akka.contrib.pattern

ClusterSingletonManager

class ClusterSingletonManager extends Actor with FSM[State, Data]

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, which can be determined by akka.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 singleton actor can at any time send a message to its parent ClusterSingletonManager and this message will be passed to the singletonProps factory on the new oldest node when a graceful hand-over is performed.

The cluster failure detector will notice when oldest node becomes unreachable due to things like JVM crash, hard shut down, or network failure. 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 actorSelection using the names you have specified when creating the ClusterSingletonManager. You can subscribe to akka.cluster.ClusterEvent.MemberEvent and sort the members by age (akka.cluster.ClusterEvent.Member#isOlderThan) to keep track of oldest member. Alternatively the singleton actor may broadcast its existence when it is started.

Use factory method to create the akka.actor.Props for the actor.

Arguments

singletonProps Factory for akka.actor.Props of the singleton actor instance. The Option parameter is the the handOverData sent from previous singleton. handOverData might be None when no hand-over took place, or when the there is no need for sending data to the new singleton. The handOverData is typically passed as parameter to the constructor of the singleton actor. Note that the singletonProps function is applied when creating the singleton actor and it must not use members that are not thread safe, e.g. mutable state in enclosing actor.

singletonName The actor name of the child singleton actor.

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. It can sending a message back to the parent ClusterSingletonManager, which will passed to the singletonProps factory on the new oldest node. The hand-over to the new oldest node is completed when the singleton actor is terminated. Note that akka.actor.PoisonPill is a perfectly fine terminationMessage if you only need to stop the actor.

role Singleton among the nodes tagged with specified role. If the role is not specified it's a singleton among all nodes in the cluster.

maxHandOverRetries When a node is becoming oldest it sends hand-over request to previous oldest. This is retried with the retryInterval until the previous oldest confirms that the hand over has started, or this maxHandOverRetries limit has been reached. If the retry limit is reached it takes the decision to be the new oldest if previous oldest is unknown (typically removed), otherwise it initiates a new round by throwing akka.contrib.pattern.ClusterSingletonManagerIsStuck and expecting restart with fresh state. For a cluster with many members you might need to increase this retry limit because it takes longer time to propagate changes across all nodes.

maxTakeOverRetries When a oldest node is not oldest any more it sends take over request to the new oldest to initiate the normal hand-over process. This is especially useful when new node joins and becomes oldest immediately, without knowing who was previous oldest. This is retried with the retryInterval until this retry limit has been reached. If the retry limit is reached it initiates a new round by throwing akka.contrib.pattern.ClusterSingletonManagerIsStuck and expecting restart with fresh state. This will also cause the singleton actor to be stopped. maxTakeOverRetries must be less than maxHandOverRetries to ensure that new oldest doesn't start singleton actor before previous is stopped for certain corner cases.

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  4. Listeners
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Instance Constructors

  1. new ClusterSingletonManager(singletonProps: (Option[Any]) ⇒ Props, singletonName: String, terminationMessage: Any, role: Option[String], maxHandOverRetries: Int, maxTakeOverRetries: Int, retryInterval: FiniteDuration)

Type Members

  1. case class Event(event: Any, stateData: D) extends NoSerializationVerificationNeeded with Product with Serializable

    All messages sent to the akka.actor.FSM will be wrapped inside an Event, which allows pattern matching to extract both state and data.

  2. type Receive = PartialFunction[Any, Unit]

    Definition Classes
    Actor
  3. type State = actor.FSM.State[ClusterSingletonManager.State, Data]

    Definition Classes
    FSM
  4. type StateFunction = PartialFunction[Event, State]

    Definition Classes
    FSM
  5. case class StopEvent(reason: Reason, currentState: S, stateData: D) extends NoSerializationVerificationNeeded with Product with Serializable

    Case class representing the state of the akka.actor.FSM whithin the onTermination block.

