Re: mod_proxy_html, HTML rewrite and content compression

Thomas Eckert <Thomas.Eckert@xxxxxxxxxx> · Fri, 16 Nov 2012 11:31:38 +0100

On 11/14/2012 06:12 PM, Nick Kew wrote:

On 14 Nov 2012, at 15:53, Thomas Eckert wrote:

Is there a way to work around this ? I do want the call to mod_xml2enc to happen but I also want the reverse proxy to support content compression.

That's a lot of correct analysis.

The output chain you want is INFLATE;xml2enc;proxy-html;DEFLATE .
What problems do you encounter (apart from processing overhead)
when you set all that?

I guess ideally ProxyHTMLEnable should detect compressed content
and insert INFLATE where necessary.  Maybe even have an option to
set DEFLATE.  But as of now it doesn't: I got the impression most
users prefer to disable compression, and avoid the substantial
processing overhead of zipping in a proxy.

Thanks for the hint but unfortunately "manually" adding xml2enc to the 

filtering chain does not help. The output is still broken. One thing I 

noticed was the "DEFLATE" filter is not necessary, since apache will do 

the compression anyway (even though I removed "AddOutputFilter text/html 

DEFLATE" from my global config). That's why it's not present below.

Here are some debug log extracts which confuse me. Note, I patched 

mod_proxy_html.c with a one-liner to get me "Running proxy_html_filter" 

into the log, otherwise mod_proxy_html only gives feedback in error 

situations and I wouldn't be able to defer from the log when 

mod_proxy_html is running.

    "SetOutputFilter INFLATE;proxy-html" gets the page displayed correctly

[pid 14245:tid 2714090352] proxy_util.c(1998): AH00943: http: has 

released connection for (vhost01.backend03.local)

[pid 14245:tid 2714090352] mod_deflate.c(1283): [client 

10.10.10.10:40375] AH01398: Zlib: Inflated 348 to 674 : URL /

[pid 14245:tid 2714090352] [client 10.128.128.60:40375] Running 

proxy_html_filter

[pid 14245:tid 2714090352] mod_deflate.c(763): [client 

10.10.10.60:40375] AH01384: Zlib: Compressed 655 to 342 : URL /

< customized log message from LogFormat+CustomLog appears here >

    "SetOutputFilter INFLATE;xml2enc;proxy-html" results in "curl: (52) 

Empty reply from server"

[pid 15039:tid 3007834992] proxy_util.c(1998): AH00943: http: has 

released connection for (vhost01.backend03.local)

[pid 15039:tid 3007834992] mod_deflate.c(1283): [client 

10.10.10.10:40388] AH01398: Zlib: Inflated 348 to 674 : URL /

[pid 15039:tid 3007834992] mod_xml2enc.c(183): [client 

10.10.10.10:40388] AH01430: Content-Type is text/html

[pid 15039:tid 3007834992] mod_xml2enc.c(259): [client 

10.10.10.10:40388] AH01434: Charset ISO-8859-1 not supported by libxml2; 

trying apr_xlate

[pid 15039:tid 3007834992] mod_xml2enc.c(463): [client 

10.10.10.10:40388] AH01439: xml2enc: consuming 674 bytes from bucket

[pid 15039:tid 3007834992] mod_xml2enc.c(490): [client 

10.10.10.10:40388] AH01441: xml2enc: converted 674/674 bytes

[pid 15039:tid 3007834992] [client 10.10.10.10:40388] Running 

proxy_html_filter

[pid 15039:tid 3007834992] mod_deflate.c(763): [client 

10.10.10.10:40388] AH01384: Zlib: Compressed 655 to 342 : URL /

[pid 15039:tid 3007834992] mod_xml2enc.c(463): [client 

10.10.10.10:40388] AH01439: xml2enc: consuming 10 bytes from bucket

[pid 15039:tid 3007834992] mod_xml2enc.c(490): (22)Invalid argument: 

[client 10.10.10.10:40388] AH01441: xml2enc: converted 1/1 bytes

[pid 15039:tid 3007834992] [client 10.10.10.10:40388] AH01444: Skipping 