Akka/akka.cluster.ddata/ORSet

ORSet

@SerialVersionUID(1L)
final class ORSet[A] extends DeltaReplicatedData with ReplicatedDataSerialization with RemovedNodePruning with FastMerge

Implements a 'Observed Remove Set' CRDT, also called a 'OR-Set'. Elements can be added and removed any number of times. Concurrent add wins over remove.

It is not implemented as in the paper A comprehensive study of Convergent and Commutative Replicated Data Types. This is more space efficient and doesn't accumulate garbage for removed elements. It is described in the paper An optimized conflict-free replicated set The implementation is inspired by the Riak DT riak_dt_orswot.

The ORSet has a version vector that is incremented when an element is added to the set. The node -> count pair for that increment is stored against the element as its "birth dot". Every time the element is re-added to the set, its "birth dot" is updated to that of the node -> count version vector entry resulting from the add. When an element is removed, we simply drop it, no tombstones.

When an element exists in replica A and not replica B, is it because A added it and B has not yet seen that, or that B removed it and A has not yet seen that? In this implementation we compare the dot of the present element to the version vector in the Set it is absent from. If the element dot is not "seen" by the Set version vector, that means the other set has yet to see this add, and the item is in the merged Set. If the Set version vector dominates the dot, that means the other Set has removed this element already, and the item is not in the merged Set.

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

Companion:
object
Source:
ORSet.scala
trait FastMerge
trait Serializable
class Object
trait Matchable
class Any

Type members

Types

type D = DeltaOp
type T = ORSet[A]

Value members

Concrete methods

def :+(element: A)(implicit node: SelfUniqueAddress): ORSet[A]

Adds an element to the set.

Adds an element to the set.

Source:
ORSet.scala
def add(node: SelfUniqueAddress, element: A): ORSet[A]

Adds an element to the set.

Adds an element to the set.

Source:
ORSet.scala
def clear(@unused node: SelfUniqueAddress): ORSet[A]

Removes all elements from the set, but keeps the history. This has the same result as using ORSet#remove for each element, but it is more efficient.

Removes all elements from the set, but keeps the history. This has the same result as using ORSet#remove for each element, but it is more efficient.

Source:
ORSet.scala
def contains(a: A): Boolean
def elements: Set[A]

Scala API

Scala API

Source:
ORSet.scala
override def equals(o: Any): Boolean
Definition Classes
Any
Source:
ORSet.scala
def getElements(): Set[A]

Java API

Java API

Source:
ORSet.scala
override def hashCode: Int
Definition Classes
Any
Source:
ORSet.scala
override def merge(that: ORSet[A]): ORSet[A]

When element is in this Set but not in that Set: Compare the "birth dot" of the present element to the version vector in the Set it is absent from. If the element dot is not "seen" by other Set version vector, that means the other set has yet to see this add, and the element is to be in the merged Set. If the other Set version vector dominates the dot, that means the other Set has removed the element already, and the element is not to be in the merged Set.

When element is in this Set but not in that Set: Compare the "birth dot" of the present element to the version vector in the Set it is absent from. If the element dot is not "seen" by other Set version vector, that means the other set has yet to see this add, and the element is to be in the merged Set. If the other Set version vector dominates the dot, that means the other Set has removed the element already, and the element is not to be in the merged Set.

When element in both this Set and in that Set: Some dots may still need to be shed. If this Set has dots that the other Set does not have, and the other Set version vector dominates those dots, then we need to drop those dots. Keep only common dots, and dots that are not dominated by the other sides version vector

Definition Classes
Source:
ORSet.scala
override def mergeDelta(thatDelta: DeltaOp): ORSet[A]
Definition Classes
Source:
ORSet.scala
override def modifiedByNodes: Set[UniqueAddress]
Definition Classes
Source:
ORSet.scala
override def needPruningFrom(removedNode: UniqueAddress): Boolean
Definition Classes
Source:
ORSet.scala
override def prune(removedNode: UniqueAddress, collapseInto: UniqueAddress): ORSet[A]
Definition Classes
Source:
ORSet.scala
override def pruningCleanup(removedNode: UniqueAddress): ORSet[A]
Definition Classes
Source:
ORSet.scala
def remove(element: A)(implicit node: SelfUniqueAddress): ORSet[A]

Scala API Removes an element from the set.

Scala API Removes an element from the set.

Source:
ORSet.scala
def remove(node: SelfUniqueAddress, element: A): ORSet[A]

Java API Removes an element from the set.

Java API Removes an element from the set.

Source:
ORSet.scala
override def resetDelta: ORSet[A]
Definition Classes
Source:
ORSet.scala
def size: Int
override def toString: String
Definition Classes
Any
Source:
ORSet.scala

Deprecated methods

@deprecated("Use `:+` that takes a `SelfUniqueAddress` parameter instead.", since = "2.5.20")
def +(element: A)(implicit node: Cluster): ORSet[A]
Deprecated
[Since version 2.5.20]
Source:
ORSet.scala
@deprecated("Use `remove` that takes a `SelfUniqueAddress` parameter instead.", since = "2.5.20")
def -(element: A)(implicit node: Cluster): ORSet[A]

Removes an element from the set.

Removes an element from the set.

Deprecated
[Since version 2.5.20]
Source:
ORSet.scala
@/ @deprecated("Use `add` that takes a `SelfUniqueAddress` parameter instead.", since = "2.5.20")
def add(node: Cluster, element: A): ORSet[A]
Deprecated
[Since version 2.5.20]
Source:
ORSet.scala
@deprecated("Use `remove` that takes a `SelfUniqueAddress` parameter instead.", since = "2.5.20")
def clear(@unused node: Cluster): ORSet[A]
Deprecated
[Since version 2.5.20]
Source:
ORSet.scala
@deprecated("Use `remove` that takes a `SelfUniqueAddress` parameter instead.", since = "2.5.20")
def remove(node: Cluster, element: A): ORSet[A]

Removes an element from the set.

Removes an element from the set.

Deprecated
[Since version 2.5.20]
Source:
ORSet.scala

Concrete fields

override val delta: Option[DeltaOp]