Terminating idle mysql connections

Question

I see a lot of connections are open and remain idle for a long time, say 5 minutes.

Is there any solution to terminate / close it from server without restarting the mysql service?

I am maintaining a legacy PHP system and can not close the connections those are established to execute the query.

Should I reduce the timeout values in my.cnf file those defaults to 8 hours?

# default 28800 seconds

interactive_timeout=60
wait_timeout=60

Answer 1

I don't see any problem, unless you are not managing them using a connection pool.

If you use connection pool, these connections are re-used instead of initiating new connections. so basically, leaving open connections and re-use them it is less problematic than re-creating them each time.

Answer 2

Manual cleanup:

You can KILL the processid.

mysql> show full processlist;
+---------+------------+-------------------+------+---------+-------+-------+-----------------------+
| Id      | User       | Host              | db   | Command | Time  | State | Info                  |
+---------+------------+-------------------+------+---------+-------+-------+-----------------------+
| 1193777 | TestUser12 | 192.168.1.11:3775 | www  | Sleep   | 25946 |       | NULL                  |
+---------+------------+-------------------+------+---------+-------+-------+-----------------------+

mysql> kill 1193777;

But:

• the php application might report errors (or the webserver, check the error logs)
• don't fix what is not broken - if you're not short on connections, just leave them be.

Automatic cleaner service ;)

Or you configure your mysql-server by setting a shorter timeout on wait_timeout and interactive_timeout

mysql> show variables like "%timeout%";
+--------------------------+-------+
| Variable_name            | Value |
+--------------------------+-------+
| connect_timeout          | 5     |
| delayed_insert_timeout   | 300   |
| innodb_lock_wait_timeout | 50    |
| interactive_timeout      | 28800 |
| net_read_timeout         | 30    |
| net_write_timeout        | 60    |
| slave_net_timeout        | 3600  |
| table_lock_wait_timeout  | 50    |
| wait_timeout             | 28800 |
+--------------------------+-------+
9 rows in set (0.00 sec)

Set with:

set global wait_timeout=3;
set global interactive_timeout=3;

(and also set in your configuration file, for when your server restarts)

But you're treating the symptoms instead of the underlying cause - why are the connections open? If the PHP script finished, shouldn't they close? Make sure your webserver is not using connection pooling...