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.ApplyLogEntries;
  25 import org.opendaylight.controller.cluster.raft.base.messages.ApplySnapshot;
  26 import org.opendaylight.controller.cluster.raft.base.messages.ApplyState;
  27 import org.opendaylight.controller.cluster.raft.base.messages.CaptureSnapshot;
  28 import org.opendaylight.controller.cluster.raft.base.messages.CaptureSnapshotReply;
  29 import org.opendaylight.controller.cluster.raft.base.messages.Replicate;
  30 import org.opendaylight.controller.cluster.raft.base.messages.SendHeartBeat;
  31 import org.opendaylight.controller.cluster.raft.behaviors.Candidate;
  32 import org.opendaylight.controller.cluster.raft.behaviors.Follower;
  33 import org.opendaylight.controller.cluster.raft.behaviors.Leader;
  34 import org.opendaylight.controller.cluster.raft.behaviors.RaftActorBehavior;
  35 import org.opendaylight.controller.cluster.raft.client.messages.AddRaftPeer;
  36 import org.opendaylight.controller.cluster.raft.client.messages.FindLeader;
  37 import org.opendaylight.controller.cluster.raft.client.messages.FindLeaderReply;
  38 import org.opendaylight.controller.cluster.raft.client.messages.RemoveRaftPeer;
  39 import org.opendaylight.controller.cluster.raft.messages.AppendEntriesReply;
  40 import org.opendaylight.controller.cluster.raft.protobuff.client.messages.Payload;
  41 import org.opendaylight.controller.protobuff.messages.cluster.raft.AppendEntriesMessages;
  42
  43 import java.io.Serializable;
  44 import java.util.Map;
  45
  46 /**
  47  * RaftActor encapsulates a state machine that needs to be kept synchronized
  48  * in a cluster. It implements the RAFT algorithm as described in the paper
  49  * <a href='https://ramcloud.stanford.edu/wiki/download/attachments/11370504/raft.pdf'>
  50  * In Search of an Understandable Consensus Algorithm</a>
  51  * <p/>
  52  * RaftActor has 3 states and each state has a certain behavior associated
  53  * with it. A Raft actor can behave as,
  54  * <ul>
  55  * <li> A Leader </li>
  56  * <li> A Follower (or) </li>
  57  * <li> A Candidate </li>
  58  * </ul>
  59  * <p/>
  60  * <p/>
  61  * A RaftActor MUST be a Leader in order to accept requests from clients to
  62  * change the state of it's encapsulated state machine. Once a RaftActor becomes
  63  * a Leader it is also responsible for ensuring that all followers ultimately
  64  * have the same log and therefore the same state machine as itself.
  65  * <p/>
  66  * <p/>
  67  * The current behavior of a RaftActor determines how election for leadership
  68  * is initiated and how peer RaftActors react to request for votes.
  69  * <p/>
  70  * <p/>
  71  * Each RaftActor also needs to know the current election term. It uses this
  72  * information for a couple of things. One is to simply figure out who it
  73  * voted for in the last election. Another is to figure out if the message
  74  * it received to update it's state is stale.
  75  * <p/>
  76  * <p/>
  77  * The RaftActor uses akka-persistence to store it's replicated log.
