Terminating idle mysql connections

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臣服心动
臣服心动 2020-11-27 16:10

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

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  • 2020-11-27 16:27

    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...

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  • 2020-11-27 16:31

    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.

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