opendaylight/md-sal/sal-akka-raft/src/main/java/org/opendaylight/controller/cluster/raft/SnapshotManager.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 package org.opendaylight.controller.cluster.raft;
   9
  10 import akka.persistence.SnapshotSelectionCriteria;
  11 import com.google.common.annotations.VisibleForTesting;
  12 import com.google.common.io.ByteSource;
  13 import java.io.IOException;
  14 import java.io.OutputStream;
  15 import java.util.List;
  16 import java.util.Optional;
  17 import java.util.function.Consumer;
  18 import org.eclipse.jdt.annotation.NonNull;
  19 import org.opendaylight.controller.cluster.io.FileBackedOutputStream;
  20 import org.opendaylight.controller.cluster.raft.base.messages.ApplySnapshot;
  21 import org.opendaylight.controller.cluster.raft.base.messages.CaptureSnapshot;
  22 import org.opendaylight.controller.cluster.raft.base.messages.SendInstallSnapshot;
  23 import org.opendaylight.controller.cluster.raft.base.messages.SnapshotComplete;
  24 import org.opendaylight.controller.cluster.raft.behaviors.RaftActorBehavior;
  25 import org.opendaylight.controller.cluster.raft.persisted.EmptyState;
  26 import org.opendaylight.controller.cluster.raft.persisted.Snapshot;
  27 import org.slf4j.Logger;
  28
  29 /**
  30  * Manages the capturing of snapshots for a RaftActor.
  31  *
  32  * @author Moiz Raja
  33  * @author Thomas Pantelis
  34  */
  35 public class SnapshotManager implements SnapshotState {
  36
  37     @SuppressWarnings("checkstyle:MemberName")
  38     private final SnapshotState IDLE = new Idle();
  39
  40     @SuppressWarnings({"checkstyle:MemberName", "checkstyle:AbbreviationAsWordInName"})
  41     private final SnapshotState PERSISTING = new Persisting();
  42
  43     @SuppressWarnings({"checkstyle:MemberName", "checkstyle:AbbreviationAsWordInName"})
  44     private final SnapshotState CREATING = new Creating();
  45
  46     private final Logger log;
  47     private final RaftActorContext context;
  48     private final LastAppliedTermInformationReader lastAppliedTermInformationReader =
  49             new LastAppliedTermInformationReader();
  50     private final ReplicatedToAllTermInformationReader replicatedToAllTermInformationReader =
  51             new ReplicatedToAllTermInformationReader();
  52
  53
  54     private SnapshotState currentState = IDLE;
  55     private CaptureSnapshot captureSnapshot;
  56     private long lastSequenceNumber = -1;
  57
  58     private Consumer<Optional<OutputStream>> createSnapshotProcedure = null;
  59
  60     private ApplySnapshot applySnapshot;
  61     private RaftActorSnapshotCohort snapshotCohort = NoopRaftActorSnapshotCohort.INSTANCE;
  62
  63     /**
  64      * Constructs an instance.
  65      *
  66      * @param context the RaftActorContext
  67      * @param logger the Logger
  68      */
  69     public SnapshotManager(final RaftActorContext context, final Logger logger) {
  70         this.context = context;
  71         this.log = logger;
  72     }
  73
  74     public boolean isApplying() {
  75         return applySnapshot != null;
  76     }
  77
  78     @Override
  79     public boolean isCapturing() {
  80         return currentState.isCapturing();
  81     }
  82
  83     @Override
  84     public boolean captureToInstall(final ReplicatedLogEntry lastLogEntry, final long replicatedToAllIndex,
  85             final String targetFollower) {
  86         return currentState.captureToInstall(lastLogEntry, replicatedToAllIndex, targetFollower);
  87     }
  88
  89     @Override
  90     public boolean capture(final ReplicatedLogEntry lastLogEntry, final long replicatedToAllIndex) {
  91         return currentState.capture(lastLogEntry, replicatedToAllIndex);
  92     }
  93
  94     @Override
