Can stamina be configured to respect 429 Too Many Requests and Retry-After?

[danielballan]

It would be convenient if the retry timing could be configured respect an HTTP Retry-After header, if set. I think this is not currently possible, because the on predicate returns a yes/no determination only. There is no way to inject the logic, "Retry no sooner than X seconds."

Building on #63 and #70, this could be introduced in a backward compatible way, by enabling the on predicate to return the minimum number of seconds to wait before retrying.

def retry_only_on_real_errors(exc: Exception) -> bool:
    # If the error is an HTTP status error, only retry on 5xx errors.
    if isinstance(exc, httpx.HTTPStatusError):
        if exc.status_code == httpx.codes.TOO_MANY_REQUESTS:
            # If server has asked us to wait for some interval before retrying, wait at least that long.
            retry_after = exc.response.headers.get("Retry-After")
            if retry_after is not None:
                return float(retry_after)
        return exc.response.status_code >= 500

Because a nonzero number is "truth-y", this extension is backward-compatible. Is this too "clever" or nonintuitive? Are there other potential meanings for "predicate returns a number" for which this interface should be reserved?

I could not find any prior discussion of Retry-After or 429 Too Many Requests.

Is this of interest and in scope? I would be happy to contribute a PR.

[danielballan]

Oh—I meant to add: thank you for this excellent project and especially the thorough documentation and background information!

[jayqi]

Would the retry_context/Attempt pattern be the way to do this? It would be great to have an example in the documentation, since this is common use case for making HTTP requests.

[hynek]

I have opened a PR in #125 -- I'm super sorry for the delays, I've had half-implemented solutions for months but never got it to the point of something releasable.

[danielballan]

Not at all! Thank you for considering the suggestion.

[danielballan]

I would be enthusiastic about a release with this new feature.

[hynek]

I really, really tried to get it out before my vacation but sadly life happened and I'm not comfortable to push a release from the beach not being able to fix stuff if I broke something.