[whatwg] AppCache can't serve different contents for different users at the same URL

[Aryeh Gregor]

On Mon, Aug 3, 2009 at 4:20 AM, Mike Wilson<mikewse at hotmail.com> wrote:
> A problem with this is that it will treat all cookies for
> the page in one lump. In 1997 there was a proposal for
> identifying individual cookies, f ex:
>  Vary: Cookie.USERID
> or
>  Vary-Cookie: USERID
> but it seems it was dropped. Anyway, maybe it is
> interesting to reread the discussion to find correlations
> to current AppCache topics:
> http://lists.w3.org/Archives/Public/ietf-http-wg-old/1997MayAug/0334.html

FWIW, Wikimedia uses a non-standard X-Vary-Options header for exactly
this purpose, which they've patched Squid to recognize.  Of course,
since it's non-standard it only benefits their own reverse proxies,
not any regular proxies that might be used elsewhere (unless those
happen to be running the patched Squid for some reason).  Varying on
Accept-Encoding is very useful for cache hit rate as well.

Reference: http://www.mail-archive.com/squid-dev@squid-cache.org/msg07066.html