  95     public boolean captureWithForcedTrim(final ReplicatedLogEntry lastLogEntry, final long replicatedToAllIndex) {
  96         return currentState.captureWithForcedTrim(lastLogEntry, replicatedToAllIndex);
  97     }
  98
  99     @Override
 100     public void apply(final ApplySnapshot snapshot) {
 101         currentState.apply(snapshot);
 102     }
 103
 104     @Override
 105     public void persist(final Snapshot.State state, final Optional<OutputStream> installSnapshotStream,
 106             final long totalMemory) {
 107         currentState.persist(state, installSnapshotStream, totalMemory);
 108     }
 109
 110     @Override
 111     public void commit(final long sequenceNumber, final long timeStamp) {
 112         currentState.commit(sequenceNumber, timeStamp);
 113     }
 114
 115     @Override
 116     public void rollback() {
 117         currentState.rollback();
 118     }
 119
 120     @Override
 121     public long trimLog(final long desiredTrimIndex) {
 122         return currentState.trimLog(desiredTrimIndex);
 123     }
 124
 125     @SuppressWarnings("checkstyle:hiddenField")
 126     void setCreateSnapshotConsumer(final Consumer<Optional<OutputStream>> createSnapshotProcedure) {
 127         this.createSnapshotProcedure = createSnapshotProcedure;
 128     }
 129
 130     void setSnapshotCohort(final RaftActorSnapshotCohort snapshotCohort) {
 131         this.snapshotCohort = snapshotCohort;
 132     }
 133
 134     public Snapshot.@NonNull State convertSnapshot(final ByteSource snapshotBytes) throws IOException {
 135         return snapshotCohort.deserializeSnapshot(snapshotBytes);
 136     }
 137
 138     public long getLastSequenceNumber() {
 139         return lastSequenceNumber;
 140     }
 141
 142     @VisibleForTesting
 143     public CaptureSnapshot getCaptureSnapshot() {
 144         return captureSnapshot;
 145     }
 146
 147     private boolean hasFollowers() {
 148         return context.hasFollowers();
 149     }
 150
 151     private String persistenceId() {
 152         return context.getId();
 153     }
 154
 155     /**
 156      * Constructs a CaptureSnapshot instance.
 157      *
 158      * @param lastLogEntry the last log entry for the snapshot.
 159      * @param replicatedToAllIndex the index of the last entry replicated to all followers.
 160      * @return a new CaptureSnapshot instance.
 161      */
 162     public CaptureSnapshot newCaptureSnapshot(final ReplicatedLogEntry lastLogEntry, final long replicatedToAllIndex,
 163                                               final boolean mandatoryTrim) {
 164         TermInformationReader lastAppliedTermInfoReader =
 165                 lastAppliedTermInformationReader.init(context.getReplicatedLog(), context.getLastApplied(),
 166                         lastLogEntry, hasFollowers());
 167
 168         long lastAppliedIndex = lastAppliedTermInfoReader.getIndex();
 169         long lastAppliedTerm = lastAppliedTermInfoReader.getTerm();
 170
 171         TermInformationReader replicatedToAllTermInfoReader =
 172                 replicatedToAllTermInformationReader.init(context.getReplicatedLog(), replicatedToAllIndex);
 173
 174         long newReplicatedToAllIndex = replicatedToAllTermInfoReader.getIndex();
 175         long newReplicatedToAllTerm = replicatedToAllTermInfoReader.getTerm();
 176
 177         List<ReplicatedLogEntry> unAppliedEntries = context.getReplicatedLog().getFrom(lastAppliedIndex + 1);
 178
 179         final long lastLogEntryIndex;
 180         final long lastLogEntryTerm;
 181         if (lastLogEntry == null) {
 182             // When we don't have journal present, for example two captureSnapshots executed right after another with no
 183             // new journal we still want to preserve the index and term in the snapshot.
