MYSQL 8.0-INNODB的死锁基础

死锁产生的前提：
多个事务互相持有其他事务所需要的锁，并且这些事务都在等待其他事务释放锁资源，但是这些互相持有锁的事务没有一个释放持有的其他事务所需要的锁。

死锁的案例

这个案例来自官方文档

步骤	事务A	事务B
步骤1	START TRANSACTION;
步骤2	SELECT value FROM Animals WHERE name='Aardvark' FOR SHARE;
步骤3		START TRANSACTION;
步骤4		SELECT value FROM Birds WHERE name='Buzzard' FOR SHARE;
步骤5		UPDATE Animals SET value=30 WHERE name='Aardvark';
步骤6	UPDATE Birds SET value=40 WHERE name='Buzzard';
步骤7	ROLLBACK
步骤8		ROLLBAKC

在步骤4执行完成后，可以查看锁状态

mysql> SELECT ENGINE_TRANSACTION_ID as Trx_Id, 
              OBJECT_NAME as `Table`, 
              INDEX_NAME as `Index`, 
              LOCK_DATA as Data, 
              LOCK_MODE as Mode, 
              LOCK_STATUS as Status, 
              LOCK_TYPE as Type 
        FROM performance_schema.data_locks;
+-----------------+---------+---------+------------+---------------+---------+--------+
| Trx_Id          | Table   | Index   | Data       | Mode          | Status  | Type   |
+-----------------+---------+---------+------------+---------------+---------+--------+
| 421291106147544 | Animals | NULL    | NULL       | IS            | GRANTED | TABLE  |
| 421291106147544 | Animals | PRIMARY | 'Aardvark' | S,REC_NOT_GAP | GRANTED | RECORD |
| 421291106148352 | Birds   | NULL    | NULL       | IS            | GRANTED | TABLE  |
| 421291106148352 | Birds   | PRIMARY | 'Buzzard'  | S,REC_NOT_GAP | GRANTED | RECORD |
+-----------------+---------+---------+------------+---------------+---------+--------+
4 rows in set (0.00 sec)

步骤6执行完成后，因为死锁而回滚数据

mysql> UPDATE Birds SET value=40 WHERE name='Buzzard';
ERROR 1213 (40001): Deadlock found when trying to get lock; try restarting transaction

mysql> SELECT `count` FROM INFORMATION_SCHEMA.INNODB_METRICS
          WHERE NAME="lock_deadlocks";
+-------+
| count |
+-------+
|     1 |
+-------+
1 row in set (0.00 sec)

可以通过`SHOW ENGIN INNODB STATUS` 指令可以获取最近一条死锁的日志

mysql> SHOW ENGINE INNODB STATUS;
------------------------
LATEST DETECTED DEADLOCK
------------------------
2022-11-25 15:58:22 139815661168384
*** (1) TRANSACTION:
TRANSACTION 43260, ACTIVE 186 sec starting index read
mysql tables in use 1, locked 1
LOCK WAIT 4 lock struct(s), heap size 1128, 2 row lock(s)
MySQL thread id 19, OS thread handle 139815619204864, query id 143 localhost u2 updating
UPDATE Animals SET value=30 WHERE name='Aardvark'

*** (1) HOLDS THE LOCK(S):
RECORD LOCKS space id 28 page no 4 n bits 72 index PRIMARY of table `test`.`Birds` trx id 43260 lock mode S locks rec but not gap
Record lock, heap no 2 PHYSICAL RECORD: n_fields 4; compact format; info bits 0
 0: len 7; hex 42757a7a617264; asc Buzzard;;
 1: len 6; hex 00000000a8fb; asc       ;;
 2: len 7; hex 82000000e40110; asc        ;;
 3: len 4; hex 80000014; asc     ;;


