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             onLeaderChanged(oldBehavior.getLeaderId(), currentBehavior.getLeaderId());
 267         }
 268     }
 269
 270     public java.util.Set<String> getPeers() {
 271         return context.getPeerAddresses().keySet();
 272     }
 273
 274     protected String getReplicatedLogState() {
 275         return "snapshotIndex=" + context.getReplicatedLog().getSnapshotIndex()
 276             + ", snapshotTerm=" + context.getReplicatedLog().getSnapshotTerm()
 277             + ", im-mem journal size=" + context.getReplicatedLog().size();
 278     }
 279
 280
 281     /**
 282      * When a derived RaftActor needs to persist something it must call
 283      * persistData.
 284      *
 285      * @param clientActor
 286      * @param identifier
 287      * @param data
 288      */
 289     protected void persistData(ActorRef clientActor, String identifier,
 290         Payload data) {
 291
 292         ReplicatedLogEntry replicatedLogEntry = new ReplicatedLogImplEntry(
 293             context.getReplicatedLog().lastIndex() + 1,
 294             context.getTermInformation().getCurrentTerm(), data);
 295
 296         LOG.debug("Persist data {}", replicatedLogEntry);
 297
 298         replicatedLog
 299             .appendAndPersist(clientActor, identifier, replicatedLogEntry);
 300     }
 301
 302     protected String getId() {
 303         return context.getId();
 304     }
 305
 306     /**
 307      * Derived actors can call the isLeader method to check if the current
 308      * RaftActor is the Leader or not
 309      *
 310      * @return true it this RaftActor is a Leader false otherwise
 311      */
 312     protected boolean isLeader() {
 313         return context.getId().equals(currentBehavior.getLeaderId());
 314     }
 315
 316     /**
 317      * Derived actor can call getLeader if they need a reference to the Leader.
 318      * This would be useful for example in forwarding a request to an actor
 319      * which is the leader
 320      *
 321      * @return A reference to the leader if known, null otherwise
 322      */
 323     protected ActorSelection getLeader(){
 324         String leaderAddress = getLeaderAddress();
 325
 326         if(leaderAddress == null){
 327             return null;
 328         }
 329
 330         return context.actorSelection(leaderAddress);
 331     }
 332
 333     /**
 334      *
 335      * @return the current leader's id
 336      */
 337     protected String getLeaderId(){
 338         return currentBehavior.getLeaderId();
 339     }
 340
 341     protected RaftState getRaftState() {
 342         return currentBehavior.state();
 343     }
 344
 345     protected ReplicatedLogEntry getLastLogEntry() {
 346         return replicatedLog.last();
 347     }
 348
 349     protected Long getCurrentTerm(){
 350         return context.getTermInformation().getCurrentTerm();
 351     }
 352
 353     protected Long getCommitIndex(){
 354         return context.getCommitIndex();
 355     }
 356
 357     protected Long getLastApplied(){
 358         return context.getLastApplied();
 359     }
 360
 361     /**
 362      * setPeerAddress sets the address of a known peer at a later time.
 363      * <p>
 364      * This is to account for situations where a we know that a peer
 365      * exists but we do not know an address up-front. This may also be used in
 366      * situations where a known peer starts off in a different location and we
 367      * need to change it's address
 368      * <p>
 369      * Note that if the peerId does not match the list of peers passed to
 370      * this actor during construction an IllegalStateException will be thrown.
 371      *
 372      * @param peerId
 373      * @param peerAddress
 374      */
 375     protected void setPeerAddress(String peerId, String peerAddress){
 376         context.setPeerAddress(peerId, peerAddress);
 377     }
 378
 379
 380
 381     /**
 382      * The applyState method will be called by the RaftActor when some data
 383      * needs to be applied to the actor's state
 384      *
 385      * @param clientActor A reference to the client who sent this message. This
 386      *                    is the same reference that was passed to persistData
 387      *                    by the derived actor. clientActor may be null when
 388      *                    the RaftActor is behaving as a follower or during
 389      *                    recovery.
 390      * @param identifier  The identifier of the persisted data. This is also
 391      *                    the same identifier that was passed to persistData by
 392      *                    the derived actor. identifier may be null when
 393      *                    the RaftActor is behaving as a follower or during
 394      *                    recovery
 395      * @param data        A piece of data that was persisted by the persistData call.
 396      *                    This should NEVER be null.
 397      */
 398     protected abstract void applyState(ActorRef clientActor, String identifier,
 399         Object data);
 400
 401     /**
 402      * This method will be called by the RaftActor when a snapshot needs to be
 403      * created. The derived actor should respond with its current state.
 404      * <p/>
 405      * During recovery the state that is returned by the derived actor will
 406      * be passed back to it by calling the applySnapshot  method
 407      *
 408      * @return The current state of the actor
 409      */
 410     protected abstract void createSnapshot();
 411
 412     /**
 413      * This method will be called by the RaftActor during recovery to
 414      * reconstruct the state of the actor.
