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