The MySQL Galera cluster contains three nodes. If one node fails,
the MySQL database does not have an outage. Solve the problem by
restarting the mysql service on the failed node. If the node cannot
be rejoined to the cluster after restart, remove the following files from the
/var/lib/mysql/ directory and restart the mysql service again:
rm -rf /var/lib/mysql/grastate*
rm -rf /var/lib/mysql/ib_log*
service mysql start