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. 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 pekko.cluster.Member#isOlderThan. 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 JVM 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 factory method ClusterSingletonManager#props to create the pekko.actor.Props for the actor.
Not intended for subclassing by user code.
Value parameters
- settings
- singletonProps
-
pekko.actor.Props of the singleton actor instance.
- terminationMessage
-
When handing over to a new oldest node this
terminationMessageis 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 pekko.actor.PoisonPill is a perfectly fineterminationMessageif you only need to stop the actor.
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- Companion
- object
- Source
- ClusterSingletonManager.scala
- Graph
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- Supertypes
Members list
Type members
Inherited classlikes
Value members
Concrete methods
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Call onTermination hook; if you want to retain this behavior when overriding make sure to call super.postStop().
Call onTermination hook; if you want to retain this behavior when overriding make sure to call super.postStop().
Please note that this method is called by default from preRestart(), so override that one if onTermination shall not be called during restart.
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- Definition Classes
- Source
- ClusterSingletonManager.scala
User overridable callback.
User overridable callback.
Is called when an Actor is started. Actors are automatically started asynchronously when created. Empty default implementation.
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- Definition Classes
- Source
- ClusterSingletonManager.scala
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Inherited methods
Sends the supplied message to all current listeners using the provided sender() as sender.
Sends the supplied message to all current listeners using the provided sender() as sender.
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- Inherited from:
- Listeners
- Source
- Listeners.scala
Produce transition to other state. Return this from a state function in order to effect the transition.
Produce transition to other state. Return this from a state function in order to effect the transition.
This method always triggers transition events, even for A -> A transitions. If you want to stay in the same state without triggering an state transition event use stay instead.
Value parameters
- nextStateName
-
state designator for the next state
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Verify existence of initial state and setup timers. This should be the last call within the constructor, or pekko.actor.Actor#preStart and pekko.actor.Actor#postRestart
Verify existence of initial state and setup timers. This should be the last call within the constructor, or pekko.actor.Actor#preStart and pekko.actor.Actor#postRestart
An initial currentState -> currentState notification will be triggered by calling this method.
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Inquire whether the named timer is still active. Returns true unless the timer does not exist, has previously been canceled or if it was a single-shot timer whose message was already received.
Chain this into the receive function.
Chain this into the receive function.
def receive = listenerManagement orElse …
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- Inherited from:
- Listeners
- Source
- Listeners.scala
Set handler which is called upon termination of this FSM actor. Calling this method again will overwrite the previous contents.
Set handler which is called upon each state transition, i.e. not when staying in the same state. This may use the pair extractor defined in the FSM companion object like so:
Set handler which is called upon each state transition, i.e. not when staying in the same state. This may use the pair extractor defined in the FSM companion object like so:
onTransition {
case Old -> New => doSomething
}
It is also possible to supply a 2-ary function object:
onTransition(handler _)
private def handler(from: S, to: S) { ... }
The underscore is unfortunately necessary to enable the nicer syntax shown above (it uses the implicit conversion total2pf under the hood).
Multiple handlers may be installed, and every one of them will be called, not only the first one matching.
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User overridable callback: By default it calls preStart().
User overridable callback: By default it calls preStart().
Value parameters
- reason
-
the Throwable that caused the restart to happen Is called right AFTER restart on the newly created Actor to allow reinitialization after an Actor crash.
Attributes
- Inherited from:
- Actor
- Source
- Actor.scala
Scala API: User overridable callback: '''By default it disposes of all children and then calls postStop().'''
Scala API: User overridable callback: '''By default it disposes of all children and then calls postStop().'''
Value parameters
- message
-
optionally the current message the actor processed when failing, if applicable Is called on a crashed Actor right BEFORE it is restarted to allow clean up of resources before Actor is terminated.
- reason
-
the Throwable that caused the restart to happen
Attributes
- Inherited from:
- Actor
- Source
- Actor.scala
The reference sender Actor of the last received message. Is defined if the message was sent from another Actor, else deadLetters in pekko.actor.ActorSystem.
The reference sender Actor of the last received message. Is defined if the message was sent from another Actor, else deadLetters in pekko.actor.ActorSystem.
WARNING: Only valid within the Actor itself, so do not close over it and publish it to other threads!
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- Inherited from:
- Actor
- Source
- Actor.scala
Start a timer that will send msg once to the self actor after the given delay.
Start a timer that will send msg once to the self actor after the given delay.
Each timer has a name and if a new timer with same name is started the previous is cancelled. It is guaranteed that a message from the previous timer is not received, even if it was already enqueued in the mailbox when the new timer was started.
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Schedules a message to be sent repeatedly to the self actor with a given frequency.
Schedules a message to be sent repeatedly to the self actor with a given frequency.