  6. type Timeout = Option[FiniteDuration]

    Definition Classes
    FSM
  7. final class TransformHelper extends AnyRef

    Definition Classes
    FSM
  8. type TransitionHandler = PartialFunction[(ClusterSingletonManager.State, ClusterSingletonManager.State), Unit]

    Definition Classes
    FSM

Value Members

  1. final def !=(arg0: AnyRef): Boolean

    Definition Classes
    AnyRef
  2. final def !=(arg0: Any): Boolean

    Definition Classes
    Any
  3. final def ##(): Int

    Definition Classes
    AnyRef → Any
  4. def +(other: String): String

    Implicit information
    This member is added by an implicit conversion from ClusterSingletonManager to StringAdd performed by method any2stringadd in scala.Predef.
    Definition Classes
    StringAdd
  5. val ->: actor.FSM.->.type

    This extractor is just convenience for matching a (S, S) pair, including a reminder what the new state is.

    This extractor is just convenience for matching a (S, S) pair, including a reminder what the new state is.

    Definition Classes
    FSM
  6. final def ==(arg0: AnyRef): Boolean

    Definition Classes
    AnyRef
  7. final def ==(arg0: Any): Boolean

    Definition Classes
    Any
  8. val StateTimeout: actor.FSM.StateTimeout.type

    This case object is received in case of a state timeout.

    This case object is received in case of a state timeout.

    Definition Classes
    FSM
  9. def addRemoved(address: Address): Unit

  10. final def asInstanceOf[T0]: T0

    Definition Classes
    Any
  11. final def cancelTimer(name: String): Unit

    Cancel named timer, ensuring that the message is not subsequently delivered (no race).

    Cancel named timer, ensuring that the message is not subsequently delivered (no race).

    name

    of the timer to cancel

    Definition Classes
    FSM
  12. def cleanupOverdueNotMemberAnyMore(): Unit

  13. def clone(): AnyRef

    Attributes
    protected[java.lang]
    Definition Classes
    AnyRef
    Annotations
    @throws( ... )
  14. val cluster: Cluster

  15. implicit val context: ActorContext

    Stores the context for this actor, including self, and sender.

    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!

    akka.actor.ActorContext is the Scala API. getContext returns a akka.actor.UntypedActorContext, which is the Java API of the actor context.

    Definition Classes
    Actor
  16. def ensuring(cond: (ClusterSingletonManager) ⇒ Boolean, msg: ⇒ Any): ClusterSingletonManager

    Implicit information
    This member is added by an implicit conversion from ClusterSingletonManager to Ensuring[ClusterSingletonManager] performed by method any2Ensuring in scala.Predef.
    Definition Classes
    Ensuring
  17. def ensuring(cond: (ClusterSingletonManager) ⇒ Boolean): ClusterSingletonManager

    Implicit information
    This member is added by an implicit conversion from ClusterSingletonManager to Ensuring[ClusterSingletonManager] performed by method any2Ensuring in scala.Predef.
    Definition Classes
    Ensuring
  18. def ensuring(cond: Boolean, msg: ⇒ Any): ClusterSingletonManager

    Implicit information
    This member is added by an implicit conversion from ClusterSingletonManager to Ensuring[ClusterSingletonManager] performed by method any2Ensuring in scala.Predef.
    Definition Classes
    Ensuring
  19. def ensuring(cond: Boolean): ClusterSingletonManager

    Implicit information
    This member is added by an implicit conversion from ClusterSingletonManager to Ensuring[ClusterSingletonManager] performed by method any2Ensuring in scala.Predef.
    Definition Classes
    Ensuring
  20. final def eq(arg0: AnyRef): Boolean

    Definition Classes
    AnyRef
  21. def equals(arg0: Any): Boolean

    Definition Classes
    AnyRef → Any
  22. def finalize(): Unit

    Attributes
    protected[java.lang]
    Definition Classes
    AnyRef
    Annotations
    @throws( classOf[java.lang.Throwable] )
  23. def formatted(fmtstr: String): String

    Implicit information
    This member is added by an implicit conversion from ClusterSingletonManager to StringFormat performed by method any2stringfmt in scala.Predef.
    Definition Classes
    StringFormat
    Annotations
    @inline()
  24. final def getClass(): Class[_]

    Definition Classes
    AnyRef → Any
  25. def getNextOldestChanged(): Unit

  26. def gossip(msg: Any)(implicit sender: ActorRef = Actor.noSender): Unit

    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.

    msg
    sender

    Attributes
    protected
    Definition Classes
    Listeners
  27. final def goto(nextStateName: ClusterSingletonManager.State): State

    Produce transition to other state.

