I was using MediaWiki 1.30.0 downloaded from https://releases.wikimedia.org/mediawiki/1.30/mediawiki-1.30.0.tar.gz when I first reported this. I've since moved on from that job and no longer have access to the server in question, so I can't tell you if the problem still manifests after your recent patches. Sorry :-( But thanks for making those improvements! I think it's perfectly reasonable to close this, in light of those changes.

Thanks for working on this, @aaron. I'm not familiar with the Mediawiki source code but your change seems reasonable to me. Assuming I understand this correctly, could I suggest updating https://www.mediawiki.org/wiki/Manual:$wgDBservers and/or https://www.mediawiki.org/wiki/Manual:$wgDBname and mentioning that $wgDBname should be set even if $wgDBservers is used? And that they should have the same value? I think that would have helped me. It looks like I probably have access to update those pages, but I think you'd probably do a better job since you're familiar with the rationale behind the requirement.

Thanks for working on this, @aaron. So if the user sets $wgDBname in their config file, does that mean it won't be necessary to set $wgLocalDatabases in the config file? If so, perfect--just want to make sure I understand correctly.

Hi, @aaron. Here are the relevant parts of our config: