数据库

MySQL锁阻塞的深入分析
数据库 2024/10/6 佚名
3 2

日常维护中，经常会碰到线程被阻塞，导致数据库响应非常慢，下面就看看如何获取是哪个线程导致了阻塞的。

1. 环境说明

RHEL 6.4 x86_64 + MySQL 5.6.19

事务隔离级别：RR

2. 测试过程

MySQL锁阻塞的深入分析

3. 查看锁阻塞线程信息

这里用几中方法进行分析：

3.1  使用show processlist查看

MySQL [(none)]> show processlist;
+----+------+-----------+------+---------+------+--------------+------------------------------------------+
| Id | User | Host  | db | Command | Time | State  | Info          |
+----+------+-----------+------+---------+------+--------------+------------------------------------------+
| 2 | root | localhost | NULL | Query | 0 | init   | show processlist       |
| 3 | root | localhost | test | Query | 70 | Sending data | select count(*) from t3 a,t3 b   |
| 4 | root | localhost | test | Query | 65 | updating  | delete from emp where empno=7788   |
| 7 | root | localhost | test | Query | 68 | updating  | update emp set sal=3500 where empno=7788 |
+----+------+-----------+------+---------+------+--------------+------------------------------------------+
4 rows in set (0.00 sec)

如果数据库存在较多线程的话，这种方法确实不太好确认的。

3.2  直接使用show engine innodb status查看

------------
TRANSACTIONS
------------
Trx id counter 4131
Purge done for trx's n:o < 4119 undo n:o < 0 state: running but idle
History list length 126
LIST OF TRANSACTIONS FOR EACH SESSION:
---TRANSACTION 0, not started
MySQL thread id 2, OS thread handle 0x7f953ffff700, query id 115 localhost root init
show engine innodb status
---TRANSACTION 4130, ACTIVE 41 sec starting index read
mysql tables in use 1, locked 1
LOCK WAIT 2 lock struct(s), heap size 360, 1 row lock(s)
MySQL thread id 4, OS thread handle 0x7f953ff9d700, query id 112 localhost root updating
delete from emp where empno=7788
------- TRX HAS BEEN WAITING 41 SEC FOR THIS LOCK TO BE GRANTED: ## 等待了41s
RECORD LOCKS space id 16 page no 3 n bits 88 index `PRIMARY` of table `test`.`emp` trx id 4130 lock_mode X locks rec but not gap waiting
Record lock, heap no 9 PHYSICAL RECORD: n_fields 10; compact format; info bits 0 ## 线程4在等待往test.emp中的主键上加X锁，page num=3
 0: len 4; hex 80001e6c; asc l;;
 1: len 6; hex 000000001018; asc  ;;
 2: len 7; hex 91000001420084; asc  B ;;
 3: len 5; hex 53434f5454; asc SCOTT;;
 4: len 7; hex 414e414c595354; asc ANALYST;;
 5: len 4; hex 80001d8e; asc  ;;
 6: len 4; hex 208794f0; asc  ;;
 7: len 4; hex 80000bb8; asc  ;;
 8: SQL NULL;
 9: len 4; hex 80000014; asc  ;;
 
------------------
---TRANSACTION 4129, ACTIVE 45 sec starting index read
mysql tables in use 1, locked 1
LOCK WAIT 2 lock struct(s), heap size 360, 1 row lock(s)
MySQL thread id 7, OS thread handle 0x7f953ff6c700, query id 111 localhost root updating
update emp set sal=3500 where empno=7788
------- TRX HAS BEEN WAITING 45 SEC FOR THIS LOCK TO BE GRANTED: ## 等待了45s
RECORD LOCKS space id 16 page no 3 n bits 88 index `PRIMARY` of table `test`.`emp` trx id 4129 lock_mode X locks rec but not gap waiting
Record lock, heap no 9 PHYSICAL RECORD: n_fields 10; compact format; info bits 0 ## 线程7在等待往test.emp中的主键上加X锁，page num=3
 0: len 4; hex 80001e6c; asc l;;
 1: len 6; hex 000000001018; asc  ;;
 2: len 7; hex 91000001420084; asc  B ;;
 3: len 5; hex 53434f5454; asc SCOTT;;
 4: len 7; hex 414e414c595354; asc ANALYST;;
 5: len 4; hex 80001d8e; asc  ;;
 6: len 4; hex 208794f0; asc  ;;
 7: len 4; hex 80000bb8; asc  ;;
 8: SQL NULL;
 9: len 4; hex 80000014; asc  ;;
 