 184             lastAppliedIndex = lastLogEntryIndex = context.getReplicatedLog().getSnapshotIndex();
 185             lastAppliedTerm = lastLogEntryTerm = context.getReplicatedLog().getSnapshotTerm();
 186
 187             log.debug("{}: Capturing Snapshot : lastLogEntry is null. Using snapshot values lastAppliedIndex {} and "
 188                     + "lastAppliedTerm {} instead.", persistenceId(), lastAppliedIndex, lastAppliedTerm);
 189         } else {
 190             lastLogEntryIndex = lastLogEntry.getIndex();
 191             lastLogEntryTerm = lastLogEntry.getTerm();
 192         }
 193
 194         return new CaptureSnapshot(lastLogEntryIndex, lastLogEntryTerm, lastAppliedIndex, lastAppliedTerm,
 195                 newReplicatedToAllIndex, newReplicatedToAllTerm, unAppliedEntries, mandatoryTrim);
 196     }
 197
 198     private class AbstractSnapshotState implements SnapshotState {
 199
 200         @Override
 201         public boolean isCapturing() {
 202             return true;
 203         }
 204
 205         @Override
 206         public boolean capture(final ReplicatedLogEntry lastLogEntry, final long replicatedToAllIndex) {
 207             log.debug("capture should not be called in state {}", this);
 208             return false;
 209         }
 210
 211         @Override
 212         public boolean captureToInstall(final ReplicatedLogEntry lastLogEntry, final long replicatedToAllIndex,
 213                 final String targetFollower) {
 214             log.debug("captureToInstall should not be called in state {}", this);
 215             return false;
 216         }
 217
 218         @Override
 219         public boolean captureWithForcedTrim(final ReplicatedLogEntry lastLogEntry, final long replicatedToAllIndex) {
 220             log.debug("captureWithForcedTrim should not be called in state {}", this);
 221             return false;
 222         }
 223
 224         @Override
 225         public void apply(final ApplySnapshot snapshot) {
 226             log.debug("apply should not be called in state {}", this);
 227         }
 228
 229         @Override
 230         public void persist(final Snapshot.State state, final Optional<OutputStream> installSnapshotStream,
 231                 final long totalMemory) {
 232             log.debug("persist should not be called in state {}", this);
 233         }
 234
 235         @Override
 236         public void commit(final long sequenceNumber, final long timeStamp) {
 237             log.debug("commit should not be called in state {}", this);
 238         }
 239
 240         @Override
 241         public void rollback() {
 242             log.debug("rollback should not be called in state {}", this);
 243         }
 244
 245         @Override
 246         public long trimLog(final long desiredTrimIndex) {
 247             log.debug("trimLog should not be called in state {}", this);
 248             return -1;
 249         }
 250
 251         protected long doTrimLog(final long desiredTrimIndex) {
 252             //  we would want to keep the lastApplied as its used while capturing snapshots
 253             long lastApplied = context.getLastApplied();
 254             long tempMin = Math.min(desiredTrimIndex, lastApplied > -1 ? lastApplied - 1 : -1);
 255
 256             if (log.isTraceEnabled()) {
 257                 log.trace("{}: performSnapshotWithoutCapture: desiredTrimIndex: {}, lastApplied: {}, tempMin: {}",
 258                         persistenceId(), desiredTrimIndex, lastApplied, tempMin);
 259             }
 260
 261             if (tempMin > -1 && context.getReplicatedLog().isPresent(tempMin)) {
 262                 log.debug("{}: fakeSnapshot purging log to {} for term {}", persistenceId(), tempMin,
 263                         context.getTermInformation().getCurrentTerm());
 264
 265                 //use the term of the temp-min, since we check for isPresent, entry will not be null
 266                 ReplicatedLogEntry entry = context.getReplicatedLog().get(tempMin);
 267                 context.getReplicatedLog().snapshotPreCommit(tempMin, entry.getTerm());
 268                 context.getReplicatedLog().snapshotCommit();
 269                 return tempMin;
 270             }
 271
 272             final RaftActorBehavior currentBehavior = context.getCurrentBehavior();
 273             if (tempMin > currentBehavior.getReplicatedToAllIndex()) {
 274                 // It's possible a follower was lagging and an install snapshot advanced its match index past
 275                 // the current replicatedToAllIndex. Since the follower is now caught up we should advance the
 276                 // replicatedToAllIndex (to tempMin). The fact that tempMin wasn't found in the log is likely
 277                 // due to a previous snapshot triggered by the memory threshold exceeded, in that case we
 278                 // trim the log to the last applied index even if previous entries weren't replicated to all followers.
