MySQL锁阻塞的深入分析

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

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)