Write an Rx “RetryAfter” extension method

Question

In the book IntroToRx the author suggest to write a \"smart\" retry for I/O which retry an I/O request, like a network request, after a period of time.

Here is the e

Answer 1

Here's another slightly different implementation I came up with while studying how Rxx does it. So it's largely a cutdown version of Rxx's approach.

The signature is slightly different from Markus' version. You specify a type of Exception to retry on, and the delay strategy takes the exception and the retry count, so you could have longer delays for each successive retry, etc.

I can't guarantee it's bug proof, or the best approach, but it seems to work.

public static IObservable RetryWithDelay(this IObservable source, Func delayFactory, IScheduler scheduler = null)
where TException : Exception
{
    return Observable.Create(observer =>
    {
        scheduler = scheduler ?? Scheduler.CurrentThread;
        var disposable = new SerialDisposable();
        int retryCount = 0;

        var scheduleDisposable = scheduler.Schedule(TimeSpan.Zero,
        self =>
        {
            var subscription = source.Subscribe(
            observer.OnNext,
            ex =>
            {
                var typedException = ex as TException;
                if (typedException != null)
                {
                    var retryDelay = delayFactory(typedException, ++retryCount);
                    self(retryDelay);
                }
                else
                {
                    observer.OnError(ex);
                }
            },
            observer.OnCompleted);

            disposable.Disposable = subscription;
        });

        return new CompositeDisposable(scheduleDisposable, disposable);
    });
}