KILL 线程

最近更新时间:2019-04-16 12:06:34

在使用数据库运行某些语句时,会因数据量太大而导致死锁,没有反映。这个时候,就需要 kill 掉某个正在消耗资源的 query 语句即可,KILL 命令的语法格式如下:

    KILL [CONNECTION | QUERY] thread_id

每个与 mysqld 的连接都在一个独立的线程里运行,您可以使用 SHOW PROCESSLIST 语句查看哪些线程正在运行,并使用 KILL thread_id 语句终止一个线程。

    mysql> show processlist;
    +--------+------------+----------------+------+---------+------+------------+---------------------+-----------+---------------+
    | Id     | User       | Host           | db   | Command | Time | State      | Info                | Rows_sent | Rows_examined |
    +--------+------------+----------------+------+---------+------+------------+---------------------+-----------+---------------+
    | 924107 | sutest | 10.0.0.8:38314 | NULL | Query   |    0 | starting   | show processlist    |         0 |             0 |
    | 924114 | sutest | 10.0.0.8:38318 | test | Query   |  264 | User sleep | select sleep(20000) |         0 |             0 |
    +--------+------------+----------------+------+---------+------+------------+---------------------+-----------+---------------+
    2 rows in set (0.00 sec)

    mysql> kill 924114;
    Query OK, 0 rows affected (0.00 sec)

如果您的业务有较多线程,无法准确判断哪些事务未提交,可以采用类似 SQL 进行查询线程 ID(举例):

    SELECT 
      it.trx_id AS trx_id,
      it.trx_state AS trx_state,
      it.trx_started AS trx_started,
      it.trx_mysql_thread_id AS trx_mysql_thread_id,
      CURRENT_TIMESTAMP - it.trx_started AS RUN_TIME,
      pl.user AS USER,
      pl.host AS HOST,
      pl.db AS db,
      pl.time AS trx_run_time,
      pl.INFO as INFO
    FROM
      information_schema.INNODB_TRX it,
      information_schema.processlist pl
    WHERE
      pl.id=it.trx_mysql_thread_id
    ORDER BY RUN_TIME DESC LIMIT 10;

如果您的业务有较多线程,无法准确判断哪些事务处于锁等待,可以采用类似 SQL 进行查询线程 ID(举例):

    SELECT 
    r.trx_id waiting_trx_id, 
    r.trx_mysql_thread_id waiting_thread, 
    TIMESTAMPDIFF( SECOND, r.trx_wait_started, CURRENT_TIMESTAMP ) wait_time, 
    r.trx_query waiting_query, 
    l.lock_table waiting_table_lock, 
    b.trx_id blocking_trx_id, 
    b.trx_mysql_thread_id blocking_thread,
    SUBSTRING( p. HOST, 1, INSTR(p. HOST, ':') - 1 ) blocking_host, 
    SUBSTRING(p. HOST, INSTR(p. HOST, ':') + 1) blocking_port,
    IF (p.COMMAND = 'Sleep', p.TIME, 0) idel_in_trx, 
    b.trx_query blocking_query FROM information_schema.INNODB_LOCK_WAITS w INNER JOIN information_schema.INNODB_TRX b ON b.trx_id = w.blocking_trx_id INNER JOIN information_schema.INNODB_TRX r ON r.trx_id = w.requesting_trx_id INNER JOIN information_schema.INNODB_LOCKS l ON w.requested_lock_id = l.lock_id LEFT JOIN information_schema. PROCESSLIST p ON p.ID = b.trx_mysql_thread_id ORDER BY wait_time DESC;

风险提示:大事务 kill 之后,事务需要回滚,数据量较大的情况下也需等待很久,此时可以到控制台单击主从切换,将从机切换为主,以快速恢复业务。但请务必知悉:使用异步同步、强同步(可退化)复制方案时,由于主从数据同步有延迟,可能丢失/错乱部分数据,请谨慎操作主从切换。