What's a good way to run periodic tasks using Rx, with a single concurrent execution restriction?

Question

I want to run periodic tasks in with a restriction that at most only one execution of a method is running at any given time.

I was experimenting with Rx, but I am no

Answer 1

Here is a factory function that does exactly what you are asking for.

public static IObservable Periodic(TimeSpan timeSpan)
{
    return Observable.Return(Unit.Default).Concat(Observable.Return(Unit.Default).Delay(timeSpan).Repeat());
}

Here is an example usage

Periodic(TimeSpan.FromSeconds(1))
    .Subscribe(x =>
    {
        Console.WriteLine(DateTime.Now.ToString("mm:ss:fff"));
        Thread.Sleep(500);
    });

If you run this, each console print will be roughly 1.5 seconds apart.

Note, If you don't want the first tick to run immediately, you could instead use this factory, which won't send the first Unit until after the timespan.

public static IObservable DelayedPeriodic(TimeSpan timeSpan)
{
    return Observable.Return(Unit.Default).Delay(timeSpan).Repeat();
}