Class VectorClock

Representation of a Vector-based clock (counting clock), inspired by Lamport logical clocks.

Reference:

Leslie Lamport (1978). "Time, clocks, and the ordering of events in a distributed system". Communications of the ACM 21 (7): 558-565.
Friedemann Mattern (1988). "Virtual Time and Global States of Distributed Systems". Workshop on Parallel and Distributed Algorithms: pp. 215-226

Based on code from the 'vlock' VectorClock library by Coda Hale.

Inheritance

object

VectorClock

Inherited Members

object.Equals(object, object)

object.GetType()

object.ReferenceEquals(object, object)

Namespace: Akka.Cluster

Assembly: Akka.Cluster.dll

Syntax

public sealed class VectorClock

Properties

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Versions

The list of vector clock values for each node.

Declaration

public ImmutableSortedDictionary<VectorClock.Node, long> Versions { get; }

Property Value

Type	Description
ImmutableSortedDictionary<VectorClock.Node, long>

Methods

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CompareTo(VectorClock)

Compares the current vector clock with the supplied vector clock. The outcome will be one of the following:

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

Declaration

public VectorClock.Ordering CompareTo(VectorClock that)

Parameters

Type	Name	Description
VectorClock	that	The vector clock used to compare against.

Returns

Type	Description
VectorClock.Ordering	TBD

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Create()

Creates a new VectorClock

Declaration

public static VectorClock Create()

Returns

Type	Description
VectorClock	A new VectorClock.

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Create(ImmutableSortedDictionary<Node, long>)

Creates a VectorClock from some initial seed values.

Declaration

public static VectorClock Create(ImmutableSortedDictionary<VectorClock.Node, long> seedValues)

Parameters

Type	Name	Description
ImmutableSortedDictionary<VectorClock.Node, long>	seedValues	Preliminary values that will be used by the vectorclock.

Returns

Type	Description
VectorClock	A new VectorClock.

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Equals(object)

Declaration

public override bool Equals(object obj)

Parameters

Type	Name	Description
object	obj

Returns

Type	Description
bool

Overrides

object.Equals(object)

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GetHashCode()

Declaration

public override int GetHashCode()

Returns

Type	Description
int

Overrides

object.GetHashCode()

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Increment(Node)

Increment the version for the node passed as argument. Returns a new VectorClock.

Declaration

public VectorClock Increment(VectorClock.Node node)

Parameters

Type	Name	Description
VectorClock.Node	node	Increment the vector clock value for a particular node.

Returns

Type	Description
VectorClock	An updated VectorClock instance.

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IsAfter(VectorClock)

Returns true if

this

is after

that

else false.

Declaration

public bool IsAfter(VectorClock that)

Parameters

Type	Name	Description
VectorClock	that	The other VectorClock to check.

Returns

Type	Description
bool	`true` if this vectorclock comes after the one we're comparing.

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IsBefore(VectorClock)

Returns true if

this

is before

that

else false.

Declaration

public bool IsBefore(VectorClock that)

Parameters

Type	Name	Description
VectorClock	that	The other VectorClock to check.

Returns

Type	Description
bool	`true` if this vectorclock comes before the one we're comparing.

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IsConcurrentWith(VectorClock)

Returns true if

this

and

that

are concurrent else false.

Declaration

public bool IsConcurrentWith(VectorClock that)

Parameters

Type	Name	Description
VectorClock	that	The other VectorClock to check.

Returns

Type	Description
bool	`true` if both vector clocks contain concurrent modifications that need to be merged.

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IsSameAs(VectorClock)

Returns true if this VectorClock has the same history as the 'that' VectorClock else false.

Declaration

public bool IsSameAs(VectorClock that)

Parameters

Type	Name	Description
VectorClock	that	The other VectorClock to check.

Returns

Type	Description
bool	`true` if this vectorclock is the same as the one we're comparing.

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Merge(VectorClock)

Merges the vector clock with another VectorClock (e.g. merges its versioned history).

Declaration

public VectorClock Merge(VectorClock that)

Parameters

Type	Name	Description
VectorClock	that	The vector clock to merge into the current clock.

Returns

Type	Description
VectorClock	A newly created VectorClock with the current vector clock and the given vector clock merged.

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Prune(Node)

Removes the specified node from the current vector clock.

Declaration

public VectorClock Prune(VectorClock.Node removedNode)

Parameters

Type	Name	Description
VectorClock.Node	removedNode	The node that is being removed.

Returns

Type	Description
VectorClock	A newly created VectorClock that has the given node removed.

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ToString()

Declaration

public override string ToString()

Returns

Type	Description
string

Overrides

object.ToString()

Operators

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operator ==(VectorClock, VectorClock)

Compares two specified vector clocks for equality.

Declaration

public static bool operator ==(VectorClock left, VectorClock right)

Parameters

Type	Name	Description
VectorClock	left	The first vector clock used for comparison
VectorClock	right	The second vector clock used for comparison

Returns

Type	Description
bool	`true` if both vector clocks are equal; otherwise `false`

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operator >(VectorClock, VectorClock)

Compares two specified vector clocks to see if the first one is greater than the other one.

Declaration

public static bool operator >(VectorClock left, VectorClock right)

Parameters

Type	Name	Description
VectorClock	left	The first vector clock used for comparison
VectorClock	right	The second vector clock used for comparison

Returns

Type	Description
bool	`true` if the first vector clock is greater than the other one; otherwise `false`

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operator !=(VectorClock, VectorClock)

Compares two specified vector clocks for inequality.

Declaration

public static bool operator !=(VectorClock left, VectorClock right)

Parameters

Type	Name	Description
VectorClock	left	The first vector clock used for comparison
VectorClock	right	The second vector clock used for comparison

Returns

Type	Description
bool	`true` if both vector clocks are not equal; otherwise `false`

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operator <(VectorClock, VectorClock)

Compares two specified vector clocks to see if the first one is less than the other one.

Declaration

public static bool operator <(VectorClock left, VectorClock right)

Parameters

Type	Name	Description
VectorClock	left	The first vector clock used for comparison
VectorClock	right	The second vector clock used for comparison

Returns

Type	Description
bool	`true` if the first vector clock is less than the other one; otherwise `false`

Extension Methods

ObjectExtensions.IsDefaultForType<T>(T)

ObjectExtensions.AsOption<T>(T)

Extensions.AsInstanceOf<T>(object)