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     private 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.debug("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
 138             LOG.debug("Applied snapshot to replicatedLog. " +
 139                 "snapshotIndex={}, snapshotTerm={}, journal-size={}",
 140                 replicatedLog.snapshotIndex, replicatedLog.snapshotTerm,
 141                 replicatedLog.size());
 142
 143             // Apply the snapshot to the actors state
 144             applySnapshot(ByteString.copyFrom(snapshot.getState()));
 145
 146         } else if (message instanceof ReplicatedLogEntry) {
 147             ReplicatedLogEntry logEntry = (ReplicatedLogEntry) message;
 148
 149             // Apply State immediately
 150             replicatedLog.append(logEntry);
 151             applyState(null, "recovery", logEntry.getData());
 152             context.setLastApplied(logEntry.getIndex());
 153             context.setCommitIndex(logEntry.getIndex());
 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(), ((UpdateElectionTerm) message).getVotedFor());
 158         } else if (message instanceof RecoveryCompleted) {
 159             LOG.debug(
 160                 "RecoveryCompleted - Switching actor to Follower - " +
 161                     "Persistence Id =  " + persistenceId() +
 162                     " Last index in log:{}, snapshotIndex={}, snapshotTerm={}, " +
 163                     "journal-size={}",
 164                 replicatedLog.lastIndex(), replicatedLog.snapshotIndex,
 165                 replicatedLog.snapshotTerm, replicatedLog.size());
 166             currentBehavior = switchBehavior(RaftState.Follower);
 167             onStateChanged();
 168         }
 169     }
 170
 171     @Override public void onReceiveCommand(Object message) {
 172         if (message instanceof ApplyState){
 173             ApplyState applyState = (ApplyState) message;
 174
 175             LOG.debug("Applying state for log index {} data {}",
 176                 applyState.getReplicatedLogEntry().getIndex(),
 177                 applyState.getReplicatedLogEntry().getData());
 178
 179             applyState(applyState.getClientActor(), applyState.getIdentifier(),
 180                 applyState.getReplicatedLogEntry().getData());
 181
 182         } else if(message instanceof ApplySnapshot ) {
 183             Snapshot snapshot = ((ApplySnapshot) message).getSnapshot();
 184
 185             LOG.debug("ApplySnapshot called on Follower Actor " +
 186                 "snapshotIndex:{}, snapshotTerm:{}", snapshot.getLastAppliedIndex(),
 187                 snapshot.getLastAppliedTerm());
 188             applySnapshot(ByteString.copyFrom(snapshot.getState()));
 189
 190             //clears the followers log, sets the snapshot index to ensure adjusted-index works
 191             replicatedLog = new ReplicatedLogImpl(snapshot);
 192             context.setReplicatedLog(replicatedLog);
 193             context.setLastApplied(snapshot.getLastAppliedIndex());
 194
 195         } else if (message instanceof FindLeader) {
 196             getSender().tell(
 197                 new FindLeaderReply(getLeaderAddress()),
 198                 getSelf()
 199             );
 200
 201         } else if (message instanceof SaveSnapshotSuccess) {
 202             SaveSnapshotSuccess success = (SaveSnapshotSuccess) message;
 203             LOG.info("SaveSnapshotSuccess received for snapshot");
 204
 205             context.getReplicatedLog().snapshotCommit();
 206
 207             // TODO: Not sure if we want to be this aggressive with trimming stuff
 208             trimPersistentData(success.metadata().sequenceNr());
 209
 210         } else if (message instanceof SaveSnapshotFailure) {
 211             SaveSnapshotFailure saveSnapshotFailure = (SaveSnapshotFailure) message;
 212
 213             LOG.info("saveSnapshotFailure.metadata():{}", saveSnapshotFailure.metadata().toString());
 214             LOG.error(saveSnapshotFailure.cause(), "SaveSnapshotFailure received for snapshot Cause:");
 215
 216             context.getReplicatedLog().snapshotRollback();
 217
 218             LOG.info("Replicated Log rollbacked. Snapshot will be attempted in the next cycle." +
 219                 "snapshotIndex:{}, snapshotTerm:{}, log-size:{}",
 220                 context.getReplicatedLog().getSnapshotIndex(),
 221                 context.getReplicatedLog().getSnapshotTerm(),
 222                 context.getReplicatedLog().size());
 223
 224         } else if (message instanceof AddRaftPeer){
 225
 226             // FIXME : Do not add raft peers like this.
