mysql 查看死锁和去除死锁

本文转载自查看原文 2019-09-09 14:26 8042 通用实践/ 高并发/ 开发经验/ Mysql/ 性能优化/ java经验集锦/ SQL优化/ 大数据/ DB/ SQL

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> 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 specified
mysql> 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 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：

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>

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：http://blog.csdn.net/hw_libo/article/details/39080809

原文地址：https://www.cnblogs.com/duanxz/p/4394641.html

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