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 statestay using Data(...)
for staying in the same state, but with different datastay forMax 5.millis
for staying with a state timeout; can be combined withusing
goto(...)
for changing into a different state; also supportsusing
andforMax
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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- By Inheritance
- FSM
- ActorLogging
- Listeners
- Actor
- AnyRef
- Any
- by any2stringadd
- by StringFormat
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- by ArrowAssoc
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- Public
- Protected
Type Members
- type Event = FSM.Event[D]
- type Receive = PartialFunction[Any, Unit]
- Definition Classes
- Actor
- type State = FSM.State[S, D]
- type StateFunction = PartialFunction[Event, State]
- type StopEvent = FSM.StopEvent[S, D]
- type Timeout = Option[FiniteDuration]
- final class TransformHelper extends AnyRef
- type TransitionHandler = PartialFunction[(S, S), Unit]
Value Members
- final def !=(arg0: Any): Boolean
- Definition Classes
- AnyRef → Any
- final def ##: Int
- Definition Classes
- AnyRef → Any
- def +(other: String): String
- val ->: FSM.->.type
This extractor is just convenience for matching a (S, S) pair, including a reminder what the new state is.
- final def ==(arg0: Any): Boolean
- Definition Classes
- AnyRef → Any
- val Event: FSM.Event.type
- val StateTimeout: FSM.StateTimeout.type
This case object is received in case of a state timeout.
- val StopEvent: FSM.StopEvent.type
- def aroundPostRestart(reason: Throwable): Unit
INTERNAL API.
INTERNAL API.
Can be overridden to intercept calls to
postRestart
. CallspostRestart
by default.- Attributes
- protected[akka]
- Definition Classes
- Actor
- Annotations
- @InternalApi()
- def aroundPostStop(): Unit
INTERNAL API.
INTERNAL API.
Can be overridden to intercept calls to
postStop
. CallspostStop
by default.- Attributes
- protected[akka]
- Definition Classes
- Actor
- Annotations
- @InternalApi()
- def aroundPreRestart(reason: Throwable, message: Option[Any]): Unit
INTERNAL API.
INTERNAL API.
Can be overridden to intercept calls to
preRestart
. CallspreRestart
by default.- Attributes
- protected[akka]
- Definition Classes
- Actor
- Annotations
- @InternalApi()
- def aroundPreStart(): Unit
INTERNAL API.
INTERNAL API.
Can be overridden to intercept calls to
preStart
. CallspreStart
by default.- Attributes
- protected[akka]
- Definition Classes
- Actor
- Annotations
- @InternalApi()
- 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()
- final def asInstanceOf[T0]: T0
- Definition Classes
- Any
- 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
- def clone(): AnyRef
- Attributes
- protected[lang]
- Definition Classes
- AnyRef
- Annotations
- @throws(classOf[java.lang.CloneNotSupportedException]) @native() @HotSpotIntrinsicCandidate()
- 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
- def ensuring(cond: (FSM[S, D]) => Boolean, msg: => Any): FSM[S, D]
- def ensuring(cond: (FSM[S, D]) => Boolean): FSM[S, D]
- def ensuring(cond: Boolean, msg: => Any): FSM[S, D]
- def ensuring(cond: Boolean): FSM[S, D]
- final def eq(arg0: AnyRef): Boolean
- Definition Classes
- AnyRef
- def equals(arg0: AnyRef): Boolean
- Definition Classes
- AnyRef → Any
- final def getClass(): Class[_ <: AnyRef]
- Definition Classes
- AnyRef → Any
- Annotations
- @native() @HotSpotIntrinsicCandidate()
- 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
- 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
- def hashCode(): Int
- Definition Classes
- AnyRef → Any
- Annotations
- @native() @HotSpotIntrinsicCandidate()
- 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
- final def isInstanceOf[T0]: Boolean
- Definition Classes
- Any
- 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.
- 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
- val listeners: Set[ActorRef]
- Attributes
- protected
- Definition Classes
- Listeners
- def log: LoggingAdapter
- Definition Classes
- ActorLogging
- 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
- final def ne(arg0: AnyRef): Boolean
- Definition Classes
- AnyRef
- final def nextStateData: D
Return next state data (available in onTransition handlers)
- final def notify(): Unit
- Definition Classes
- AnyRef
- Annotations
- @native() @HotSpotIntrinsicCandidate()
- final def notifyAll(): Unit
- Definition Classes
- AnyRef
- Annotations
- @native() @HotSpotIntrinsicCandidate()
- 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.
