mysql死锁或锁表分析

五、 mysql 查看死锁和去除死锁

现象： 应用服务器报表查询转圈，超时，查看服务器top: CPU 400%

1、打开Navicate, 或者服务器登录mysql -uroot -p , 查询进程

 show processlist其中第一列为占用mysql的进程Id 

2、 查询到相对应的进程，然后 kill id
对应 Time 列，显示sql 语句已经执行的时长

验证（kill后再看是否还有锁）

 -- 验证是否还有死锁或锁表show OPEN TABLES where In_use > 0;

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> show OPEN TABLES where In_use > 0;
+--------------+---------+--------+-------------+
| Database     | Table   | In_use | Name_locked |
+--------------+---------+--------+-------------+
| account_data | account |      1 |           0 |
+--------------+---------+--------+-------------+
1 row in set (0.00 sec)
mysql> select * from information_schema.innodb_locks\G;
Empty set, 1 warning (0.00 sec)ERROR:
No query specifiedmysql> show processlist\G;
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 specifiedmysql>

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：

root@127.0.0.1 : information_schema 13:28:38> desc innodb_locks;
+————-+———————+——+—–+———+——-+
| Field       | Type                | Null | Key | Default | Extra |
+————-+———————+——+—–+———+——-+
| lock_id     | varchar(81)         | NO   |     |         |       |#锁ID
| lock_trx_id | varchar(18)         | NO   |     |         |       |#拥有锁的事务ID
| lock_mode   | varchar(32)         | NO   |     |         |       |#锁模式
| lock_type   | varchar(32)         | NO   |     |         |       |#锁类型
| lock_table  | varchar(1024)       | NO   |     |         |       |#被锁的表
| lock_index  | varchar(1024)       | YES  |     | NULL    |       |#被锁的索引
| lock_space  | bigint(21) unsigned | YES  |     | NULL    |       |#被锁的表空间号
| lock_page   | bigint(21) unsigned | YES  |     | NULL    |       |#被锁的页号
| lock_rec    | bigint(21) unsigned | YES  |     | NULL    |       |#被锁的记录号
| lock_data   | varchar(8192)       | YES  |     | NULL    |       |#被锁的数据
+————-+———————+——+—–+———+——-+
10 rows in set (0.00 sec)
root@127.0.0.1 : information_schema 13:28:56> desc innodb_lock_waits;
+——————-+————-+——+—–+———+——-+
| Field | Type | Null | Key | Default | Extra |
+——————-+————-+——+—–+———+——-+
| requesting_trx_id | varchar(18) | NO | | | |#请求锁的事务ID
| requested_lock_id | varchar(81) | NO | | | |#请求锁的锁ID
| blocking_trx_id | varchar(18) | NO | | | |#当前拥有锁的事务ID
| blocking_lock_id | varchar(81) | NO | | | |#当前拥有锁的锁ID
+——————-+————-+——+—–+———+——-+
4 rows in set (0.00 sec)root@127.0.0.1 : information_schema 13:29:05> desc innodb_trx ;
+—————————-+———————+——+—–+———————+——-+
| Field | Type | Null | Key | Default | Extra |
+—————————-+———————+——+—–+———————+——-+
| trx_id | varchar(18) | NO | | | |#事务ID
| trx_state | varchar(13) | NO | | | |#事务状态：
| trx_started | datetime | NO | | 0000-00-00 00:00:00 | |#事务开始时间；
| trx_requested_lock_id | varchar(81) | YES | | NULL | |#innodb_locks.lock_id
| trx_wait_started | datetime | YES | | NULL | |#事务开始等待的时间
| trx_weight | bigint(21) unsigned | NO | | 0 | |#
| trx_mysql_thread_id | bigint(21) unsigned | NO | | 0 | |#事务线程ID
| trx_query | varchar(1024) | YES | | NULL | |#具体SQL语句
| trx_operation_state | varchar(64) | YES | | NULL | |#事务当前操作状态
| trx_tables_in_use | bigint(21) unsigned | NO | | 0 | |#事务中有多少个表被使用
| trx_tables_locked | bigint(21) unsigned | NO | | 0 | |#事务拥有多少个锁
| trx_lock_structs | bigint(21) unsigned | NO | | 0 | |#
| trx_lock_memory_bytes | bigint(21) unsigned | NO | | 0 | |#事务锁住的内存大小（B）
| trx_rows_locked | bigint(21) unsigned | NO | | 0 | |#事务锁住的行数
| trx_rows_modified | bigint(21) unsigned | NO | | 0 | |#事务更改的行数
| trx_concurrency_tickets | bigint(21) unsigned | NO | | 0 | |#事务并发票数
| trx_isolation_level | varchar(16) | NO | | | |#事务隔离级别
| trx_unique_checks | int(1) | NO | | 0 | |#是否唯一性检查
| trx_foreign_key_checks | int(1) | NO | | 0 | |#是否外键检查
| trx_last_foreign_key_error | varchar(256) | YES | | NULL | |#最后的外键错误
| trx_adaptive_hash_latched | int(1) | NO | | 0 | |#
| trx_adaptive_hash_timeout | bigint(21) unsigned | NO | | 0 | |#
+—————————-+———————+——+—–+———————+——-+
22 rows in set (0.01 sec)

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 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。

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> show status like 'InnoDB_row_lock%';
+-------------------------------+--------+
| Variable_name                 | Value  |
+-------------------------------+--------+
| Innodb_row_lock_current_waits | 0      |
| Innodb_row_lock_time          | 159372 |
| Innodb_row_lock_time_avg      | 39843  |
| Innodb_row_lock_time_max      | 51154  |
| Innodb_row_lock_waits         | 4      |
+-------------------------------+--------+
5 rows in set (0.01 sec)
mysql>