    Produce transition to other state. Return this from a state function in order to effect the transition.

    nextStateName

    state designator for the next state

    returns

    state transition descriptor

    Definition Classes
    FSM
  28. def gotoHandingOver(singleton: ActorRef, singletonTerminated: Boolean, handOverData: Option[Any], handOverTo: Option[ActorRef]): State

  29. def gotoOldest(handOverData: Option[Any]): State

  30. def handOverDone(handOverTo: Option[ActorRef], handOverData: Option[Any]): State

  31. def hashCode(): Int

    Definition Classes
    AnyRef → Any
  32. final def initialize(): Unit

    Verify existence of initial state and setup timers.

    Verify existence of initial state and setup timers. This should be the last call within the constructor, or akka.actor.Actor#preStart and akka.actor.Actor#postRestart

    Definition Classes
    FSM
    See also

    #startWith

  33. final def isInstanceOf[T0]: Boolean

    Definition Classes
    Any
  34. final def isTimerActive(name: String): Boolean

    Inquire whether the named timer is still active.

    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.

    Definition Classes
    FSM
  35. def listenerManagement: actor.Actor.Receive

    Chain this into the receive function.

    Chain this into the receive function.

    def receive = listenerManagement orElse ￉
    Attributes
    protected
    Definition Classes
    Listeners
  36. val listeners: Set[ActorRef]

    Attributes
    protected
    Definition Classes
    Listeners
  37. val log: LoggingAdapter

    Definition Classes
    ActorLogging
  38. def logInfo(template: String, arg1: Any, arg2: Any): Unit

  39. def logInfo(template: String, arg1: Any): Unit

  40. def logInfo(message: String): Unit

  41. def logTermination(reason: Reason): Unit

    By default FSM.Failure is logged at error level and other reason types are not logged.

    By default FSM.Failure is logged at error level and other reason types are not logged. It is possible to override this behavior.

    Attributes
    protected
    Definition Classes
    FSM
  42. final def ne(arg0: AnyRef): Boolean

    Definition Classes
    AnyRef
  43. final def nextStateData: Data

    Return next state data (available in onTransition handlers)

    Return next state data (available in onTransition handlers)

    Definition Classes
    FSM
  44. final def notify(): Unit

    Definition Classes
    AnyRef
  45. final def notifyAll(): Unit

    Definition Classes
    AnyRef
  46. var oldestChangedBuffer: ActorRef

  47. var oldestChangedReceived: Boolean

  48. final def onTermination(terminationHandler: PartialFunction[StopEvent, Unit]): Unit

    Set handler which is called upon termination of this FSM actor.

    Set handler which is called upon termination of this FSM actor. Calling this method again will overwrite the previous contents.

    Definition Classes
    FSM
  49. final def onTransition(transitionHandler: TransitionHandler): Unit

    Set handler which is called upon each state transition, i.

    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.

    Definition Classes
    FSM
  50. def peer(at: Address): ActorSelection

  51. def postRestart(reason: Throwable): Unit

    User overridable callback: By default it calls preStart().

    User overridable callback: By default it calls preStart().

    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.

    Definition Classes
    Actor
    Annotations
    @throws( classOf[Exception] )
  52. def postStop(): Unit

    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.

    Definition Classes
    ClusterSingletonManagerFSMActor
  53. def preRestart(reason: Throwable, message: Option[Any]): Unit

    User overridable callback: By default it disposes of all children and then calls postStop().

    User overridable callback: By default it disposes of all children and then calls postStop().

    reason

    the Throwable that caused the restart to happen

    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.

    Definition Classes
    Actor
    Annotations
    @throws( classOf[Exception] )
  54. def preStart(): Unit

    User overridable callback.

    User overridable callback.

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

    Definition Classes
    ClusterSingletonManagerActor
  55. def receive: Receive

    This defines the initial actor behavior, it must return a partial function with the actor logic.

    This defines the initial actor behavior, it must return a partial function with the actor logic.

    Definition Classes
    FSMActor
  56. var removed: Map[Address, Deadline]

  57. implicit final val self: ActorRef

    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
    

    Definition Classes
    Actor
  58. val selfAddressOption: Some[Address]

  59. var selfExited: Boolean

  60. final def sender: ActorRef

    The reference sender Actor of the last received message.

