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 akka.persistence.UntypedPersistentActor;
  22 import com.google.common.base.Optional;
  23 import com.google.protobuf.ByteString;
  24 import org.opendaylight.controller.cluster.raft.base.messages.ApplySnapshot;
  25 import org.opendaylight.controller.cluster.raft.base.messages.ApplyState;
  26 import org.opendaylight.controller.cluster.raft.base.messages.CaptureSnapshot;
  27 import org.opendaylight.controller.cluster.raft.base.messages.CaptureSnapshotReply;
  28 import org.opendaylight.controller.cluster.raft.base.messages.Replicate;
  29 import org.opendaylight.controller.cluster.raft.base.messages.SendHeartBeat;
  30 import org.opendaylight.controller.cluster.raft.behaviors.Candidate;
  31 import org.opendaylight.controller.cluster.raft.behaviors.Follower;
  32 import org.opendaylight.controller.cluster.raft.behaviors.Leader;
  33 import org.opendaylight.controller.cluster.raft.behaviors.RaftActorBehavior;
  34 import org.opendaylight.controller.cluster.raft.client.messages.AddRaftPeer;
  35 import org.opendaylight.controller.cluster.raft.client.messages.FindLeader;
  36 import org.opendaylight.controller.cluster.raft.client.messages.FindLeaderReply;
  37 import org.opendaylight.controller.cluster.raft.client.messages.RemoveRaftPeer;
  38 import org.opendaylight.controller.cluster.raft.messages.AppendEntriesReply;
  39 import org.opendaylight.controller.cluster.raft.protobuff.client.messages.Payload;
  40 import org.opendaylight.controller.protobuff.messages.cluster.raft.AppendEntriesMessages;
  41
  42 import java.io.Serializable;
  43 import java.util.Map;
  44
  45 /**
  46  * RaftActor encapsulates a state machine that needs to be kept synchronized
  47  * in a cluster. It implements the RAFT algorithm as described in the paper
  48  * <a href='https://ramcloud.stanford.edu/wiki/download/attachments/11370504/raft.pdf'>
  49  * In Search of an Understandable Consensus Algorithm</a>
  50  * <p/>
  51  * RaftActor has 3 states and each state has a certain behavior associated
  52  * with it. A Raft actor can behave as,
  53  * <ul>
  54  * <li> A Leader </li>
  55  * <li> A Follower (or) </li>
  56  * <li> A Candidate </li>
  57  * </ul>
  58  * <p/>
  59  * <p/>
  60  * A RaftActor MUST be a Leader in order to accept requests from clients to
  61  * change the state of it's encapsulated state machine. Once a RaftActor becomes
  62  * a Leader it is also responsible for ensuring that all followers ultimately
  63  * have the same log and therefore the same state machine as itself.
  64  * <p/>
  65  * <p/>
  66  * The current behavior of a RaftActor determines how election for leadership
  67  * is initiated and how peer RaftActors react to request for votes.
  68  * <p/>
  69  * <p/>
  70  * Each RaftActor also needs to know the current election term. It uses this
  71  * information for a couple of things. One is to simply figure out who it
  72  * voted for in the last election. Another is to figure out if the message
  73  * it received to update it's state is stale.
  74  * <p/>
  75  * <p/>
  76  * The RaftActor uses akka-persistence to store it's replicated log.
