In the night the mysql was stop and not start, the error log is
170429 10:29:56 mysqld_safe mysqld from pid file /var/lib/mysql/xxx.xxxx.xxxx.pid ended
170429 10:30:01 mysqld_safe Starting mysqld daemon with databases from /var/lib/mysql
2017-04-29 10:30:02 0 [Warning] 'THREAD_CONCURRENCY' is...