------------------
---TRANSACTION 4128, ACTIVE 51 sec
2 lock struct(s), heap size 360, 1 row lock(s)
MySQL thread id 3, OS thread handle 0x7f953ffce700, query id 110 localhost root cleaning up

我们知道，主要根因还是thread=3引起的，但从innodb status中却无法分析得到这个结果。

从上面来看，线程4和线程7都在等待往test.emp中的主键上加X锁，page num=3，但是线程7等待的时间为45s，而线程4等待的时间为41s，是较线程7之后申请的锁，所以可以判断是线程7阻塞了线程4。至于线程7为什么出现等待，这里分析不到根因。

3.3  使用mysqladmin debug查看

# mysqladmin -S /tmp/mysql3306.sock debug

然后在error日志中，会看到：

Thread database.table_name   Locked/Waiting  Lock_type
 
 
3  test.t3      Locked - read   Low priority read lock
7  test.emp     Locked - write  High priority write lock

这种方法中，能找到线程ID=3和7是阻塞者，但还是不太准确，判断不出来线程7也是被线程ID=3阻塞的。

3.4  使用innodb_lock_monitor来获取阻塞锁线程

MySQL [test]> CREATE TABLE innodb_lock_monitor (a INT) ENGINE=INNODB; ## 随便在一个数据库中创建这个表，就会打开lock monitor
Query OK, 0 rows affected, 1 warning (0.07 sec)
 
MySQL [test]> show warnings\G
*************************** 1. row ***************************
 Level: Warning
 Code: 131
Message: Using the table name innodb_lock_monitor to enable diagnostic output is deprecated and may be removed in future releases. Use INFORMATION_SCHEMA or PERFORMANCE_SCHEMA tables or SET GLOBAL innodb_status_output=ON.
1 row in set (0.00 sec)

说明：这个在5.6中有一个warning，但不影响使用。

然后再使用show engine innodb status查看：

------------
TRANSACTIONS
------------
Trx id counter 4667
Purge done for trx's n:o < 4659 undo n:o < 0 state: running but idle
History list length 138
LIST OF TRANSACTIONS FOR EACH SESSION:
---TRANSACTION 0, not started
MySQL thread id 9, OS thread handle 0x7f813c5f7700, query id 152 localhost root init
show engine innodb status
---TRANSACTION 4663, ACTIVE 78 sec starting index read
mysql tables in use 1, locked 1
LOCK WAIT 2 lock struct(s), heap size 360, 1 row lock(s)
MySQL thread id 4, OS thread handle 0x7f813c628700, query id 149 localhost root updating
delete from emp where empno=7788
------- TRX HAS BEEN WAITING 78 SEC FOR THIS LOCK TO BE GRANTED:  ## 等待了78s
RECORD LOCKS space id 16 page no 3 n bits 88 index `PRIMARY` of table `test`.`emp` trx id 4663 lock_mode X locks rec but not gap waiting
Record lock, heap no 9 PHYSICAL RECORD: n_fields 10; compact format; info bits 0 ## 线程4在等待往test.emp中的主键上加X锁，page num=3
 0: len 4; hex 80001e6c; asc  l;;
 1: len 6; hex 000000001018; asc    ;;
 2: len 7; hex 91000001420084; asc   B ;;
 3: len 5; hex 53434f5454; asc SCOTT;;
 4: len 7; hex 414e414c595354; asc ANALYST;;
 5: len 4; hex 80001d8e; asc   ;;
 6: len 4; hex 208794f0; asc   ;;
 7: len 4; hex 80000bb8; asc   ;;
 8: SQL NULL;
 9: len 4; hex 80000014; asc   ;;
 
