Class LogIndex

  • All Implemented Interfaces:
    java.io.Serializable, java.lang.Comparable<AnyObjectId>

    public class LogIndex
    extends ObjectId
    An ObjectId for a commit extended with incrementing log index.

    For any two LogIndex instances, A is an ancestor of C reachable through parent edges in the graph if A.index < C.index. LogIndex provides a performance optimization for Ketch, the same information can be obtained from RevWalk.

    Index values are only valid within a single KetchLeader instance after it has won an election. By restricting scope to a single leader new leaders do not need to traverse the entire history to determine the next index for new proposals. This differs from Raft, where leader election uses the log index and the term number to determine which replica holds a sufficiently up-to-date log. Since Ketch uses Git objects for storage of its replicated log, it keeps the term number as Raft does but uses standard Git operations to imply the log index.

    Round.runAsync(AnyObjectId) bumps the index as each new round is constructed.

    See Also:
    Serialized Form
    • Field Detail

      • index

        private final long index
    • Constructor Detail

      • LogIndex

        private LogIndex​(AnyObjectId id,
                         long index)
    • Method Detail

      • getIndex

        public long getIndex()
        Get index provided by the current leader instance.
        Returns:
        index provided by the current leader instance.
      • isBefore

        boolean isBefore​(LogIndex c)
        Check if this log position committed before another log position.

        Only valid for log positions in memory for the current leader.

        Parameters:
        c - other (more recent) log position.
        Returns:
        true if this log position was before c or equal to c and therefore any agreement of c implies agreement on this log position.
      • describeForLog

        public java.lang.String describeForLog()
        Create string suitable for debug logging containing the log index and abbreviated ObjectId.
        Returns:
        string suitable for debug logging containing the log index and abbreviated ObjectId.