Last modified: 2014-01-29 02:55:59 UTC
This can be reproduced by running: php /vagrant/mediawiki/tests/phpunit/phpunit.php --use-bagostuff=redis /vagrant/mediawiki/tests/phpunit/includes/objectcache/BagOStuffTest.php on https://gerrit.wikimedia.org/r/#/c/91138/ . I was able to eliminate the error by dropping RedisBagOStuff->incr (falling back on the parent's incr, lock, and unlock), but I'm not sure if that's an acceptable solution. This breaks the ping limiter (tested), and probably a couple other things (not tested), when Redis is the main cache (as it is with MediaWiki-Vagrant).
The reason it doesn't work is that the value gets written as e.g. "i:0;", and Redis can't increment that.
I don't think this is a bug with MediaWiki, because the RedisBagOStuff class does not do any serializing. That is handled by the underlying phpredis library. Then again, I don't have much experience with Redis, so I could be wrong.
To clarify, by "This breaks", I mean master, not the proposed fix (using the parent's).
It's a bug with how MW uses Redis and the libraries. We specifically request to use the PHP serializer *and* use Redis's INCR call (which does the increment on the server, rather than the client sending the new value); that's the conflict. See https://git.wikimedia.org/blob/mediawiki%2Fcore.git/d987f43b24a24a6f3fcd5886fedaf483fa3c6891/includes%2Fobjectcache%2FRedisBagOStuff.php#L58 and https://git.wikimedia.org/blob/mediawiki%2Fcore.git/d987f43b24a24a6f3fcd5886fedaf483fa3c6891/includes%2Fobjectcache%2FRedisBagOStuff.php#L297
Change 91296 had a related patch set uploaded by Mattflaschen: Fix Redis increment behavior https://gerrit.wikimedia.org/r/91296
Change 91296 merged by jenkins-bot: Fix Redis increment behavior by using BagOStuff->incr instead https://gerrit.wikimedia.org/r/91296
