码迷,mamicode.com
首页 > 数据库 > 详细

MySQL5.6锁阻塞分析

时间:2018-12-31 17:15:09      阅读:234      评论:0      收藏:0      [点我收藏+]

标签:tail   --   情况   started   disable   declare   线程   并且   mysql5.6   

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。
blog地址:http://blog.csdn.net/hw_libo/article/details/39080809
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
 

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。
blog地址:http://blog.csdn.net/hw_libo/article/details/39080809
---------------------
原文:https://blog.csdn.net/hw_libo/article/details/39080809
 
MySQL 5.7中的方式是:
The specially named tables used to enable and disable the standard InnoDB Monitor and InnoDB Lock Monitor (innodb_monitor and innodb_lock_monitor) are removed and replaced by two dynamic system variables: innodb_status_output and innodb_status_output_locks. For additional information, see Section 14.17, “InnoDB Monitors”.
 
 

MySQL5.6锁阻塞分析

标签:tail   --   情况   started   disable   declare   线程   并且   mysql5.6   

原文地址:https://www.cnblogs.com/DataArt/p/10202097.html

(0)
(0)
   
举报
评论 一句话评论(0
登录后才能评论!
© 2014 mamicode.com 版权所有  联系我们:gaon5@hotmail.com
迷上了代码!