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

[Slava Bizyayev]

Vary is fully configurable in Apache::Dynagzip since version 0.07. I didn't
have a chance to investigate how it was fixed (or not) in mod_deflate after
the discussion I mentioned previously. They just had the similar problem,
and Apache::Dynagzip didn't. I guess it depends on how you create different
combinations of HTTP headers in your response.

When you wish to control the client side cache you would consider to provide
the appropriate Expires header first. You can set the lifetime of your
response in client's cache up to 1 year. This client will never bother you
again until the expiration date (unless the user hits the Refresh button
earlier).

Vary comes from some different requirements. All modern clients default to
plain (uncompressed) response. To activate the gzip decompression (for the
most of them) you would consider to provide the 'Content-Encoding: gzip'
accompanied with 'Vary: Accept-Encoding'. For the dynamic content it is
necessary to have something like 'Vary: *' sometimes. No 'Vary: User-Agent'
could be of interest of the real web client these days, because every
User-Agent creates the own cache to date (as far as I know).

Since we satisfied the client's requirements fully, we can look into
proxies' requirements (to minimize possible damage from them ;-). If we use
Vary combined with *, no one of them would ever cache our response. Even
Squid 2.5... You might wish to create some other behavior with proxies
sometimes, that's another story...

Thanks,
Slava


----- Original Message -----
From: "Jordan Russell" <jr-list-mod_gzip@quo.to>
To: <mod_gzip@lists.over.net>
Sent: Saturday, December 07, 2002 12:24 AM
Subject: Re: [Mod_gzip] "mod_gzip_send_vary=Yes" disables caching on IE?
(1.3.26.1a)


> Slava Bizyayev wrote:
> > I was lucky to demonstrate that Vary works fine (with M$IE)
> > even when you need to cache content locally. Apache::Dynagzip is using
> this
> > approach effectively.
>
> I checked the Apache::Dynagzip source code (I don't have mod_perl to test)
> and it appears that it only sends a Vary header when sending gzipped
> content. (Am I right?)
>
> > That was very similar issue with mod_deflate.
>
> I checked the mod_deflate and also the PHP source code and it appears they
> do it the same way -- no Vary header unless sending gzipped content.
>
> So it seems mod_gzip is alone in its sending of Vary headers for both
> gzipped and non-gzipped content?
>
> Jordan Russell
>
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