Zero delay in ExponentialBackoff strategy after few retries

[PeterMaco]

Setup ExponentialBackoff strategy with the following settings: RetryCount = 100 MinBackoff = 1 second MaxBackoff = 120 seconds DeltaBackoff = 2 seconds

Use it in RetryPolicy and simulate retries (throw exception in ExecuteAsync).

Current Behaviour: After 22 retries it starts to execute the action with delay 0.

Expected Behaviour Action is executed with MaxBackoff delay (120 seconds).

Cause of the issue: There is a bug in GetShouldRetry algorithm on this line: int backoffMillisecond = (int)((Math.Pow(2.0, currentRetryCount) - 1.0) * random.Next((int)(this.deltaBackoff.TotalMilliseconds * 0.8), (int)(this.deltaBackoff.TotalMilliseconds * 1.2)));

There is a multiplication of 2 quite high integers and the result is greater than int.MaxValue. It results in overflow and negative result which is then set to 0 in RetryPolicy class: if (zero.TotalMilliseconds < 0.0) { zero = TimeSpan.Zero; }