So I built a master-slave Mysql replication architecture in production because of a database FOO that I wanted to query (slave node) without affecting the performance of the main site (master node).
The thing is, I was afraid of someone breaking replication by inserting data in the slave which would conflict from data coming from master, so as soon as I created the slave node, I removed all privileged users (e.g. dba1, dba2) in the slave node and added a single readonly one (with the SELECT grant): readonlyUser.
The problem I have now is that suddenly dba1 has changed his password, and the result is this replication error:
Replication reported error 1396:
Error 'Operation ALTER USER failed for 'dba1'@'localhost'' on query.
Default database: 'mysql'.
Query: 'ALTER USER 'dba1'@'localhost' IDENTIFIED WITH 'mysql_native_password' AS '*DAB3A57F75AD41285552E115420DA2EFD756CD19''
Should I prevent the replication of the mysql DB then? I'm afraid that, if I do this, any structure changes for my FOO database will not be replicated, because the structure of the tables is stored in the mysql database, right?
Or should I just ignore errors of type 1396? Is error1396 always related to users or is it more broad?