  77  * Furthermore through it's behaviors a Raft Actor determines
  78  * <p/>
  79  * <ul>
  80  * <li> when a log entry should be persisted </li>
  81  * <li> when a log entry should be applied to the state machine (and) </li>
  82  * <li> when a snapshot should be saved </li>
  83  * </ul>
  84  */
  85 public abstract class RaftActor extends UntypedPersistentActor {
  86     protected final LoggingAdapter LOG =
  87         Logging.getLogger(getContext().system(), this);
  88
  89     /**
  90      * The current state determines the current behavior of a RaftActor
  91      * A Raft Actor always starts off in the Follower State
  92      */
  93     private RaftActorBehavior currentBehavior;
  94
  95     /**
  96      * This context should NOT be passed directly to any other actor it is
  97      * only to be consumed by the RaftActorBehaviors
  98      */
  99     protected RaftActorContext context;
 100
 101     /**
 102      * The in-memory journal
 103      */
 104     private ReplicatedLogImpl replicatedLog = new ReplicatedLogImpl();
 105
 106     private CaptureSnapshot captureSnapshot = null;
 107
 108     private volatile boolean hasSnapshotCaptureInitiated = false;
 109
 110     public RaftActor(String id, Map<String, String> peerAddresses) {
 111         this(id, peerAddresses, Optional.<ConfigParams>absent());
 112     }
 113
 114     public RaftActor(String id, Map<String, String> peerAddresses,
 115          Optional<ConfigParams> configParams) {
 116
 117         context = new RaftActorContextImpl(this.getSelf(),
 118             this.getContext(), id, new ElectionTermImpl(),
 119             -1, -1, replicatedLog, peerAddresses,
 120             (configParams.isPresent() ? configParams.get(): new DefaultConfigParamsImpl()),
 121             LOG);
 122     }
 123
 124     @Override public void onReceiveRecover(Object message) {
 125         if (message instanceof SnapshotOffer) {
 126             LOG.info("SnapshotOffer called..");
 127             SnapshotOffer offer = (SnapshotOffer) message;
 128             Snapshot snapshot = (Snapshot) offer.snapshot();
 129
 130             // Create a replicated log with the snapshot information
 131             // The replicated log can be used later on to retrieve this snapshot
 132             // when we need to install it on a peer
 133             replicatedLog = new ReplicatedLogImpl(snapshot);
 134
 135             context.setReplicatedLog(replicatedLog);
 136             context.setLastApplied(snapshot.getLastAppliedIndex());
 137             context.setCommitIndex(snapshot.getLastAppliedIndex());
 138
 139             LOG.info("Applied snapshot to replicatedLog. " +
 140                     "snapshotIndex={}, snapshotTerm={}, journal-size={}",
 141                 replicatedLog.snapshotIndex, replicatedLog.snapshotTerm,
 142                 replicatedLog.size()
 143             );
 144
 145             // Apply the snapshot to the actors state
 146             applySnapshot(ByteString.copyFrom(snapshot.getState()));
 147
 148         } else if (message instanceof ReplicatedLogEntry) {
 149             ReplicatedLogEntry logEntry = (ReplicatedLogEntry) message;
 150
 151             // Apply State immediately
 152             replicatedLog.append(logEntry);
 153             applyState(null, "recovery", logEntry.getData());
 154             context.setLastApplied(logEntry.getIndex());
 155             context.setCommitIndex(logEntry.getIndex());
 156
 157         } else if (message instanceof DeleteEntries) {
 158             replicatedLog.removeFrom(((DeleteEntries) message).getFromIndex());
 159
 160         } else if (message instanceof UpdateElectionTerm) {
 161             context.getTermInformation().update(((UpdateElectionTerm) message).getCurrentTerm(),
 162                 ((UpdateElectionTerm) message).getVotedFor());
 163
 164         } else if (message instanceof RecoveryCompleted) {
 165             LOG.info(
 166                 "RecoveryCompleted - Switching actor to Follower - " +
 167                     "Persistence Id =  " + persistenceId() +
 168                     " Last index in log:{}, snapshotIndex={}, snapshotTerm={}, " +
 169                     "journal-size={}",
 170                 replicatedLog.lastIndex(), replicatedLog.snapshotIndex,
 171                 replicatedLog.snapshotTerm, replicatedLog.size());
 172             currentBehavior = switchBehavior(RaftState.Follower);
