sample_of_retry_in_flatMap.kt

fun setupCoffeeMachine(...) {
    val debounceClicks: Observable<Unit> = btBrewCoffee.clicks()
        .debounce(250L, TimeUnit.MILLISECONDS)
    
    debounceClicks
        .switchMapSingle {
            brewCoffee() // Return Single<Coffee>
                .timeout(3, TimeUnit.MINUTES, Schedulers.computation())
                // Retry at position #1 <--------------------------------------
                .retryWhen { errorObservable ->
                    // Will attempt 3 retries, where each is back-off 5^attempts
                    errorObservable
                        .zipWith(Observable.range(1, 3) { (_, i) -> i }
                        .flatMap { i -> Observable.timer(Math.pow(5, i), ...) }
                }
        }
        // Retry at position #2 <----------------------------------------------
        .retry()
        .observeOn(AndroidSchedulers.mainThread())
        .subscribe({ coffee ->
            Timber.v("A good $coffee makes me a good day!")
        }, Timber::e)
        .disposeOnDestroy()
}