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Re: draft-ietf-httpbis-p6-cache-06

From: Mark Nottingham <mnot@mnot.net>
Date: Tue, 2 Jun 2009 14:00:23 +1000
Cc: "'Thomas Broyer'" <t.broyer@gmail.com>, "'HTTP Working Group'" <ietf-http-wg@w3.org>
Message-Id: <CAEAD5AE-6342-4015-8CF1-C526270E35E5@mnot.net>
To: Brian Smith <brian@briansmith.org>

On 28/05/2009, at 1:31 AM, Brian Smith wrote:

> Thomas Broyer wrote:
>> Brian Smith <brian@briansmith.org> wrote:
>>> It's not invalid, but it doesn't mean anything. POST responses are
>>> never cacheable; caches must write POST requests through to the
>>> server, and a cache can't use a POST response to respond to a
>>> GET/HEAD request.

2616 says:
> Responses to this method are not cacheable, unless the response  
> includes appropriate Cache-Control or Expires header fields.



>> Even when the POST response has a Content-Location?
>
> There's nothing in RFC2616 or the latest HTTPbis drafts that says a  
> cached POST response can be returned in response to a GET/HEAD  
> request.

No, but there is accommodation for it; see p6 2.1 and 2.2, in  
particular the TODO note in the latter.


> Applying Postel's rule, a cache shouldn't return a cached POST  
> response to a GET/HEAD request, and servers shouldn't include Cache- 
> Control/Expires headers in POST responses. That should be explicit  
> in the specification.

There has been considerable discussion on this, and your conclusion  
wasn't suggested AFAIK, nor was it the direction we've chosen to move  
in. See:
    http://trac.tools.ietf.org/wg/httpbis/trac/ticket/139
    http://www.w3.org/mid/08345F97-7D4D-40AD-98E2- 
EF73E93C031F@mnot.net (entire thread)



--
Mark Nottingham     http://www.mnot.net/
Received on Tuesday, 2 June 2009 04:01:00 GMT

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