Iirc we originally used Content-encoding: identity but found this broke some clients. Probably worth pulling out the old bugs to check if the issue is still present.
-- brion On Mar 15, 2011 3:25 PM, "Platonides" Platonides@gmail.com wrote:
Dan Nessett wrote:
On Thu, 10 Mar 2011 01:29:15 +0100, Platonides wrote:
Looks very odd.
Do you get the same Content-Encoding if performing the from the squid? And if sent directly to the apache?
It was a good question. I hadn't tried to bypass squid. However, when I do, I get the same result.
Ok, I have been able to reproduce it. This comes as a combination of mod_deflate, ob_gzhandler and mediawiki.
When serving files, mediawiki clears any gzipping layer, including its own one. You seem to have at php.ini output_handler=ob_gzhandler. When mediawiki detects that ob_gzhandler is active, performs ob_end_clean() and does header( 'Content-Encoding:' ); in order to clean the Content-Encoding field (otherwise you would get plain data with header saying it's in gzip). Then, you also have mod_deflate into the mix. It detects an existing Content-Encoding header, and apr_table_mergen "merges" adding ', gzip' despite the header being empty.
Where is the bug? mod_deflate shouldn't concatenate if the field is empty. php could skip passing Content-Encoding to other modules if empty. MediaWiki could use the header( 'Content-Encoding: identity' ); instead of header( 'Content-Encoding:' );
How can _you_ fix it right now? You don't need having three compressing layers. I'd deactivate mod_deflate and output_handler=ob_gzhandler, letting mediawiki compress the pages automatically for you. Just disabling mod_deflate or output_handler=ob_gzhandler would work too, but note that keeping mod_deflate with your current configuration will compress streamed files, which is likely to be inefficient.
rfc2616 section 14.11 defines Content-Encoding header as "Content-Encoding" ":" 1#content-coding The #rule (see section 2) requires at least one content-coding to be present, which MediaWiki is currently violating (yes, the empty header does arrive at the user browser).
I have explicitely set the Content-Encoding as identity in r84060, using header_remove if available.
Opened it as bug 28069 https://bugzilla.wikimedia.org/show_bug.cgi?id=28069
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