 227             // When adding a new Peer we have to ensure that the a majority of
 228             // the peers know about the new Peer. Doing it this way may cause
 229             // a situation where multiple Leaders may emerge
 230             AddRaftPeer arp = (AddRaftPeer)message;
 231            context.addToPeers(arp.getName(), arp.getAddress());
 232
 233         } else if (message instanceof RemoveRaftPeer){
 234
 235             RemoveRaftPeer rrp = (RemoveRaftPeer)message;
 236             context.removePeer(rrp.getName());
 237
 238         } else if (message instanceof CaptureSnapshot) {
 239             LOG.debug("CaptureSnapshot received by actor");
 240             CaptureSnapshot cs = (CaptureSnapshot)message;
 241             captureSnapshot = cs;
 242             createSnapshot();
 243
 244         } else if (message instanceof CaptureSnapshotReply){
 245             LOG.debug("CaptureSnapshotReply received by actor");
 246             CaptureSnapshotReply csr = (CaptureSnapshotReply) message;
 247
 248             ByteString stateInBytes = csr.getSnapshot();
 249             LOG.debug("CaptureSnapshotReply stateInBytes size:{}", stateInBytes.size());
 250             handleCaptureSnapshotReply(stateInBytes);
 251
 252         } else {
 253             if (!(message instanceof AppendEntriesMessages.AppendEntries)
 254                 && !(message instanceof AppendEntriesReply) && !(message instanceof SendHeartBeat)) {
 255                 LOG.debug("onReceiveCommand: message:" + message.getClass());
 256             }
 257
 258             RaftState state =
 259                 currentBehavior.handleMessage(getSender(), message);
 260             RaftActorBehavior oldBehavior = currentBehavior;
 261             currentBehavior = switchBehavior(state);
 262             if(oldBehavior != currentBehavior){
 263                 onStateChanged();
 264             }
 265         }
 266     }
 267
 268     public java.util.Set<String> getPeers() {
 269         return context.getPeerAddresses().keySet();
 270     }
 271
 272     protected String getReplicatedLogState() {
 273         return "snapshotIndex=" + context.getReplicatedLog().getSnapshotIndex()
 274             + ", snapshotTerm=" + context.getReplicatedLog().getSnapshotTerm()
 275             + ", im-mem journal size=" + context.getReplicatedLog().size();
 276     }
 277
 278
 279     /**
 280      * When a derived RaftActor needs to persist something it must call
 281      * persistData.
 282      *
 283      * @param clientActor
 284      * @param identifier
 285      * @param data
 286      */
 287     protected void persistData(ActorRef clientActor, String identifier,
 288         Payload data) {
 289
 290         ReplicatedLogEntry replicatedLogEntry = new ReplicatedLogImplEntry(
 291             context.getReplicatedLog().lastIndex() + 1,
 292             context.getTermInformation().getCurrentTerm(), data);
 293
 294         LOG.debug("Persist data {}", replicatedLogEntry);
 295
 296         replicatedLog
 297             .appendAndPersist(clientActor, identifier, replicatedLogEntry);
 298     }
 299
 300     protected String getId() {
 301         return context.getId();
 302     }
 303
 304     /**
 305      * Derived actors can call the isLeader method to check if the current
 306      * RaftActor is the Leader or not
 307      *
 308      * @return true it this RaftActor is a Leader false otherwise
 309      */
 310     protected boolean isLeader() {
 311         return context.getId().equals(currentBehavior.getLeaderId());
 312     }
 313
 314     /**
 315      * Derived actor can call getLeader if they need a reference to the Leader.
