akka.cluster.ddata

Class LWWMap<A>

java.lang.Object

akka.cluster.ddata.LWWMap<A>

All Implemented Interfaces:

RemovedNodePruning, ReplicatedData, ReplicatedDataSerialization, java.io.Serializable

public final class LWWMap<A>
extends java.lang.Object
implements ReplicatedData, ReplicatedDataSerialization, RemovedNodePruning

Specialized ORMap with LWWRegister values.

LWWRegister relies on synchronized clocks and should only be used when the choice of value is not important for concurrent updates occurring within the clock skew.

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 LWWMap 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.

See Also:

Serialized Form

Constructor Summary

Constructors

Constructor and Description
LWWMap(ORMap<LWWRegister<A>> underlying)

Method Summary

Modifier and Type	Method and Description
static LWWMap<java.lang.Object>	apply()
boolean	contains(java.lang.String key)
static <A> LWWMap<A>	create() Java API
static <A> LWWMap<A>	empty()
scala.collection.immutable.Map<java.lang.String,A>	entries() Scala API: All entries of the map.
boolean	equals(java.lang.Object o)
scala.Option<A>	get(java.lang.String key)
java.util.Map<java.lang.String,A>	getEntries() Java API: All entries of the map.
int	hashCode()
boolean	isEmpty()
LWWMap<A>	merge(LWWMap<A> that)
boolean	needPruningFrom(UniqueAddress removedNode) Does it have any state changes from a specific node, which has been removed from the cluster.
LWWMap<A>	prune(UniqueAddress removedNode, UniqueAddress collapseInto) When the removed node has been removed from the cluster the state changes from that node will be pruned by collapsing the data entries to another node.
LWWMap<A>	pruningCleanup(UniqueAddress removedNode) Remove data entries from a node that has been removed from the cluster and already been pruned.
LWWMap<A>	put(Cluster node, java.lang.String key, A value) Adds an entry to the map
LWWMap<A>	put(Cluster node, java.lang.String key, A value, LWWRegister.Clock<A> clock) Adds an entry to the map.
LWWMap<A>	put(java.lang.String key, A value, Cluster node, LWWRegister.Clock<A> clock) Adds an entry to the map.
LWWMap<A>	put(UniqueAddress node, java.lang.String key, A value, LWWRegister.Clock<A> clock) INTERNAL API
LWWMap<A>	remove(Cluster node, java.lang.String key) Removes an entry from the map.
LWWMap<A>	remove(UniqueAddress node, java.lang.String key) INTERNAL API
int	size()
java.lang.String	toString()
static <A> scala.Option<scala.collection.immutable.Map<java.lang.String,A>>	unapply(LWWMap<A> m) Extract the entries().
ORMap<LWWRegister<A>>	underlying()

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Methods inherited from interface akka.cluster.ddata.ReplicatedData

merge

Constructor Detail

LWWMap

public LWWMap(ORMap<LWWRegister<A>> underlying)

Method Detail

empty

public static <A> LWWMap<A> empty()

apply

public static LWWMap<java.lang.Object> apply()

create

public static <A> LWWMap<A> create()

Java API

Returns:

(undocumented)

unapply

public static <A> scala.Option<scala.collection.immutable.Map<java.lang.String,A>> unapply(LWWMap<A> m)

Extract the entries().

Parameters:

m - (undocumented)

Returns:

(undocumented)

underlying

public ORMap<LWWRegister<A>> underlying()

entries

public scala.collection.immutable.Map<java.lang.String,A> entries()

Scala API: All entries of the map.

Returns:

(undocumented)

getEntries

public java.util.Map<java.lang.String,A> getEntries()

Java API: All entries of the map.

Returns:

(undocumented)

get

public scala.Option<A> get(java.lang.String key)

contains

public boolean contains(java.lang.String key)

isEmpty

public boolean isEmpty()

size

public int size()

put

public LWWMap<A> put(Cluster node,
                     java.lang.String key,
                     A value)

Adds an entry to the map

Parameters:

node - (undocumented)

key - (undocumented)

value - (undocumented)

Returns:

(undocumented)

put

public LWWMap<A> put(Cluster node,
                     java.lang.String key,
                     A value,
                     LWWRegister.Clock<A> clock)

Adds an entry to the map.

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

Parameters:

node - (undocumented)

key - (undocumented)

value - (undocumented)

clock - (undocumented)

Returns:

(undocumented)

put

public LWWMap<A> put(java.lang.String key,
                     A value,
                     Cluster node,
                     LWWRegister.Clock<A> clock)

Adds an entry to the map.

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

Parameters:

key - (undocumented)

value - (undocumented)

node - (undocumented)

clock - (undocumented)

Returns:

(undocumented)

put

public LWWMap<A> put(UniqueAddress node,
                     java.lang.String key,
                     A value,
                     LWWRegister.Clock<A> clock)

INTERNAL API

Parameters:

node - (undocumented)

key - (undocumented)

value - (undocumented)

clock - (undocumented)

Returns:

(undocumented)

remove

public LWWMap<A> remove(Cluster node,
                        java.lang.String key)

Removes an entry from the map. Note that if there is a conflicting update on another node the entry will not be removed after merge.

Parameters:

node - (undocumented)

key - (undocumented)

Returns:

(undocumented)

remove

public LWWMap<A> remove(UniqueAddress node,
                        java.lang.String key)

INTERNAL API

Parameters:

node - (undocumented)

key - (undocumented)

Returns:

(undocumented)

merge

public LWWMap<A> merge(LWWMap<A> that)

needPruningFrom

public boolean needPruningFrom(UniqueAddress removedNode)

Description copied from interface: RemovedNodePruning

Does it have any state changes from a specific node, which has been removed from the cluster.

Specified by:

needPruningFrom in interface RemovedNodePruning

Parameters:

removedNode - (undocumented)

Returns:

(undocumented)

prune

public LWWMap<A> prune(UniqueAddress removedNode,
                       UniqueAddress collapseInto)

Description copied from interface: RemovedNodePruning

When the removed node has been removed from the cluster the state changes from that node will be pruned by collapsing the data entries to another node.

Specified by:

prune in interface RemovedNodePruning

Parameters:

removedNode - (undocumented)

collapseInto - (undocumented)

Returns:

(undocumented)

pruningCleanup

public LWWMap<A> pruningCleanup(UniqueAddress removedNode)

Description copied from interface: RemovedNodePruning

Remove data entries from a node that has been removed from the cluster and already been pruned.

Specified by:

pruningCleanup in interface RemovedNodePruning

Parameters:

removedNode - (undocumented)

Returns:

(undocumented)

toString

public java.lang.String toString()

Overrides:

toString in class java.lang.Object

equals

public boolean equals(java.lang.Object o)

Overrides:

equals in class java.lang.Object

hashCode

public int hashCode()

Overrides:

hashCode in class java.lang.Object