On May 17, 2013, at 6:49 AM, Wendy Roome <[email protected]> wrote:
> I assume you're referring to {13.2} of RFC 2616. That section strikes me as
> "a royal kludge." (Privately I'd apply a much stronger adjective, but I'm too
> much of a lady to use such language in public.)
>
> The problem is that HTTP defines multiple ways to declare expiration times --
> Expires header, cache directives, etc. Those mechanisms have evolved over
> time, and not all servers use them consistently. So I think {13.2} is mostly
> about how to cope with legacy HTTP servers and missing or inconsistent
> information.
>
> Since we're starting fresh, why not just say that if an ALTO server wants to
> indicate a polling interval, it SHOULD set the Expires and the Date headers,
> and the client SHOULD use the difference as the approximate polling interval?
My suggestion: Give up on cache headers.
Rather, all fetches should use a CACHE-busting NONCE (if you are behind an
in-path web cache, there is a ~50% chance the cache is busted and will provide
stale data, EVEN IF the server's headers say "don't cache this at all"), and
any signaling to the client about what rate it should poll should be explicit
in the protocol for the Alto data, not implicit using HTTP headers.
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