 173             onStateChanged();
 174         }
 175     }
 176
 177     @Override public void onReceiveCommand(Object message) {
 178         if (message instanceof ApplyState){
 179             ApplyState applyState = (ApplyState) message;
 180
 181             if(LOG.isDebugEnabled()) {
 182                 LOG.debug("Applying state for log index {} data {}",
 183                     applyState.getReplicatedLogEntry().getIndex(),
 184                     applyState.getReplicatedLogEntry().getData());
 185             }
 186
 187             applyState(applyState.getClientActor(), applyState.getIdentifier(),
 188                 applyState.getReplicatedLogEntry().getData());
 189
 190         } else if(message instanceof ApplySnapshot ) {
 191             Snapshot snapshot = ((ApplySnapshot) message).getSnapshot();
 192
 193             if(LOG.isDebugEnabled()) {
 194                 LOG.debug("ApplySnapshot called on Follower Actor " +
 195                         "snapshotIndex:{}, snapshotTerm:{}", snapshot.getLastAppliedIndex(),
 196                     snapshot.getLastAppliedTerm()
 197                 );
 198             }
 199             applySnapshot(ByteString.copyFrom(snapshot.getState()));
 200
 201             //clears the followers log, sets the snapshot index to ensure adjusted-index works
 202             replicatedLog = new ReplicatedLogImpl(snapshot);
 203             context.setReplicatedLog(replicatedLog);
 204             context.setLastApplied(snapshot.getLastAppliedIndex());
 205
 206         } else if (message instanceof FindLeader) {
 207             getSender().tell(
 208                 new FindLeaderReply(getLeaderAddress()),
 209                 getSelf()
 210             );
 211
 212         } else if (message instanceof SaveSnapshotSuccess) {
 213             SaveSnapshotSuccess success = (SaveSnapshotSuccess) message;
 214             LOG.info("SaveSnapshotSuccess received for snapshot");
 215
 216             context.getReplicatedLog().snapshotCommit();
 217
 218             // TODO: Not sure if we want to be this aggressive with trimming stuff
 219             trimPersistentData(success.metadata().sequenceNr());
 220
 221         } else if (message instanceof SaveSnapshotFailure) {
 222             SaveSnapshotFailure saveSnapshotFailure = (SaveSnapshotFailure) message;
 223
 224             LOG.info("saveSnapshotFailure.metadata():{}", saveSnapshotFailure.metadata().toString());
 225             LOG.error(saveSnapshotFailure.cause(), "SaveSnapshotFailure received for snapshot Cause:");
 226
 227             context.getReplicatedLog().snapshotRollback();
 228
 229             LOG.info("Replicated Log rollbacked. Snapshot will be attempted in the next cycle." +
 230                 "snapshotIndex:{}, snapshotTerm:{}, log-size:{}",
 231                 context.getReplicatedLog().getSnapshotIndex(),
 232                 context.getReplicatedLog().getSnapshotTerm(),
 233                 context.getReplicatedLog().size());
 234
 235         } else if (message instanceof AddRaftPeer){
 236
 237             // FIXME : Do not add raft peers like this.
 238             // When adding a new Peer we have to ensure that the a majority of
 239             // the peers know about the new Peer. Doing it this way may cause
 240             // a situation where multiple Leaders may emerge
 241             AddRaftPeer arp = (AddRaftPeer)message;
 242            context.addToPeers(arp.getName(), arp.getAddress());
 243
 244         } else if (message instanceof RemoveRaftPeer){
 245
 246             RemoveRaftPeer rrp = (RemoveRaftPeer)message;
 247             context.removePeer(rrp.getName());
 248
 249         } else if (message instanceof CaptureSnapshot) {
 250             LOG.info("CaptureSnapshot received by actor");
 251             CaptureSnapshot cs = (CaptureSnapshot)message;
 252             captureSnapshot = cs;
 253             createSnapshot();
 254
 255         } else if (message instanceof CaptureSnapshotReply){
 256             LOG.info("CaptureSnapshotReply received by actor");
 257             CaptureSnapshotReply csr = (CaptureSnapshotReply) message;
 258
 259             ByteString stateInBytes = csr.getSnapshot();
 260             LOG.info("CaptureSnapshotReply stateInBytes size:{}", stateInBytes.size());
 261             handleCaptureSnapshotReply(stateInBytes);
 262
 263         } else {
