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Re: proxy algorithms

From: Yves Lafon <ylafon@w3.org>
Date: Tue, 12 May 1998 10:25:00 +0200 (MET DST)
To: Roman Dusek <dusek@club.cz>
cc: Jigsaw conference <www-jigsaw@w3.org>
Message-ID: <Pine.GSO.3.96.980512092445.13267D-100000@tarantula.inria.fr>
On Sun, 10 May 1998, Roman Dusek wrote:

> Hi,
> I would like to place my own algorithms into Jigsaw (acting as proxy)
> instead of contemporary heuristics and clean-up algorithms (I can be more
> specific if somebody is interested). I've spent many hours examining the
> way request is processed and response generated from cache or received from
> origin server, but I'm still not sure about the principle enough.
> Can anybody describe the way caching (hit/mis/revalidation) is performed in
> the structure of Jigsaw?

Well, I will try to make it short and if you want more details on some

There are two ways of doing filtering in Jigsaw, the server side filtering
and the client side filtering.
As the cache is a client thing, everything is done in a client side
The processing of a client side filter is the following:
1/ incoming filters
2/ request processing
3/ if the request fails (exception due to a network pb)
   -> exception filters
4/ outgoing filters

The cache use step 1 and 4,
at step 1 the cache tries to get the version from the cache
If the resource is not found, the request is processed.
And at step 4, the reply is cached according to the indication given by
the target server (If none, the default caching time is 1 day) 

If it is found in the cache, it serves the resource if it is fresh enough,
otherwise it tries to revalidate it.
In case of a revalidation the caching informations are updated.
For more details, you can read the "caching" section of the HTTP/1.1 spec
see http://www.w3.org/Protocols

> Thanks a lot in advance,
> R. Dusek

      /\          - Yves Lafon - World Wide Web Consortium - 
  /\ /  \                Architecture Domain - Jigsaw
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Received on Tuesday, 12 May 1998 04:25:21 UTC

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