Re: accessing cached objects direct from the cache

From: Henrik Nordstrom <>
Date: Thu, 19 Mar 1998 23:28:26 +0100

George Michaelson wrote:

> We've come up with a scheme to re-use the objects in the cache
> explicitly from the cache. It depends on exposing the hash function
> from the URL so a client can put in a GET cache_object: request in
> some efficient manner to let the cache send back the specific object.
> This has some 'social engineering' consequences, like bypassing the
> cookie and other access control on the real object. None-the-less,
> the data is in the cache, its known to be in the cache, and it could
> be bloody useful to be able to 'see' it direct from the cache.

This kind of operation is already defined in HTTP 1.1.

Cache-Control: only-if-cached

RFC 2068, section 14.9 (Cache-Control:)

   In some cases, such as times of extremely poor network connectivity,
   a client may want a cache to return only those responses that it
   currently has stored, and not to reload or revalidate with the origin
   server. To do this, the client may include the only-if-cached
   directive in a request. If it receives this directive, a cache SHOULD
   either respond using a cached entry that is consistent with the other
   constraints of the request, or respond with a 504 (Gateway Timeout)
   status. However, if a group of caches is being operated as a unified
   system with good internal connectivity, such a request MAY be
   forwarded within that group of caches.

I don't think this is implemented in Squid yet, but it should be quite
trivial to implement.. ;-)

Henrik Nordström
Sparetime Squid Hacker
Received on Thu Mar 19 1998 - 15:05:06 MST

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