  78  * Furthermore through it's behaviors a Raft Actor determines
  79  * <p/>
  80  * <ul>
  81  * <li> when a log entry should be persisted </li>
  82  * <li> when a log entry should be applied to the state machine (and) </li>
  83  * <li> when a snapshot should be saved </li>
  84  * </ul>
  85  */
  86 public abstract class RaftActor extends UntypedPersistentActor {
  87     protected final LoggingAdapter LOG =
  88         Logging.getLogger(getContext().system(), this);
  89
  90     /**
  91      * The current state determines the current behavior of a RaftActor
  92      * A Raft Actor always starts off in the Follower State
  93      */
  94     private RaftActorBehavior currentBehavior;
  95
  96     /**
  97      * This context should NOT be passed directly to any other actor it is
  98      * only to be consumed by the RaftActorBehaviors
  99      */
 100     protected RaftActorContext context;
 101
 102     /**
 103      * The in-memory journal
 104      */
 105     private ReplicatedLogImpl replicatedLog = new ReplicatedLogImpl();
 106
 107     private CaptureSnapshot captureSnapshot = null;
 108
 109     private volatile boolean hasSnapshotCaptureInitiated = false;
 110
 111     public RaftActor(String id, Map<String, String> peerAddresses) {
 112         this(id, peerAddresses, Optional.<ConfigParams>absent());
 113     }
 114
 115     public RaftActor(String id, Map<String, String> peerAddresses,
 116          Optional<ConfigParams> configParams) {
 117
 118         context = new RaftActorContextImpl(this.getSelf(),
 119             this.getContext(), id, new ElectionTermImpl(),
 120             -1, -1, replicatedLog, peerAddresses,
 121             (configParams.isPresent() ? configParams.get(): new DefaultConfigParamsImpl()),
 122             LOG);
 123     }
 124
 125     @Override public void onReceiveRecover(Object message) {
 126         if (message instanceof SnapshotOffer) {
 127             LOG.info("SnapshotOffer called..");
 128             SnapshotOffer offer = (SnapshotOffer) message;
 129             Snapshot snapshot = (Snapshot) offer.snapshot();
 130
 131             // Create a replicated log with the snapshot information
 132             // The replicated log can be used later on to retrieve this snapshot
 133             // when we need to install it on a peer
 134             replicatedLog = new ReplicatedLogImpl(snapshot);
 135
 136             context.setReplicatedLog(replicatedLog);
 137             context.setLastApplied(snapshot.getLastAppliedIndex());
 138             context.setCommitIndex(snapshot.getLastAppliedIndex());
 139
 140             LOG.info("Applied snapshot to replicatedLog. " +
 141                     "snapshotIndex={}, snapshotTerm={}, journal-size={}",
 142                 replicatedLog.snapshotIndex, replicatedLog.snapshotTerm,
 143                 replicatedLog.size()
 144             );
 145
 146             // Apply the snapshot to the actors state
 147             applySnapshot(ByteString.copyFrom(snapshot.getState()));
 148
 149         } else if (message instanceof ReplicatedLogEntry) {
 150             ReplicatedLogEntry logEntry = (ReplicatedLogEntry) message;
 151             LOG.info("Received ReplicatedLogEntry for recovery:{}", logEntry.getIndex());
 152             replicatedLog.append(logEntry);
 153
 154         } else if (message instanceof ApplyLogEntries) {
 155             ApplyLogEntries ale = (ApplyLogEntries) message;
 156
 157             LOG.info("Received ApplyLogEntries for recovery, applying to state:{} to {}",
 158                 context.getLastApplied() + 1, ale.getToIndex());
 159
 160             for (long i = context.getLastApplied() + 1; i <= ale.getToIndex(); i++) {
 161                 applyState(null, "recovery", replicatedLog.get(i).getData());
 162             }
 163             context.setLastApplied(ale.getToIndex());
 164             context.setCommitIndex(ale.getToIndex());
 165
 166         } else if (message instanceof DeleteEntries) {
 167             replicatedLog.removeFrom(((DeleteEntries) message).getFromIndex());
 168
 169         } else if (message instanceof UpdateElectionTerm) {
 170             context.getTermInformation().update(((UpdateElectionTerm) message).getCurrentTerm(),
