* Have a master with several databases, including one empty (e.g. a new application that is going to be deployed)
* Create a backup of the master
* Load into a replica, expecting to have an accurate copy of the master
* Setup replication -everything works as expected
* The application starts writing to the database
* Replication breaks because a missing database on the queries, including those that are not empty
How this can lead to an outage:
* Have a master with several databases, including one empty (e.g. a new application that is going to be deployed)
* Create a backup of the master
* Load into a replica, expecting to have an accurate copy of the master
* Setup replication -everything works as expected
* The application starts writing to the database
* Replication breaks because a missing database on the queries, including those that are not empty
This lead to a Wikimedia databases incident at https:/ /phabricator. wikimedia. org/T192875# 4241019