 264             if (!(message instanceof AppendEntriesMessages.AppendEntries)
 265                 && !(message instanceof AppendEntriesReply) && !(message instanceof SendHeartBeat)) {
 266                 if(LOG.isDebugEnabled()) {
 267                     LOG.debug("onReceiveCommand: message:" + message.getClass());
 268                 }
 269             }
 270
 271             RaftState state =
 272                 currentBehavior.handleMessage(getSender(), message);
 273             RaftActorBehavior oldBehavior = currentBehavior;
 274             currentBehavior = switchBehavior(state);
 275             if(oldBehavior != currentBehavior){
 276                 onStateChanged();
 277             }
 278
 279             onLeaderChanged(oldBehavior.getLeaderId(), currentBehavior.getLeaderId());
 280         }
 281     }
 282
 283     public java.util.Set<String> getPeers() {
 284         return context.getPeerAddresses().keySet();
 285     }
 286
 287     protected String getReplicatedLogState() {
 288         return "snapshotIndex=" + context.getReplicatedLog().getSnapshotIndex()
 289             + ", snapshotTerm=" + context.getReplicatedLog().getSnapshotTerm()
 290             + ", im-mem journal size=" + context.getReplicatedLog().size();
 291     }
 292
 293
 294     /**
 295      * When a derived RaftActor needs to persist something it must call
 296      * persistData.
 297      *
 298      * @param clientActor
 299      * @param identifier
 300      * @param data
 301      */
 302     protected void persistData(ActorRef clientActor, String identifier,
 303         Payload data) {
 304
 305         ReplicatedLogEntry replicatedLogEntry = new ReplicatedLogImplEntry(
 306             context.getReplicatedLog().lastIndex() + 1,
 307             context.getTermInformation().getCurrentTerm(), data);
 308
 309         if(LOG.isDebugEnabled()) {
 310             LOG.debug("Persist data {}", replicatedLogEntry);
 311         }
 312
 313         replicatedLog
 314             .appendAndPersist(clientActor, identifier, replicatedLogEntry);
 315     }
 316
 317     protected String getId() {
 318         return context.getId();
 319     }
 320
 321     /**
 322      * Derived actors can call the isLeader method to check if the current
 323      * RaftActor is the Leader or not
 324      *
 325      * @return true it this RaftActor is a Leader false otherwise
 326      */
 327     protected boolean isLeader() {
 328         return context.getId().equals(currentBehavior.getLeaderId());
 329     }
 330
 331     /**
 332      * Derived actor can call getLeader if they need a reference to the Leader.
 333      * This would be useful for example in forwarding a request to an actor
 334      * which is the leader
 335      *
 336      * @return A reference to the leader if known, null otherwise
 337      */
 338     protected ActorSelection getLeader(){
 339         String leaderAddress = getLeaderAddress();
 340
 341         if(leaderAddress == null){
 342             return null;
 343         }
 344
 345         return context.actorSelection(leaderAddress);
 346     }
 347
 348     /**
 349      *
 350      * @return the current leader's id
 351      */
 352     protected String getLeaderId(){
 353         return currentBehavior.getLeaderId();
 354     }
 355
 356     protected RaftState getRaftState() {
 357         return currentBehavior.state();
 358     }
 359
 360     protected ReplicatedLogEntry getLastLogEntry() {
 361         return replicatedLog.last();
 362     }
 363
 364     protected Long getCurrentTerm(){
 365         return context.getTermInformation().getCurrentTerm();
 366     }
 367
 368     protected Long getCommitIndex(){
 369         return context.getCommitIndex();
 370     }
 371
 372     protected Long getLastApplied(){
 373         return context.getLastApplied();
 374     }
 375
 376     /**
 377      * setPeerAddress sets the address of a known peer at a later time.
 378      * <p>
 379      * This is to account for situations where a we know that a peer
 380      * exists but we do not know an address up-front. This may also be used in
 381      * situations where a known peer starts off in a different location and we
 382      * need to change it's address
 383      * <p>
 384      * Note that if the peerId does not match the list of peers passed to
 385      * this actor during construction an IllegalStateException will be thrown.
