TLDR: If you use $wgDebugLogGroups['profileoutput'] in LocalSettings.php as
a way to collect performance profiles from Tideways/XHProf, this will no
longer receive messages in MediaWiki 1.35 and later.
-------
Hi,
I've been auditing the Profiler component in MediaWiki and deprecating or
removing various legacy features that either don't fit the current model
very well and/or that seem to be broken, unused or undocumented. [1] The
objective here is to keep offering the same functionalities for developers,
but in a way that's easier to use, with fewer moving parts, and lower
maintenance costs for us.
Today I'm writing about the "profileoutput" debug log channel. As part of
the PSR-3/Monolog refactor many years ago, this feature was grandfathered
into the LegacyLogger.
The $wgProfiler variable controls which collector and output are used at
run-time. For example, you can collect the call graph with XHProf/Tideways,
and then output it to an HTML comment, or dump to a file on disk, etc. Any
number of outputs can be implemented and enabled.
The "profileoutput" debug log channel was effectively another way of
achieving the same thing, by assigning $wgDebugLogGroups['profileoutput']
to a file path.
If you're currently using this, see
https://phabricator.wikimedia.org/T245835 for how to make this work via
$wgProfiler instead.
-- Timo
[1]
https://phabricator.wikimedia.org/T231366