private long checkInconsistentAppendEntries()

in ratis-server/src/main/java/org/apache/ratis/server/impl/RaftServerImpl.java [1712:1743]

• 25 lines of code
• 9 McCabe index (conditional complexity)

  private long checkInconsistentAppendEntries(TermIndex previous, List<LogEntryProto> entries) {
    // Check if a snapshot installation through state machine is in progress.
    final long installSnapshot = snapshotInstallationHandler.getInProgressInstallSnapshotIndex();
    if (installSnapshot != RaftLog.INVALID_LOG_INDEX) {
      LOG.info("{}: Failed appendEntries as snapshot ({}) installation is in progress", getMemberId(), installSnapshot);
      return state.getNextIndex();
    }

    // Check that the first log entry is greater than the snapshot index in the latest snapshot and follower's last
    // committed index. If not, reply to the leader the new next index.
    if (entries != null && !entries.isEmpty()) {
      final long firstEntryIndex = entries.get(0).getIndex();
      final long snapshotIndex = state.getSnapshotIndex();
      final long commitIndex =  state.getLog().getLastCommittedIndex();
      final long nextIndex = Math.max(snapshotIndex, commitIndex);
      if (nextIndex > RaftLog.INVALID_LOG_INDEX && nextIndex >= firstEntryIndex) {
        LOG.info("{}: Failed appendEntries as the first entry (index {})" +
                " already exists (snapshotIndex: {}, commitIndex: {})",
            getMemberId(), firstEntryIndex, snapshotIndex, commitIndex);
        return nextIndex + 1;
      }
    }

    // Check if "previous" is contained in current state.
    if (previous != null && !(appendLogTermIndices.contains(previous) || state.containsTermIndex(previous))) {
      final long replyNextIndex = Math.min(state.getNextIndex(), previous.getIndex());
      LOG.info("{}: Failed appendEntries as previous log entry ({}) is not found", getMemberId(), previous);
      return replyNextIndex;
    }

    return RaftLog.INVALID_LOG_INDEX;
  }