Package akka.cluster.ddata

Class VersionVector

  • All Implemented Interfaces:
    RemovedNodePruning, ReplicatedData, ReplicatedDataSerialization, java.io.Serializable
    Direct Known Subclasses:
    ManyVersionVector, OneVersionVector
    public abstract class VersionVector
extends java.lang.Object
implements ReplicatedData, ReplicatedDataSerialization, RemovedNodePruning
    Representation of a Vector-based clock (counting clock), inspired by Lamport logical clocks. 
    
 Reference:
    1) Leslie Lamport (1978). "Time, clocks, and the ordering of events in a distributed system". Communications of the ACM 21 (7): 558-565.
    2) Friedemann Mattern (1988). "Virtual Time and Global States of Distributed Systems". Workshop on Parallel and Distributed Algorithms: pp. 215-226

    Based on code from akka.cluster.VectorClock.

    This class is immutable, i.e. "modifying" methods return a new instance.

    See Also:
    Serialized Form

    • Constructor Detail

      • VersionVector

        public VersionVector()

    • Method Detail

      • AfterInstance

        public static VersionVector.After$ AfterInstance()
        Java API: The VersionVector.After instance

      • BeforeInstance

        public static VersionVector.Before$ BeforeInstance()
        Java API: The VersionVector.Before instance

      • SameInstance

        public static VersionVector.Same$ SameInstance()
        Java API: The VersionVector.Same instance

      • ConcurrentInstance

        public static VersionVector.Concurrent$ ConcurrentInstance()
        Java API: The VersionVector.Concurrent instance

      • $colon$plus

        public VersionVector $colon$plus​(SelfUniqueAddress node)
        Increment the version for the node passed as argument. Returns a new VersionVector.

      • increment

        public VersionVector increment​(SelfUniqueAddress node)
        Increment the version for the node passed as argument. Returns a new VersionVector.

      • isEmpty

        public abstract boolean isEmpty()

      • $less$greater

        public boolean $less$greater​(VersionVector that)
        Returns true if this and that are concurrent else false.

      • $less

        public boolean $less​(VersionVector that)
        Returns true if this is before that else false.

      • $greater

        public boolean $greater​(VersionVector that)
        Returns true if this is after that else false.

      • $eq$eq

        public boolean $eq$eq​(VersionVector that)
        Returns true if this VersionVector has the same history as the 'that' VersionVector else false.

      • compareTo

        public VersionVector.Ordering compareTo​(VersionVector that)
        Compare two version vectors. The outcome will be one of the following: 

        
   1. Version 1 is SAME (==)       as Version 2 iff for all i c1(i) == c2(i)
   2. Version 1 is BEFORE (<)      Version 2 iff for all i c1(i) <= c2(i) and there exist a j such that c1(j) < c2(j)
   3. Version 1 is AFTER (>)       Version 2 iff for all i c1(i) >= c2(i) and there exist a j such that c1(j) > c2(j).
   4. Version 1 is CONCURRENT (<>) to Version 2 otherwise.

      • merge

        public abstract VersionVector merge​(VersionVector that)
        Merges this VersionVector with another VersionVector. E.g. merges its versioned history.