MySQL锁阻塞分析_MySQL

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.gaodaima.com/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 |+----+------+---<p>本文来源gao!%daima.com搞$代*!码9网(</p>--------+------+---------+------+--------------+------------------------------------------+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 4131Purge done for trx's n:o < 4119 undo n:o < 0 state: running but idleHistory list length 126LIST OF TRANSACTIONS FOR EACH SESSION:---TRANSACTION 0, not startedMySQL thread id 2, OS thread handle 0x7f953ffff700, query id 115 localhost root initshow engine innodb status---TRANSACTION 4130, ACTIVE 41 sec starting index readmysql tables in use 1, locked 1LOCK 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 updatingdelete from emp where empno=7788------- TRX HAS BEEN WAITING 41 SEC FOR THIS LOCK TO BE GRANTED:   ## 等待了41sRECORD 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 waitingRecord 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 readmysql tables in use 1, locked 1LOCK 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 updatingupdate emp set sal=3500 where empno=7788------- TRX HAS BEEN WAITING 45 SEC FOR THIS LOCK TO BE GRANTED:   ## 等待了45sRECORD 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 waitingRecord 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 sec2 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。

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