Re: 103 Early Hints

I'm strongly in favor of updating the doc and moving out of experimental.

I'm on the fence for the client advertising the acceptance of EH even
though it's not strictly required for 1xx response codes. It's already
suggested to only be used over HTTP/2+ contexts to reduce the risks of
client and middle-box incompatibility but there have been some hiccups with
clients not correctly ignoring 1xx responses that they don't understand.
Advertising acceptance of early-hints would reduce the compatibility
concerns (though still leaves incompatible middle-boxes in play) but it
also doesn't encourage fixing broken clients (which would mean likely
needing an opt-in for any other future 1xx responses).

On Sat, Jun 10, 2023 at 3:13 PM Lucas Pardue <lucaspardue.24.7@gmail.com>
wrote:

> Hi folks,
>
> RFC 8297, defining 103 Early Hints was published in 2017. It's been a bit
> of a sleeper hit, in the last 18 months or so we've seen uptake and
> deployment on client and server sides.
>
> As is natural, we've been gaining experience through deployment. Helping
> to identify the areas with Early Hints helps, and areas where there might
> be some possible tweaks. One example is that it isn't always useful to emit
> a 103 Early Hint in response to every request that is received, because the
> client's processing context would ignore it.
>
> Client Hints (RFC 8942) has some text that deals with considerations we
> are now learning about Early Hints. For instance, a server could emit an
> Accept-CH header, and Section 5 of RFC 8942 describes considerations for
> the cost of sending Client Hints.
>
> After some chatter on Twitter the past week, a few different people
> suggested that something like an Accept-EH request header field might be
> useful to help clients to indicate when Early Hints are useful or not. If
> we made this a list of field names, it could allow some tailoring of the
> emission and content of the hints.
>
> My thinking was maybe its time to upgrade Early Hints from experimental
> and roll in some of the learnings / proposals into the update document.
>
> Thoughts?
>
> Cheers,
> Lucas
>