Packages

trait FSM[S, D] extends Actor with Listeners with 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) { ... }
    initialize()
  }

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 -> _ => 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
  cancelTimer("tock")
  isTimerActive("tock")

Source
FSM.scala
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  1. FSM
  2. ActorLogging
  3. Listeners
  4. Actor
  5. AnyRef
  6. Any
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  1. by any2stringadd
  2. by StringFormat
  3. by Ensuring
  4. by ArrowAssoc
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Type Members

  1. type Event = FSM.Event[D]
  2. type Receive = PartialFunction[Any, Unit]
    Definition Classes
    Actor
  3. type State = FSM.State[S, D]
  4. type StateFunction = PartialFunction[Event, State]
  5. type StopEvent = FSM.StopEvent[S, D]
  6. type Timeout = Option[FiniteDuration]
  7. final class TransformHelper extends AnyRef
  8. type TransitionHandler = PartialFunction[(S, S), Unit]

Value Members

  1. final def !=(arg0: Any): Boolean
    Definition Classes
    AnyRef → Any
  2. final def ##(): Int
    Definition Classes
    AnyRef → Any
  3. def +(other: String): String
    Implicit
    This member is added by an implicit conversion from FSM[S, D] to any2stringadd[FSM[S, D]] performed by method any2stringadd in scala.Predef.
    Definition Classes
    any2stringadd
  4. val ->: FSM.->.type

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

  5. final def ==(arg0: Any): Boolean
    Definition Classes
    AnyRef → Any
  6. val Event: FSM.Event.type
  7. val StateTimeout: FSM.StateTimeout.type

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

  8. val StopEvent: FSM.StopEvent.type
  9. def aroundPostRestart(reason: Throwable): Unit

    INTERNAL API.

    INTERNAL API.

    Can be overridden to intercept calls to postRestart. Calls postRestart by default.

    Attributes
    protected[akka]
    Definition Classes
    Actor
    Annotations
    @InternalApi()
  10. def aroundPostStop(): Unit

    INTERNAL API.

    INTERNAL API.

    Can be overridden to intercept calls to postStop. Calls postStop by default.

    Attributes
    protected[akka]
    Definition Classes
    Actor
    Annotations
    @InternalApi()
  11. def aroundPreRestart(reason: Throwable, message: Option[Any]): Unit

    INTERNAL API.

    INTERNAL API.

    Can be overridden to intercept calls to preRestart. Calls preRestart by default.

    Attributes
    protected[akka]
    Definition Classes
    Actor
    Annotations
    @InternalApi()
  12. def aroundPreStart(): Unit

    INTERNAL API.

    INTERNAL API.

    Can be overridden to intercept calls to preStart. Calls preStart by default.

    Attributes
    protected[akka]
    Definition Classes
    Actor
    Annotations
    @InternalApi()
  13. def aroundReceive(receive: Actor.Receive, msg: Any): Unit

    INTERNAL API.

    INTERNAL API.

    Can be overridden to intercept calls to this actor's current behavior.

    receive

    current behavior.

    msg

    current message.

    Attributes
    protected[akka]
    Definition Classes
    Actor
    Annotations
    @InternalApi()
  14. final def asInstanceOf[T0]: T0
    Definition Classes
    Any
  15. 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

  16. def clone(): AnyRef
    Attributes
    protected[lang]
    Definition Classes
    AnyRef
    Annotations
    @throws( ... ) @native() @HotSpotIntrinsicCandidate()
  17. implicit val context: ActorContext

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

    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!

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

    Definition Classes
    Actor
  18. def ensuring(cond: (FSM[S, D]) ⇒ Boolean, msg: ⇒ Any): FSM[S, D]
    Implicit
    This member is added by an implicit conversion from FSM[S, D] to Ensuring[FSM[S, D]] performed by method Ensuring in scala.Predef.
    Definition Classes
    Ensuring
  19. def ensuring(cond: (FSM[S, D]) ⇒ Boolean): FSM[S, D]
    Implicit
    This member is added by an implicit conversion from FSM[S, D] to Ensuring[FSM[S, D]] performed by method Ensuring in scala.Predef.
    Definition Classes
    Ensuring
  20. def ensuring(cond: Boolean, msg: ⇒ Any): FSM[S, D]
    Implicit
    This member is added by an implicit conversion from FSM[S, D] to Ensuring[FSM[S, D]] performed by method Ensuring in scala.Predef.
    Definition Classes
    Ensuring
  21. def ensuring(cond: Boolean): FSM[S, D]
    Implicit
    This member is added by an implicit conversion from FSM[S, D] to Ensuring[FSM[S, D]] performed by method Ensuring in scala.Predef.
    Definition Classes
    Ensuring
  22. final def eq(arg0: AnyRef): Boolean
    Definition Classes
    AnyRef
  23. def equals(arg0: Any): Boolean
    Definition Classes
    AnyRef → Any
  24. def formatted(fmtstr: String): String
    Implicit
    This member is added by an implicit conversion from FSM[S, D] to StringFormat[FSM[S, D]] performed by method StringFormat in scala.Predef.
    Definition Classes
    StringFormat
    Annotations
    @inline()
  25. final def getClass(): Class[_]
    Definition Classes
    AnyRef → Any
    Annotations
    @native() @HotSpotIntrinsicCandidate()
  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.

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

    Produce transition to other state.