 316      * This would be useful for example in forwarding a request to an actor
 317      * which is the leader
 318      *
 319      * @return A reference to the leader if known, null otherwise
 320      */
 321     protected ActorSelection getLeader(){
 322         String leaderAddress = getLeaderAddress();
 323
 324         if(leaderAddress == null){
 325             return null;
 326         }
 327
 328         return context.actorSelection(leaderAddress);
 329     }
 330
 331     /**
 332      *
 333      * @return the current leader's id
 334      */
 335     protected String getLeaderId(){
 336         return currentBehavior.getLeaderId();
 337     }
 338
 339     protected RaftState getRaftState() {
 340         return currentBehavior.state();
 341     }
 342
 343     protected ReplicatedLogEntry getLastLogEntry() {
 344         return replicatedLog.last();
 345     }
 346
 347     protected Long getCurrentTerm(){
 348         return context.getTermInformation().getCurrentTerm();
 349     }
 350
 351     protected Long getCommitIndex(){
 352         return context.getCommitIndex();
 353     }
 354
 355     protected Long getLastApplied(){
 356         return context.getLastApplied();
 357     }
 358
 359     /**
 360      * setPeerAddress sets the address of a known peer at a later time.
 361      * <p>
 362      * This is to account for situations where a we know that a peer
 363      * exists but we do not know an address up-front. This may also be used in
 364      * situations where a known peer starts off in a different location and we
 365      * need to change it's address
 366      * <p>
 367      * Note that if the peerId does not match the list of peers passed to
 368      * this actor during construction an IllegalStateException will be thrown.
 369      *
 370      * @param peerId
 371      * @param peerAddress
 372      */
 373     protected void setPeerAddress(String peerId, String peerAddress){
 374         context.setPeerAddress(peerId, peerAddress);
 375     }
 376
 377
 378
 379     /**
 380      * The applyState method will be called by the RaftActor when some data
 381      * needs to be applied to the actor's state
 382      *
 383      * @param clientActor A reference to the client who sent this message. This
 384      *                    is the same reference that was passed to persistData
 385      *                    by the derived actor. clientActor may be null when
 386      *                    the RaftActor is behaving as a follower or during
 387      *                    recovery.
 388      * @param identifier  The identifier of the persisted data. This is also
 389      *                    the same identifier that was passed to persistData by
 390      *                    the derived actor. identifier may be null when
 391      *                    the RaftActor is behaving as a follower or during
 392      *                    recovery
 393      * @param data        A piece of data that was persisted by the persistData call.
 394      *                    This should NEVER be null.
 395      */
 396     protected abstract void applyState(ActorRef clientActor, String identifier,
 397         Object data);
 398
 399     /**
 400      * This method will be called by the RaftActor when a snapshot needs to be
 401      * created. The derived actor should respond with its current state.
 402      * <p/>
 403      * During recovery the state that is returned by the derived actor will
 404      * be passed back to it by calling the applySnapshot  method
 405      *
 406      * @return The current state of the actor
 407      */
 408     protected abstract void createSnapshot();
 409
 410     /**
 411      * This method will be called by the RaftActor during recovery to
 412      * reconstruct the state of the actor.
 413      * <p/>
 414      * This method may also be called at any other point during normal
 415      * operations when the derived actor is out of sync with it's peers
 416      * and the only way to bring it in sync is by applying a snapshot
 417      *
 418      * @param snapshot A snapshot of the state of the actor
 419      */
 420     protected abstract void applySnapshot(ByteString snapshot);
 421
 422     /**
 423      * This method will be called by the RaftActor when the state of the
 424      * RaftActor changes. The derived actor can then use methods like
 425      * isLeader or getLeader to do something useful
 426      */
 427     protected abstract void onStateChanged();
 428
 429     private RaftActorBehavior switchBehavior(RaftState state) {
 430         if (currentBehavior != null) {
 431             if (currentBehavior.state() == state) {
 432                 return currentBehavior;
 433             }
 434             LOG.info("Switching from state " + currentBehavior.state() + " to "
 435                 + state);
 436
 437             try {
 438                 currentBehavior.close();
 439             } catch (Exception e) {
 440                 LOG.error(e,
 441                     "Failed to close behavior : " + currentBehavior.state());
 442             }
 443
 444         } else {
 445             LOG.info("Switching behavior to " + state);
 446         }
 447         RaftActorBehavior behavior = null;
 448         if (state == RaftState.Candidate) {
 449             behavior = new Candidate(context);
 450         } else if (state == RaftState.Follower) {
 451             behavior = new Follower(context);
 452         } else {
 453             behavior = new Leader(context);
 454         }
 455
 456
 457
 458         return behavior;
 459     }
 460
 461     private void trimPersistentData(long sequenceNumber) {
 462         // Trim akka snapshots
 463         // FIXME : Not sure how exactly the SnapshotSelectionCriteria is applied
 464         // For now guessing that it is ANDed.
