RE: Warning: header, need origin

I like this better than max-age=0 and must-revalidate. A browsert that
just obeys the max-age=0 can support the Cache-exception: 42 with 0
extra work.

>----------
>From: 	koen@win.tue.nl[SMTP:koen@win.tue.nl]
>Sent: 	Wednesday, April 10, 1996 12:32 PM
>To: 	masinter@parc.xerox.com
>Cc: 	fielding@avron.ics.uci.edu; koen@win.tue.nl; mogul@pa.dec.com;
>http-caching@pa.dec.com
>Subject: 	Re: Warning: header, need origin
>
>Larry Masinter:
>>
>>> must-revalidate is just a max-age=0 with a special warning attached.
>>> If you want to trade must-revalidate for a Warning: header code with
>>> the same semantics, I have no big problem.
>>
>>It seems that max-age=0 with a special warning attached is more
>>general, if not more useful, than must-revalidate.
>
>>So what's the "special warning"?
>
>If we split the special warning off
>
>  Cache-Control: must-revalidate
>
>we would get
>
>  Cache-Control: max-age=0
>  Warning: 42 Revalidation Essential
>
>or, if we rename Jeff's warning header because it can carry
>prescriptive codes:
>
>  Cache-Control: max-age=0
>  Cache-Exception: 42 Revalidation Essential
>
>We would then get a definition like this:
>
> 42 Revalidation Essential
>
>    Indicates that the revalidation of stale responses is essential
>    for the correct operation of the service offered by the origin
>    server.  Service authors can generate this exception code along
>    with a "Cache-Control: max-age=0" header to warn that a failure to
>    revalidate a request on the entity could result in significantly
>    incorrect operation, such as incorrect reporting on the nature of
>    a financial transaction about to be executed.
>
>    Proxy caches which fail to, or are unwilling to, revalidate a
>    response with this code MUST NOT return a stale response with a 13
>    (?) (revalidation failed) exception code, but MUST return a 504
>    (Gateway Timeout) error response.  User agent caches failing to
>    revalidate a response with a 42 (Revalidation Essential) code MUST
>    also return a 504 (Gateway Timeout) error response.  
>
>    User agent caches which are configured to return stale responses
>    because of severe connectivity constraints SHOULD return a 504
>    error response instead of a stale response with a 42 (Revalidation
>    Essential) code, but MAY also, if specifically configured to allow
>    this, return the stale response accompanied by a clear warning
>    that the service author cannot guarantee correct operation of the
>    service under these caching conditions.
>
>> Is there some risk that the warning
>>would get ignored when 'must-revalidate' would not?
>
>I don't think so.  I'd be happy with this being a special warning.
>
>Koen.
>

Received on Wednesday, 10 April 1996 20:51:08 UTC