 171                 ((UpdateElectionTerm) message).getVotedFor());
 172
 173         } else if (message instanceof RecoveryCompleted) {
 174             LOG.info(
 175                 "RecoveryCompleted - Switching actor to Follower - " +
 176                     "Persistence Id =  " + persistenceId() +
 177                     " Last index in log:{}, snapshotIndex={}, snapshotTerm={}, " +
 178                     "journal-size={}",
 179                 replicatedLog.lastIndex(), replicatedLog.snapshotIndex,
 180                 replicatedLog.snapshotTerm, replicatedLog.size());
 181             currentBehavior = switchBehavior(RaftState.Follower);
 182             onStateChanged();
 183         }
 184     }
 185
 186     @Override public void onReceiveCommand(Object message) {
 187         if (message instanceof ApplyState){
 188             ApplyState applyState = (ApplyState) message;
 189
 190             if(LOG.isDebugEnabled()) {
 191                 LOG.debug("Applying state for log index {} data {}",
 192                     applyState.getReplicatedLogEntry().getIndex(),
 193                     applyState.getReplicatedLogEntry().getData());
 194             }
 195
 196             applyState(applyState.getClientActor(), applyState.getIdentifier(),
 197                 applyState.getReplicatedLogEntry().getData());
 198
 199         } else if (message instanceof ApplyLogEntries){
 200             ApplyLogEntries ale = (ApplyLogEntries) message;
 201             LOG.info("Persisting ApplyLogEntries with index={}", ale.getToIndex());
 202             persist(new ApplyLogEntries(ale.getToIndex()), new Procedure<ApplyLogEntries>() {
 203                 @Override
 204                 public void apply(ApplyLogEntries param) throws Exception {
 205                 }
 206             });
 207
 208         } else if(message instanceof ApplySnapshot ) {
 209             Snapshot snapshot = ((ApplySnapshot) message).getSnapshot();
 210
 211             if(LOG.isDebugEnabled()) {
 212                 LOG.debug("ApplySnapshot called on Follower Actor " +
 213                         "snapshotIndex:{}, snapshotTerm:{}", snapshot.getLastAppliedIndex(),
 214                     snapshot.getLastAppliedTerm()
 215                 );
 216             }
 217             applySnapshot(ByteString.copyFrom(snapshot.getState()));
 218
 219             //clears the followers log, sets the snapshot index to ensure adjusted-index works
 220             replicatedLog = new ReplicatedLogImpl(snapshot);
 221             context.setReplicatedLog(replicatedLog);
 222             context.setLastApplied(snapshot.getLastAppliedIndex());
 223
 224         } else if (message instanceof FindLeader) {
 225             getSender().tell(
 226                 new FindLeaderReply(getLeaderAddress()),
 227                 getSelf()
 228             );
 229
 230         } else if (message instanceof SaveSnapshotSuccess) {
 231             SaveSnapshotSuccess success = (SaveSnapshotSuccess) message;
 232             LOG.info("SaveSnapshotSuccess received for snapshot");
 233
 234             context.getReplicatedLog().snapshotCommit();
 235
 236             // TODO: Not sure if we want to be this aggressive with trimming stuff
 237             trimPersistentData(success.metadata().sequenceNr());
 238
 239         } else if (message instanceof SaveSnapshotFailure) {
 240             SaveSnapshotFailure saveSnapshotFailure = (SaveSnapshotFailure) message;
 241
 242             LOG.info("saveSnapshotFailure.metadata():{}", saveSnapshotFailure.metadata().toString());
 243             LOG.error(saveSnapshotFailure.cause(), "SaveSnapshotFailure received for snapshot Cause:");
 244
 245             context.getReplicatedLog().snapshotRollback();
 246
 247             LOG.info("Replicated Log rollbacked. Snapshot will be attempted in the next cycle." +
 248                 "snapshotIndex:{}, snapshotTerm:{}, log-size:{}",
 249                 context.getReplicatedLog().getSnapshotIndex(),
 250                 context.getReplicatedLog().getSnapshotTerm(),
 251                 context.getReplicatedLog().size());
 252
 253         } else if (message instanceof AddRaftPeer){
 254
 255             // FIXME : Do not add raft peers like this.
