nutcracker is running on silver/wikitech right now. It sometimes causes problems and in theory is contributing nothing at all.
We tried to simply remove it via wmf-config a few months ago but it caused failures. This needs a second more effective attempt.
This is the quick revert we did when ripping out nutcracker broke things:
https://gerrit.wikimedia.org/r/#/c/158238/1/wmf-config/CommonSettings.php
Simply removing mc.php results in
[Thu Jul 09 15:01:49.276847 2015] [:error] [pid 1496] [client 2620:0:861:119:d6ae:52ff:fe76:4515:38897] PHP Notice: Undefined variable: endpointURL in /srv/mediawiki/php-1.26wmf13/extensions/OpenStackManager/nova/OpenStackNovaController.php on line 836
Change 224087 had a related patch set uploaded (by Andrew Bogott):
Don't use nutcracker on wikitech
(from IRC):
godog: any particular reason why we're special casing wikitech with/without nutcracker btw?
andrewbogott: godog: mostly because nutcracker has failed a couple of times in the last couple of weeks. And also the wikitech use case is dumb — nutcracker is just a proxy so it’s not contributing anything.
andrewbogott: So it’s a choice between needless complexity in config vs. needless complexity of actually running software
To expand on that, I think that the failures we've seen with nutcracker on silver have manifested in production too, see also T105131: intermittent nutcracker failures though not as frequent. Still it'd be nice to get to the bottom of this
Wikitech is no longer using nutcracker for mediawiki. Nutcracker is still installed, though.
Is uninstalling it something we want to do? If so, is it part of this task? Will we want to revert this after T105131: intermittent nutcracker failures is fixed?
I'm ambivalent. Wikitech config differing from prod is bad, wikitech using a component that doesn't do anything is bad; either way we lose :)
everything else being equal I'm in the "symmetry wins" camp, IOW nutcracker in wikitech
@Andrew, you don't actually reduce complexity by not using nutcracker on wikitech; you simply shift it around and make it somebody else's problem. Right now, it is mine, because I need to make changes to how redis is configured in production for T111575, and the fact that wikitech is a special case is causing me all manners of headache.
Change 244347 had a related patch set uploaded (by Ori.livneh):
Revert "Don't use nutcracker on wikitech"
I noticed i had this comment i started to write once but never submitted: "Now we learned that sometimes it causes problems and sometimes doesn't and that wikitech is different from production again.", so yea..