Class ClusterSingletonManager

Manages singleton actor instance among all cluster nodes or a group of nodes tagged with a specific role. At most one singleton instance is running at any point in time.

The ClusterSingletonManager is supposed to be started on all nodes, or all nodes with specified role, in the cluster with ActorOf(Props, String). The actual singleton is started on the oldest node by creating a child actor from the supplied singletonProps.

The singleton actor is always running on the oldest member with specified role. The oldest member is determined by IsOlderThan(Member). This can change when removing members. A graceful hand over can normally be performed when current oldest node is leaving the cluster. Be aware that there is a short time period when there is no active singleton during the hand-over process.

The cluster failure detector will notice when oldest node becomes unreachable due to things like CLR crash, hard shut down, or network failure. When the crashed node has been removed (via down) from the cluster then a new oldest node will take over and a new singleton actor is created.For these failure scenarios there will not be a graceful hand-over, but more than one active singletons is prevented by all reasonable means. Some corner cases are eventually resolved by configurable timeouts.

You access the singleton actor with ClusterSingletonProxy. Alternatively the singleton actor may broadcast its existence when it is started.

Use one of the factory methods ClusterSingletonManager.Props to create the Props for the actor.

Inheritance
Object
ActorBase
FSMBase
FSM<ClusterSingletonState, IClusterSingletonData>
ClusterSingletonManager
Implements
Inherited Members
Namespace: Akka.Cluster.Tools.Singleton
Assembly: Akka.Cluster.Tools.dll
Syntax
public sealed class ClusterSingletonManager : FSM<ClusterSingletonState, IClusterSingletonData>, IInternalActor, IListeners, IInternalSupportsTestFSMRef<ClusterSingletonState, IClusterSingletonData>

Constructors

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ClusterSingletonManager(Props, Object, ClusterSingletonManagerSettings)

Declaration
public ClusterSingletonManager(Props singletonProps, object terminationMessage, ClusterSingletonManagerSettings settings)
Parameters
Type Name Description
Props singletonProps
Object terminationMessage
ClusterSingletonManagerSettings settings

Methods

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DefaultConfig()

Returns default HOCON configuration for the cluster singleton.

Declaration
[Obsolete("Deprecated and will be removed in v1.6, please use ClusterSingleton.DefaultConfig() instead. Since 1.5.32.")]
public static Config DefaultConfig()
Returns
Type Description
Config

TBD
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PostStop()

User overridable callback.

Is called asynchronously after 'actor.stop()' is invoked. Empty default implementation.

Declaration
protected override void PostStop()
Overrides
Akka.Actor.FSM<Akka.Cluster.Tools.Singleton.ClusterSingletonState, Akka.Cluster.Tools.Singleton.IClusterSingletonData>.PostStop()
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PreStart()

User overridable callback.

Is called when an Actor is started. Actors are automatically started asynchronously when created. Empty default implementation.

Declaration
protected override void PreStart()
Overrides
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Props(Props, ClusterSingletonManagerSettings)

Creates props for the current cluster singleton manager using PoisonPill as the default termination message.

Declaration
public static Props Props(Props singletonProps, ClusterSingletonManagerSettings settings)
Parameters
Type Name Description
Props singletonProps

Props of the singleton actor instance.
ClusterSingletonManagerSettings settings

Cluster singleton manager settings.
Returns
Type Description
Props

Props for the ClusterSingletonManager.
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Props(Props, Object, ClusterSingletonManagerSettings)

Creates props for the current cluster singleton manager.

Declaration
public static Props Props(Props singletonProps, object terminationMessage, ClusterSingletonManagerSettings settings)
Parameters
Type Name Description
Props singletonProps

Props of the singleton actor instance.
Object terminationMessage

When handing over to a new oldest node this terminationMessage is sent to the singleton actor to tell it to finish its work, close resources, and stop. The hand-over to the new oldest node is completed when the singleton actor is terminated. Note that PoisonPill is a perfectly fine terminationMessage if you only need to stop the actor.
ClusterSingletonManagerSettings settings

Cluster singleton manager settings.
Returns
Type Description
Props

Props for the ClusterSingletonManager.

Implements

Extension Methods