 415      * <p/>
 416      * This method may also be called at any other point during normal
 417      * operations when the derived actor is out of sync with it's peers
 418      * and the only way to bring it in sync is by applying a snapshot
 419      *
 420      * @param snapshot A snapshot of the state of the actor
 421      */
 422     protected abstract void applySnapshot(ByteString snapshot);
 423
 424     /**
 425      * This method will be called by the RaftActor when the state of the
 426      * RaftActor changes. The derived actor can then use methods like
 427      * isLeader or getLeader to do something useful
 428      */
 429     protected abstract void onStateChanged();
 430
 431     protected void onLeaderChanged(String oldLeader, String newLeader){};
 432
 433     private RaftActorBehavior switchBehavior(RaftState state) {
 434         if (currentBehavior != null) {
 435             if (currentBehavior.state() == state) {
 436                 return currentBehavior;
 437             }
 438             LOG.info("Switching from state " + currentBehavior.state() + " to "
 439                 + state);
 440
 441             try {
 442                 currentBehavior.close();
 443             } catch (Exception e) {
 444                 LOG.error(e,
 445                     "Failed to close behavior : " + currentBehavior.state());
 446             }
 447
 448         } else {
 449             LOG.info("Switching behavior to " + state);
 450         }
 451         RaftActorBehavior behavior = null;
 452         if (state == RaftState.Candidate) {
 453             behavior = new Candidate(context);
 454         } else if (state == RaftState.Follower) {
 455             behavior = new Follower(context);
 456         } else {
 457             behavior = new Leader(context);
 458         }
 459
 460
 461
 462         return behavior;
 463     }
 464
 465     private void trimPersistentData(long sequenceNumber) {
 466         // Trim akka snapshots
 467         // FIXME : Not sure how exactly the SnapshotSelectionCriteria is applied
 468         // For now guessing that it is ANDed.
 469         deleteSnapshots(new SnapshotSelectionCriteria(
 470             sequenceNumber - context.getConfigParams().getSnapshotBatchCount(), 43200000));
 471
 472         // Trim akka journal
 473         deleteMessages(sequenceNumber);
 474     }
 475
 476     private String getLeaderAddress(){
 477         if(isLeader()){
 478             return getSelf().path().toString();
 479         }
 480         String leaderId = currentBehavior.getLeaderId();
 481         if (leaderId == null) {
 482             return null;
 483         }
 484         String peerAddress = context.getPeerAddress(leaderId);
 485         LOG.debug("getLeaderAddress leaderId = " + leaderId + " peerAddress = "
 486             + peerAddress);
 487
 488         return peerAddress;
 489     }
 490
 491     private void handleCaptureSnapshotReply(ByteString stateInBytes) {
 492         // create a snapshot object from the state provided and save it
 493         // when snapshot is saved async, SaveSnapshotSuccess is raised.
 494
 495         Snapshot sn = Snapshot.create(stateInBytes.toByteArray(),
 496             context.getReplicatedLog().getFrom(captureSnapshot.getLastAppliedIndex() + 1),
 497             captureSnapshot.getLastIndex(), captureSnapshot.getLastTerm(),
 498             captureSnapshot.getLastAppliedIndex(), captureSnapshot.getLastAppliedTerm());
 499
 500         saveSnapshot(sn);
 501
 502         LOG.info("Persisting of snapshot done:{}", sn.getLogMessage());
 503
 504         //be greedy and remove entries from in-mem journal which are in the snapshot
 505         // and update snapshotIndex and snapshotTerm without waiting for the success,
 506
 507         context.getReplicatedLog().snapshotPreCommit(stateInBytes,
 508             captureSnapshot.getLastAppliedIndex(),
 509             captureSnapshot.getLastAppliedTerm());
 510
 511         LOG.info("Removed in-memory snapshotted entries, adjusted snaphsotIndex:{} " +
 512             "and term:{}", captureSnapshot.getLastAppliedIndex(),
 513             captureSnapshot.getLastAppliedTerm());
 514
 515         captureSnapshot = null;
 516         hasSnapshotCaptureInitiated = false;
 517     }
 518
 519
 520     private class ReplicatedLogImpl extends AbstractReplicatedLogImpl {
 521
 522         public ReplicatedLogImpl(Snapshot snapshot) {
 523             super(ByteString.copyFrom(snapshot.getState()),
 524                 snapshot.getLastAppliedIndex(), snapshot.getLastAppliedTerm(),
 525                 snapshot.getUnAppliedEntries());
 526         }
 527
 528         public ReplicatedLogImpl() {
 529             super();
 530         }
 531
 532         @Override public void removeFromAndPersist(long logEntryIndex) {
 533             int adjustedIndex = adjustedIndex(logEntryIndex);
 534
 535             if (adjustedIndex < 0) {
 536                 return;
 537             }
 538
 539             // FIXME: Maybe this should be done after the command is saved
 540             journal.subList(adjustedIndex , journal.size()).clear();
 541
 542             persist(new DeleteEntries(adjustedIndex), new Procedure<DeleteEntries>(){
 543
 544                 @Override public void apply(DeleteEntries param)
 545                     throws Exception {
 546                     //FIXME : Doing nothing for now
 547                 }
 548             });
 549         }
 550
 551         @Override public void appendAndPersist(
 552             final ReplicatedLogEntry replicatedLogEntry) {
 553             appendAndPersist(null, null, replicatedLogEntry);
 554         }
 555
 556         public void appendAndPersist(final ActorRef clientActor,
 557             final String identifier,
 558             final ReplicatedLogEntry replicatedLogEntry) {
 559             context.getLogger().debug(
 560                 "Append log entry and persist {} ", replicatedLogEntry);
 561             // FIXME : By adding the replicated log entry to the in-memory journal we are not truly ensuring durability of the logs
 562             journal.add(replicatedLogEntry);
 563
 564             // When persisting events with persist it is guaranteed that the
 565             // persistent actor will not receive further commands between the
 566             // persist call and the execution(s) of the associated event
 567             // handler. This also holds for multiple persist calls in context
 568             // of a single command.