------------------
TABLE LOCK table `test`.`emp` trx id 4663 lock mode IX  ## 在给主键行上加X锁之前，先要在表上加意向锁IX
RECORD LOCKS space id 16 page no 3 n bits 88 index `PRIMARY` of table `test`.`emp` trx id 4663 lock_mode X locks rec but not gap waiting
Record lock, heap no 9 PHYSICAL RECORD: n_fields 10; compact format; info bits 0
 0: len 4; hex 80001e6c; asc  l;;
 1: len 6; hex 000000001018; asc    ;;
 2: len 7; hex 91000001420084; asc   B ;;
 3: len 5; hex 53434f5454; asc SCOTT;;
 4: len 7; hex 414e414c595354; asc ANALYST;;
 5: len 4; hex 80001d8e; asc   ;;
 6: len 4; hex 208794f0; asc   ;;
 7: len 4; hex 80000bb8; asc   ;;
 8: SQL NULL;
 9: len 4; hex 80000014; asc   ;;
 
---TRANSACTION 4662, ACTIVE 81 sec starting index read
mysql tables in use 1, locked 1
LOCK WAIT 2 lock struct(s), heap size 360, 1 row lock(s)
MySQL thread id 7, OS thread handle 0x7f813c5c6700, query id 148 localhost root updating
update emp set sal=3500 where empno=7788
------- TRX HAS BEEN WAITING 81 SEC FOR THIS LOCK TO BE GRANTED: ## 等待了81s
RECORD LOCKS space id 16 page no 3 n bits 88 index `PRIMARY` of table `test`.`emp` trx id 4662 lock_mode X locks rec but not gap waiting
Record lock, heap no 9 PHYSICAL RECORD: n_fields 10; compact format; info bits 0 ## 线程7在等待往test.emp中的主键上加X锁，page num=3
 0: len 4; hex 80001e6c; asc  l;;
 1: len 6; hex 000000001018; asc    ;;
 2: len 7; hex 91000001420084; asc   B ;;
 3: len 5; hex 53434f5454; asc SCOTT;;
 4: len 7; hex 414e414c595354; asc ANALYST;;
 5: len 4; hex 80001d8e; asc   ;;
 6: len 4; hex 208794f0; asc   ;;
 7: len 4; hex 80000bb8; asc   ;;
 8: SQL NULL;
 9: len 4; hex 80000014; asc   ;;
 
------------------
TABLE LOCK table `test`.`emp` trx id 4662 lock mode IX  ## 在给主键行上加X锁之前，先要在表上加意向锁IX
RECORD LOCKS space id 16 page no 3 n bits 88 index `PRIMARY` of table `test`.`emp` trx id 4662 lock_mode X locks rec but not gap waiting
Record lock, heap no 9 PHYSICAL RECORD: n_fields 10; compact format; info bits 0
 0: len 4; hex 80001e6c; asc  l;;
 1: len 6; hex 000000001018; asc    ;;
 2: len 7; hex 91000001420084; asc   B ;;
 3: len 5; hex 53434f5454; asc SCOTT;;
 4: len 7; hex 414e414c595354; asc ANALYST;;
 5: len 4; hex 80001d8e; asc   ;;
 6: len 4; hex 208794f0; asc   ;;
 7: len 4; hex 80000bb8; asc   ;;
 8: SQL NULL;
 9: len 4; hex 80000014; asc   ;;
 
