final class LWWRegister[A] extends ReplicatedData with ReplicatedDataSerialization
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 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 System.currentTimeMillis() 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.
The defaultClock is using max value of System.currentTimeMillis() and currentTimestamp + 1.
This means that the timestamp is increased for changes on the same node that occurs within
the same millisecond. It also means that it is safe to use the LWWRegister without
synchronized clocks when there is only one active writer, e.g. a Cluster Singleton. Such a
single writer should then first read current value with ReadMajority (or more) before
changing and writing the value with WriteMajority (or more).
For first-write-wins semantics you can use the LWWRegister#reverseClock instead of the LWWRegister#defaultClock
This class is immutable, i.e. "modifying" methods return a new instance.
- Annotations
- @SerialVersionUID()
- Source
- LWWRegister.scala
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- By Inheritance
- LWWRegister
- ReplicatedDataSerialization
- Serializable
- ReplicatedData
- AnyRef
- Any
- by any2stringadd
- by StringFormat
- by Ensuring
- by ArrowAssoc
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Type Members
- type T = LWWRegister[A]
The type of the concrete implementation, e.g.
The type of the concrete implementation, e.g.
GSet[A]. To be specified by subclass.- Definition Classes
- LWWRegister → ReplicatedData
Value Members
- final def !=(arg0: Any): Boolean
- Definition Classes
- AnyRef → Any
- final def ##: Int
- Definition Classes
- AnyRef → Any
- def +(other: String): String
- Implicit
- This member is added by an implicit conversion from LWWRegister[A] toany2stringadd[LWWRegister[A]] performed by method any2stringadd in scala.Predef.
- Definition Classes
- any2stringadd
- def ->[B](y: B): (LWWRegister[A], B)
- Implicit
- This member is added by an implicit conversion from LWWRegister[A] toArrowAssoc[LWWRegister[A]] performed by method ArrowAssoc in scala.Predef.
- Definition Classes
- ArrowAssoc
- Annotations
- @inline()
- final def ==(arg0: Any): Boolean
- Definition Classes
- AnyRef → Any
- final def asInstanceOf[T0]: T0
- Definition Classes
- Any
- def clone(): AnyRef
- Attributes
- protected[lang]
- Definition Classes
- AnyRef
- Annotations
- @throws(classOf[java.lang.CloneNotSupportedException]) @HotSpotIntrinsicCandidate() @native()
- def ensuring(cond: (LWWRegister[A]) => Boolean, msg: => Any): LWWRegister[A]
- Implicit
- This member is added by an implicit conversion from LWWRegister[A] toEnsuring[LWWRegister[A]] performed by method Ensuring in scala.Predef.
- Definition Classes
- Ensuring
- def ensuring(cond: (LWWRegister[A]) => Boolean): LWWRegister[A]
- Implicit
- This member is added by an implicit conversion from LWWRegister[A] toEnsuring[LWWRegister[A]] performed by method Ensuring in scala.Predef.
- Definition Classes
- Ensuring
- def ensuring(cond: Boolean, msg: => Any): LWWRegister[A]
- Implicit
- This member is added by an implicit conversion from LWWRegister[A] toEnsuring[LWWRegister[A]] performed by method Ensuring in scala.Predef.
- Definition Classes
- Ensuring
- def ensuring(cond: Boolean): LWWRegister[A]
- Implicit
- This member is added by an implicit conversion from LWWRegister[A] toEnsuring[LWWRegister[A]] performed by method Ensuring in scala.Predef.
- Definition Classes
- Ensuring
- final def eq(arg0: AnyRef): Boolean
- Definition Classes
- AnyRef
- def equals(o: Any): Boolean
- Definition Classes
- LWWRegister → AnyRef → Any
- final def getClass(): Class[_ <: AnyRef]
- Definition Classes
- AnyRef → Any
- Annotations
- @HotSpotIntrinsicCandidate() @native()
- def getValue(): A
Java API
- def hashCode(): Int
- Definition Classes
- LWWRegister → AnyRef → Any
- final def isInstanceOf[T0]: Boolean
- Definition Classes
- Any
- def merge(that: LWWRegister[A]): LWWRegister[A]
Monotonic merge function.
Monotonic merge function.
- Definition Classes
- LWWRegister → ReplicatedData
- final def ne(arg0: AnyRef): Boolean
- Definition Classes
- AnyRef
- final def notify(): Unit
- Definition Classes
- AnyRef
- Annotations
- @HotSpotIntrinsicCandidate() @native()
- final def notifyAll(): Unit
- Definition Classes
- AnyRef
- Annotations
- @HotSpotIntrinsicCandidate() @native()
- final def synchronized[T0](arg0: => T0): T0
- Definition Classes
- AnyRef
- val timestamp: Long
- def toString(): String
- Definition Classes
- LWWRegister → AnyRef → Any
- def updatedBy: UniqueAddress
The current
valuewas set by this node. - val value: A
- final def wait(arg0: Long, arg1: Int): Unit
- Definition Classes
- AnyRef
- Annotations
- @throws(classOf[java.lang.InterruptedException])
- final def wait(arg0: Long): Unit
- Definition Classes
- AnyRef
- Annotations
- @throws(classOf[java.lang.InterruptedException]) @native()
- final def wait(): Unit
- Definition Classes
- AnyRef
- Annotations
- @throws(classOf[java.lang.InterruptedException])
- def withValue(node: SelfUniqueAddress, value: A): LWWRegister[A]
Change the value of the register.
- def withValue(node: SelfUniqueAddress, value: A, clock: Clock[A]): LWWRegister[A]
Change the value of the register.
Change the value of the register.
You can provide your
clockimplementation instead of using timestamps based onSystem.currentTimeMillis()time. The timestamp can for example be an increasing version number from a database record that is used for optimistic concurrency control. - def withValueOf(value: A)(implicit node: SelfUniqueAddress, clock: Clock[A] = defaultClock[A]): LWWRegister[A]
Change the value of the register.
Change the value of the register.
You can provide your
clockimplementation instead of using timestamps based onSystem.currentTimeMillis()time. The timestamp can for example be an increasing version number from a database record that is used for optimistic concurrency control.
Deprecated Value Members
- def finalize(): Unit
- Attributes
- protected[lang]
- Definition Classes
- AnyRef
- Annotations
- @throws(classOf[java.lang.Throwable]) @Deprecated
- Deprecated
(Since version 9)
- def formatted(fmtstr: String): String
- Implicit
- This member is added by an implicit conversion from LWWRegister[A] toStringFormat[LWWRegister[A]] performed by method StringFormat in scala.Predef.
- Definition Classes
- StringFormat
- Annotations
- @deprecated @inline()
- Deprecated
(Since version 2.12.16) Use
formatString.format(value)instead ofvalue.formatted(formatString), or use thef""string interpolator. In Java 15 and later,formattedresolves to the new method in String which has reversed parameters.
- def →[B](y: B): (LWWRegister[A], B)
- Implicit
- This member is added by an implicit conversion from LWWRegister[A] toArrowAssoc[LWWRegister[A]] performed by method ArrowAssoc in scala.Predef.
- Definition Classes
- ArrowAssoc
- Annotations
- @deprecated
- Deprecated
(Since version 2.13.0) Use
->instead. If you still wish to display it as one character, consider using a font with programming ligatures such as Fira Code.