With Rx, how do I ignore all-except-the-latest value when my Subscribe method is running

Question

Using Reactive Extensions, I want to ignore messages coming from my event stream that occur while my Subscribe method is running. I.e. it sometimes takes me lon

Answer 1

Yet another solution.

This is not pretty, because it mixes Task and Observable, so it's not really testable using ReactiveTest (though to be honest, I'm not sure how I'd implement a 'slow' subscriber with ReactiveTest either).

public static IObservable ShedLoad(this IObservable source)
{
    return Observable.Create(observer =>
    {
        Task task = Task.FromResult(0);
        return source.Subscribe(t =>
        {
            if(task.IsCompleted)
                task = Task.Run(() => observer.OnNext(t));
            else
                Debug.WriteLine("Skip, task not finished");
        }, observer.OnError, observer.OnCompleted);
    });
}

I'm guessing there might be a race condition in there, but to my mind, if we're at the stage where we're ditching stuff because it's going too fast, I don't mind ditching one too many or too few. Oh, and each OnNext is called (potentially) on a different thread (I guess I could put a Synchronize on the back of the Create).

I admit I couldn't get the Materialize extension to work properly (I hooked it up to a FromEventPattern(MouseMove) and then subscribed with a deliberately slow Subscribe, and weirdly it would let bursts of events through, rather than one at at time)