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

Based on Markus' answer I wrote the following:

public static class ObservableExtensions
{
    private static IObservable BackOffAndRetry(
        this IObservable source,
        Func strategy,
        Func retryOnError,
        int attempt)
    {
        return Observable
            .Defer(() =>
            {
                var delay = attempt == 0 ? TimeSpan.Zero : strategy(attempt);
                var s = delay == TimeSpan.Zero ? source : source.DelaySubscription(delay);

                return s
                    .Catch(e =>
                    {
                        if (retryOnError(attempt, e))
                        {
                            return source.BackOffAndRetry(strategy, retryOnError, attempt + 1);
                        }
                        return Observable.Throw(e);
                    });
            });
    }

    public static IObservable BackOffAndRetry(
        this IObservable source,
        Func strategy,
        Func retryOnError)
    {
        return source.BackOffAndRetry(strategy, retryOnError, 0);
    }
}

I like it more because

• it doesn't modify attempts but uses recursion.
• It doesn't use retries but passes the number of attempts to retryOnError