RE: default cache_stoplist question

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Hi Jon. We've met, albeit a long time ago and only briefly (in the
Mond room if you must know) :-).

The problem is that GETs aren't guaranteed to be idempotent and POST
isn't used, because POST is only really for filling in forms, rather
than just navigating around things. So if you just want to go to a
URL which must, for whatever reason, produce dynamic data, you can
just enter the URL rather than go to a URL and then press a button to
submit a form which returns the data you want.

Similarly, things like imagemaps just couldn't be done with POST (at
least not with the current browser standards), and although indeed in
most cases, the result of clicking on an image _could_ be cached, it
would be a) pointless, because if someone clicked on the same icon,
but one pixel away it wouldn't know to use the cached copy, and b)
its difficult to tell between when the output should and should not
be cached.

squid doesn't cache cgi-bin and ? because these are the most common
methods of showing that something is a dynamically-generated page in
the URL. Other methods using HTTP headers exist, but are more
difficult to use, and aren't portable between different brands of web
server, so users tend not to use them.

Hope this answers your question :-).

Jonathan L.

Origin, 323 Cambridge Science Park,Cambridge,UK. Tel:+44 (1223)
423355
 ---[ It is impossible to enjoy idling thoroughly unless one has ]---
 ------------[ plenty of work to do - Jerome K. Jerome ]-------------
Fight spam! http://spam.abuse.net/ These opinions are all my fault

- ----------
From: Jon Peatfield
Sent: 16 October 1997 00:36
To: squid-users@nlanr.net
Subject: default cache_stoplist question

Can someone explain to me (in short words) why the default squid
cache_stoplist contains '?' (and 'cgi-bin' for that matter)?

As I understand http a GET request is always idempotent, so can be
cached
unless for some reason the server knows best (in which case it should
say so).
 If a request can case a change of state in the server then it ought
to use
POST.

Which sites would cause problems if I set this to allow everything to
be
cached?

[ As an aside why do so many sites use POST for things which would
work happily
  as
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Received on Thu Oct 16 1997 - 06:41:17 MDT