mysqladmin命令有一个debug参数,可以分析当前MySQL服务的状态信息,同时也可以用来帮助我们定位当前锁的详细情况,这里我们通过该命令分析一下当前MySQL服务的详细状态,执行mysqladmin命令如下:
  [root@phpmysql02 data]# mysqladmin -ujss -p -S /data/3306/mysql.sock debug
  Enter password:
  debug会将状态信息生成到mysql的错误文件,一般锁的信息都会保存在后几行,这里我们在操作系统层error log后几行:
[root@phpmysql02 data]# tail -10 phpmysql02.err
Thread database.table_name          Locked/Waiting        Lock_type
2       hdpic.t_wiki_zutu           Waiting - write       Highest priority write lock
123890  hdpic.t_wiki_zutu_category  Locked - read         Low priority read lock
123890  hdpic.t_wiki_zutu_photo     Locked - read         Low priority read lock
123890  hdpic.t_wiki_zutu           Locked - read         Low priority read lock
124906  hdpic.t_wiki_zutu           Waiting - read        Low priority read lock
  从上述信息可以看出,123890持有的读锁阻塞了2的写入和124906的读操作,这个状态符合我们的推论,接下来处理比较单纯了,如果现状不可接受,不能继续等待,将123890杀掉,释放资源即可:
  mysql> kill 123890;
  Query OK, 0 rows affected (0.00 sec)
  再次执行show processlist查看:
mysql> show processlist;
+--------+-------------+--------------------+-------+---------+--------+----------------------------------+------------------+
| Id     | User        | Host               | db    | Command | Time   | State                            | Info             |
+--------+-------------+--------------------+-------+---------+--------+----------------------------------+------------------+
|      1 | system user |                    | NULL  | Connect | 342390 | Waiting for master to send event | NULL             |
| 124906 | hdpic_read  | 192.168.1.39:18844 | hdpic | Sleep   |      1 |                                  | NULL             |
| 124912 | hdpic_read  | 192.168.1.39:18862 | hdpic | Sleep   |      2 |                                  | NULL             |
| 124914 | hdpic_read  | 192.168.1.39:18865 | hdpic | Sleep   |      1 |                                  | NULL             |
| 124917 | hdpic_read  | 192.168.1.39:18875 | hdpic | Sleep   |      1 |                                  | NULL             |
| 124919 | hdpic_read  | 192.168.1.39:18877 | hdpic | Sleep   |      2 |                                  | NULL             |
................
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  已经没有Locked的连接,此时向前端人员询问,告知响应慢的现象也已经消除,服务恢复正常。