labsdb1001 was lagging today because a transaction created from the user s51114 that belongs to the group tools.enwp10 was keeping the replica from being executed because Waiting for table metadata lock.

The killed transaction was open since 22k seconds and was executing many queries on it, there wasn't a single particularly long running query. This is a bad practice and you should avoud

---TRANSACTION 35432803735, ACTIVE 22221 sec starting index read
mysql tables in use 2, locked 0
, holds adaptive hash latch
MySQL thread id 74988385, OS thread handle 0x7efc5dfff700, query id 4364880313 10.68.18.40 s51114 Sending data