Common issues to look out for when you are using MySQL are as follows:
- too many connections
- waiting for table metadata lock
- slow running queries
As a diagnostic step run these commands after you login to MySQL server
show processlist;to get detailed information run
show full processlist;to get detailed information and to filter using WHERE clause run
SELECT * FROM INFORMATION_SCHEMA.PROCESSLIST;To kill a long running thread run
kill <process id>