this RaftActor is a Leader false otherwise
424      */
425     protected boolean isLeader() {
426         return context.getId().equals(currentBehavior.getLeaderId());
427     }
428
429     /**
430      * Derived actor can call getLeader if they need a reference to the Leader.
431      * This would be useful for example in forwarding a request to an actor
432      * which is the leader
433      *
434      * @return A reference to the leader if known, null otherwise
435      */
436     protected ActorSelection getLeader(){
437         String leaderAddress = getLeaderAddress();
438
439         if(leaderAddress == null){
440             return null;
441         }
442
443         return context.actorSelection(leaderAddress);
444     }
445
446     /**
447      *
448      * @return the current leader's id
449      */
450     protected String getLeaderId(){
451         return currentBehavior.getLeaderId();
452     }
453
454     protected RaftState getRaftState() {
455         return currentBehavior.state();
456     }
457
458     protected ReplicatedLogEntry getLastLogEntry() {
459         return replicatedLog.last();
460     }
461
462     protected Long getCurrentTerm(){
463         return context.getTermInformation().getCurrentTerm();
464     }
465
466     protected Long getCommitIndex(){
467         return context.getCommitIndex();
468     }
469
470     protected Long getLastApplied(){
471         return context.getLastApplied();
472     }
473
474     protected RaftActorContext getRaftActorContext() {
475         return context;
476     }
477
478     /**
479      * setPeerAddress sets the address of a known peer at a later time.
480      * <p>
481      * This is to account for situations where a we know that a peer
482      * exists but we do not know an address up-front. This may also be used in
483      * situations where a known peer starts off in a different location and we
484      * need to change it's address
485      * <p>
486      * Note that if the peerId does not match the list of peers passed to
487      * this actor during construction an IllegalStateException will be thrown.
488      *
489      * @param peerId
490      * @param peerAddress
491      */
492     protected void setPeerAddress(String peerId, String peerAddress){
493         context.setPeerAddress(peerId, peerAddress);
494     }
495
496     protected void commitSnapshot(long sequenceNumber) {
497         context.getReplicatedLog().snapshotCommit();
498
499         // TODO: Not sure if we want to be this aggressive with trimming stuff
500         trimPersistentData(sequenceNumber);
501     }
502
503     /**
504      * The applyState method will be called by the RaftActor when some data
505      * needs to be applied to the actor's state
506      *
507      * @param clientActor A reference to the client who sent this message. This
508      *                    is the same reference that was passed to persistData
509      *                    by the derived actor. clientActor may be null when
510      *                    the RaftActor is behaving as a follower or during
511      *                    recovery.
512      * @param identifier  The identifier of the persisted data. This is also
513      *                    the same identifier that was passed to persistData by
514      *                    the derived actor. identifier may be null when
515      *                    the RaftActor is behaving as a follower or during
516      *                    recovery
517      * @param data        A piece of data that was persisted by the persistData call.
518      *                    This should NEVER be null.
519      */
520     protected abstract void applyState(ActorRef clientActor, String identifier,
521         Object data);
522
523     /**
524      * This method is called during recovery at the start of a batch of state entries. Derived
525      * classes should perform any initialization needed to start a batch.
526      */
527     protected abstract void startLogRecoveryBatch(int maxBatchSize);
528
529     /**
530      * This method is called during recovery to append state data to the current batch. This method
531      * is called 1 or more times after {@link #startLogRecoveryBatch}.
532      *
533      * @param data the state data
534      */
535     protected abstract void appendRecoveredLogEntry(Payload data);
536
537     /**
538      * This method is called during recovery to reconstruct the state of the actor.
539      *
540      * @param snapshot A snapshot of the state of the actor
541      */
542     protected abstract void applyRecoverySnapshot(ByteString snapshot);
543
544     /**
545      * This method is called during recovery at the end of a batch to apply the current batched
546      * log entries. This method is called after {@link #appendRecoveredLogEntry}.
547      */
548     protected abstract void applyCurrentLogRecoveryBatch();
549
550     /**
551      * This method is called when recovery is complete.
552      */
553     protected abstract void onRecoveryComplete();
554
555     /**
556      * This method will be called by the RaftActor when a snapshot needs to be
557      * created. The derived actor should respond with its current state.
558      * <p/>
559      * During recovery the state that is returned by the derived actor will
560      * be passed back to it by calling the applySnapshot  method
561      *
562      * @return The current state of the actor
563      */
564     protected abstract void createSnapshot();
565
566     /**
567      * This method can be called at any other point during normal
568      * operations when the derived actor is out of sync with it's peers
569      * and the only way to bring it in sync is by applying a snapshot
570      *
571      * @param snapshot A snapshot of the state of the actor
572      */
573     protected abstract void applySnapshot(ByteString snapshot);
574
575     /**
576      * This method will be called by the RaftActor when the state of the
577      * RaftActor changes. The derived actor can then use methods like
578      * isLeader or getLeader to do something useful
579      */
580     protected abstract void onStateChanged();
581
582     protected abstract DataPersistenceProvider persistence();
583
584     /**
585      * Notifier Actor for this RaftActor to notify when a role change happens
586      * @return ActorRef - ActorRef of the notifier or Optional.absent if none.