 386      *
 387      * @param peerId
 388      * @param peerAddress
 389      */
 390     protected void setPeerAddress(String peerId, String peerAddress){
 391         context.setPeerAddress(peerId, peerAddress);
 392     }
 393
 394
 395
 396     /**
 397      * The applyState method will be called by the RaftActor when some data
 398      * needs to be applied to the actor's state
 399      *
 400      * @param clientActor A reference to the client who sent this message. This
 401      *                    is the same reference that was passed to persistData
 402      *                    by the derived actor. clientActor may be null when
 403      *                    the RaftActor is behaving as a follower or during
 404      *                    recovery.
 405      * @param identifier  The identifier of the persisted data. This is also
 406      *                    the same identifier that was passed to persistData by
 407      *                    the derived actor. identifier may be null when
 408      *                    the RaftActor is behaving as a follower or during
 409      *                    recovery
 410      * @param data        A piece of data that was persisted by the persistData call.
 411      *                    This should NEVER be null.
 412      */
 413     protected abstract void applyState(ActorRef clientActor, String identifier,
 414         Object data);
 415
 416     /**
 417      * This method will be called by the RaftActor when a snapshot needs to be
 418      * created. The derived actor should respond with its current state.
 419      * <p/>
 420      * During recovery the state that is returned by the derived actor will
 421      * be passed back to it by calling the applySnapshot  method
 422      *
 423      * @return The current state of the actor
 424      */
 425     protected abstract void createSnapshot();
 426
 427     /**
 428      * This method will be called by the RaftActor during recovery to
 429      * reconstruct the state of the actor.
 430      * <p/>
 431      * This method may also be called at any other point during normal
 432      * operations when the derived actor is out of sync with it's peers
 433      * and the only way to bring it in sync is by applying a snapshot
 434      *
 435      * @param snapshot A snapshot of the state of the actor
 436      */
 437     protected abstract void applySnapshot(ByteString snapshot);
 438
 439     /**
 440      * This method will be called by the RaftActor when the state of the
 441      * RaftActor changes. The derived actor can then use methods like
 442      * isLeader or getLeader to do something useful
 443      */
 444     protected abstract void onStateChanged();
 445
 446     protected void onLeaderChanged(String oldLeader, String newLeader){};
 447
 448     private RaftActorBehavior switchBehavior(RaftState state) {
 449         if (currentBehavior != null) {
 450             if (currentBehavior.state() == state) {
 451                 return currentBehavior;
 452             }
 453             LOG.info("Switching from state " + currentBehavior.state() + " to "
 454                 + state);
 455
 456             try {
 457                 currentBehavior.close();
 458             } catch (Exception e) {
 459                 LOG.error(e,
 460                     "Failed to close behavior : " + currentBehavior.state());
 461             }
 462
 463         } else {
 464             LOG.info("Switching behavior to " + state);
 465         }
 466         RaftActorBehavior behavior = null;
 467         if (state == RaftState.Candidate) {
 468             behavior = new Candidate(context);
 469         } else if (state == RaftState.Follower) {
 470             behavior = new Follower(context);
 471         } else {
 472             behavior = new Leader(context);
 473         }
 474
 475
 476
 477         return behavior;
 478     }
 479
 480     private void trimPersistentData(long sequenceNumber) {
 481         // Trim akka snapshots
 482         // FIXME : Not sure how exactly the SnapshotSelectionCriteria is applied
 483         // For now guessing that it is ANDed.
