Re: Clarification on Alternative Service Connection Failures

On Fri, Sep 29, 2017 at 6:27 AM, Patrick McManus <mcmanus@ducksong.com>
wrote:

> The text is referring to any failure - the client MAY want to try a
> different alternative in that case. Its just saying don't feel pinned down
> by an Alt-Svc announcement just because you started to use it - you can
> always use a different one (or the default) if you think it would work
> better. A 500 seems a reasonable input to that choice to me.
>

​Wow, really? Hm. While I understand your reasoning here, I don't love it.
It seems like we might want to have more concrete advice to browsers about
what kinds of failures should count as a failure. Otherwise we'll end up
with different behavior in different browsers for no terribly good reason.
For example, what about 4xx errors? Should all 4xx and all 5xx errors
count? What behavior should servers be able to count on? Is it "safe" to
advertise an alternative which is not current reachable (I think so). What
about one which 404s for all requests, or one which 500s every request?
Should this be considered "safe" for a server to advertise?

I'm not sure I have a terribly well thought out idea here, but this makes
me a bit nervous.