 279                 currentBehavior.setReplicatedToAllIndex(tempMin);
 280             }
 281             return -1;
 282         }
 283     }
 284
 285     private class Idle extends AbstractSnapshotState {
 286
 287         @Override
 288         public boolean isCapturing() {
 289             return false;
 290         }
 291
 292         @SuppressWarnings("checkstyle:IllegalCatch")
 293         private boolean capture(final ReplicatedLogEntry lastLogEntry, final long replicatedToAllIndex,
 294                 final String targetFollower, final boolean mandatoryTrim) {
 295             captureSnapshot = newCaptureSnapshot(lastLogEntry, replicatedToAllIndex, mandatoryTrim);
 296
 297             OutputStream installSnapshotStream = null;
 298             if (targetFollower != null) {
 299                 installSnapshotStream = context.getFileBackedOutputStreamFactory().newInstance();
 300                 log.info("{}: Initiating snapshot capture {} to install on {}",
 301                         persistenceId(), captureSnapshot, targetFollower);
 302             } else {
 303                 log.info("{}: Initiating snapshot capture {}", persistenceId(), captureSnapshot);
 304             }
 305
 306             lastSequenceNumber = context.getPersistenceProvider().getLastSequenceNumber();
 307
 308             log.debug("{}: lastSequenceNumber prior to capture: {}", persistenceId(), lastSequenceNumber);
 309
 310             SnapshotManager.this.currentState = CREATING;
 311
 312             try {
 313                 createSnapshotProcedure.accept(Optional.ofNullable(installSnapshotStream));
 314             } catch (Exception e) {
 315                 SnapshotManager.this.currentState = IDLE;
 316                 log.error("Error creating snapshot", e);
 317                 return false;
 318             }
 319
 320             return true;
 321         }
 322
 323         @Override
 324         public boolean capture(final ReplicatedLogEntry lastLogEntry, final long replicatedToAllIndex) {
 325             return capture(lastLogEntry, replicatedToAllIndex, null, false);
 326         }
 327
 328         @Override
 329         public boolean captureToInstall(final ReplicatedLogEntry lastLogEntry, final long replicatedToAllIndex,
 330                 final String targetFollower) {
 331             return capture(lastLogEntry, replicatedToAllIndex, targetFollower, false);
 332         }
 333
 334         @Override
 335         public boolean captureWithForcedTrim(final ReplicatedLogEntry lastLogEntry, final long replicatedToAllIndex) {
 336             return capture(lastLogEntry, replicatedToAllIndex, null, true);
 337         }
 338
 339         @Override
 340         public void apply(final ApplySnapshot toApply) {
 341             SnapshotManager.this.applySnapshot = toApply;
 342
 343             lastSequenceNumber = context.getPersistenceProvider().getLastSequenceNumber();
 344
 345             log.debug("lastSequenceNumber prior to persisting applied snapshot: {}", lastSequenceNumber);
 346
 347             context.getPersistenceProvider().saveSnapshot(toApply.getSnapshot());
 348
 349             SnapshotManager.this.currentState = PERSISTING;
 350         }
 351
 352         @Override
 353         public String toString() {
 354             return "Idle";
 355         }
 356
 357         @Override
 358         public long trimLog(final long desiredTrimIndex) {
 359             return doTrimLog(desiredTrimIndex);
 360         }
 361     }
 362
 363     private class Creating extends AbstractSnapshotState {
 364
 365         @Override
 366         public void persist(final Snapshot.State snapshotState, final Optional<OutputStream> installSnapshotStream,
 367                 final long totalMemory) {
 368             // create a snapshot object from the state provided and save it
 369             // when snapshot is saved async, SaveSnapshotSuccess is raised.
 370
 371             Snapshot snapshot = Snapshot.create(snapshotState,
 372                     captureSnapshot.getUnAppliedEntries(),
 373                     captureSnapshot.getLastIndex(), captureSnapshot.getLastTerm(),
 374                     captureSnapshot.getLastAppliedIndex(), captureSnapshot.getLastAppliedTerm(),
 375                     context.getTermInformation().getCurrentTerm(),
 376                     context.getTermInformation().getVotedFor(), context.getPeerServerInfo(true));
 377
 378             context.getPersistenceProvider().saveSnapshot(snapshot);
 379
 380             log.info("{}: Persisting of snapshot done: {}", persistenceId(), snapshot);
 381
 382             long dataThreshold = totalMemory * context.getConfigParams().getSnapshotDataThresholdPercentage() / 100;
 383             boolean dataSizeThresholdExceeded = context.getReplicatedLog().dataSize() > dataThreshold;
 384
 385             boolean logSizeExceededSnapshotBatchCount =
 386                     context.getReplicatedLog().size() >= context.getConfigParams().getSnapshotBatchCount();
 387
 388             final RaftActorBehavior currentBehavior = context.getCurrentBehavior();
 389             if (dataSizeThresholdExceeded || logSizeExceededSnapshotBatchCount || captureSnapshot.isMandatoryTrim()) {
 390                 if (log.isDebugEnabled()) {
 391                     if (dataSizeThresholdExceeded) {
 392                         log.debug("{}: log data size {} exceeds the memory threshold {} - doing snapshotPreCommit "
 393                                 + "with index {}", context.getId(), context.getReplicatedLog().dataSize(),
 394                                 dataThreshold, captureSnapshot.getLastAppliedIndex());
 395                     } else if (logSizeExceededSnapshotBatchCount) {
 396                         log.debug("{}: log size {} exceeds the snapshot batch count {} - doing snapshotPreCommit with "
 397                                 + "index {}", context.getId(), context.getReplicatedLog().size(),
 398                                 context.getConfigParams().getSnapshotBatchCount(),
 399                                 captureSnapshot.getLastAppliedIndex());
 400                     } else {
 401                         log.debug("{}: user triggered or root overwrite snapshot encountered, trimming log up to "
 402                                 + "last applied index {}", context.getId(), captureSnapshot.getLastAppliedIndex());
 403                     }
 404                 }
 405
 406                 // We either exceeded the memory threshold or the log size exceeded the snapshot batch
 407                 // count so, to keep the log memory footprint in check, clear the log based on lastApplied.
