Few days ago i was trying to test plesk 12.1.15 (testing) control panel on Ubuntu 14.04 then i ran into the following error which was unknown to me at that time mysql was removed.
ERROR: PleskDBException: Unable to connect to database: mysql_connect(): No such file or directory (Error code: 2002) (Abstract.php:69)
After searching and finding out what the problem is i noticed that Plesk installed mysql 5.5 has been removed. So what i did was install mysql5.6 following this tutorial.
This seems to have fixed the problem has i have restarted my server and mysql server is still installed and working properly apart from cpu and memory usage problem everything looks fine.