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Re: Proposal for i23: no-store invalidation [#117]

From: Mark Nottingham <mnot@mnot.net>
Date: Thu, 31 Dec 2009 10:01:23 +1100
Cc: Henrik Nordstrom <henrik@henriknordstrom.net>, HTTP Working Group <ietf-http-wg@w3.org>
Message-Id: <D5E7864C-A193-4D97-8E8A-6A5AA16C35CB@mnot.net>
To: Jamie Lokier <jamie@shareable.org>
Agreed. My personal .02 is that there shouldn't be a requirement at all; we'd be too likely to make an existing implementation non-conformation, for dubious gain.

I do think we need to examine the existing HEAD requirement, as it doesn't make it clear as to which cache entry to mark stale. I'm wondering if we could reword it to say that a HEAD response can be cached as a partial response, thereby having the same effect as invalidating the older responses...

On 31/12/2009, at 9:52 AM, Jamie Lokier wrote:

>   I think there is no satisfactory answer which offers useful
>   guarantees (in the HTTP cache model), just as there is no way for
>   invalidation-due-to-newer-response to offer useful guarantees to
>   clients because they may connect via different caching proxies.
>   Because there are no useful guarantees, there is probably no
>   benefit to making invalidation-due-to-newer-response a MUST level
>   requirement.  SHOULD or MAY might be useful practically, but there
>   is no technical benefit I can see for making it a MUST.  Clients
>   and servers must have other strategies to avoid problems due to old
>   cached responses, such as not using long cache times, using Etags
>   where it is important, or using content-dependent URIs in referring
>   documents.

Mark Nottingham     http://www.mnot.net/
Received on Wednesday, 30 December 2009 23:01:56 UTC

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