Mysql detect slow logs

Mysql provides a way to detect slow log. You can config it in folder: /etc/mysql/mysql.conf.d/mysqld.cnf.

slow_query_log		= 1
slow_query_log_file	= /var/log/mysql/mysql-slow.log
long_query_time = 2
log-queries-not-using-indexes

btw, we have some gem in Rails, which can help you detect slow queries too, such as rack-mini-profiler, bullet, …