AuthManagerStatsdHandler is in WikimediaEvents, which is now not loaded on closed wikis, resulting in a missing class error. A quick & dirty fix is in https://gerrit.wikimedia.org/r/#/c/342778/. For a proper fix, the options that have been raised and their drawbacks:
- disable AuthManager stats on closed wikis (ie. just keep the current fix). These are SUL wikis so they might still be abused in ways that the auth stats are intended to monitor (e.g. spambot registration).
- re-enable WikimediaEvents on all wikis, use some config flag to disable the rest of its features. The main reason for disabling it was to not load unnecessary JS; just defining a ResourceLoader module results in JS being loaded (not the module itself, but the module definition); conditionally defining the module would require moving the module definition from JSON to PHP, which is the opposite of how we want our configuration in general.
- move AuthManagerStatsdHandler to operations/mediawiki-config. That repo is not well prepared for holding classes (although it does contain a few): there are limitations to testing (both in CI and locally), the code update workflow becomes more awkward, and code outside the mediawiki/ repo tree is easier to miss when doing deprecations.
- move the class to another extension, possibly a new one. The other existing WM extensions (WikimediaMessages and WikimediaMaintenance) don't really make sense, and creating a new extension is a lot of overhead.