无论如何限制MySQL查询执行时间？

Question

Hi I'm having issues on my server at the minute because some of the MySQL queries are taking a very long time to run, and hogging the resources on the server.

I'm already in the process of optimising all the queries to improve the performance, but as we use a fair amount of 3rd party applications on the server using mysql I was hoping to put in place a safeguard to prevent future issues.

What I need is something I can put in place server wide that will apply to all queries but with the possibility of overriding it on a per query basis for some of the more complex reports that do take some time to run.

I've spent time googling to find a solution but so far no luck,

Thanks for your help

Answer 1

you can use the following procedure to check for queries running longer than 300secs. the event runs the procedure periodically and kills all long running queries.

    CREATE PROCEDURE DBNAME.kill_long_running_queries ()
BEGIN

  DECLARE v_qid BIGINT;
  DECLARE v_finished INT DEFAULT 0;
  DECLARE c_queries CURSOR FOR SELECT ID FROM INFORMATION_SCHEMA.PROCESSLIST WHERE COMMAND = 'Query' AND TIME > 300;
  DECLARE CONTINUE HANDLER FOR NOT FOUND SET v_finished = 1;

  OPEN c_queries;

  l_fetch_queries: LOOP
    FETCH c_queries INTO v_qid;
    IF v_qid > 0 THEN
      KILL QUERY v_qid;
    END IF;
    IF v_finished THEN
      LEAVE l_fetch_queries;
    END IF;
  END LOOP l_fetch_queries;
  CLOSE c_queries;

END

CREATE EVENT kill_long_running_queries
ON SCHEDULE EVERY 60 SECOND
DO CALL DBNAME.kill_long_running_queries();

Answer 2

This is a purely php solution that seems to be the simplest solution from what I've managed to find so far.

$result = mysql_query("SHOW FULL PROCESSLIST");
while ($row=mysql_fetch_array($result)) 
{
  $process_id = $row["Id"];
  if ($row["Time"] > 200 ) 
  {
    $sql="KILL {$process_id}";
    mysql_query($sql);
  }
}

And running this from a CRON script every 60 seconds.

If anyone does find a better solution to this issue please let me know

Answer 3

I can recommend http://www.percona.com/doc/percona-toolkit/2.1/pt-kill.html which is designed specifically for that. From man page:

pt-kill - Kill MySQL queries that match certain criteria.

Answer 4

There is no way to do it using MySQL options. But you can still do it using daemon process as @rabudde advised.

In this case, if you kill process you will abort transaction and it will be rollback.