- 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.
- 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])
- def postStop(): Unit
Call
onTermination
hook; if you want to retain this behavior when overriding make sure to callsuper.postStop()
. - 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])
- 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])
- def receive: Receive
Scala API: This defines the initial actor behavior, it must return a partial function with the actor logic.
- 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
- 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
- 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.
- def startSingleTimer(name: String, msg: Any, delay: FiniteDuration): Unit
Start a timer that will send
msg
once to theself
actor after the givendelay
.Start a timer that will send
msg
once to theself
actor after the givendelay
.Each timer has a
name
and if a new timer with samename
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. - 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. ThereforestartTimerWithFixedDelay
is often preferred.Each timer has a
name
and if a new timer with samename
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. - def startTimerWithFixedDelay(name: String, msg: Any, delay: FiniteDuration): Unit
Schedules a message to be sent repeatedly to the
self
actor with a fixeddelay
between messages.Schedules a message to be sent repeatedly to the
self
actor with a fixeddelay
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 samename
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. - 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
- final def stateData: D
Return current state data (i.e.
Return current state data (i.e. object of type D)
- final def stateName: S
Return current state name (i.e.
Return current state name (i.e. object of type S)
- 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
foronTransition
to handle usegoto
instead.- returns
descriptor for staying in current state
- final def stop(reason: Reason, stateData: D): State
Produce change descriptor to stop this FSM actor including specified reason.
- final def stop(reason: Reason): State
Produce change descriptor to stop this FSM actor including specified reason.
- final def stop(): State
Produce change descriptor to stop this FSM actor with reason "Normal".
- 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
- final def synchronized[T0](arg0: => T0): T0
- Definition Classes
- AnyRef
- def toString(): String
- Definition Classes
- AnyRef → Any
- 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.
- final def transform(func: StateFunction): TransformHelper
- 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
- final def wait(arg0: Long, arg1: Int): Unit
- Definition Classes
- AnyRef
- Annotations
- @throws(classOf[java.lang.InterruptedException])
- final def wait(arg0: Long): Unit
- Definition Classes
- AnyRef
- Annotations
- @throws(classOf[java.lang.InterruptedException]) @native()
- final def wait(): Unit
- Definition Classes
- AnyRef
- Annotations
- @throws(classOf[java.lang.InterruptedException])
- 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
- 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
Shadowed Implicit Value Members
- def ->[B](y: B): (FSM[S, D], B)
- Implicit
- This member is added by an implicit conversion from FSM[S, D] toArrowAssoc[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
- def finalize(): Unit
- Attributes
- protected[lang]
- Definition Classes
- AnyRef
- Annotations
- @throws(classOf[java.lang.Throwable]) @Deprecated
- Deprecated
- def formatted(fmtstr: String): String
- Implicit
- This member is added by an implicit conversion from FSM[S, D] toStringFormat[FSM[S, D]] performed by method StringFormat in scala.Predef.
- Definition Classes
- StringFormat
- Annotations
- @deprecated @inline()
- Deprecated
(Since version 2.12.16) Use
formatString.format(value)
instead ofvalue.formatted(formatString)
, or use thef""
string interpolator. In Java 15 and later,formatted
resolves to the new method in String which has reversed parameters.
- 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) Use startSingleTimer, startTimerWithFixedDelay or startTimerAtFixedRate instead. This has the same semantics as startTimerAtFixedRate, but startTimerWithFixedDelay is often preferred.
- def →[B](y: B): (FSM[S, D], B)
- Implicit
- This member is added by an implicit conversion from FSM[S, D] toArrowAssoc[FSM[S, D]] performed by method ArrowAssoc in scala.Predef.
- Definition Classes
- ArrowAssoc
- Annotations
- @deprecated
- Deprecated
(Since version 2.13.0) Use
->
instead. If you still wish to display it as one character, consider using a font with programming ligatures such as Fira Code.