https://bugzilla.wikimedia.org/show_bug.cgi?id=28069
Summary: MediaWiki fails streaming files when mod_deflate and
ob_gzhandler are also set ("Content-Encoding: ,
gzip")
Product: MediaWiki
Version: 1.18-svn
Platform: All
URL: http://thread.gmane.org/gmane.org.wikimedia.mediawiki/
36969
OS/Version: All
Status: NEW
Severity: normal
Priority: Normal
Component: General/Unknown
AssignedTo: [email protected]
ReportedBy: [email protected]
Dan Nesset reports in mediawiki-l that when serving files from ConfirmAccount,
the response contains "Content-Encoding: , gzip", which "befuddles
some browsers, such as FF, IE and Safari and they fail to decompress the
file."
This comes as a combination of mod_deflate, PHP's 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).
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