Can you check, whether the galera cluster exists, please run this command on any of cluster node: mysql -u root -p<password> -e "show status like 'wsrep%’"

Also, how are you referring to nodes in galera cluster in, conf file. Can you put, sql_connection of any conf file.

If you are running an HA setup where there are multiple mysql servers, then you can see the error

2006, 'MySQL server has gone away

as it refers to the fact that the connection has been closed for some reason. This can be for a variety of reasons including haproxy moving the connection to another endpoint, or that the connection idle long enough that the socket was closed.

https://dev.mysql.com/doc/refman/5.0/...

Option 1:

It clearly says "2015-04-25 14:44:50.871 2216 TRACE keystone.common.wsgi DBConnectionError: (OperationalError) (2006, 'MySQL server has gone away'"

You have dbconnectionerror, check the username and password, if everything is correct try to restart the mysql and mariadb. Hope this will fix your problem.

Option 2:

a. Server timed out and closed the connection. To fix, check that “wait_timeout” mysql variable in your my.cnf configuration file is large enough.

b. Server dropped an incorrect or too large packet. If mysqld gets a packet that is too large or incorrect, it assumes that something has gone wrong with the client and closes the connection. To fix, you can increase the maximal packet size limit “max_allowed_packet” in my.cnf file, eg. set max_allowed_packet = 128M, then sudo /etc/init.d/mysql restart.

Option 3:

Check whether all your services are running or not? especially check for rabbitmq status. If its stoped restart it and restart other services.

As Nicholas said try increasing wait_timeout to something like 28800 in my.cnf . Also if using haproxy increase the timeout in haproxy aswell!