 484         deleteSnapshots(new SnapshotSelectionCriteria(
 485             sequenceNumber - context.getConfigParams().getSnapshotBatchCount(), 43200000));
 486
 487         // Trim akka journal
 488         deleteMessages(sequenceNumber);
 489     }
 490
 491     private String getLeaderAddress(){
 492         if(isLeader()){
 493             return getSelf().path().toString();
 494         }
 495         String leaderId = currentBehavior.getLeaderId();
 496         if (leaderId == null) {
 497             return null;
 498         }
 499         String peerAddress = context.getPeerAddress(leaderId);
 500         if(LOG.isDebugEnabled()) {
 501             LOG.debug("getLeaderAddress leaderId = " + leaderId + " peerAddress = "
 502                 + peerAddress);
 503         }
 504
 505         return peerAddress;
 506     }
 507
 508     private void handleCaptureSnapshotReply(ByteString stateInBytes) {
 509         // create a snapshot object from the state provided and save it
 510         // when snapshot is saved async, SaveSnapshotSuccess is raised.
 511
 512         Snapshot sn = Snapshot.create(stateInBytes.toByteArray(),
 513             context.getReplicatedLog().getFrom(captureSnapshot.getLastAppliedIndex() + 1),
 514             captureSnapshot.getLastIndex(), captureSnapshot.getLastTerm(),
 515             captureSnapshot.getLastAppliedIndex(), captureSnapshot.getLastAppliedTerm());
 516
 517         saveSnapshot(sn);
 518
 519         LOG.info("Persisting of snapshot done:{}", sn.getLogMessage());
 520
 521         //be greedy and remove entries from in-mem journal which are in the snapshot
 522         // and update snapshotIndex and snapshotTerm without waiting for the success,
 523
 524         context.getReplicatedLog().snapshotPreCommit(stateInBytes,
 525             captureSnapshot.getLastAppliedIndex(),
 526             captureSnapshot.getLastAppliedTerm());
 527
 528         LOG.info("Removed in-memory snapshotted entries, adjusted snaphsotIndex:{} " +
 529             "and term:{}", captureSnapshot.getLastAppliedIndex(),
 530             captureSnapshot.getLastAppliedTerm());
 531
 532         captureSnapshot = null;
 533         hasSnapshotCaptureInitiated = false;
 534     }
 535
 536
 537     private class ReplicatedLogImpl extends AbstractReplicatedLogImpl {
 538
 539         public ReplicatedLogImpl(Snapshot snapshot) {
 540             super(ByteString.copyFrom(snapshot.getState()),
 541                 snapshot.getLastAppliedIndex(), snapshot.getLastAppliedTerm(),
 542                 snapshot.getUnAppliedEntries());
 543         }
 544
 545         public ReplicatedLogImpl() {
 546             super();
 547         }
 548
 549         @Override public void removeFromAndPersist(long logEntryIndex) {
 550             int adjustedIndex = adjustedIndex(logEntryIndex);
 551
 552             if (adjustedIndex < 0) {
 553                 return;
 554             }
 555
 556             // FIXME: Maybe this should be done after the command is saved
 557             journal.subList(adjustedIndex , journal.size()).clear();
 558
 559             persist(new DeleteEntries(adjustedIndex), new Procedure<DeleteEntries>(){
 560
 561                 @Override public void apply(DeleteEntries param)
 562                     throws Exception {
 563                     //FIXME : Doing nothing for now
 564                 }
 565             });
 566         }
 567
 568         @Override public void appendAndPersist(
 569             final ReplicatedLogEntry replicatedLogEntry) {
 570             appendAndPersist(null, null, replicatedLogEntry);
 571         }
 572
 573         public void appendAndPersist(final ActorRef clientActor,
 574             final String identifier,
 575             final ReplicatedLogEntry replicatedLogEntry) {
 576             context.getLogger().debug(
 577                 "Append log entry and persist {} ", replicatedLogEntry);
 578             // FIXME : By adding the replicated log entry to the in-memory journal we are not truly ensuring durability of the logs
 579             journal.add(replicatedLogEntry);
 580
 581             // When persisting events with persist it is guaranteed that the
 582             // persistent actor will not receive further commands between the
 583             // persist call and the execution(s) of the associated event
 584             // handler. This also holds for multiple persist calls in context
 585             // of a single command.