*** (1) WAITING FOR THIS LOCK TO BE GRANTED:
RECORD LOCKS space id 27 page no 4 n bits 72 index PRIMARY of table `test`.`Animals` trx id 43260 lock_mode X locks rec but not gap waiting
Record lock, heap no 2 PHYSICAL RECORD: n_fields 4; compact format; info bits 0
 0: len 8; hex 416172647661726b; asc Aardvark;;
 1: len 6; hex 00000000a8f9; asc       ;;
 2: len 7; hex 82000000e20110; asc        ;;
 3: len 4; hex 8000000a; asc     ;;


*** (2) TRANSACTION:
TRANSACTION 43261, ACTIVE 209 sec starting index read
mysql tables in use 1, locked 1
LOCK WAIT 4 lock struct(s), heap size 1128, 2 row lock(s)
MySQL thread id 18, OS thread handle 139815618148096, query id 146 localhost u1 updating
UPDATE Birds SET value=40 WHERE name='Buzzard'

*** (2) HOLDS THE LOCK(S):
RECORD LOCKS space id 27 page no 4 n bits 72 index PRIMARY of table `test`.`Animals` trx id 43261 lock mode S locks rec but not gap
Record lock, heap no 2 PHYSICAL RECORD: n_fields 4; compact format; info bits 0
 0: len 8; hex 416172647661726b; asc Aardvark;;
 1: len 6; hex 00000000a8f9; asc       ;;
 2: len 7; hex 82000000e20110; asc        ;;
 3: len 4; hex 8000000a; asc     ;;


*** (2) WAITING FOR THIS LOCK TO BE GRANTED:
RECORD LOCKS space id 28 page no 4 n bits 72 index PRIMARY of table `test`.`Birds` trx id 43261 lock_mode X locks rec but not gap waiting
Record lock, heap no 2 PHYSICAL RECORD: n_fields 4; compact format; info bits 0
 0: len 7; hex 42757a7a617264; asc Buzzard;;
 1: len 6; hex 00000000a8fb; asc       ;;
 2: len 7; hex 82000000e40110; asc        ;;
 3: len 4; hex 80000014; asc     ;;

*** WE ROLL BACK TRANSACTION (2)
------------
TRANSACTIONS
------------
Trx id counter 43262
Purge done for trx's n:o < 43256 undo n:o < 0 state: running but idle
History list length 0
LIST OF TRANSACTIONS FOR EACH SESSION:
---TRANSACTION 421291106147544, not started
0 lock struct(s), heap size 1128, 0 row lock(s)
---TRANSACTION 421291106146736, not started
0 lock struct(s), heap size 1128, 0 row lock(s)
---TRANSACTION 421291106145928, not started
0 lock struct(s), heap size 1128, 0 row lock(s)
---TRANSACTION 43260, ACTIVE 219 sec
4 lock struct(s), heap size 1128, 2 row lock(s), undo log entries 1
MySQL thread id 19, OS thread handle 139815619204864, query id 143 localhost u2

日志中具体的参数含义可以看看另外一篇优秀的博客：https://blog.csdn.net/oddrock/article/details/130201152

通过`@@error_log` 查看事务和锁中的错误信息

mysql> SELECT @@log_error;
+---------------------+
| @@log_error         |
+---------------------+
| /var/log/mysqld.log |
+---------------------+
1 row in set (0.00 sec)

TRANSACTION 43260, ACTIVE 186 sec starting index read
mysql tables in use 1, locked 1
LOCK WAIT 4 lock struct(s), heap size 1128, 2 row lock(s)
MySQL thread id 19, OS thread handle 139815619204864, query id 143 localhost u2 updating
UPDATE Animals SET value=30 WHERE name='Aardvark'
RECORD LOCKS space id 28 page no 4 n bits 72 index PRIMARY of table `test`.`Birds` trx id 43260 lock mode S locks rec but not gap
Record lock, heap no 2 PHYSICAL RECORD: n_fields 4; compact format; info bits 0
 0: len 7; hex 42757a7a617264; asc Buzzard;;
 1: len 6; hex 00000000a8fb; asc       ;;
 2: len 7; hex 82000000e40110; asc        ;;
 3: len 4; hex 80000014; asc     ;;