 408                 // This could/should only happen if one of the followers is down as normally we keep
 409                 // removing from the log as entries are replicated to all.
 410                 context.getReplicatedLog().snapshotPreCommit(captureSnapshot.getLastAppliedIndex(),
 411                         captureSnapshot.getLastAppliedTerm());
 412
 413                 // Don't reset replicatedToAllIndex to -1 as this may prevent us from trimming the log after an
 414                 // install snapshot to a follower.
 415                 if (captureSnapshot.getReplicatedToAllIndex() >= 0) {
 416                     currentBehavior.setReplicatedToAllIndex(captureSnapshot.getReplicatedToAllIndex());
 417                 }
 418
 419             } else if (captureSnapshot.getReplicatedToAllIndex() != -1) {
 420                 // clear the log based on replicatedToAllIndex
 421                 context.getReplicatedLog().snapshotPreCommit(captureSnapshot.getReplicatedToAllIndex(),
 422                         captureSnapshot.getReplicatedToAllTerm());
 423
 424                 currentBehavior.setReplicatedToAllIndex(captureSnapshot.getReplicatedToAllIndex());
 425             } else {
 426                 // The replicatedToAllIndex was not found in the log
 427                 // This means that replicatedToAllIndex never moved beyond -1 or that it is already in the snapshot.
 428                 // In this scenario we may need to save the snapshot to the akka persistence
 429                 // snapshot for recovery but we do not need to do the replicated log trimming.
 430                 context.getReplicatedLog().snapshotPreCommit(context.getReplicatedLog().getSnapshotIndex(),
 431                         context.getReplicatedLog().getSnapshotTerm());
 432             }
 433
 434             log.info("{}: Removed in-memory snapshotted entries, adjusted snaphsotIndex: {} and term: {}",
 435                     context.getId(), context.getReplicatedLog().getSnapshotIndex(),
 436                     context.getReplicatedLog().getSnapshotTerm());
 437
 438             if (installSnapshotStream.isPresent()) {
 439                 if (context.getId().equals(currentBehavior.getLeaderId())) {
 440                     try {
 441                         ByteSource snapshotBytes = ((FileBackedOutputStream)installSnapshotStream.get()).asByteSource();
 442                         currentBehavior.handleMessage(context.getActor(),
 443                                 new SendInstallSnapshot(snapshot, snapshotBytes));
 444                     } catch (IOException e) {
 445                         log.error("{}: Snapshot install failed due to an unrecoverable streaming error",
 446                                 context.getId(), e);
 447                     }
 448                 } else {
 449                     ((FileBackedOutputStream)installSnapshotStream.get()).cleanup();
 450                 }
 451             }
 452
 453             captureSnapshot = null;
 454             SnapshotManager.this.currentState = PERSISTING;
 455         }
 456
 457         @Override
 458         public String toString() {
 459             return "Creating";
 460         }
 461
 462     }
 463
 464     private class Persisting extends AbstractSnapshotState {
 465
 466         @Override
 467         @SuppressWarnings("checkstyle:IllegalCatch")
 468         public void commit(final long sequenceNumber, final long timeStamp) {
 469             log.debug("{}: Snapshot success -  sequence number: {}", persistenceId(), sequenceNumber);
 470
 471             if (applySnapshot != null) {
 472                 try {
 473                     Snapshot snapshot = applySnapshot.getSnapshot();
 474
 475                     //clears the followers log, sets the snapshot index to ensure adjusted-index works
 476                     context.setReplicatedLog(ReplicatedLogImpl.newInstance(snapshot, context));
 477                     context.setLastApplied(snapshot.getLastAppliedIndex());
 478                     context.setCommitIndex(snapshot.getLastAppliedIndex());
 479                     context.getTermInformation().update(snapshot.getElectionTerm(), snapshot.getElectionVotedFor());
 480
 481                     if (snapshot.getServerConfiguration() != null) {
 482                         context.updatePeerIds(snapshot.getServerConfiguration());
 483                     }
 484
 485                     if (!(snapshot.getState() instanceof EmptyState)) {
 486                         snapshotCohort.applySnapshot(snapshot.getState());
 487                     }
 488
 489                     applySnapshot.getCallback().onSuccess();
 490                 } catch (Exception e) {
 491                     log.error("{}: Error applying snapshot", context.getId(), e);
 492                 }
 493             } else {
 494                 context.getReplicatedLog().snapshotCommit();
 495             }
 496
 497             context.getPersistenceProvider().deleteSnapshots(new SnapshotSelectionCriteria(scala.Long.MaxValue(),
 498                     timeStamp - 1, 0L, 0L));
 499
 500             context.getPersistenceProvider().deleteMessages(lastSequenceNumber);
 501
 502             snapshotComplete();
 503         }
 504
 505         @Override
 506         public void rollback() {
 507             // Nothing to rollback if we're applying a snapshot from the leader.