 465         deleteSnapshots(new SnapshotSelectionCriteria(
 466             sequenceNumber - context.getConfigParams().getSnapshotBatchCount(), 43200000));
 467
 468         // Trim akka journal
 469         deleteMessages(sequenceNumber);
 470     }
 471
 472     private String getLeaderAddress(){
 473         if(isLeader()){
 474             return getSelf().path().toString();
 475         }
 476         String leaderId = currentBehavior.getLeaderId();
 477         if (leaderId == null) {
 478             return null;
 479         }
 480         String peerAddress = context.getPeerAddress(leaderId);
 481         LOG.debug("getLeaderAddress leaderId = " + leaderId + " peerAddress = "
 482             + peerAddress);
 483
 484         return peerAddress;
 485     }
 486
 487     private void handleCaptureSnapshotReply(ByteString stateInBytes) {
 488         // create a snapshot object from the state provided and save it
 489         // when snapshot is saved async, SaveSnapshotSuccess is raised.
 490
 491         Snapshot sn = Snapshot.create(stateInBytes.toByteArray(),
 492             context.getReplicatedLog().getFrom(captureSnapshot.getLastAppliedIndex() + 1),
 493             captureSnapshot.getLastIndex(), captureSnapshot.getLastTerm(),
 494             captureSnapshot.getLastAppliedIndex(), captureSnapshot.getLastAppliedTerm());
 495
 496         saveSnapshot(sn);
 497
 498         LOG.info("Persisting of snapshot done:{}", sn.getLogMessage());
 499
 500         //be greedy and remove entries from in-mem journal which are in the snapshot
 501         // and update snapshotIndex and snapshotTerm without waiting for the success,
 502
 503         context.getReplicatedLog().snapshotPreCommit(stateInBytes,
 504             captureSnapshot.getLastAppliedIndex(),
 505             captureSnapshot.getLastAppliedTerm());
 506
 507         LOG.info("Removed in-memory snapshotted entries, adjusted snaphsotIndex:{} " +
 508             "and term:{}", captureSnapshot.getLastAppliedIndex(),
 509             captureSnapshot.getLastAppliedTerm());
 510
 511         captureSnapshot = null;
 512         hasSnapshotCaptureInitiated = false;
 513     }
 514
 515
 516     private class ReplicatedLogImpl extends AbstractReplicatedLogImpl {
 517
 518         public ReplicatedLogImpl(Snapshot snapshot) {
 519             super(ByteString.copyFrom(snapshot.getState()),
 520                 snapshot.getLastAppliedIndex(), snapshot.getLastAppliedTerm(),
 521                 snapshot.getUnAppliedEntries());
 522         }
 523
 524         public ReplicatedLogImpl() {
 525             super();
 526         }
 527
 528         @Override public void removeFromAndPersist(long logEntryIndex) {
 529             int adjustedIndex = adjustedIndex(logEntryIndex);
 530
 531             if (adjustedIndex < 0) {
 532                 return;
 533             }
 534
 535             // FIXME: Maybe this should be done after the command is saved
 536             journal.subList(adjustedIndex , journal.size()).clear();
 537
 538             persist(new DeleteEntries(adjustedIndex), new Procedure<DeleteEntries>(){
 539
 540                 @Override public void apply(DeleteEntries param)
 541                     throws Exception {
 542                     //FIXME : Doing nothing for now
 543                 }
 544             });
 545         }
 546
 547         @Override public void appendAndPersist(
 548             final ReplicatedLogEntry replicatedLogEntry) {
 549             appendAndPersist(null, null, replicatedLogEntry);
 550         }
 551
 552         public void appendAndPersist(final ActorRef clientActor,
 553             final String identifier,
 554             final ReplicatedLogEntry replicatedLogEntry) {
 555             context.getLogger().debug(
 556                 "Append log entry and persist {} ", replicatedLogEntry);
 557             // FIXME : By adding the replicated log entry to the in-memory journal we are not truly ensuring durability of the logs
 558             journal.add(replicatedLogEntry);
 559
 560             // When persisting events with persist it is guaranteed that the
 561             // persistent actor will not receive further commands between the
 562             // persist call and the execution(s) of the associated event
 563             // handler. This also holds for multiple persist calls in context
 564             // of a single command.
