processorOf FSM with Timer states

[Stas Shevchenko]

Hi All,

Probably there are some best practices for my case:

There is an Actor that implements State Machine, in some moment of time it has defined State and react according to it. 

It is well mapped to Processor while sequence of Messages leads his States.

When I do 

extension.recover

It's predictable and reliable to return it to the last state. But in my State Machine there is side effect - it has Timers Inside, for example it can stay in some Stay for limited period of Time, and then it doesn't accept messages of some type

for example Akka's FSM:

class MyFSM extends Actor with FSM[State, Data] {

  when(NormalState) {

    case Event(DoIt(sDuration), _) =>

      goto(TimerState) forMax  (sDuration seconds)

  }

  when(TimerState) {

    case Event(StateTimeout, _) =>

      goto(NormalState)

    case Event(otherMessages, _) =>

      stay forMax  (...)

  }

  ....

}

Recovering is impossible because of dependencies from Time. Is there any good way how to put MyFSM into Processor rails? Probably making snapshots after each time depended state?

Stas

[Martin Krasser]

Hi Stas,

In general, you can approach problems of this kind by journaling timer
events. This ensures that the sequence of all messages/events incl.
timer events are the same on replay. Since the timer events sent by FSM
are not wrapped into Message, you'll need to do that yourself using an
additional stackable trait (TimerEventInterceptor) that intercepts timer
events and then wraps them into Message. Important is that this
interceptor is mixed in after Eventsourced.

class MyFSM extends ... with Eventsourced with MyTimerEventInterceptor

Cheers,
Martin

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