 569             persist(replicatedLogEntry,
 570                 new Procedure<ReplicatedLogEntry>() {
 571                     public void apply(ReplicatedLogEntry evt) throws Exception {
 572                         // when a snaphsot is being taken, captureSnapshot != null
 573                         if (hasSnapshotCaptureInitiated == false &&
 574                             journal.size() % context.getConfigParams().getSnapshotBatchCount() == 0) {
 575
 576                             LOG.info("Initiating Snapshot Capture..");
 577                             long lastAppliedIndex = -1;
 578                             long lastAppliedTerm = -1;
 579
 580                             ReplicatedLogEntry lastAppliedEntry = get(context.getLastApplied());
 581                             if (lastAppliedEntry != null) {
 582                                 lastAppliedIndex = lastAppliedEntry.getIndex();
 583                                 lastAppliedTerm = lastAppliedEntry.getTerm();
 584                             }
 585
 586                             LOG.debug("Snapshot Capture logSize: {}", journal.size());
 587                             LOG.debug("Snapshot Capture lastApplied:{} ", context.getLastApplied());
 588                             LOG.debug("Snapshot Capture lastAppliedIndex:{}", lastAppliedIndex);
 589                             LOG.debug("Snapshot Capture lastAppliedTerm:{}", lastAppliedTerm);
 590
 591                             // send a CaptureSnapshot to self to make the expensive operation async.
 592                             getSelf().tell(new CaptureSnapshot(
 593                                 lastIndex(), lastTerm(), lastAppliedIndex, lastAppliedTerm),
 594                                 null);
 595                             hasSnapshotCaptureInitiated = true;
 596                         }
 597                         // Send message for replication
 598                         if (clientActor != null) {
 599                             currentBehavior.handleMessage(getSelf(),
 600                                 new Replicate(clientActor, identifier,
 601                                     replicatedLogEntry)
 602                             );
 603                         }
 604                     }
 605                 }
 606             );
 607         }
 608
 609     }
 610
 611     private static class DeleteEntries implements Serializable {
 612         private final int fromIndex;
 613
 614
 615         public DeleteEntries(int fromIndex) {
 616             this.fromIndex = fromIndex;
 617         }
 618
 619         public int getFromIndex() {
 620             return fromIndex;
 621         }
 622     }
 623
 624
 625     private class ElectionTermImpl implements ElectionTerm {
 626         /**
 627          * Identifier of the actor whose election term information this is
 628          */
 629         private long currentTerm = 0;
 630         private String votedFor = null;
 631
 632         public long getCurrentTerm() {
 633             return currentTerm;
 634         }
 635
 636         public String getVotedFor() {
 637             return votedFor;
 638         }
 639
 640         @Override public void update(long currentTerm, String votedFor) {
 641             LOG.debug("Set currentTerm={}, votedFor={}", currentTerm, votedFor);
 642
 643             this.currentTerm = currentTerm;
 644             this.votedFor = votedFor;
 645         }
 646
 647         @Override
 648         public void updateAndPersist(long currentTerm, String votedFor){
 649             update(currentTerm, votedFor);
 650             // FIXME : Maybe first persist then update the state
 651             persist(new UpdateElectionTerm(this.currentTerm, this.votedFor), new Procedure<UpdateElectionTerm>(){
 652
 653                 @Override public void apply(UpdateElectionTerm param)
 654                     throws Exception {
 655
 656                 }
 657             });
 658         }
 659     }
 660
 661     private static class UpdateElectionTerm implements Serializable {
 662         private final long currentTerm;
 663         private final String votedFor;
 664
 665         public UpdateElectionTerm(long currentTerm, String votedFor) {
 666             this.currentTerm = currentTerm;
 667             this.votedFor = votedFor;
 668         }
 669
 670         public long getCurrentTerm() {
 671             return currentTerm;
 672         }
 673
 674         public String getVotedFor() {
 675             return votedFor;
 676         }
 677     }
 678
 679 }