 256             // When adding a new Peer we have to ensure that the a majority of
 257             // the peers know about the new Peer. Doing it this way may cause
 258             // a situation where multiple Leaders may emerge
 259             AddRaftPeer arp = (AddRaftPeer)message;
 260            context.addToPeers(arp.getName(), arp.getAddress());
 261
 262         } else if (message instanceof RemoveRaftPeer){
 263
 264             RemoveRaftPeer rrp = (RemoveRaftPeer)message;
 265             context.removePeer(rrp.getName());
 266
 267         } else if (message instanceof CaptureSnapshot) {
 268             LOG.info("CaptureSnapshot received by actor");
 269             CaptureSnapshot cs = (CaptureSnapshot)message;
 270             captureSnapshot = cs;
 271             createSnapshot();
 272
 273         } else if (message instanceof CaptureSnapshotReply){
 274             LOG.info("CaptureSnapshotReply received by actor");
 275             CaptureSnapshotReply csr = (CaptureSnapshotReply) message;
 276
 277             ByteString stateInBytes = csr.getSnapshot();
 278             LOG.info("CaptureSnapshotReply stateInBytes size:{}", stateInBytes.size());
 279             handleCaptureSnapshotReply(stateInBytes);
 280
 281         } else {
 282             if (!(message instanceof AppendEntriesMessages.AppendEntries)
 283                 && !(message instanceof AppendEntriesReply) && !(message instanceof SendHeartBeat)) {
 284                 if(LOG.isDebugEnabled()) {
 285                     LOG.debug("onReceiveCommand: message:" + message.getClass());
 286                 }
 287             }
 288
 289             RaftState state =
 290                 currentBehavior.handleMessage(getSender(), message);
 291             RaftActorBehavior oldBehavior = currentBehavior;
 292             currentBehavior = switchBehavior(state);
 293             if(oldBehavior != currentBehavior){
 294                 onStateChanged();
 295             }
 296
 297             onLeaderChanged(oldBehavior.getLeaderId(), currentBehavior.getLeaderId());
 298         }
 299     }
 300
 301     public java.util.Set<String> getPeers() {
 302         return context.getPeerAddresses().keySet();
 303     }
 304
 305     protected String getReplicatedLogState() {
 306         return "snapshotIndex=" + context.getReplicatedLog().getSnapshotIndex()
 307             + ", snapshotTerm=" + context.getReplicatedLog().getSnapshotTerm()
 308             + ", im-mem journal size=" + context.getReplicatedLog().size();
 309     }
 310
 311
 312     /**
 313      * When a derived RaftActor needs to persist something it must call
 314      * persistData.
 315      *
 316      * @param clientActor
 317      * @param identifier
 318      * @param data
 319      */
 320     protected void persistData(ActorRef clientActor, String identifier,
 321         Payload data) {
 322
 323         ReplicatedLogEntry replicatedLogEntry = new ReplicatedLogImplEntry(
 324             context.getReplicatedLog().lastIndex() + 1,
 325             context.getTermInformation().getCurrentTerm(), data);
 326
 327         if(LOG.isDebugEnabled()) {
 328             LOG.debug("Persist data {}", replicatedLogEntry);
 329         }
 330
 331         replicatedLog
 332             .appendAndPersist(clientActor, identifier, replicatedLogEntry);
 333     }
 334
 335     protected String getId() {
 336         return context.getId();
 337     }
 338
 339     /**
 340      * Derived actors can call the isLeader method to check if the current
 341      * RaftActor is the Leader or not
 342      *
 343      * @return true it this RaftActor is a Leader false otherwise
 344      */
 345     protected boolean isLeader() {
 346         return context.getId().equals(currentBehavior.getLeaderId());
 347     }
 348
 349     /**
 350      * Derived actor can call getLeader if they need a reference to the Leader.
 351      * This would be useful for example in forwarding a request to an actor
 352      * which is the leader
 353      *
 354      * @return A reference to the leader if known, null otherwise
 355      */
 356     protected ActorSelection getLeader(){
 357         String leaderAddress = getLeaderAddress();
 358
 359         if(leaderAddress == null){
 360             return null;
 361         }
 362
 363         return context.actorSelection(leaderAddress);
 364     }
 365
 366     /**
 367      *
 368      * @return the current leader's id
 369      */
 370     protected String getLeaderId(){
 371         return currentBehavior.getLeaderId();
 372     }
 373
 374     protected RaftState getRaftState() {
 375         return currentBehavior.state();
 376     }
 377
 378     protected ReplicatedLogEntry getLastLogEntry() {
 379         return replicatedLog.last();
 380     }
 381
 382     protected Long getCurrentTerm(){
 383         return context.getTermInformation().getCurrentTerm();
 384     }
 385
 386     protected Long getCommitIndex(){
 387         return context.getCommitIndex();
 388     }
 389
 390     protected Long getLastApplied(){
 391         return context.getLastApplied();
 392     }
 393
 394     /**
 395      * setPeerAddress sets the address of a known peer at a later time.
