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From Erik Abele <e...@codefaktor.de>
Subject Re: need an idea :)
Date Sat, 06 Sep 2003 21:33:08 GMT
On 06/09/2003, at 01:41, André Malo wrote:

> mod_deflate docs
> (<http://httpd.apache.org/docs-2.0/mod/mod_deflate.html#recommended>) 
> give
> this example config:
>
> # Don't compress images
> SetEnvIfNoCase Request_URI \
> \.(?:gif|jpe?g|png)$ no-gzip dont-vary
>
> # Make sure proxies don't deliver the wrong content
> Header append Vary User-Agent env=!dont-vary
>
> The problem is that a lot of people don't read carefully enough and 
> seem to
> assume that dont-vary is a magic variable, recognized by the httpd or 
> the
> like. Any idea how (where?) to clarify that misunderstanding better?

Ahh, I see. Perhaps we can pick up the 'Header append' part from the 
example config and further explain it in the 'Dealing with proxy 
servers' section below.

just a quick shot but for example:

---
The following directive and especially the test against the 'dont-vary' 
environment variable, taken from the example configuration above, is 
needed to explicitly tell the server to only append the Vary: 
User-Agent header when serving one of the (possibly) compressed 
resources and to omit it for always excluded files (in the given 
example configuration the GIF, JPEG and PNG files).

     # Make sure proxies don't deliver the wrong content
     Header append Vary User-Agent env=!dont-vary

Be sure to include the additional test when dealing with a similar 
setup, otherwise the 'dont-vary' variable won't be recognized by the 
server and a Vary: User-Agent header will be appended to every 
response. As a result, any involved proxy or cache server would have to 
unnecessarily request and store two or more copies of the same file, 
depending on the client request conditions; in the mentioned example 
configuration the GIF, JPEG and PNG files depending on the user agent 
used.
---

> Thanks, nd

HTH.

Cheers,
Erik


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