    The reference sender Actor of the last received message. Is defined if the message was sent from another Actor, else deadLetters in akka.actor.ActorSystem.

    WARNING: Only valid within the Actor itself, so do not close over it and publish it to other threads!

    Definition Classes
    Actor
  61. final def setStateTimeout(state: ClusterSingletonManager.State, timeout: Timeout): Unit

    Set state timeout explicitly.

    Set state timeout explicitly. This method can safely be used from within a state handler.

    Definition Classes
    FSM
  62. final def setTimer(name: String, msg: Any, timeout: FiniteDuration, repeat: Boolean): Unit

    Schedule named timer to deliver message after given delay, possibly repeating.

    Schedule named timer to deliver message after given delay, possibly repeating.

    name

    identifier to be used with cancelTimer()

    msg

    message to be delivered

    timeout

    delay of first message delivery and between subsequent messages

    repeat

    send once if false, scheduleAtFixedRate if true

    returns

    current state descriptor

    Definition Classes
    FSM
  63. final def startWith(stateName: ClusterSingletonManager.State, stateData: Data, timeout: Timeout = None): Unit

    Set initial state.

    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 akka.actor.Actor#preStart and akka.actor.Actor#postRestart.

    stateName

    initial state designator

    stateData

    initial state data

    timeout

    state timeout for the initial state, overriding the default timeout for that state

    Definition Classes
    FSM
  64. final def stateData: Data

    Return current state data (i.

    Return current state data (i.e. object of type D)

    Definition Classes
    FSM
  65. final def stateName: ClusterSingletonManager.State

    Return current state name (i.

    Return current state name (i.e. object of type S)

    Definition Classes
    FSM
  66. final def stay(): State

    Produce "empty" transition descriptor.

    Produce "empty" transition descriptor. Return this from a state function when no state change is to be effected.

    returns

    descriptor for staying in current state

    Definition Classes
    FSM
  67. final def stop(reason: Reason, stateData: Data): State

    Produce change descriptor to stop this FSM actor including specified reason.

    Produce change descriptor to stop this FSM actor including specified reason.

    Definition Classes
    FSM
  68. final def stop(reason: Reason): State

    Produce change descriptor to stop this FSM actor including specified reason.

    Produce change descriptor to stop this FSM actor including specified reason.

    Definition Classes
    FSM
  69. final def stop(): State

    Produce change descriptor to stop this FSM actor with reason "Normal".

    Produce change descriptor to stop this FSM actor with reason "Normal".

    Definition Classes
    FSM
  70. def supervisorStrategy: SupervisorStrategy

    User overridable definition the strategy to use for supervising child actors.

    User overridable definition the strategy to use for supervising child actors.

    Definition Classes
    Actor
  71. final def synchronized[T0](arg0: ⇒ T0): T0

    Definition Classes
    AnyRef
  72. def toString(): String

    Definition Classes
    AnyRef → Any
  73. implicit final def total2pf(transitionHandler: (ClusterSingletonManager.State, ClusterSingletonManager.State) ⇒ Unit): TransitionHandler

    Convenience wrapper for using a total function instead of a partial function literal.

    Convenience wrapper for using a total function instead of a partial function literal. To be used with onTransition.

    Definition Classes
    FSM
  74. final def transform(func: StateFunction): TransformHelper

    Definition Classes
    FSM
  75. def unhandled(message: Any): Unit

    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 akka.actor.DeathPactException (in case of an unhandled akka.actor.Terminated message) or publishes an akka.actor.UnhandledMessage to the actor's system's akka.event.EventStream

    Definition Classes
    Actor
  76. final def wait(): Unit

    Definition Classes
    AnyRef
    Annotations
    @throws( ... )
  77. final def wait(arg0: Long, arg1: Int): Unit

    Definition Classes
    AnyRef
    Annotations
    @throws( ... )
  78. final def wait(arg0: Long): Unit

    Definition Classes
    AnyRef
    Annotations
    @throws( ... )
  79. final def when(stateName: ClusterSingletonManager.State, stateTimeout: FiniteDuration = null)(stateFunction: StateFunction): Unit

    Insert a new StateFunction at the end of the processing chain for the given state.