 396      * <p>
 397      * This is to account for situations where a we know that a peer
 398      * exists but we do not know an address up-front. This may also be used in
 399      * situations where a known peer starts off in a different location and we
 400      * need to change it's address
 401      * <p>
 402      * Note that if the peerId does not match the list of peers passed to
 403      * this actor during construction an IllegalStateException will be thrown.
 404      *
 405      * @param peerId
 406      * @param peerAddress
 407      */
 408     protected void setPeerAddress(String peerId, String peerAddress){
 409         context.setPeerAddress(peerId, peerAddress);
 410     }
 411
 412
 413
 414     /**
 415      * The applyState method will be called by the RaftActor when some data
 416      * needs to be applied to the actor's state
 417      *
 418      * @param clientActor A reference to the client who sent this message. This
 419      *                    is the same reference that was passed to persistData
 420      *                    by the derived actor. clientActor may be null when
 421      *                    the RaftActor is behaving as a follower or during
 422      *                    recovery.
 423      * @param identifier  The identifier of the persisted data. This is also
 424      *                    the same identifier that was passed to persistData by
 425      *                    the derived actor. identifier may be null when
 426      *                    the RaftActor is behaving as a follower or during
 427      *                    recovery
 428      * @param data        A piece of data that was persisted by the persistData call.
 429      *                    This should NEVER be null.
 430      */
 431     protected abstract void applyState(ActorRef clientActor, String identifier,
 432         Object data);
 433
 434     /**
 435      * This method will be called by the RaftActor when a snapshot needs to be
 436      * created. The derived actor should respond with its current state.
 437      * <p/>
 438      * During recovery the state that is returned by the derived actor will
 439      * be passed back to it by calling the applySnapshot  method
 440      *
 441      * @return The current state of the actor
 442      */
 443     protected abstract void createSnapshot();
 444
 445     /**
 446      * This method will be called by the RaftActor during recovery to
 447      * reconstruct the state of the actor.
 448      * <p/>
 449      * This method may also be called at any other point during normal
 450      * operations when the derived actor is out of sync with it's peers
 451      * and the only way to bring it in sync is by applying a snapshot
 452      *
 453      * @param snapshot A snapshot of the state of the actor
 454      */
 455     protected abstract void applySnapshot(ByteString snapshot);
 456
 457     /**
 458      * This method will be called by the RaftActor when the state of the
 459      * RaftActor changes. The derived actor can then use methods like
 460      * isLeader or getLeader to do something useful
 461      */
 462     protected abstract void onStateChanged();
 463
 464     protected void onLeaderChanged(String oldLeader, String newLeader){};
 465
 466     private RaftActorBehavior switchBehavior(RaftState state) {
 467         if (currentBehavior != null) {
 468             if (currentBehavior.state() == state) {
 469                 return currentBehavior;
 470             }
 471             LOG.info("Switching from state " + currentBehavior.state() + " to "
 472                 + state);
 473
 474             try {
 475                 currentBehavior.close();
 476             } catch (Exception e) {
 477                 LOG.error(e,
 478                     "Failed to close behavior : " + currentBehavior.state());
 479             }
 480
 481         } else {
 482             LOG.info("Switching behavior to " + state);
 483         }
 484         RaftActorBehavior behavior = null;
 485         if (state == RaftState.Candidate) {
 486             behavior = new Candidate(context);
 487         } else if (state == RaftState.Follower) {
 488             behavior = new Follower(context);
 489         } else {
 490             behavior = new Leader(context);
 491         }
 492
 493
 494
 495         return behavior;
 496     }
 497
 498     private void trimPersistentData(long sequenceNumber) {
 499         // Trim akka snapshots
 500         // FIXME : Not sure how exactly the SnapshotSelectionCriteria is applied
 501         // For now guessing that it is ANDed.
