3 node percona cluster - 2 nodes got out of sync but 1 node was still up

MySQL & MariaDB Percona XtraDB Cluster 8.x
1

We were under the impression that if 1 node remained in the cluster that it would shutdown because only 1 node was left. You would need to bootstrap the last node alive to make sure the other 2 nodes synced with it for most recent data. Is this still the case for clusters?

Issue we experience was had 2 nodes go out of sync (but mysql was still running) and after restarting mysql on the other 2 nodes all was good again. the only node that was left was saying it was primary. site however was having issues at that time but after the mysql restarts on 2 of the nodes all was good again.

for the gcomm://nodename,nodename,nodename can these be IP’s and or Hostnames?? or must they be IP’s? Does one way work better than the other and if so why?

2

Hello, by design if nodes leave the cluster gracefully (which seems to be what happened as you did a normal shutdown of mysql) then the quorum is not lost, so even with 1 node the cluster will keep running in this case. For gcomm either IP or hostnames will work. You might want to use IPs to avoid relying on DNS service.

3

So, - two exited the cluster, somehow (we don’t know why this happens, and thus far it is more regular than can be considered acceptable)

  • we don’t know why the 1 primary node still reported OK given it shouldn’t have had a quorum (as we believe that it was not due to a graceful exiting of the cluster).