587      */
588     protected abstract Optional<ActorRef> getRoleChangeNotifier();
589
590     protected void onLeaderChanged(String oldLeader, String newLeader){};
591
592     private void trimPersistentData(long sequenceNumber) {
593         // Trim akka snapshots
594         // FIXME : Not sure how exactly the SnapshotSelectionCriteria is applied
595         // For now guessing that it is ANDed.
596         persistence().deleteSnapshots(new SnapshotSelectionCriteria(
597             sequenceNumber - context.getConfigParams().getSnapshotBatchCount(), 43200000));
598
599         // Trim akka journal
600         persistence().deleteMessages(sequenceNumber);
601     }
602
603     private String getLeaderAddress(){
604         if(isLeader()){
605             return getSelf().path().toString();
606         }
607         String leaderId = currentBehavior.getLeaderId();
608         if (leaderId == null) {
609             return null;
610         }
611         String peerAddress = context.getPeerAddress(leaderId);
612         if(LOG.isDebugEnabled()) {
613             LOG.debug("getLeaderAddress leaderId = {} peerAddress = {}",
614                     leaderId, peerAddress);
615         }
616
617         return peerAddress;
618     }
619
620     private void handleCaptureSnapshotReply(ByteString stateInBytes) {
621         // create a snapshot object from the state provided and save it
622         // when snapshot is saved async, SaveSnapshotSuccess is raised.
623
624         Snapshot sn = Snapshot.create(stateInBytes.toByteArray(),
625             context.getReplicatedLog().getFrom(captureSnapshot.getLastAppliedIndex() + 1),
626             captureSnapshot.getLastIndex(), captureSnapshot.getLastTerm(),
627             captureSnapshot.getLastAppliedIndex(), captureSnapshot.getLastAppliedTerm());
628
629         persistence().saveSnapshot(sn);
630
631         LOG.info("Persisting of snapshot done:{}", sn.getLogMessage());
632
633         //be greedy and remove entries from in-mem journal which are in the snapshot
634         // and update snapshotIndex and snapshotTerm without waiting for the success,
635
636         context.getReplicatedLog().snapshotPreCommit(
637             captureSnapshot.getLastAppliedIndex(),
638             captureSnapshot.getLastAppliedTerm());
639
640         LOG.info("Removed in-memory snapshotted entries, adjusted snaphsotIndex:{} " +
641             "and term:{}", captureSnapshot.getLastAppliedIndex(),
642             captureSnapshot.getLastAppliedTerm());
643
644         if (isLeader() && captureSnapshot.isInstallSnapshotInitiated()) {
645             // this would be call straight to the leader and won't initiate in serialization
646             currentBehavior.handleMessage(getSelf(), new SendInstallSnapshot(stateInBytes));
647         }
648
649         captureSnapshot = null;
650         hasSnapshotCaptureInitiated = false;
651     }
652
653     private class ReplicatedLogImpl extends AbstractReplicatedLogImpl {
654
655         public ReplicatedLogImpl(Snapshot snapshot) {
656             super(snapshot.getLastAppliedIndex(), snapshot.getLastAppliedTerm(),
657                 snapshot.getUnAppliedEntries());
658         }
659
660         public ReplicatedLogImpl() {
661             super();
662         }
663
664         @Override public void removeFromAndPersist(long logEntryIndex) {
665             int adjustedIndex = adjustedIndex(logEntryIndex);
666
667             if (adjustedIndex < 0) {
668                 return;
669             }
670
671             // FIXME: Maybe this should be done after the command is saved
672             journal.subList(adjustedIndex , journal.size()).clear();
673
674             persistence().persist(new DeleteEntries(adjustedIndex), new Procedure<DeleteEntries>(){
675
676                 @Override public void apply(DeleteEntries param)
677                     throws Exception {
678                     //FIXME : Doing nothing for now
679                 }
680             });
681         }
682
683         @Override public void appendAndPersist(
684             final ReplicatedLogEntry replicatedLogEntry) {
685             appendAndPersist(null, null, replicatedLogEntry);
686         }
687
688         public void appendAndPersist(final ActorRef clientActor,
689             final String identifier,
690             final ReplicatedLogEntry replicatedLogEntry) {
691
692             if(LOG.isDebugEnabled()) {
693                 LOG.debug("Append log entry and persist {} ", replicatedLogEntry);
694             }
695
696             // FIXME : By adding the replicated log entry to the in-memory journal we are not truly ensuring durability of the logs
697             journal.add(replicatedLogEntry);
698
699             // When persisting events with persist it is guaranteed that the
700             // persistent actor will not receive further commands between the
701             // persist call and the execution(s) of the associated event
702             // handler. This also holds for multiple persist calls in context
703             // of a single command.
