Change the MySQL Timeout on a Server

When an application fails to close an unused connection, a low wait_timeout value helps you avoid exceeding the permitted number of connections. Use the following instructions to set this vakue:

1. Log in to your server by using Secure Shell® (SSH).

2. Use the sudo command to edit my.cnf, the MySQL® configuration file.

   $ sudo vi /etc/my.cnf
   

3. Locate the timeout configuration and make the adjustments that fit your server.

   wait_timeout = 28800
   interactive_timeout = 28800
   

   • The interactive_timeout value does not affect any web application connections. A low wait_timeout is a normal best practice.

   • Stateless PHP environments do well with a 60-second timeout or less. Applications that use a connection pool (Java®, .NET®, and so on) need to adjust the wait_timeout value to match their connection pool settings. The default 8 hours = 28800 seconds works well with properly-configured connection pools.

   • Configure the wait_timeout to be slightly longer than the application connection pool's expected connection lifetime as a safety check. Consider changing the value online because that does not require a MySQL restart, and you can adjusted it while the server runs without incurring downtime. Change the value to set global wait_timeout=60, and any newly created sessions inherit it. Be sure to preserve the setting in my.cnf. Any existing connections need to hit the old value of wait_timeout if the application abandoned the connection. If you do have reporting jobs that do longer local processing while in a transaction, you might consider having such jobs issue set session wait_timeout=3600 upon connecting.

4. Save the changes and exit the editor.

5. Use the following command to restart MySQL and apply the changes, if required:

   $ sudo /etc/init.d/mysql restart