I think you are having a split brain situation
The rule is that after any kind of failure, a galera node will
consider itself part of the primary partition if it can still see a
majority of the nodes that were in the cluster before the failure.
Majority > 50%.
So if you have 3 nodes and one goes away, the 2 remaining are fine.
If you have 3 nodes and 2 go away simultaneously, the 1 remaining must
assume it is the one having problems and will go offline.
If you have 3 nodes and 1 go way, then you have a 2 node cluster. This
is not good. Now if any 1 node goes away, the other one alone is not
in majority so it will have to be offline. The same is true if you
have a 4 node cluster and simultaneously lose 2 nodes. Etc…
But all is not lost. The node is still there, and if you as a human
being know it is the right thing to do, then you can run some manual
command to re-activate that node again (such as the command given by
Haris, or just restart, etc…).
There was a whole article on unknown commands and split brain situations on the perconas site but I cant seem to find it
In order to restore the cluster, execute below command on the working node and it will establish this node to form the primary component again and restarting previously crashed nodes will join the cluster hopefully.
mysql> SET GLOBAL wsrep_provider_options=‘pc.bootstrap=true’;
ariable wsrep_ready variable is set to 0)