I tried backporting https://gerrit.wikimedia.org/r/190375 during a SWAT window earlier tonight and it appeared to work fine, except I had forgotten that there needed to be a config patch associated with the patch, so it ended up queuing LocalGlobalUserPageCacheUpdateJob's on every single wiki. When this happens, the job runner goes into a tight loop and spams the exception log that the job class doesn't exist (T87398)

The GlobalUserPage updates have been reverted, and Ori deleted the keys out of redis to get the job runner to drop those jobs. labswiki is still complaining about DBConnectionError's though.