 508             if (applySnapshot == null) {
 509                 context.getReplicatedLog().snapshotRollback();
 510
 511                 log.info("{}: Replicated Log rolled back. Snapshot will be attempted in the next cycle."
 512                         + "snapshotIndex:{}, snapshotTerm:{}, log-size:{}", persistenceId(),
 513                         context.getReplicatedLog().getSnapshotIndex(),
 514                         context.getReplicatedLog().getSnapshotTerm(),
 515                         context.getReplicatedLog().size());
 516             } else {
 517                 applySnapshot.getCallback().onFailure();
 518             }
 519
 520             snapshotComplete();
 521         }
 522
 523         private void snapshotComplete() {
 524             lastSequenceNumber = -1;
 525             applySnapshot = null;
 526             SnapshotManager.this.currentState = IDLE;
 527
 528             context.getActor().tell(SnapshotComplete.INSTANCE, context.getActor());
 529         }
 530
 531         @Override
 532         public String toString() {
 533             return "Persisting";
 534         }
 535
 536     }
 537
 538     private interface TermInformationReader {
 539         long getIndex();
 540
 541         long getTerm();
 542     }
 543
 544     static class LastAppliedTermInformationReader implements TermInformationReader {
 545         private long index;
 546         private long term;
 547
 548         LastAppliedTermInformationReader init(final ReplicatedLog log, final long originalIndex,
 549                 final ReplicatedLogEntry lastLogEntry, final boolean hasFollowers) {
 550             ReplicatedLogEntry entry = log.get(originalIndex);
 551             this.index = -1L;
 552             this.term = -1L;
 553             if (!hasFollowers) {
 554                 if (lastLogEntry != null) {
 555                     // since we have persisted the last-log-entry to persistent journal before the capture,
 556                     // we would want to snapshot from this entry.
 557                     index = lastLogEntry.getIndex();
 558                     term = lastLogEntry.getTerm();
 559                 }
 560             } else if (entry != null) {
 561                 index = entry.getIndex();
 562                 term = entry.getTerm();
 563             } else if (log.getSnapshotIndex() > -1) {
 564                 index = log.getSnapshotIndex();
 565                 term = log.getSnapshotTerm();
 566             }
 567             return this;
 568         }
 569
 570         @Override
 571         public long getIndex() {
 572             return this.index;
 573         }
 574
 575         @Override
 576         public long getTerm() {
 577             return this.term;
 578         }
 579     }
 580
 581     private static class ReplicatedToAllTermInformationReader implements TermInformationReader {
 582         private long index;
 583         private long term;
 584
 585         ReplicatedToAllTermInformationReader init(final ReplicatedLog log, final long originalIndex) {
 586             ReplicatedLogEntry entry = log.get(originalIndex);
 587             this.index = -1L;
 588             this.term = -1L;
 589
 590             if (entry != null) {
 591                 index = entry.getIndex();
 592                 term = entry.getTerm();
 593             }
 594
 595             return this;
 596         }
 597
 598         @Override
 599         public long getIndex() {
 600             return this.index;
 601         }
 602
 603         @Override
 604         public long getTerm() {
 605             return this.term;
 606         }
 607     }
 608 }