---TRANSACTION 4615, ACTIVE 1579 sec, thread declared inside InnoDB 1222
mysql tables in use 2, locked 0
2 lock struct(s), heap size 360, 1 row lock(s)
MySQL thread id 3, OS thread handle 0x7f813c659700, query id 147 localhost root Sending data
select count(*) from t3 a,t3 b  ## 这是线程3当前正在执行的SQL
Trx read view will not see trx with id >= 4662, sees < 4659
TABLE LOCK table `test`.`emp` trx id 4615 lock mode IX ## 线程3中正在拥有表上的意向IX锁，并且有test.emp表上主键的行级X锁，page num=3
RECORD LOCKS space id 16 page no 3 n bits 88 index `PRIMARY` of table `test`.`emp` trx id 4615 lock_mode X locks rec but not gap
Record lock, heap no 9 PHYSICAL RECORD: n_fields 10; compact format; info bits 0
 0: len 4; hex 80001e6c; asc  l;;
 1: len 6; hex 000000001018; asc    ;;
 2: len 7; hex 91000001420084; asc   B ;;
 3: len 5; hex 53434f5454; asc SCOTT;;
 4: len 7; hex 414e414c595354; asc ANALYST;;
 5: len 4; hex 80001d8e; asc   ;;
 6: len 4; hex 208794f0; asc   ;;
 7: len 4; hex 80000bb8; asc   ;;
 8: SQL NULL;
 9: len 4; hex 80000014; asc   ;;

为什么线程3当前执行的是一个select t3表操作，但却锁住了test.emp表上page num=3？

有可能是线程3之前对test.emp表的操作事务没有及时提交导致。

所以得出：线程3阻塞了线程7，而线程7又阻塞了线程4，所以根因就是线程3，让线程3尽快提交或是kill掉即可。

4. 结论

在分析innodb中锁阻塞时，几种方法的对比情况：

（1）使用show processlist查看不靠谱；

（2）直接使用show engine innodb status查看，无法判断到问题的根因；

（3）使用mysqladmin debug查看，能看到所有产生锁的线程，但无法判断哪个才是根因；

（4）开启innodb_lock_monitor后，再使用show engine innodb status查看，能够找到锁阻塞的根因。

原文链接：https://blog.csdn.net/hw_libo/article/details/39080809

标签：
mysql锁阻塞,mysql查看锁,mysql释放锁
免责声明：本站文章均来自网站采集或用户投稿，网站不提供任何软件下载或自行开发的软件！ 如有用户或公司发现本站内容信息存在侵权行为，请邮件告知！ 858582#qq.com
白云城资源网 Copyright www.dyhadc.com

评论“MySQL锁阻塞的深入分析”

暂无“MySQL锁阻塞的深入分析”评论...
www.dyhadc.com 白云城资源网
129,905影音资源
244,626技术资源
111,817软件资源
578,645站长资源

《魔兽世界》大逃杀！60人新游玩模式《强袭风暴》3月21日上线

暴雪近日发布了《魔兽世界》10.2.6 更新内容，新游玩模式《强袭风暴》即将于3月21 日在亚服上线，届时玩家将前往阿拉希高地展开一场 60 人大逃杀对战。

艾泽拉斯的冒险者已经征服了艾泽拉斯的大地及遥远的彼岸。他们在对抗世界上最致命的敌人时展现出过人的手腕，并且成功阻止终结宇宙等级的威胁。当他们在为即将于《魔兽世界》资料片《地心之战》中来袭的萨拉塔斯势力做战斗准备时，他们还需要在熟悉的阿拉希高地面对一个全新的敌人──那就是彼此。在《巨龙崛起》10.2.6 更新的《强袭风暴》中，玩家将会进入一个全新的海盗主题大逃杀式限时活动，其中包含极高的风险和史诗级的奖励。

《强袭风暴》不是普通的战场，作为一个独立于主游戏之外的活动，玩家可以用大逃杀的风格来体验《魔兽世界》，不分职业、不分装备（除了你在赛局中捡到的），光是技巧和战略的强弱之分就能决定出谁才是能坚持到最后的赢家。本次活动将会开放单人和双人模式，玩家在加入海盗主题的预赛大厅区域前，可以从强袭风暴角色画面新增好友。游玩游戏将可以累计名望轨迹，《巨龙崛起》和《魔兽世界：巫妖王之怒 经典版》的玩家都可以获得奖励。

更新日志

友情链接

杰晶网络 DDR爱好者之家 南强小屋 黑松山资源网 白云城资源网 更多链接
白云城资源网 Copyright www.dyhadc.com