I have been tasked with replacing a MySQL 5.1 server with MySQL 8.0.
So I built a CentOS 7 machine with MySQL 5.7 and now I am replicating from 5.1 => 5.7 Then I built a RHEL 9 machine with MySQL 8.0 and now I am replicating from 5.7 => 8.0
This chain of woe seems to be working just fine but now I need to change it so that some other downstream replicas are using the MySQL 8.0 server because I want to get rid of both the MySQL 5.1 and 5.7 server(s) for comically obvious reasons.
I'm sort of confused what parameters I want to use on the downstream replicas in the:
CHANGE MASTER TO command as far as the MASTER_LOG_FILE and MASTER_LOG_POS command goes
because all of the replicas are currently up to date.
Do I just pull that from the new MySQL 8 host?
Also when I am ready to decommission the old host(s) do I need to somehow specify that the MySQL 8 server is now the new main replica?
I obviously will not be writing to the MySQL 8 server (directly) until the downstream replicas are using it but when I am ready to do that is there something I need to change on the MySQL 8 host to tell it that it is the captain now?
Luckily for me the applications attached to the downstream replicas are read-only so that makes it somewhat less complicated.