    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.

    stateName

    designator for the state

    stateTimeout

    default state timeout for this state

    stateFunction

    partial function describing response to input

    Definition Classes
    FSM
  80. final def whenUnhandled(stateFunction: StateFunction): Unit

    Set handler which is called upon reception of unhandled messages.

    Set handler which is called upon reception of unhandled messages. Calling this method again will overwrite the previous contents.

    The current state may be queried using stateName.

    Definition Classes
    FSM
  81. def [B](y: B): (ClusterSingletonManager, B)

    Implicit information
    This member is added by an implicit conversion from ClusterSingletonManager to ArrowAssoc[ClusterSingletonManager] performed by method any2ArrowAssoc in scala.Predef.
    Definition Classes
    ArrowAssoc

Shadowed Implicit Value Members

  1. def ->[B](y: B): (ClusterSingletonManager, B)

    Implicit information
    This member is added by an implicit conversion from ClusterSingletonManager to ArrowAssoc[ClusterSingletonManager] performed by method any2ArrowAssoc in scala.Predef.
    Shadowing
    This implicitly inherited member is shadowed by one or more members in this class.
    To access this member you can use a type ascription:
    (clusterSingletonManager: ArrowAssoc[ClusterSingletonManager]).->(y)
    Definition Classes
    ArrowAssoc
    Annotations
    @inline()
  2. val self: Any

    Implicit information
    This member is added by an implicit conversion from ClusterSingletonManager to StringAdd performed by method any2stringadd in scala.Predef.
    Shadowing
    This implicitly inherited member is shadowed by one or more members in this class.
    To access this member you can use a type ascription:
    (clusterSingletonManager: StringAdd).self
    Definition Classes
    StringAdd
  3. val self: Any

    Implicit information
    This member is added by an implicit conversion from ClusterSingletonManager to StringFormat performed by method any2stringfmt in scala.Predef.
    Shadowing
    This implicitly inherited member is shadowed by one or more members in this class.
    To access this member you can use a type ascription:
    (clusterSingletonManager: StringFormat).self
    Definition Classes
    StringFormat

Deprecated Value Members

  1. final def timerActive_?(name: String): Boolean

    Inquire whether the named timer is still active.

    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.

    Definition Classes
    FSM
    Annotations
    @deprecated
    Deprecated

    (Since version 2.2) use isTimerActive instead

  2. def x: ClusterSingletonManager

    Implicit information
    This member is added by an implicit conversion from ClusterSingletonManager to ArrowAssoc[ClusterSingletonManager] performed by method any2ArrowAssoc in scala.Predef.
    Shadowing
    This implicitly inherited member is ambiguous. One or more implicitly inherited members have similar signatures, so calling this member may produce an ambiguous implicit conversion compiler error.
    To access this member you can use a type ascription:
    (clusterSingletonManager: ArrowAssoc[ClusterSingletonManager]).x
    Definition Classes
    ArrowAssoc
    Annotations
    @deprecated
    Deprecated

    (Since version 2.10.0) Use leftOfArrow instead

  3. def x: ClusterSingletonManager

    Implicit information
    This member is added by an implicit conversion from ClusterSingletonManager to Ensuring[ClusterSingletonManager] performed by method any2Ensuring in scala.Predef.
    Shadowing
    This implicitly inherited member is ambiguous. One or more implicitly inherited members have similar signatures, so calling this member may produce an ambiguous implicit conversion compiler error.
    To access this member you can use a type ascription:
    (clusterSingletonManager: Ensuring[ClusterSingletonManager]).x
    Definition Classes
    Ensuring
    Annotations
    @deprecated
    Deprecated

    (Since version 2.10.0) Use resultOfEnsuring instead

Inherited from ActorLogging

Inherited from Listeners

Inherited from Actor

Inherited from AnyRef

Inherited from Any

Inherited by implicit conversion any2stringadd from ClusterSingletonManager to StringAdd

Inherited by implicit conversion any2stringfmt from ClusterSingletonManager to StringFormat

Inherited by implicit conversion any2ArrowAssoc from ClusterSingletonManager to ArrowAssoc[ClusterSingletonManager]

Inherited by implicit conversion any2Ensuring from ClusterSingletonManager to Ensuring[ClusterSingletonManager]

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