Change a Scheduled Timer

[alexzm1]

Is there any way to change the FireAfter TimeSpan of a Timer after being scheduled?

Here is a code snipped of what we're trying to do

`

public class TestWorkflow : Workflow {
//WorkflowDescription setup skiped
public TestWorkflow(){

	ScheduleActivity<TriggerTimerActivity>().OnCompletion(_=> Ignore);
	
	ScheduleTimer("TimerTest")
		.When(_=>false)
		.FireAfter(TimeSpan.FromMinutes(2)) //This might be changed by a Workflow Signal
		.OnFired(_ =>
			{
				return FailWorkflow("Failed Cancel Timer", "Failed to cancel TimerTest"); //Executed after timer's TimeSpan (2 minutes in this case)
			})
		.OnCancelled(_ =>
			{
				return CompleteWorkflow("Workflow Execution Completed"); //Not Executed After timer cancellation
			}
		);

}

[WorkflowEvent(EventName.Signal)]
public WorkflowAction OnSignal(WorkflowSignaledEvent @event)
{
	if("start timer".EqualsIgnoreCase(@event.SignalName))
	{
		//Start the "TimerTest" using the @event.Input value as FireAfter TimeSpan value to setup
	}
	if ("cancel timer".EqualsIgnoreCase(@event.SignalName))
	{
		return CancelRequest.ForTimer(name: "TimerTest"); // Timer is cancelled after returning this
	}
	
	return Ignore;
}

}
`

[gurmitteotia]

I have reread you question and I am sorry I am not able to fully match your question with the code. Timer.OnCancelled is not supported, and a new API Timer.OnCancel is added.
In version 1.1.14 I have also added a new Timer.FireAfter API which accepts the lambda and it will give you the flexibility to dynamically provide timeout.

Now regarding your question. If you want to reschedule a timer, which you have already scheduled then there is no nicer support in Amazon SWF for it. It would have been simpler if cancellation timer has raised the DecisionTaskScheduled event or it has allowed cancellation and scheduling in same decision. i.e.

 if (Timer("SomeTimer").IsActive)
     return CancelRequest.ForTimer("SomeTimer") + Jump.ToTimer("SomeTimer");

But none of above options are available and you have to use following workaround:

    public class OrderWorkflow : Workflow
    {
        public OrderWorkflow()
        {
            ScheduleTimer("GracePeriod").FireAfter(GracePeriodTimeout);
            ScheduleActivity<CancelOrder>().AfterTimer("GracePeriod")
                                               .When(a=> a.ParentTimer().IsCancelled()) ;

            ScheduleActivity<ShipOrder>().AfterTimer("GracePeriod");
            ScheduleTimer("GracePeriodReschedule").When(_ => false)
                                     .OnFired(_ => Jump.ToTimer("GracePeriod"));
        }

        private TimeSpan GracePeriodTimeout(ITimerItem item)
        {
            if (AllSignalEvents.Any(a => a.SignalName == "change_time"))
                return TimeSpan.FromMinutes(20); // new time or read it is from signal details

            return TimeSpan.FromMinutes(10); //Default timeout
        }
        [WorkflowEvent(EventName.Signal)]
        public WorkflowAction Signal(WorkflowSignaledEvent @event)
        {
            var timer = Timer("GracePeriod");
            if (@event.SignalName == "change_time")
                if (timer.IsActive) return CancelRequest.For(timer) + Jump.ToTimer("GracePeriodReschedule");

            return Ignore;
        }
    }

In future I'm planning to support dynamic timers, where you can schedule timers independent of workflow steps and it will make above workaround more sensible.

[gurmitteotia]

I think it will be useful to have Timer.Reset() and Timer.Reschedule API available. These API are quite generic and and could be useful in many scenarios. I can see that implementation of these APIs will help in setting up the foundation for ParallelForEach feature. So in future you will be able to either reschedule or reset the timer as below (For simplicity and to stay focused I have removed other details from example) :

public class OrderWorkflow : Workflow
    {
        public OrderWorkflow()
        {
            ScheduleTimer("GracePeriod").FireAfter(TimeSpan.FromMinutes(30));
           
            ScheduleActivity<ShipOrder>().AfterTimer("GracePeriod");
        }

       [WorkflowEvent(EventName.Signal)]
        public WorkflowAction Signal(WorkflowSignaledEvent @event)
        {
            var timer = Timer("GracePeriod");
            if (@event.SignalName == "change_time")
                if (timer.IsActive) return timer.Reschedule(TimeSpan.FromMinutes(10));

            return Ignore;
        }
    }

[gurmitteotia]

I have created a ticket with initial ideas. Any input will be useful.

[gurmitteotia]

This feature is implemented in version 1.2.15.