tools-db-2 will become the new replica after tools-db-1 is promoted to primary.
We can set up chain replication from tools-db-1, without having to wait for it to be a primary. To start the replication, I think we might be able to leverage Cinder snapshots, creating a snapshot of the Cinder volume in tools-db-1, then creating a new volume from that snapshot and attaching it to tools-db-2.