2014/08/23--OJ and related websites are slow to open, and the Training Plan login directly reports an error!

2014/08/23--OJ and related websites are slow to open, and the Training Plan login directly reports an error!

Problem:

This problem has been around for nearly a week. At the beginning, it was found that OJ and related websites were sometimes slow to open, and at that time they did not care about it. Later, the slow speed became more and more frequent; this morning, it was very slow to open (no matter what time, this situation). There were also errors in training plans and exercise statistics, the login of the training plan has been error since yesterday until today! The problem is serious. I am asking for help!

Solution:

Enter the database server, enter mysql, and useShow processlistCommand to view, found that there are many unauthenticated user;

Google L:

This is a MySQL bug. no matter whether the connection is through hosts or ip address, MySQL will reverse query the DNS and IP address to the DNS. The reverse query speed is too slow.

(Whether it is a problem with the dns server provided by the isp or other reasons), a large number of queries are hard to cope with. If the thread is not enough, it will increase the thread, but it will not be released, therefore, MySQL will be "suspended ".

The solution is simple. End the reverse lookup process and prohibit any parsing.

Open the mysql configuration file (my. cnf) and add a line under [mysqld:

Skip-name-resolve

Reload the configuration file or restart the MySQL service.