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[Bug 4998] Validator sometimes uses cached content (cache-control header on requests would be useful)

From: <bugzilla@wiggum.w3.org>
Date: Mon, 03 Sep 2007 12:42:14 +0000
To: www-validator-cvs@w3.org
Message-Id: <E1ISBFu-0001fV-1E@wiggum.w3.org>


------- Comment #2 from bugs@timj.co.uk  2007-09-03 12:42 -------
This can be easily reproduced by:

* placing any caching proxy (e.g. Squid) in reverse proxy mode in front of a
* requesting validation of a page on that site
* changing the content of the page which was validated
* re-requesting validation within the time period for which the page is cached
(according to HTTP rules) by the intermediate proxy

The cache is not misbehaving by returning cached content (as long as it's in
accordance with HTTP rules, for example based on Expires, Cache-control or
other headers in the response) in the absence of an explicit request from the
client (the Validator) to force a freshness check; it's doing exactly what it's
supposed to do. And neither is the Validator actually misbehaving.  The point
is that with the current HTTP request headers from the Validator, it's
acceptable (under some circumstances) for an intermediate cache to return a
cached representation. BUT, the point is that the user will generally not want
to validate cached content, so adding the Cache-Control header to the request
would make the Validator work more intuitively. (On reflection it should
probably be "Cache-control: no-cache", although the practical effect should be
Received on Monday, 3 September 2007 12:42:18 UTC

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