    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.

    nextStateName

    state designator for the next state

    returns

    state transition descriptor

  28. def hashCode(): Int
    Definition Classes
    AnyRef → Any
    Annotations
    @native() @HotSpotIntrinsicCandidate()
  29. 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

    An initial currentState -> currentState notification will be triggered by calling this method.

    See also

    #startWith

  30. final def isInstanceOf[T0]: Boolean
    Definition Classes
    Any
  31. 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.

  32. def listenerManagement: Actor.Receive

    Chain this into the receive function.

    Chain this into the receive function.

    def receive = listenerManagement orElse …
    Attributes
    protected
    Definition Classes
    Listeners
  33. val listeners: Set[ActorRef]
    Attributes
    protected
    Definition Classes
    Listeners
  34. def log: LoggingAdapter
    Definition Classes
    ActorLogging
  35. 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
  36. final def ne(arg0: AnyRef): Boolean
    Definition Classes
    AnyRef
  37. final def nextStateData: D

    Return next state data (available in onTransition handlers)

  38. final def notify(): Unit
    Definition Classes
    AnyRef
    Annotations
    @native() @HotSpotIntrinsicCandidate()
  39. final def notifyAll(): Unit
    Definition Classes
    AnyRef
    Annotations
    @native() @HotSpotIntrinsicCandidate()
  40. 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.

  41. final def onTransition(transitionHandler: TransitionHandler): Unit

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

    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.

  42. 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] )
  43. 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
    FSMActor
  44. def preRestart(reason: Throwable, message: Option[Any]): Unit

    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().

    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] )
  45. 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
    Actor
    Annotations
    @throws( classOf[Exception] )
  46. def receive: Receive

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

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

    Definition Classes
    FSMActor
  47. 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
  48. 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
  49. final def setStateTimeout(state: S, timeout: Timeout): Unit

    Set state timeout explicitly.

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

  50. def startSingleTimer(name: String, msg: Any, delay: FiniteDuration): Unit

    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 and it's guaranteed that a message from the previous timer is not received, even though it might already be enqueued in the mailbox when the new timer is started.

  51. def startTimerAtFixedRate(name: String, msg: Any, interval: FiniteDuration): Unit

    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 and it's guaranteed that a message from the previous timer is not received, even though it might already be enqueued in the mailbox when the new timer is started.

  52. def startTimerWithFixedDelay(name: String, msg: Any, delay: FiniteDuration): Unit

    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 and it's guaranteed that a message from the previous timer is not received, even though it might already be enqueued in the mailbox when the new timer is started.

  53. final def startWith(stateName: S, stateData: D, 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

  54. final def stateData: D

    Return current state data (i.e.

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

  55. final def stateName: S

    Return current state name (i.e.

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

  56. 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.

    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.

    returns

    descriptor for staying in current state

  57. final def stop(reason: Reason, stateData: D): State

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

  58. final def stop(reason: Reason): State

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

  59. final def stop(): State

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

  60. 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
  61. final def synchronized[T0](arg0: ⇒ T0): T0
    Definition Classes
    AnyRef
  62. def toString(): String
    Definition Classes
    AnyRef → Any
  63. implicit final def total2pf(transitionHandler: (S, S) ⇒ 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.

  64. final def transform(func: StateFunction): TransformHelper
  65. 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
  66. final def wait(arg0: Long, arg1: Int): Unit
    Definition Classes
    AnyRef
    Annotations
    @throws( ... )
  67. final def wait(arg0: Long): Unit
    Definition Classes
    AnyRef
    Annotations
    @throws( ... ) @native()
  68. final def wait(): Unit
    Definition Classes
    AnyRef
    Annotations
    @throws( ... )
  69. final def when(stateName: S, 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

  70. 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.

  71. def [B](y: B): (FSM[S, D], B)
    Implicit
    This member is added by an implicit conversion from FSM[S, D] to ArrowAssoc[FSM[S, D]] performed by method ArrowAssoc in scala.Predef.
    Definition Classes
    ArrowAssoc

Shadowed Implicit Value Members

  1. def ->[B](y: B): (FSM[S, D], B)
    Implicit
    This member is added by an implicit conversion from FSM[S, D] to ArrowAssoc[FSM[S, D]] performed by method ArrowAssoc 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:
    (fSM: ArrowAssoc[FSM[S, D]]).->(y)
    Definition Classes
    ArrowAssoc
    Annotations
    @inline()

Deprecated Value Members

  1. def finalize(): Unit
    Attributes
    protected[lang]
    Definition Classes
    AnyRef
    Annotations
    @throws( classOf[java.lang.Throwable] ) @Deprecated @deprecated
    Deprecated

    (Since version ) see corresponding Javadoc for more information.

  2. final def setTimer(name: String, msg: Any, timeout: FiniteDuration, repeat: Boolean = false): Unit

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

    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.

    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

    Annotations
    @deprecated
    Deprecated

    (Since version 2.6.0)

Inherited from ActorLogging

Inherited from Listeners

Inherited from Actor

Inherited from AnyRef

Inherited from Any

Inherited by implicit conversion any2stringadd from FSM[S, D] to any2stringadd[FSM[S, D]]

Inherited by implicit conversion StringFormat from FSM[S, D] to StringFormat[FSM[S, D]]

Inherited by implicit conversion Ensuring from FSM[S, D] to Ensuring[FSM[S, D]]

Inherited by implicit conversion ArrowAssoc from FSM[S, D] to ArrowAssoc[FSM[S, D]]

Ungrouped