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From Rainer Sabelka <sabe...@iue.tuwien.ac.at>
Subject Re: [users@httpd] Use Apache for compression offloading
Date Tue, 24 Jun 2008 10:05:03 GMT
On Tuesday 24 June 2008 09:22:47 André Warnier wrote:
> Hi.
>
> I'm not a specialist of that kind of thing, but I'm curious and I just
> wonder about the following kind of scenario :
>
> - In the proxy server, unset the Accept-encoding header, but set another
> non-standard one (or an environment value) that will not be recognised
> by the back-end server
> - condition the SetOutputFilter DEFLATE by this other header/value
> - do the proxying.

Hm. I think the check for the Accept-encoding header is hard-coded in 
mod_deflate. No matter if I SetOutputFilter DEFLATE conditionally or 
unconditionally, the filter won't compress the output as soon as I unset the 
Accept-encoding header.

> The back-end server will not get the Accept-encoding
> header.  Instead it will get the new header you set, but will not react
> to it, so not do compression.
> - but the front-end server still will

> I think that mod_sentenvif and/or mod_rewrite should allow you to do the
> above.  Someone else would have to give you the specifics though.
>
> André
>
> Rainer Sabelka wrote:
> > Hi,
> >
> > I try to use apache (version 2.2.8 on Ubuntu 8.04) for compression
> > offloading. What I want to do:
> > - use mod_proxy to forward all requests to the application server
> > - use mod_deflate to compress the output
> > - remove the "Accept-Encondig:" header from the client's request before
> > sending it to the application server to avoid that the compression is
> > done there.
> >
> > My frist approach didn't work:
> >
> > <VirtualHost *:80>
> >     ServerName www.example.com
> >     <Proxy *>
> >          Order deny,allow
> >          Allow from all
> >     </Proxy>
> >     ProxyRequests Off
> >     ProxyPass / http://realserver:80/
> >     ProxyPreserveHost on
> >     RequestHeader unset Accept-Encoding
> >     SetOutputFilter DEFLATE
> > </VirtualHost>
> >
> > The problem with this approach: when I use "RequestHeader unset Accept-
> > Encoding" then the application server gives me uncompressed output (good)
> > but also mod_deflate won't comress the output (bad).
> >
> > So, this is my second approch, which actually works, but I think is a bit
> > an over-kill:
> >
> > <VirtualHost *:80>
> >     ServerName www.example.com
> >     <Proxy *>
> >          Order deny,allow
> >          Allow from all
> >     </Proxy>
> >     ProxyRequests Off
> >     ProxyPass / http://localhost:8000/
> >     ProxyPreserveHost on
> >     RequestHeader unset Accept-Encoding
> >     SetOutputFilter DEFLATE
> > </VirtualHost>
> >
> > <VirtualHost localhost:8000>
> >     ServerName www.example.com
> >     <Proxy *>
> >          Order deny,allow
> >          Allow from all
> >     </Proxy>
> >     ProxyRequests Off
> >     ProxyPass / http://realserver:80/
> >     ProxyPreserveHost on
> >     RequestHeader unset Accept-Encoding
> > </VirtualHost>
> >
> > Here I have 2 instances of apache in proxy-mode connected in series. The
> > first one forwards the request to the second one and does the compression
> > of the output. The second instance just removes the Accept-Encoding
> > header before it forwards the request to the application server.
> >
> > But I think there must be a an easier solution. Has any body an idea how
> > to get this working with only a single instance of apache?
> >
> > Thanks,
> > -Rainer
> >
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