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From Manuel Lemos <>
Subject [users@httpd] Re: Preventing mod_deflate dechunking of dynamic content
Date Tue, 19 Sep 2006 05:01:08 GMT

on 09/18/2006 10:36 AM Joshua Slive said the following:
>> So I need to find another way of signaling mod_deflate/mod_gzip to not
>> dechunk the response.
>> I think I could emit a custom response header like "x-dechunk: no" or
>> something else as a flag to prevent dechunking.
>> However, I do not know how to configure mod_deflate/mod_gzip to act upon
>> that flag. Anybody has any ideas?
> I don't think you are looking at this from the right perspective.  The
> decision to use chunked encoding or not happens at a different level
> than the mod_deflate decision.  My guess is that you are not seeing
> chunking because mod_deflate needs to accumulate a bunch of content
> before compressing it in order to get the optimal compression.  This
> is controlled by the DeflateBufferSize directive.  If it happens to
> get the entire response, then the optimal decision for the chunking
> layer is to send the known content-length, rather than chunking the
> response.
> You could try reducing DeflateBufferSize, in which case it is more
> likely that incomplete responses (with unknown total content length)
> will be sent to the chunking layer, hence resulting in chunked
> responses to the client.

Joshua, thank you for the insight.

What I really need is to be able to force chunked response only on
specific requests to PHP scripts.

If it is not possible or desirable to serve compressed chunked
responses, then what I need to be able to force uncompressed chunked
responses on specific requests.

I know how to disable mod_gzip/mod_deflate for specific URI. However,
that is not what I want because I need to serve chunked responses or not
for requests to the same URI, depending on conditions evaluated
dynamically by the PHP scripts.

So, my doubt is: how can I configure Apache to return a response that
may trigger chunking/compression or not that mod_gzip/mod_deflate performs ?

I though of returning a custom header like "x-dechunk: no" from the PHP
script response. But how can I configure Apache with
mod_gzip/mod_deflate to not compress responses when that header is
returned by a PHP script?

Any other solution?


Manuel Lemos

Metastorage - Data object relational mapping layer generator

PHP Classes - Free ready to use OOP components written in PHP

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