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From Justin Erenkrantz <jus...@erenkrantz.com>
Subject Re: The Byterange filter -- a new design -- feel free to rip it to shreds
Date Sun, 01 Aug 2004 09:41:48 GMT
--On Tuesday, July 13, 2004 10:35 AM -0500 "William A. Rowe, Jr." 
<wrowe@rowe-clan.net> wrote:

> The confusion results because mod_proxy isn't implemented as a content
> handler, it's a protocol handler in its own right.  Rather than insist on the
> mod_http <> mod_proxy agreeing to streamline the response, we've put
> it on every content module author to:
>
> . remove output C-L header if the size is transformed
> . remove input range headers if the content isn't 1:1 transformed
>
> This is very kludgy and more an example of where mod_http <> mod_proxy
> didn't quite get it right, and made it a little more difficult for folks who
> are just trying to transform content bodies.
>
> It would be nice in apache 2.2 to finally clean up this contract, with two
> simple metadata element to pass through the filter chain:
>
> . this request is unfiltered
> . this request has a 1:1 filter (stateless)
> . this request has a arbitrary content transformation
>
> Each filter is the stack could promote the complexity but should never set
> it to a lower state.  This would allow http/proxy modules to negotiate less
> complex transformations in more efficient ways.

Reading the Byterange thread now, I see what OtherBill's position was. 
Tossing the C-L and Range metadata from the filters is a definite good thing. 
They just shouldn't know about that metadata.  ++1 there.

But, I'm not convinced that the benefit gained by allowing some byte-range 
optimization is going to be worth it.  As soon as you stick in mod_include 
and/or mod_deflate, you're going to have the ability to have arbitrary content 
transformation.  Even EBCDIC character conversions is not one-to-one.  In 
fact, I bet the number of filters that do a 1:1 transformation (that aren't 
logging) is small.  So, the number of cases where it isn't arbitrary would be 
extremely miniscule.  Yet, perhaps I'm wrong here...  -- justin

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