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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- LWWRegister
- ReplicatedDataSerialization
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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] to any2stringadd[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] to ArrowAssoc[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[java.lang]
- Definition Classes
- AnyRef
- Annotations
- @native() @HotSpotIntrinsicCandidate() @throws( ... )
-
def
ensuring(cond: (LWWRegister[A]) ⇒ Boolean, msg: ⇒ Any): LWWRegister[A]
- Implicit
- This member is added by an implicit conversion from LWWRegister[A] to Ensuring[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] to Ensuring[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] to Ensuring[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] to Ensuring[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
-
def
formatted(fmtstr: String): String
- Implicit
- This member is added by an implicit conversion from LWWRegister[A] to StringFormat[LWWRegister[A]] performed by method StringFormat in scala.Predef.
- Definition Classes
- StringFormat
- Annotations
- @inline()
-
final
def
getClass(): Class[_]
- Definition Classes
- AnyRef → Any
- Annotations
- @native() @HotSpotIntrinsicCandidate()
-
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
- @native() @HotSpotIntrinsicCandidate()
-
final
def
notifyAll(): Unit
- Definition Classes
- AnyRef
- Annotations
- @native() @HotSpotIntrinsicCandidate()
-
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
value
was set by this node. - val value: A
-
final
def
wait(arg0: Long, arg1: Int): Unit
- Definition Classes
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- Annotations
- @throws( ... )
-
final
def
wait(arg0: Long): Unit
- Definition Classes
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- Annotations
- @native() @throws( ... )
-
final
def
wait(): Unit
- Definition Classes
- AnyRef
- Annotations
- @throws( ... )
-
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
clock
implementation 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
clock
implementation 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
→[B](y: B): (LWWRegister[A], B)
- Implicit
- This member is added by an implicit conversion from LWWRegister[A] to ArrowAssoc[LWWRegister[A]] performed by method ArrowAssoc in scala.Predef.
- Definition Classes
- ArrowAssoc
Deprecated Value Members
-
def
finalize(): Unit
- Attributes
- protected[java.lang]
- Definition Classes
- AnyRef
- Annotations
- @Deprecated @deprecated @throws( classOf[java.lang.Throwable] )
- Deprecated
(Since version ) see corresponding Javadoc for more information.
-
def
withValue(node: Cluster, value: A, clock: Clock[A]): LWWRegister[A]
- Annotations
- @deprecated
- Deprecated
(Since version 2.5.20) Use
withValue
that takes aSelfUniqueAddress
parameter instead.
-
def
withValue(node: Cluster, value: A): LWWRegister[A]
- Annotations
- @deprecated
- Deprecated
(Since version 2.5.20) Use
withValue
that takes aSelfUniqueAddress
parameter instead.
-
def
withValue(value: A)(implicit node: Cluster, clock: Clock[A] = defaultClock[A]): LWWRegister[A]
- Annotations
- @deprecated
- Deprecated
(Since version 2.5.20) Use
withValueOf
that takes aSelfUniqueAddress
parameter instead.