A database query error has occurred. This may indicate a bug in the software.
[W@9YBwpAAEEAAJEWrsgAAABG] 2018-11-16 23:53:19: Fatal exception of type "Wikimedia\Rdbms\DBExpectedError"
when editting
https://meta.wikimedia.org/wiki/Special:CentralNoticeBanners/edit/CommunityWishlistVote
The specific error is related about database replication: "Replication wait failed: MySQL server has gone away". There are other errors on this banner that seem linked to rebuilding the Translate extension MessageGroupStats index. See these Logstash entries.
There's a possibility that this would be solved by the translation-related patches made for T203925 but not yet deployed. However, since we're in code freeze, with year-end FR banners going up soon, I'd suggest we hold off on deploying them unless really necessary. @Seddon have you seen this come up again? If it's happening often, we could still try deploying those.
No instances of this error found in Logstash for 30 days.
The only exceptions found on meta.wikimedia.org for CentralNotice-related requests (some of which are on /edit/ as well, like this report), is for BannerExistenceException – which is tracked as T149240.