I have a 3 node PXC 5.7 cluster behind a ProxySQL instance. The cluster is still running on Debian 8.
I have setup recently a testing PXC 5.7 cluster with a copy of the database on Debian 10 without issues, but now I would like to upgrade the production cluster as well.
What would be the recommended way of upgrading the PXC cluster with a minimum of downtime?
I was thinking of setting up 3 new nodes on Debian 10 and adding them to the production cluster but not adding them to the ProxySQL. Once they have all the data distributed I could downgrade the Debian 8 nodes and let the Debian 10 nodes take over in ProxySQL. After that I could remove the Debian 8 nodes from the cluster.
Another option would be to do an inplace Debian version upgrade, but that's always scary as F.