704             persistence().persist(replicatedLogEntry,
705                 new Procedure<ReplicatedLogEntry>() {
706                     @Override
707                     public void apply(ReplicatedLogEntry evt) throws Exception {
708                         // when a snaphsot is being taken, captureSnapshot != null
709                         if (hasSnapshotCaptureInitiated == false &&
710                             journal.size() % context.getConfigParams().getSnapshotBatchCount() == 0) {
711
712                             LOG.info("Initiating Snapshot Capture..");
713                             long lastAppliedIndex = -1;
714                             long lastAppliedTerm = -1;
715
716                             ReplicatedLogEntry lastAppliedEntry = get(context.getLastApplied());
717                             if (lastAppliedEntry != null) {
718                                 lastAppliedIndex = lastAppliedEntry.getIndex();
719                                 lastAppliedTerm = lastAppliedEntry.getTerm();
720                             }
721
722                             if(LOG.isDebugEnabled()) {
723                                 LOG.debug("Snapshot Capture logSize: {}", journal.size());
724                                 LOG.debug("Snapshot Capture lastApplied:{} ",
725                                     context.getLastApplied());
726                                 LOG.debug("Snapshot Capture lastAppliedIndex:{}", lastAppliedIndex);
727                                 LOG.debug("Snapshot Capture lastAppliedTerm:{}", lastAppliedTerm);
728                             }
729
730                             // send a CaptureSnapshot to self to make the expensive operation async.
731                             getSelf().tell(new CaptureSnapshot(
732                                 lastIndex(), lastTerm(), lastAppliedIndex, lastAppliedTerm),
733                                 null);
734                             hasSnapshotCaptureInitiated = true;
735                         }
736                         // Send message for replication
737                         if (clientActor != null) {
738                             currentBehavior.handleMessage(getSelf(),
739                                 new Replicate(clientActor, identifier,
740                                     replicatedLogEntry)
741                             );
742                         }
743                     }
744                 }
745             );
746         }
747
748     }
749
750     static class DeleteEntries implements Serializable {
751         private static final long serialVersionUID = 1L;
752         private final int fromIndex;
753
754         public DeleteEntries(int fromIndex) {
755             this.fromIndex = fromIndex;
756         }
757
758         public int getFromIndex() {
759             return fromIndex;
760         }
761     }
762
763
764     private class ElectionTermImpl implements ElectionTerm {
765         /**
766          * Identifier of the actor whose election term information this is
767          */
768         private long currentTerm = 0;
769         private String votedFor = null;
770
771         @Override
772         public long getCurrentTerm() {
773             return currentTerm;
774         }
775
776         @Override
777         public String getVotedFor() {
778             return votedFor;
779         }
780
781         @Override public void update(long currentTerm, String votedFor) {
782             if(LOG.isDebugEnabled()) {
783                 LOG.debug("Set currentTerm={}, votedFor={}", currentTerm, votedFor);
784             }
785             this.currentTerm = currentTerm;
786             this.votedFor = votedFor;
787         }
788
789         @Override
790         public void updateAndPersist(long currentTerm, String votedFor){
791             update(currentTerm, votedFor);
792             // FIXME : Maybe first persist then update the state
793             persistence().persist(new UpdateElectionTerm(this.currentTerm, this.votedFor), new Procedure<UpdateElectionTerm>(){
794
795                 @Override public void apply(UpdateElectionTerm param)
796                     throws Exception {
797
798                 }
799             });
800         }
801     }
802
803     static class UpdateElectionTerm implements Serializable {
804         private static final long serialVersionUID = 1L;
805         private final long currentTerm;
806         private final String votedFor;
807
808         public UpdateElectionTerm(long currentTerm, String votedFor) {
809             this.currentTerm = currentTerm;
810             this.votedFor = votedFor;
811         }
812
813         public long getCurrentTerm() {
814             return currentTerm;
815         }
816
817         public String getVotedFor() {
818             return votedFor;
819         }
820     }
821
822     protected class NonPersistentRaftDataProvider extends NonPersistentDataProvider {
823
824         public NonPersistentRaftDataProvider(){
825
826         }
827
828         /**
829          * The way snapshotting works is,
830          * <ol>
831          * <li> RaftActor calls createSnapshot on the Shard
832          * <li> Shard sends a CaptureSnapshotReply and RaftActor then calls saveSnapshot
833          * <li> When saveSnapshot is invoked on the akka-persistence API it uses the SnapshotStore to save the snapshot.
834          * The SnapshotStore sends SaveSnapshotSuccess or SaveSnapshotFailure. When the RaftActor gets SaveSnapshot
835          * success it commits the snapshot to the in-memory journal. This commitSnapshot is mimicking what is done
836          * in SaveSnapshotSuccess.
837          * </ol>
838          * @param o
839          */
840         @Override
841         public void saveSnapshot(Object o) {
842             // Make saving Snapshot successful
843             commitSnapshot(-1L);
844         }
845     }
846
847     @VisibleForTesting
848     void setCurrentBehavior(AbstractRaftActorBehavior behavior) {
849         currentBehavior = behavior;
850     }
851
852     protected RaftActorBehavior getCurrentBehavior() {
853         return currentBehavior;
854     }
855
856 }

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