[Mod_gzip] "mod_gzip_send_vary=Yes" disables caching on IE? (1.3.26.1a)

[Robert Collins]

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On Sat, 2002-12-07 at 11:36, Jordan Russell wrote:
> > > Could mod_gzip suppress the "Vary: Accept-Encoding" header when sendi=
ng
> back
> > > uncompressed data? That seems like the perfect "solution".
> >
> > This is even as bad as not sending Vary headers.
>=20
> The only reason mod_gzip is sending Vary headers in the first place is to
> prevent Squid from sending back compressed pages to clients that can't
> handle it, right?

Or netapp. Or ISA Server. Or wingate. Or <name any http cache>.

> With my proposed change, mod_gzip would still be sending Vary headers whe=
n
> sending compressed data. So Squid should still "know" not to send the
> compressed pages to clients that can't handle them. (Correct me if I'm
> wrong.)

It will mean that you are varying your response based on different
headers each time, as far as HTTP clients know, which will confuse the
heck out of them.
=20
> > In a office using a
> > proxy and some UAs not capable to handle compressed content, the
> > compressed version perhaps would never been send (uh, my English seems
> > to be very bad, I'm sorry).
>=20
> (Sorry, I don't understand what you mean here...)

If you don't issue vary on the first response, then the cache will cache
it in it's uncompressed form and give it to all the clients, even those
that can handle it compressed.

Whats worse is when the cache then recieves a compressed version it will
drop the uncompressed version because the Vary line is different. THEN
the next client that can't do compression will cause a new upstream
request. And that response will eject the compressed one from the cache,
because the Vary line is different.

Rob


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