quiver_retry_2.dart

/// Returns a [Duration] if another attempt needs to be made after
/// waiting for the returned [Duration]. Returns the error object
/// that instructs the retry mechanism to stop trying and report error
/// immediately.
typedef dynamic OnErrorFunc(Object err, int retry, Duration elapsed);
/// `onError` returns either [Duration] or an error object. If [Duration]
/// is returned, the `attempt` function will be retried after waiting
/// for the returned duration, otherwise the retry mechanism gives up
/// and evaluates the [Future] with the the error object.
Future start(
    AttemptFunc attempt, {
    OnErrorFunc onError: retriesInfinite,
    Stopwatch runTime})

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import 'package:quiver/retry.dart' as retry;

delayFn(err, retry, elapsed) =>
    is503(err)
      ? retry.randomDelay(new Duration(seconds: 1), 0.8)
      : retry.capDelay(retry.randomDelay(new Duration(seconds: 1), 0.4),
          const Duration(milliseconds: 1200));

var limited = retry.makeRetriesLimited(10, new Duration(seconds: 10), delayFn);

typedef TryAgain(bool cont, Duration delay, [NewFuture task]);

onError(err, iteration, elapsed, tryAgain) {
  tryAgain(is404(err), limited(err, iteration, elapsed), () => http.get(otherServer));
}

retry.start(doSomething, onError: onError);