Class LWWRegister<T>

Implements a 'Last Writer Wins Register' CRDT, also called a 'LWW-Register'.

It is described in the paper A comprehensive study of Convergent and Commutative Replicated Data Types.

Merge takes the register with highest timestamp. Note that this relies on synchronized clocks. LWWRegister<T> should only be used when the choice of value is not important for concurrent updates occurring within the clock skew.

Merge takes the register updated by the node with lowest address (UniqueAddress is ordered) if the timestamps are exactly the same.

Instead of using timestamps based on DateTime.UtcNow time it is possible to use a timestamp value based on something else, for example an increasing version number from a database record that is used for optimistic concurrency control.

For first-write-wins semantics you can use the ReverseClock instead of the [[LWWRegister#defaultClock]]

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

Inheritance
object
LWWRegister<T>
Implements
Inherited Members
Namespace: Akka.DistributedData
Assembly: Akka.DistributedData.dll
Syntax
[Serializable]
public sealed class LWWRegister<T> : IReplicatedData<LWWRegister<T>>, IReplicatedData, IReplicatedDataSerialization, IEquatable<LWWRegister<T>>
Type Parameters
Name Description
T

TBD

Constructors

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LWWRegister(UniqueAddress, T)

TBD

Declaration
public LWWRegister(UniqueAddress node, T initial)
Parameters
Type Name Description
UniqueAddress node

TBD
T initial

TBD
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LWWRegister(UniqueAddress, T, Clock<T>)

TBD

Declaration
public LWWRegister(UniqueAddress node, T initial, Clock<T> clock)
Parameters
Type Name Description
UniqueAddress node

TBD
T initial

TBD
Clock<T> clock

TBD
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LWWRegister(UniqueAddress, T, long)

TBD

Declaration
public LWWRegister(UniqueAddress node, T value, long timestamp)
Parameters
Type Name Description
UniqueAddress node

TBD
T value

TBD
long timestamp

TBD

Fields

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DefaultClock

Default clock is using max between DateTime.UtcNow.Ticks and current timestamp + 1.

Declaration
public static readonly Clock<T> DefaultClock
Field Value
Type Description
Clock<T>
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ReverseClock

Reverse clock can be used for first-write-wins semantics. It's counting backwards, using min between -DateTime.UtcNow.Ticks and current timestamp - 1.

Declaration
public static readonly Clock<T> ReverseClock
Field Value
Type Description
Clock<T>

Properties

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RegisterType

Declaration
public Type RegisterType { get; }
Property Value
Type Description
Type
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Timestamp

Returns a timestamp used to determine precedence in current register updates.

Declaration
public long Timestamp { get; }
Property Value
Type Description
long
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UpdatedBy

Returns a unique address of the last cluster node, that updated current register value.

Declaration
public UniqueAddress UpdatedBy { get; }
Property Value
Type Description
UniqueAddress
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Value

Returns value of the current register.

Declaration
public T Value { get; }
Property Value
Type Description
T

Methods

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Equals(LWWRegister<T>)

Declaration
public bool Equals(LWWRegister<T> other)
Parameters
Type Name Description
LWWRegister<T> other
Returns
Type Description
bool
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Equals(object)

Declaration
public override bool Equals(object obj)
Parameters
Type Name Description
object obj
Returns
Type Description
bool
Overrides
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GetHashCode()

Declaration
public override int GetHashCode()
Returns
Type Description
int
Overrides
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Merge(IReplicatedData)

TBD

Declaration
public IReplicatedData Merge(IReplicatedData other)
Parameters
Type Name Description
IReplicatedData other

TBD
Returns
Type Description
IReplicatedData

TBD
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Merge(LWWRegister<T>)

TBD

Declaration
public LWWRegister<T> Merge(LWWRegister<T> other)
Parameters
Type Name Description
LWWRegister<T> other

TBD
Returns
Type Description
LWWRegister<T>

TBD
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ToString()

Declaration
public override string ToString()
Returns
Type Description
string
Overrides
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WithValue(UniqueAddress, T, Clock<T>)

Change the value of the register.

You can provide your clock implementation instead of using timestamps based on DateTime.UtcNow.Ticks time. The timestamp can for example be an increasing version number from a database record that is used for optimistic concurrency control.

Declaration
public LWWRegister<T> WithValue(UniqueAddress node, T value, Clock<T> clock = null)
Parameters
Type Name Description
UniqueAddress node

TBD
T value

TBD
Clock<T> clock

TBD
Returns
Type Description
LWWRegister<T>

TBD

Implements

Extension Methods