context timeout via <-ctx.Done()

[georgysavva]

As I can understand from the code, Retry() function can be canceled via context timeout: here
And this check is inside the retry loop. But in case the actual operation is a long running operation or it can even block, the retry function won't be canceled after context timeout, because it will hang on operation for a long time.
I think, that In order to achieve a strict cancelation we should listen for ctx.Done() in a separate gorutine outside of the retry loop.
Is it intentionally or not?

[georgysavva]

Also what one should use to restrict total time for retries? context timeout or MaxElapsedTime. As I can see they serve pretty similar purpose.
But for context you check the next interval, that it won't exceed the deadline: here
And you don't do the same for elapsedTime: here

[cenkalti]

This is an old package and Retry function is created at a time when context package did not exists. That's why Operation function signature does not accept a context.Context parameter. If it blocks, it blocks and retrying can only be cancelled after it returns. For a strict cancellation, I recommend creating a separate context.Context with a timeout/deadline and pass to your blocking function and use backoff.WithContext function to wrap your backoff.BackOff instance. Please let me know if you need an example, I can write one.

I am going to update ExponentionBackoff.NextBackOff method to reflect the change you have asked. Can you please take a look. If it's okay I will tag the commit as new version.

[georgysavva]

Everything is clear, thanks.
I saw the commit, it's exactly what I was asking for. Thank!

[cenkalti]

Tagged the commit as v4.0.2.