Why do you need to change those values in the first place?
According to Eliot Kristan
wait_timeout variable represents the amount of time that MySQL will wait before killing an idle connection.
The default wait_timeout variable is 28800 seconds, which is 8 hours. That's a lot.
I've read in different forums/blogs that putting wait_timeout too low (e.g. 30, 60, 90) can result in MySQL has gone away error messages.
So you'll have to decide for your configuration.
Requirement: You will need admin/root access to the server.
Step 1) Edit your /etc/my.cnf file and enter the following 2 values.
[mysqld]
interactive_timeout=300
wait_timeout=300
Step 2) run the command and enter your root password
mysql -uroot -p -e"SET GLOBAL wait_timeout=300; SET GLOBAL interactive_timeout=300;"
If you are connected from the mysql console
e.g. mysql> you can run this command which will show you global and session variables.
SELECT @@global.wait_timeout, @@global.interactive_timeout, @@session.wait_timeout, @@session.interactive_timeout;
+-----------------------+------------------------------+------------------------+-------------------------------+
| @@global.wait_timeout | @@global.interactive_timeout | @@session.wait_timeout | @@session.interactive_timeout |
+-----------------------+------------------------------+------------------------+-------------------------------+
| 300 | 300 | 28800 | 28800 |
+-----------------------+------------------------------+------------------------+-------------------------------+
1 row in set (0.00 sec)
To see the the current values you can run this command
mysql> show global variables like '%timeout%';
+----------------------------+----------+
| Variable_name | Value |
+----------------------------+----------+
| connect_timeout | 10 |
| delayed_insert_timeout | 300 |
| innodb_lock_wait_timeout | 50 |
| innodb_rollback_on_timeout | OFF |
| interactive_timeout | 300 |
| lock_wait_timeout | 31536000 |
| net_read_timeout | 30 |
| net_write_timeout | 60 |
| slave_net_timeout | 3600 |
| wait_timeout | 300 |
+----------------------------+----------+
10 rows in set (0.00 sec)
Credits:
Step1 instructions from RolandoMySQLDBA
http://serverfault.com/questions/355750/mysql-lowering-wait-timeout-value-to-lower-number-of-open-connections
Step 2) Eliot Kristan's blog http://www.eliotk.net/12/21/mysql-wait_timeout-default-is-set-too-high/