 586             persist(replicatedLogEntry,
 587                 new Procedure<ReplicatedLogEntry>() {
 588                     public void apply(ReplicatedLogEntry evt) throws Exception {
 589                         // when a snaphsot is being taken, captureSnapshot != null
 590                         if (hasSnapshotCaptureInitiated == false &&
 591                             journal.size() % context.getConfigParams().getSnapshotBatchCount() == 0) {
 592
 593                             LOG.info("Initiating Snapshot Capture..");
 594                             long lastAppliedIndex = -1;
 595                             long lastAppliedTerm = -1;
 596
 597                             ReplicatedLogEntry lastAppliedEntry = get(context.getLastApplied());
 598                             if (lastAppliedEntry != null) {
 599                                 lastAppliedIndex = lastAppliedEntry.getIndex();
 600                                 lastAppliedTerm = lastAppliedEntry.getTerm();
 601                             }
 602
 603                             if(LOG.isDebugEnabled()) {
 604                                 LOG.debug("Snapshot Capture logSize: {}", journal.size());
 605                                 LOG.debug("Snapshot Capture lastApplied:{} ",
 606                                     context.getLastApplied());
 607                                 LOG.debug("Snapshot Capture lastAppliedIndex:{}", lastAppliedIndex);
 608                                 LOG.debug("Snapshot Capture lastAppliedTerm:{}", lastAppliedTerm);
 609                             }
 610
 611                             // send a CaptureSnapshot to self to make the expensive operation async.
 612                             getSelf().tell(new CaptureSnapshot(
 613                                 lastIndex(), lastTerm(), lastAppliedIndex, lastAppliedTerm),
 614                                 null);
 615                             hasSnapshotCaptureInitiated = true;
 616                         }
 617                         // Send message for replication
 618                         if (clientActor != null) {
 619                             currentBehavior.handleMessage(getSelf(),
 620                                 new Replicate(clientActor, identifier,
 621                                     replicatedLogEntry)
 622                             );
 623                         }
 624                     }
 625                 }
 626             );
 627         }
 628
 629     }
 630
 631     private static class DeleteEntries implements Serializable {
 632         private final int fromIndex;
 633
 634
 635         public DeleteEntries(int fromIndex) {
 636             this.fromIndex = fromIndex;
 637         }
 638
 639         public int getFromIndex() {
 640             return fromIndex;
 641         }
 642     }
 643
 644
 645     private class ElectionTermImpl implements ElectionTerm {
 646         /**
 647          * Identifier of the actor whose election term information this is
 648          */
 649         private long currentTerm = 0;
 650         private String votedFor = null;
 651
 652         public long getCurrentTerm() {
 653             return currentTerm;
 654         }
 655
 656         public String getVotedFor() {
 657             return votedFor;
 658         }
 659
 660         @Override public void update(long currentTerm, String votedFor) {
 661             if(LOG.isDebugEnabled()) {
 662                 LOG.debug("Set currentTerm={}, votedFor={}", currentTerm, votedFor);
 663             }
 664             this.currentTerm = currentTerm;
 665             this.votedFor = votedFor;
 666         }
 667
 668         @Override
 669         public void updateAndPersist(long currentTerm, String votedFor){
 670             update(currentTerm, votedFor);
 671             // FIXME : Maybe first persist then update the state
 672             persist(new UpdateElectionTerm(this.currentTerm, this.votedFor), new Procedure<UpdateElectionTerm>(){
 673
 674                 @Override public void apply(UpdateElectionTerm param)
 675                     throws Exception {
 676
 677                 }
 678             });
 679         }
 680     }
 681
 682     private static class UpdateElectionTerm implements Serializable {
 683         private final long currentTerm;
 684         private final String votedFor;
 685
 686         public UpdateElectionTerm(long currentTerm, String votedFor) {
 687             this.currentTerm = currentTerm;
 688             this.votedFor = votedFor;
 689         }
 690
 691         public long getCurrentTerm() {
 692             return currentTerm;
 693         }
 694
 695         public String getVotedFor() {
 696             return votedFor;
 697         }
 698     }
 699
 700 }