 565             persist(replicatedLogEntry,
 566                 new Procedure<ReplicatedLogEntry>() {
 567                     public void apply(ReplicatedLogEntry evt) throws Exception {
 568                         // when a snaphsot is being taken, captureSnapshot != null
 569                         if (hasSnapshotCaptureInitiated == false &&
 570                             journal.size() % context.getConfigParams().getSnapshotBatchCount() == 0) {
 571
 572                             LOG.info("Initiating Snapshot Capture..");
 573                             long lastAppliedIndex = -1;
 574                             long lastAppliedTerm = -1;
 575
 576                             ReplicatedLogEntry lastAppliedEntry = get(context.getLastApplied());
 577                             if (lastAppliedEntry != null) {
 578                                 lastAppliedIndex = lastAppliedEntry.getIndex();
 579                                 lastAppliedTerm = lastAppliedEntry.getTerm();
 580                             }
 581
 582                             LOG.debug("Snapshot Capture logSize: {}", journal.size());
 583                             LOG.debug("Snapshot Capture lastApplied:{} ", context.getLastApplied());
 584                             LOG.debug("Snapshot Capture lastAppliedIndex:{}", lastAppliedIndex);
 585                             LOG.debug("Snapshot Capture lastAppliedTerm:{}", lastAppliedTerm);
 586
 587                             // send a CaptureSnapshot to self to make the expensive operation async.
 588                             getSelf().tell(new CaptureSnapshot(
 589                                 lastIndex(), lastTerm(), lastAppliedIndex, lastAppliedTerm),
 590                                 null);
 591                             hasSnapshotCaptureInitiated = true;
 592                         }
 593                         // Send message for replication
 594                         if (clientActor != null) {
 595                             currentBehavior.handleMessage(getSelf(),
 596                                 new Replicate(clientActor, identifier,
 597                                     replicatedLogEntry)
 598                             );
 599                         }
 600                     }
 601                 }
 602             );
 603         }
 604
 605     }
 606
 607     private static class DeleteEntries implements Serializable {
 608         private final int fromIndex;
 609
 610
 611         public DeleteEntries(int fromIndex) {
 612             this.fromIndex = fromIndex;
 613         }
 614
 615         public int getFromIndex() {
 616             return fromIndex;
 617         }
 618     }
 619
 620
 621     private class ElectionTermImpl implements ElectionTerm {
 622         /**
 623          * Identifier of the actor whose election term information this is
 624          */
 625         private long currentTerm = 0;
 626         private String votedFor = null;
 627
 628         public long getCurrentTerm() {
 629             return currentTerm;
 630         }
 631
 632         public String getVotedFor() {
 633             return votedFor;
 634         }
 635
 636         @Override public void update(long currentTerm, String votedFor) {
 637             LOG.debug("Set currentTerm={}, votedFor={}", currentTerm, votedFor);
 638
 639             this.currentTerm = currentTerm;
 640             this.votedFor = votedFor;
 641         }
 642
 643         @Override
 644         public void updateAndPersist(long currentTerm, String votedFor){
 645             update(currentTerm, votedFor);
 646             // FIXME : Maybe first persist then update the state
 647             persist(new UpdateElectionTerm(this.currentTerm, this.votedFor), new Procedure<UpdateElectionTerm>(){
 648
 649                 @Override public void apply(UpdateElectionTerm param)
 650                     throws Exception {
 651
 652                 }
 653             });
 654         }
 655     }
 656
 657     private static class UpdateElectionTerm implements Serializable {
 658         private final long currentTerm;
 659         private final String votedFor;
 660
 661         public UpdateElectionTerm(long currentTerm, String votedFor) {
 662             this.currentTerm = currentTerm;
 663             this.votedFor = votedFor;
 664         }
 665
 666         public long getCurrentTerm() {
 667             return currentTerm;
 668         }
 669
 670         public String getVotedFor() {
 671             return votedFor;
 672         }
 673     }
 674
 675 }