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Reply-To: dev@httpd.apache.org
Subject: Re: mod_cache and multiple brigade
From: Brian Pane <brian.pane@cnet.com>
To: dev@httpd.apache.org
In-Reply-To: <3DD38AFF.1080406@ifrance.com>
References: <3DD38AFF.1080406@ifrance.com>
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Date: 15 Nov 2002 13:00:10 -0800
Message-Id: <1037394011.3935.4.camel@desktop>
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Thanks for all the diagnostic information.  I'll set aside
some time to take a look at the problem this weekend if nobody
else gets to it first.

Brian

On Thu, 2002-11-14 at 03:37, Estrade Matthieu wrote:
> Hi,
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> i will quickly draw the problem i found 1 month ago:
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> When i am with apache + mod_proxy + mod_cache
> client --> reverse_proxy_cache --> backend.
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> when the client ask for a document which will be handled with multiple=20
> brigade, the first time when mod_cache is caching the document, the=20
> client browser is able to display the document.
> When the client ask again the document, mod_cache serve it from cache=20
> and the client browser refuse to display it.
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> I found it was because the client browser received Content-Length header=20
> and Transfer-Encoding=3Dchunked header at the same time.
> I put debug in mod_proxy and mod_cache, and i found:
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> when the backend answer the first request to multiple brigade handled=20
> document:
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> backend
> -
> mod_proxy: content_length=3Dsize, no transfer-encoding headers and=20
> r->chunked =3D0.
> mod_proxy: delete content-length and Transfer-encoding headers.
> http_protocol.c: ap_set_keepalive don't find CL or TE headers so:=20
> r->chunked=3D0 at beginning, r->chunked =3D1 when ending.
> http_protocol.c: ap_http_header_filter find r->chunked=3D1 so: add header=
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> "Transfer-Encoding"=3Dchunked
> mod_cache: find Transfer-Encoding=3Dchunked headers and store it in memor=
y.
> mod_cache: know the length of data he stored in memory and and the CL=20
> header with length of data
> -
> client
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> When the backend answer the second request to multiple brigade handled=20
> document:
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> rp+cache
> -
> mod_cache:cache_out:read_ headers: read headers from what he stored in=20
> memory
> mod_cache:cache_out: send the two headers, CL and TE
> -
> client: refuse to display or use document he received.
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> On a unique brigade handled document, the ap_set_keepalive find the=20
> connection closed, so he don't put the r->chunked =3D 1 and it's working =
fine.
> The problem is only on multiple brigade handling document
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> To make my mod_mem_cache work, i did this ugly patch, removing the=20
> TE-header from headers stored in memory.
> It was working, but with ugly method.
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> Why mod_proxy is deleting this Content-length header, i understand for=20
> the TE, because the setkeepalive and http_headers_filter compute this=20
> header, but why the content_lentgh is deleted ?
> I removed the CL deleting line in the proxy_http.c code and it's now=20
> working well, but i understand this line may be usefull, so i will=20
> search how to resolve the problem better.
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> i hope you understand the problem, my english is not really good
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> regards,
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> Estrade Matthieu
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=20
> Haut d=E9bit =E0 partir de 30 euros/mois : http://www.ifrance.com/_reloc/=
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