RECORD LOCKS space id 27 page no 4 n bits 72 index PRIMARY of table `test`.`Animals` trx id 43260 lock_mode X locks rec but not gap waiting
Record lock, heap no 2 PHYSICAL RECORD: n_fields 4; compact format; info bits 0
 0: len 8; hex 416172647661726b; asc Aardvark;;
 1: len 6; hex 00000000a8f9; asc       ;;
 2: len 7; hex 82000000e20110; asc        ;;
 3: len 4; hex 8000000a; asc     ;;

TRANSACTION 43261, ACTIVE 209 sec starting index read
mysql tables in use 1, locked 1
LOCK WAIT 4 lock struct(s), heap size 1128, 2 row lock(s)
MySQL thread id 18, OS thread handle 139815618148096, query id 146 localhost u1 updating
UPDATE Birds SET value=40 WHERE name='Buzzard'
RECORD LOCKS space id 27 page no 4 n bits 72 index PRIMARY of table `test`.`Animals` trx id 43261 lock mode S locks rec but not gap
Record lock, heap no 2 PHYSICAL RECORD: n_fields 4; compact format; info bits 0
 0: len 8; hex 416172647661726b; asc Aardvark;;
 1: len 6; hex 00000000a8f9; asc       ;;
 2: len 7; hex 82000000e20110; asc        ;;
 3: len 4; hex 8000000a; asc     ;;

RECORD LOCKS space id 28 page no 4 n bits 72 index PRIMARY of table `test`.`Birds` trx id 43261 lock_mode X locks rec but not gap waiting
Record lock, heap no 2 PHYSICAL RECORD: n_fields 4; compact format; info bits 0
 0: len 7; hex 42757a7a617264; asc Buzzard;;
 1: len 6; hex 00000000a8fb; asc       ;;
 2: len 7; hex 82000000e40110; asc        ;;
 3: len 4; hex 80000014; asc     ;;

死锁的避免和分析

除了上面的两种查看死锁日志信息，可以通过innodb_print_all_deadlock指令记录最近的死锁信息。不过在死锁分析使用完毕后要关闭
保持事务最小化，并且保证事务持续时间尽可能的短。尽量不要让事务会话长时间链接
如果对一个表或者多个表进行行数据操作，那么尽可能抽象成一个方法，按照某种固定顺序执行，而不是每次使用都重写一个
如果涉及的逻辑和表场景复杂，可以调账数据库的事务级别为序列化类型

解除死锁线程的方法

1、查看正在进行中的事务

SELECT * FROM information_schema.INNODB_TRX

2、查看正在锁的事务

SELECT * FROM INFORMATION_SCHEMA.INNODB_LOCKS;

3、查看等待锁的事务

SELECT * FROM INFORMATION_SCHEMA.INNODB_LOCK_WAITS;

4、查看是否锁表

SHOW OPEN TABLES where In_use > 0;

官网文档地址：https://dev.mysql.com/doc/refman/8.0/en/innodb-deadlocks.html

posted @ 2020-05-20 15:30 PerfectLi 阅读(259) 评论(0) 编辑收藏举报

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PerfectLi

MYSQL 8.0-INNODB的死锁基础

死锁的案例

可以通过`SHOW ENGIN INNODB STATUS` 指令可以获取最近一条死锁的日志

通过`@@error_log` 查看事务和锁中的错误信息

死锁的避免和分析

解除死锁线程的方法

公告

随笔分类

阅读排行榜

推荐排行榜

PerfectLi

MYSQL 8.0-INNODB的死锁基础

死锁的案例

可以通过SHOW ENGIN INNODB STATUS 指令可以获取最近一条死锁的日志

通过@@error_log 查看事务和锁中的错误信息

死锁的避免和分析

解除死锁线程的方法

公告

随笔分类

阅读排行榜

推荐排行榜

可以通过`SHOW ENGIN INNODB STATUS` 指令可以获取最近一条死锁的日志

通过`@@error_log` 查看事务和锁中的错误信息