It will compensate the delay for a subsequent message if the sending of previous message was delayed more than specified. In such cases, the actual message interval will differ from the interval passed to the method.
If the execution is delayed longer than the interval, the subsequent message will be sent immediately after the prior one. This also has the consequence that after long garbage collection pauses or other reasons when the JVM was suspended all "missed" messages will be sent when the process wakes up again.
In the long run, the frequency of messages will be exactly the reciprocal of the specified interval.
Warning: startTimerAtFixedRate can result in bursts of scheduled messages after long garbage collection pauses, which may in worst case cause undesired load on the system. Therefore startTimerWithFixedDelay is often preferred.
Each timer has a name and if a new timer with same name is started the previous is cancelled. It is guaranteed that a message from the previous timer is not received, even if it was already enqueued in the mailbox when the new timer was started.
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Schedules a message to be sent repeatedly to the self actor with a fixed delay between messages.
Schedules a message to be sent repeatedly to the self actor with a fixed delay between messages.
It will not compensate the delay between messages if scheduling is delayed longer than specified for some reason. The delay between sending of subsequent messages will always be (at least) the given delay.
In the long run, the frequency of messages will generally be slightly lower than the reciprocal of the specified delay.
Each timer has a name and if a new timer with same name is started the previous is cancelled. It is guaranteed that a message from the previous timer is not received, even if it was already enqueued in the mailbox when the new timer was started.
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Set initial state. Call this method from the constructor before the initialize method. If different state is needed after a restart this method, followed by initialize, can be used in the actor life cycle hooks pekko.actor.Actor#preStart and pekko.actor.Actor#postRestart.
Set initial state. Call this method from the constructor before the initialize method. If different state is needed after a restart this method, followed by initialize, can be used in the actor life cycle hooks pekko.actor.Actor#preStart and pekko.actor.Actor#postRestart.
Value parameters
- stateData
-
initial state data
- stateName
-
initial state designator
- timeout
-
state timeout for the initial state, overriding the default timeout for that state
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Produce "empty" transition descriptor. Return this from a state function when no state change is to be effected.
Produce "empty" transition descriptor. Return this from a state function when no state change is to be effected.
No transition event will be triggered by stay. If you want to trigger an event like S -> S for onTransition to handle use goto instead.
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User overridable definition the strategy to use for supervising child actors.
User overridable definition the strategy to use for supervising child actors.
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- Inherited from:
- Actor
- Source
- Actor.scala
User overridable callback.
User overridable callback.
Is called when a message isn't handled by the current behavior of the actor by default it fails with either a pekko.actor.DeathPactException (in case of an unhandled pekko.actor.Terminated message) or publishes an pekko.actor.UnhandledMessage to the actor's system's pekko.event.EventStream
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- Inherited from:
- Actor
- Source
- Actor.scala
Insert a new StateFunction at the end of the processing chain for the given state. If the stateTimeout parameter is set, entering this state without a differing explicit timeout setting will trigger a StateTimeout event; the same is true when using #stay.
Insert a new StateFunction at the end of the processing chain for the given state. If the stateTimeout parameter is set, entering this state without a differing explicit timeout setting will trigger a StateTimeout event; the same is true when using #stay.
Value parameters
- stateFunction
-
partial function describing response to input
- stateName
-
designator for the state
- stateTimeout
-
default state timeout for this state
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Set handler which is called upon reception of unhandled messages. Calling this method again will overwrite the previous contents.
Deprecated and Inherited methods
Schedule named timer to deliver message after given delay, possibly repeating. Any existing timer with the same name will automatically be canceled before adding the new timer.
Schedule named timer to deliver message after given delay, possibly repeating. Any existing timer with the same name will automatically be canceled before adding the new timer.
Value parameters
- msg
-
message to be delivered
- name
-
identifier to be used with cancelTimer()
- repeat
-
send once if false, scheduleAtFixedRate if true
- timeout
-
delay of first message delivery and between subsequent messages
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Concrete fields
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Implicits
Inherited implicits
Scala API: Stores the context for this actor, including self, and sender. It is implicit to support operations such as forward.
Scala API: Stores the context for this actor, including self, and sender. It is implicit to support operations such as forward.
WARNING: Only valid within the Actor itself, so do not close over it and publish it to other threads!
pekko.actor.ActorContext is the Scala API. getContext returns a pekko.actor.AbstractActor.ActorContext, which is the Java API of the actor context.
Attributes
- Inherited from:
- Actor
- Source
- Actor.scala
The 'self' field holds the ActorRef for this actor.
The 'self' field holds the ActorRef for this actor.
Can be used to send messages to itself:
self ! message
Attributes
- Inherited from:
- Actor
- Source
- Actor.scala