Question

How can I close (KILL) connections that take too long to execute using MySQL and PHP

Answer 1

The solution is to write a Stored Procedure that kills all the connections above some time:

DELIMITER //
DROP PROCEDURE IF EXISTS ClearDB//
CREATE PROCEDURE ClearDB()
BEGIN
    DECLARE nID, bCursor INT;
    DECLARE cursorQuery CURSOR FOR 
        SELECT ID
        FROM information_schema.processlist
        WHERE `TIME` > 10;
    DECLARE CONTINUE HANDLER FOR NOT FOUND SET bCursor = 1;

    OPEN cursorQuery;
    SET bCursor = 0;

    WHILE bCursor = 0 DO
        FETCH cursorQuery INTO nID;
        KILL nID;
    END WHILE;

    CLOSE cursorQuery;
END //
DELIMITER ;

The procedure is pretty straightforward:
Get all the connection IDs with TIME greater then 10, loop through the results and kill them

And you can make a cron task to call the ClearDB() procedure or you can call it every time you open up a new connection like that:

$pDB = new mysqli('localhost', 'user', 'pass', 'database');
if ($pDB->connect_error) 
{
    // Handle the error
}
$pDB->query('CALL ClearDB()');

Hope it will help someone 🙂