 502         deleteSnapshots(new SnapshotSelectionCriteria(
 503             sequenceNumber - context.getConfigParams().getSnapshotBatchCount(), 43200000));
 504
 505         // Trim akka journal
 506         deleteMessages(sequenceNumber);
 507     }
 508
 509     private String getLeaderAddress(){
 510         if(isLeader()){
 511             return getSelf().path().toString();
 512         }
 513         String leaderId = currentBehavior.getLeaderId();
 514         if (leaderId == null) {
 515             return null;
 516         }
 517         String peerAddress = context.getPeerAddress(leaderId);
 518         if(LOG.isDebugEnabled()) {
 519             LOG.debug("getLeaderAddress leaderId = " + leaderId + " peerAddress = "
 520                 + peerAddress);
 521         }
 522
 523         return peerAddress;
 524     }
 525
 526     private void handleCaptureSnapshotReply(ByteString stateInBytes) {
 527         // create a snapshot object from the state provided and save it
 528         // when snapshot is saved async, SaveSnapshotSuccess is raised.
 529
 530         Snapshot sn = Snapshot.create(stateInBytes.toByteArray(),
 531             context.getReplicatedLog().getFrom(captureSnapshot.getLastAppliedIndex() + 1),
 532             captureSnapshot.getLastIndex(), captureSnapshot.getLastTerm(),
 533             captureSnapshot.getLastAppliedIndex(), captureSnapshot.getLastAppliedTerm());
 534
 535         saveSnapshot(sn);
 536
 537         LOG.info("Persisting of snapshot done:{}", sn.getLogMessage());
 538
 539         //be greedy and remove entries from in-mem journal which are in the snapshot
 540         // and update snapshotIndex and snapshotTerm without waiting for the success,
 541
 542         context.getReplicatedLog().snapshotPreCommit(stateInBytes,
 543             captureSnapshot.getLastAppliedIndex(),
 544             captureSnapshot.getLastAppliedTerm());
 545
 546         LOG.info("Removed in-memory snapshotted entries, adjusted snaphsotIndex:{} " +
 547             "and term:{}", captureSnapshot.getLastAppliedIndex(),
 548             captureSnapshot.getLastAppliedTerm());
 549
 550         captureSnapshot = null;
 551         hasSnapshotCaptureInitiated = false;
 552     }
 553
 554
 555     private class ReplicatedLogImpl extends AbstractReplicatedLogImpl {
 556
 557         public ReplicatedLogImpl(Snapshot snapshot) {
 558             super(ByteString.copyFrom(snapshot.getState()),
 559                 snapshot.getLastAppliedIndex(), snapshot.getLastAppliedTerm(),
 560                 snapshot.getUnAppliedEntries());
 561         }
 562
 563         public ReplicatedLogImpl() {
 564             super();
 565         }
 566
 567         @Override public void removeFromAndPersist(long logEntryIndex) {
 568             int adjustedIndex = adjustedIndex(logEntryIndex);
 569
 570             if (adjustedIndex < 0) {
 571                 return;
 572             }
 573
 574             // FIXME: Maybe this should be done after the command is saved
 575             journal.subList(adjustedIndex , journal.size()).clear();
 576
 577             persist(new DeleteEntries(adjustedIndex), new Procedure<DeleteEntries>(){
 578
 579                 @Override public void apply(DeleteEntries param)
 580                     throws Exception {
 581                     //FIXME : Doing nothing for now
 582                 }
 583             });
 584         }
 585
 586         @Override public void appendAndPersist(
 587             final ReplicatedLogEntry replicatedLogEntry) {
 588             appendAndPersist(null, null, replicatedLogEntry);
 589         }
 590
 591         public void appendAndPersist(final ActorRef clientActor,
 592             final String identifier,
 593             final ReplicatedLogEntry replicatedLogEntry) {
 594             context.getLogger().debug(
 595                 "Append log entry and persist {} ", replicatedLogEntry);
 596             // FIXME : By adding the replicated log entry to the in-memory journal we are not truly ensuring durability of the logs
 597             journal.add(replicatedLogEntry);
 598
 599             // When persisting events with persist it is guaranteed that the
 600             // persistent actor will not receive further commands between the
 601             // persist call and the execution(s) of the associated event
 602             // handler. This also holds for multiple persist calls in context
 603             // of a single command.
