MySQL Wait_Timeout - SQL

MySQL Wait_Timeout is a configuration variable that defines the number of seconds a MySQL server waits for an activity on a non-interactive connection before closing it.

Configuration

This variable can be set in the MySQL configuration file, my.cnf, or dynamically within a session using the SET GLOBAL statement.

Setting in my.cnf

To set the wait_timeout variable in the my.cnf file, add the following line to the file under the [mysqld] section.

wait_timeout = number_of_seconds

For example, to set the wait_timeout to 300 seconds, add the following line:

wait_timeout = 300

Dynamically within a session

To set the wait_timeout variable dynamically within a session, use the following statement:

SET GLOBAL wait_timeout = number_of_seconds;

For example, to set the wait_timeout to 300 seconds, use the following statement:

SET GLOBAL wait_timeout = 300;

Impact on Connections

When a non-interactive connection, such as a connection from a script or application, is idle for longer than the wait_timeout period, the MySQL server will close the connection. This can cause potential issues with long-running background processes or connection pools that are designed to reuse connections.

Recommendations

It is recommended to set the wait_timeout value to a higher value if your application relies on long-running background processes or connection pools to avoid closing connections prematurely.

However, setting wait_timeout too high can cause issues with resource utilization and may cause connections to become unresponsive. It is important to find a balance between closing idle connections and keeping them open for re-use.

Conclusion

The wait_timeout variable is an important configuration option for MySQL servers that handle non-interactive connections. Understanding how this variable works and its potential impact on your application is crucial for ensuring optimal resource utilization and avoiding unintended issues with connections.