Appccelerate state machine state with timer

Question

Ok I am sure I am not using the state machine correctly but here is subset of sample code. This is the Appccelerate.StateMachine which used to be bbvcommon.StateMachine.

fsm.In(State.Idle)
    .ExecuteOnEntry(() => { 
        // wake up and check if there are people still standing and if so restart
        if(currentlyTalkingTo.Count() > 0)
        {
            fsm.Fire(Event.PersonFound);
        }
    })
    .On(Event.PersonFound).Goto(State.WaitToRecognizePeople);

fsm.In(State.WaitToRecognizePeople)
    .ExecuteOnEntry(() => {
        Thread.Sleep(1000);
        fsm.Fire(Event.TimeOut);
    })
    .On(Event.TimeOut).Goto(State.Greet);

The issue is what the best way to handle a sleep? With this code calling fsm.Stop() when shutting the application down sometimes hangs the application. Commenting all the Thread.Sleeps() in the states fixes the issue so the application successfully shuts down.

What is the recommended way of handling states that need to time out and move to another state? Sample code would be appreciated.

Generally if you find yourself doing a `Thread.Sleep(...)` ever in your code you are probably doing something wrong. I'm not familiar with the framework you're using, but generally the way to do this with a state machine is to start a timer that will change the state after the period of time and this state transition should call your code that you currently have after your sleep. — Enigmativity, Sep 16 '15 at 01:03
Do the Thread.Sleep calls prevent shutdown completely or only delay it for (up to) the time specified in the call to Sleep? If the latter, you can use an event and wait on that instead of sleeping. That then allows you to signal the event at shutdown thus waking up the waiting (sleeping) state machine immediately so that it can be shut down without delay. — 500 - Internal Server Error, Sep 16 '15 at 01:03

score 0 · Answer 1 · answered Jan 11 '16 at 21:45

The Thread.Sleep would block the state machine, both the PassiveStateMachine and ActiveStateMachine, so that you cannot react to other events anymore during the sleep time. That might be an explanation for why a call to Stop sometimes hangs the explanation.

I assume you don't just want to wait for a given period of time but want to wait for some event under a timeout condition. I would then recommend to start a Timer in the ExecuteOnEntry of WaitToRecognizePeople that, when elapsed, fires the event Event.Timeout.

If you have many states that have associated timeouts, to avoid a lot of duplicated code, you could even implement this in a separate class as a state machine extension, like I did in one of my projects using this library. (see http://www.appccelerate.com/statemachineextensions.html).

Appccelerate state machine state with timer

1 Answers1