 604             persist(replicatedLogEntry,
 605                 new Procedure<ReplicatedLogEntry>() {
 606                     public void apply(ReplicatedLogEntry evt) throws Exception {
 607                         // when a snaphsot is being taken, captureSnapshot != null
 608                         if (hasSnapshotCaptureInitiated == false &&
 609                             journal.size() % context.getConfigParams().getSnapshotBatchCount() == 0) {
 610
 611                             LOG.info("Initiating Snapshot Capture..");
 612                             long lastAppliedIndex = -1;
 613                             long lastAppliedTerm = -1;
 614
 615                             ReplicatedLogEntry lastAppliedEntry = get(context.getLastApplied());
 616                             if (lastAppliedEntry != null) {
 617                                 lastAppliedIndex = lastAppliedEntry.getIndex();
 618                                 lastAppliedTerm = lastAppliedEntry.getTerm();
 619                             }
 620
 621                             if(LOG.isDebugEnabled()) {
 622                                 LOG.debug("Snapshot Capture logSize: {}", journal.size());
 623                                 LOG.debug("Snapshot Capture lastApplied:{} ",
 624                                     context.getLastApplied());
 625                                 LOG.debug("Snapshot Capture lastAppliedIndex:{}", lastAppliedIndex);
 626                                 LOG.debug("Snapshot Capture lastAppliedTerm:{}", lastAppliedTerm);
 627                             }
 628
 629                             // send a CaptureSnapshot to self to make the expensive operation async.
 630                             getSelf().tell(new CaptureSnapshot(
 631                                 lastIndex(), lastTerm(), lastAppliedIndex, lastAppliedTerm),
 632                                 null);
 633                             hasSnapshotCaptureInitiated = true;
 634                         }
 635                         // Send message for replication
 636                         if (clientActor != null) {
 637                             currentBehavior.handleMessage(getSelf(),
 638                                 new Replicate(clientActor, identifier,
 639                                     replicatedLogEntry)
 640                             );
 641                         }
 642                     }
 643                 }
 644             );
 645         }
 646
 647     }
 648
 649     private static class DeleteEntries implements Serializable {
 650         private final int fromIndex;
 651
 652
 653         public DeleteEntries(int fromIndex) {
 654             this.fromIndex = fromIndex;
 655         }
 656
 657         public int getFromIndex() {
 658             return fromIndex;
 659         }
 660     }
 661
 662
 663     private class ElectionTermImpl implements ElectionTerm {
 664         /**
 665          * Identifier of the actor whose election term information this is
 666          */
 667         private long currentTerm = 0;
 668         private String votedFor = null;
 669
 670         public long getCurrentTerm() {
 671             return currentTerm;
 672         }
 673
 674         public String getVotedFor() {
 675             return votedFor;
 676         }
 677
 678         @Override public void update(long currentTerm, String votedFor) {
 679             if(LOG.isDebugEnabled()) {
 680                 LOG.debug("Set currentTerm={}, votedFor={}", currentTerm, votedFor);
 681             }
 682             this.currentTerm = currentTerm;
 683             this.votedFor = votedFor;
 684         }
 685
 686         @Override
 687         public void updateAndPersist(long currentTerm, String votedFor){
 688             update(currentTerm, votedFor);
 689             // FIXME : Maybe first persist then update the state
 690             persist(new UpdateElectionTerm(this.currentTerm, this.votedFor), new Procedure<UpdateElectionTerm>(){
 691
 692                 @Override public void apply(UpdateElectionTerm param)
 693                     throws Exception {
 694
 695                 }
 696             });
 697         }
 698     }
 699
 700     private static class UpdateElectionTerm implements Serializable {
 701         private final long currentTerm;
 702         private final String votedFor;
 703
 704         public UpdateElectionTerm(long currentTerm, String votedFor) {
 705             this.currentTerm = currentTerm;
 706             this.votedFor = votedFor;
 707         }
 708
 709         public long getCurrentTerm() {
 710             return currentTerm;
 711         }
 712
 713         public String getVotedFor() {
 714             return votedFor;
 715         }
 716     }
 717
 718 }