'kill ' gives ERROR 1095 (HY000): You are not owner of thread ... even though I am I did an ALTER TABLE on a huge table on a MariaDB Galera Cluster 10.2, but after a while of waiting I changed my mind and tried to kill the connection. However, MariaDB said ERROR 1095 (HY000): You are not owner of thread 123 even though I most definitely am the owner. So what is going on?
The error message is misleading. Galera can mark user threads as high priority which means they can't be killed. Currently, this gives the ERROR 1095 (HY000): You are not owner of thread... See MDEV-12008 for details.

This will probably affect other distributions of Galera as well, such as Percona XtraDB Cluster.