Interface FSM<S,​D>

  • All Superinterfaces:
    Actor, ActorLogging, Listeners
    All Known Subinterfaces:
    All Known Implementing Classes:
    AbstractFSM, AbstractFSMWithStash, AbstractLoggingFSM, ClusterSingletonManager

    public interface FSM<S,​D>
    extends Actor, Listeners, ActorLogging
    Finite State Machine actor trait. Use as follows:

       object A {
         trait State
         case class One extends State
         case class Two extends State
         case class Data(i : Int)
       class A extends Actor with FSM[A.State, A.Data] {
         import A._
         startWith(One, Data(42))
         when(One) {
             case Event(SomeMsg, Data(x)) => ...
             case Event(SomeOtherMsg, _) => ... // when data not needed
         when(Two, stateTimeout = 5 seconds) { ... }

    Within the partial function the following values are returned for effecting state transitions:

    - stay for staying in the same state - stay using Data(...) for staying in the same state, but with different data - stay forMax 5.millis for staying with a state timeout; can be combined with using - goto(...) for changing into a different state; also supports using and forMax - stop for terminating this FSM actor

    Each of the above also supports the method replying(AnyRef) for sending a reply before changing state.

    While changing state, custom handlers may be invoked which are registered using onTransition. This is meant to enable concentrating different concerns in different places; you may choose to use when for describing the properties of a state, including of course initiating transitions, but you can describe the transitions using onTransition to avoid having to duplicate that code among multiple paths which lead to a transition:

     onTransition {
       case Active -&gt; _ =&gt; cancelTimer("activeTimer")

    Multiple such blocks are supported and all of them will be called, not only the first matching one.

    Another feature is that other actors may subscribe for transition events by sending a SubscribeTransitionCallback message to this actor. Stopping a listener without unregistering will not remove the listener from the subscription list; use UnsubscribeTransitionCallback before stopping the listener.

    State timeouts set an upper bound to the time which may pass before another message is received in the current state. If no external message is available, then upon expiry of the timeout a StateTimeout message is sent. Note that this message will only be received in the state for which the timeout was set and that any message received will cancel the timeout (possibly to be started again by the next transition).

    Another feature is the ability to install and cancel single-shot as well as repeated timers which arrange for the sending of a user-specified message:

       setTimer("tock", TockMsg, 1 second, true) // repeating
       setTimer("lifetime", TerminateMsg, 1 hour, false) // single-shot
    • Method Detail

      • akka$actor$FSM$_setter_$Event_$eq

        void akka$actor$FSM$_setter_$Event_$eq​(FSM.Event$ x$1)
      • akka$actor$FSM$_setter_$StopEvent_$eq

        void akka$actor$FSM$_setter_$StopEvent_$eq​(FSM.StopEvent$ x$1)
      • akka$actor$FSM$_setter_$StateTimeout_$eq

        void akka$actor$FSM$_setter_$StateTimeout_$eq​(FSM.StateTimeout$ x$1)
        This case object is received in case of a state timeout.
      • super$postStop

        void 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.

      • $minus$greater

        FSM.$minus$greater$ $minus$greater()
        This extractor is just convenience for matching a (S, S) pair, including a reminder what the new state is.
      • StateTimeout

        FSM.StateTimeout$ StateTimeout()
        This case object is received in case of a state timeout.
      • when

        void when​(S stateName,
                  scala.concurrent.duration.FiniteDuration stateTimeout,
                  scala.PartialFunction<FSM.Event<D>,​FSM.State<S,​D>> stateFunction)
        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
      • when$default$2

        scala.concurrent.duration.FiniteDuration when$default$2()
      • startWith

        void startWith​(S stateName,
                       D stateData,
                       scala.Option<scala.concurrent.duration.FiniteDuration> timeout)
        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 Actor.preStart() and Actor.postRestart(java.lang.Throwable).

        stateName - initial state designator
        stateData - initial state data
        timeout - state timeout for the initial state, overriding the default timeout for that state
      • startWith$default$3

        scala.Option<scala.concurrent.duration.FiniteDuration> startWith$default$3()
      • stay

        FSM.State<S,​D> stay()
        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 -&gt; S for onTransition to handle use goto instead.

        descriptor for staying in current state
      • stop

        FSM.State<S,​D> stop()
        Produce change descriptor to stop this FSM actor with reason "Normal".
      • stop

        FSM.State<S,​D> stop​(FSM.Reason reason)
        Produce change descriptor to stop this FSM actor including specified reason.
      • stop

