mysql查看死锁与去除死锁示例详解-每日运维

1、查询进程 show processlist 2、查询到相对应的进程，然后 kill id 验证（kill后再看是否还有锁） 2、查询是否锁表 show OPEN TABLES where In_use 0; 示例：新建一个会话执行如下的显示锁示例

1、查询进程

show processlist

2、查询到相对应的进程，然后 kill id

验证（kill后再看是否还有锁）

2、查询是否锁表

show OPEN TABLES where In_use > 0;

示例：

新建一个会话执行如下的显示锁示例

LOCK TABLES account_data.account READ;
SELECT SLEEP(160);
UNLOCK TABLES account_data.account;

另开启一个会话检查锁表情况：

mysql> select * from information_schema.innodb_locksG;
Empty set, 1 warning (0.00 sec)

ERROR:
No query specified

mysql> show processlistG;
*************************** 1. row ***************************
Id: 5
User: root
Host: 192.168.0.206:64294
db: NULL
Command: Sleep
Time: 4051
State:
Info: NULL
*************************** 2. row ***************************
Id: 8
User: root
Host: 192.168.0.206:64297
db: NULL
Command: Sleep
Time: 4042
State:
Info: NULL
*************************** 3. row ***************************
Id: 10
User: root
Host: localhost
db: NULL
Command: Query
Time: 0
State: starting
Info: show processlist
*************************** 4. row ***************************
Id: 19
User: root
Host: 192.168.0.206:54603
db: account_data
Command: Sleep
Time: 245
State:
Info: NULL
*************************** 5. row ***************************
Id: 20
User: root
Host: 192.168.0.206:54604
db: information_schema
Command: Query
Time: 20
State: User sleep
Info: select sleep(160)
5 rows in set (0.00 sec)

ERROR:
No query specified

mysql>

3、在5.5中，information_schema 库中增加了三个关于锁的表（innoDB引擎）：

innodb_trx ## 当前运行的所有事务

innodb_locks ## 当前出现的锁

innodb_lock_waits ## 锁等待的对应关系

先来看一下这三张表结构：

查看正在锁的事务

SELECT * FROM INFORMATION_SCHEMA.INNODB_LOCKS;

查看等待锁的事务

SELECT * FROM INFORMATION_SCHEMA.INNODB_LOCK_WAITS;

查看锁阻塞线程信息

3.1 使用show processlist查看

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 warningsG
*************************** 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。

3.5、查看表锁的情况：

mysql> show status like 'table%';
+----------------------------+---------+
| Variable_name | Value |
+----------------------------+---------+
| Table_locks_immediate | 100 |
| Table_locks_waited | 11 |
+----------------------------+---------+

3.6、查看InnoDB_row_lock状态变量来分析系统上的行锁的争夺情况：

mysql>

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。

参考：https://www.jb51.net/article/201222.htm

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