The first delay of DelegateBackoff and ExponentialBackoff is always zero.

[WU Yong]

Let's take look at an example

 // use a ConstantBackoff
 const constDelayRetry = Policy.handleAll()
    .retry()
    .attempts(3)
    .backoff(new ConstantBackoff(10, 3));

  constDelayRetry.onRetry(({ delay }) => console.log('delay for next call: ', delay));
  await constDelayRetry.execute(() => {
    throw new Error('exception');
  });

// use a DelegateBackoff
  const delegatedDelayPolicy = Policy.handleAll()
    .retry()
    .attempts(3)
    .backoff(new DelegateBackoff(() => 10));

  delegatedDelayPolicy.onRetry(({ delay }) => console.log('delay for next call: ', delay));
  await delegatedDelayPolicy.execute(() => {
    throw new Error('exception');
  });

The output looks like

delay for next call:  10
delay for next call:  10
delay for next call:  10
delay for next call:  0
delay for next call:  10
delay for next call:  10

Conceptually, I would expect all delays are 10, but unfortunately, the first delay of DelegateBackoff is always 0.
Looks like the ExponentialBackoff has the same problem.

But Polly doesn't has such problem.
It looks like RetryPolicy.execute should adjust the logic to backoff.next() first then do the delay.

[Connor Peet]

Thanks for the issue, I would be happy to take a PR, otherwise I can fix this in a couple days.

[Connor Peet]

Fixed in the linked PR