        FSM.State<S,​D> stop​(FSM.Reason reason,
                                  D stateData)
        Produce change descriptor to stop this FSM actor including specified reason.
      • startTimerWithFixedDelay

        void startTimerWithFixedDelay​(java.lang.String name,
                                      java.lang.Object msg,
                                      scala.concurrent.duration.FiniteDuration delay)
      • startTimerAtFixedRate

        void startTimerAtFixedRate​(java.lang.String name,
                                   java.lang.Object msg,
                                   scala.concurrent.duration.FiniteDuration interval)
      • startSingleTimer

        void startSingleTimer​(java.lang.String name,
                              java.lang.Object msg,
                              scala.concurrent.duration.FiniteDuration delay)
      • setTimer

        void setTimer​(java.lang.String name,
                      java.lang.Object msg,
                      scala.concurrent.duration.FiniteDuration timeout,
                      boolean repeat)
        Use startSingleTimer, startTimerWithFixedDelay or startTimerAtFixedRate instead. This has the same semantics as startTimerAtFixedRate, but startTimerWithFixedDelay is often preferred. Since 2.6.0.
      • setTimer$default$4

        boolean setTimer$default$4()
      • startTimer

        void startTimer​(java.lang.String name,
                        java.lang.Object msg,
                        scala.concurrent.duration.FiniteDuration timeout,
                        FSM.TimerMode mode)
      • cancelTimer

        void cancelTimer​(java.lang.String name)
      • isTimerActive

        boolean isTimerActive​(java.lang.String name)
      • setStateTimeout

        void setStateTimeout​(S state,
                             scala.Option<scala.concurrent.duration.FiniteDuration> timeout)
      • isStateTimerActive

        boolean isStateTimerActive()
      • onTransition

        void onTransition​(scala.PartialFunction<scala.Tuple2<S,​S>,​scala.runtime.BoxedUnit> transitionHandler)
      • total2pf

        scala.PartialFunction<scala.Tuple2<S,​S>,​scala.runtime.BoxedUnit> total2pf​(scala.Function2<S,​S,​scala.runtime.BoxedUnit> transitionHandler)
      • onTermination

        void onTermination​(scala.PartialFunction<FSM.StopEvent<S,​D>,​scala.runtime.BoxedUnit> terminationHandler)
      • whenUnhandled

        void whenUnhandled​(scala.PartialFunction<FSM.Event<D>,​FSM.State<S,​D>> stateFunction)
      • initialize

        void initialize()
      • stateName

        S stateName()
      • stateData

        D stateData()
      • nextStateData

        D nextStateData()
      • debugEvent

        boolean debugEvent()
      • currentState_$eq

        void currentState_$eq​(FSM.State<S,​D> x$1)
      • timeoutFuture_$eq

        void timeoutFuture_$eq​(scala.Option<Cancellable> x$1)
      • nextState_$eq

        void nextState_$eq​(FSM.State<S,​D> x$1)
      • generation_$eq

        void generation_$eq​(long x$1)
      • register

        void register​(S name,
                      scala.PartialFunction<FSM.Event<D>,​FSM.State<S,​D>> function,
                      scala.Option<scala.concurrent.duration.FiniteDuration> timeout)
      • handleEvent_$eq

        void handleEvent_$eq​(scala.PartialFunction<FSM.Event<D>,​FSM.State<S,​D>> x$1)
      • terminateEvent_$eq

        void terminateEvent_$eq​(scala.PartialFunction<FSM.StopEvent<S,​D>,​scala.runtime.BoxedUnit> x$1)
      • transitionEvent_$eq

        void transitionEvent_$eq​(scala.collection.immutable.List<scala.PartialFunction<scala.Tuple2<S,​S>,​scala.runtime.BoxedUnit>> x$1)
      • handleTransition

        void handleTransition​(S prev,
                              S next)
      • receive

        scala.PartialFunction<java.lang.Object,​scala.runtime.BoxedUnit> receive()
        Description copied from interface: Actor
        Scala API: This defines the initial actor behavior, it must return a partial function with the actor logic.
        Specified by:
        receive in interface Actor
      • processMsg

        void processMsg​(java.lang.Object value,
                        java.lang.Object source)
      • processEvent

        void processEvent​(FSM.Event<D> event,
                          java.lang.Object source)
      • applyState

        void applyState​(FSM.State<S,​D> nextState)
      • makeTransition

        void makeTransition​(FSM.State<S,​D> nextState)
      • postStop

        void postStop()
        Description copied from interface: Actor
        User overridable callback.

        Is called asynchronously after 'actor.stop()' is invoked. Empty default implementation.
        Specified by:
        postStop in interface Actor
      • terminate

        void terminate​(FSM.State<S,​D> nextState)
      • logTermination

        void logTermination​(FSM.Reason reason)
        By default FSM.Failure is logged at error level and other reason types are not logged. It is possible to override this behavior.