MySQL数据库innodb_rollback_on_timeout参数

2020-01-23 21:35:31 浏览数 (1)

在使用MySQL数据库时，有时会出现ERROR 1205 (HY000): Lock wait timeout exceeded; try restarting transaction 这样的报错。而在一个事务中，如果其中一条sql执行时出现此报错，对本事务的其他脚本是否有影响呢，后面如果执行commit操作，报错之前语句的结果是否成功呢？这个结果与隔离级别以及innodb_rollback_on_timeout参数设置有关。

注：

MySQL默认隔离级别为 REPEATABLE-READ，innodb_rollback_on_timeout为OFF，本文基于innodb表（支持事务）进行测试。

1. 准备工作

1.1 测试环境

MySQL 8.0

1.2 创建测试表及预备数据

创建一张测试表，并插入一条记录

代码语言：javascript复制
mysql> use testdb;
Database changed
mysql> create table test1(id int primary key,name varchar(20));
Query OK, 0 rows affected (0.01 sec)

mysql> insert into test1 values(1,'1wdrt5');
Query OK, 1 row affected (0.00 sec)

mysql> select  * from  test1;
 ---- -------- 
| id | name   |
 ---- --------
|  1 | 1wdrt5 | ---- -------- 
1 row in set (0.00 sec)

下面将根据不同的隔离级别及innodb_rollback_on_timeout启停情况进行测试。

2. 测试过程

2.1 隔离级别REPEATABLE-READ & innodb_rollback_on_timeout =OFF

a) 测试过程：

session A

session B

mysql> begin;Query OK, 0 rows affected (0.00 sec)mysql> select * from test1 where id=1 for update; ---- -------- | id | name | ---- -------- | 1 | 1wdrt5 | ---- -------- 1 row in set (0.00 sec) mysql> select * from test1; ---- -------- | id | name | ---- -------- | 1 | 1wdrt5 || 2 | 2edft6 | ---- -------- 2 rows in set (0.00 sec)

mysql> begin;Query OK, 0 rows affected (0.00 sec)mysql> select * from test1; ---- -------- | id | name | ---- -------- | 1 | 1wdrt5 | ---- -------- 1 row in set (0.00 sec)mysql> insert into test1 values(2,'2edft6');Query OK, 1 row affected (0.00 sec)mysql> delete from test1 where id=1;ERROR 1205 (HY000): Lock wait timeout exceeded; try restarting transactionmysql> commit;Query OK, 0 rows affected (0.02 sec)mysql> select * from test1; ---- -------- | id | name | ---- -------- | 1 | 1wdrt5 || 2 | 2edft6 | ---- -------- 2 rows in set (0.00 sec)

b） 测试结果：

隔离级别REPEATABLE-READ & innodb_rollback_on_timeout =OFF （2个参数均为默认值）的情况下，即使事务中有超时回滚报错，超时前的sql不会回滚，依旧执行成功。

2.2 隔离级别为READ-COMMITTED & innodb_rollback_on_timeout =OFF

a) 测试过程

session A

session B

mysql> show global variables like 'transaction_isolation'; ----------------------- ---------------- | Variable_name | Value | ----------------------- ---------------- | transaction_isolation | READ-COMMITTED | ----------------------- ---------------- 1 row in set (0.01 sec)mysql> use testdb;Database changedmysql> begin ;Query OK, 0 rows affected (0.00 sec)mysql> select * from test1; ---- -------- | id | name | ---- -------- | 1 | 1wdrt5 || 2 | 2edft6 | ---- -------- 2 rows in set (0.00 sec)mysql> select * from test1 where id =1 for update; ---- -------- | id | name | ---- -------- | 1 | 1wdrt5 | ---- -------- 1 row in set (0.00 sec) mysql> commit;Query OK, 0 rows affected (0.00 sec)mysql> select * from test1; ---- -------- | id | name | ---- -------- | 1 | 1wdrt5 || 2 | 2edft6 || 3 | 3eft6 | ---- -------- 3 rows in set (0.00 sec)

mysql> begin;Query OK, 0 rows affected (0.00 sec)mysql> select * from test1; ---- -------- | id | name | ---- -------- | 1 | 1wdrt5 || 2 | 2edft6 | ---- -------- 2 rows in set (0.00 sec)mysql> insert into test1 values(3,'3eft6');Query OK, 1 row affected (0.00 sec)mysql> delete from test1 where id=1;ERROR 1205 (HY000): Lock wait timeout exceeded; try restarting transactionmysql> commit;Query OK, 0 rows affected (0.00 sec)mysql> select * from test1; ---- -------- | id | name | ---- -------- | 1 | 1wdrt5 || 2 | 2edft6 || 3 | 3eft6 | ---- -------- 3 rows in set (0.00 sec)

b）测试结果：

隔离级别为READ-COMMITTED & innodb_rollback_on_timeout =OFF 情况下，即使事务中有超时回滚报错，超时前的sql不会回滚，依旧执行成功，同2者均为默认值的情况。

2.3 隔离级别REPEATABLE-READ & innodb_rollback_on_timeout =ON

注：innodb_rollback_on_timeout不能在线修改，需要修改配置文件后重启生效

测试过程：

a) 修改配置文件，重启数据库

在my.cnf文件里添加innodb_rollback_on_timeout=on 再重启数据库即可生效

代码语言：javascript复制
mysql> show global variables like 'transaction_isolation';
 ----------------------- ----------------- 
| Variable_name         | Value           |
 ----------------------- ----------------- 
| transaction_isolation | REPEATABLE-READ |
 ----------------------- ----------------- 
1 row in set (0.00 sec)

mysql> show global variables like 'innodb_rollback_on_timeout';
 ---------------------------- ------- 
| Variable_name              | Value |
 ---------------------------- ------- 
| innodb_rollback_on_timeout | ON    | ---------------------------- ------- 
1 row in set (0.00 sec)

b) 事务测试过程

session A

session B

mysql> select * from test1; ---- -------- | id | name | ---- -------- | 1 | 1wdrt5 || 2 | 2edft6 || 3 | 3eft6 | ---- -------- 3 rows in set (0.00 sec)mysql> select * from test1 where id=1 for update; ---- -------- | id | name | ---- -------- | 1 | 1wdrt5 | ---- -------- 1 row in set (0.00 sec) mysql> commit;Query OK, 0 rows affected (0.00 sec)mysql> select * from test1; ---- -------- | id | name | ---- -------- | 1 | 1wdrt5 || 2 | 2edft6 || 3 | 3eft6 | ---- -------- 3 rows in set (0.00 sec)

mysql> use testdb;Database changedmysql> begin;Query OK, 0 rows affected (0.00 sec)mysql> select * from test1; ---- -------- | id | name | ---- -------- | 1 | 1wdrt5 || 2 | 2edft6 || 3 | 3eft6 | ---- -------- 3 rows in set (0.00 sec)mysql> insert into test1 values(4,'4rgy7');Query OK, 1 row affected (0.00 sec)mysql> delete from test1 where id=1;ERROR 1205 (HY000): Lock wait timeout exceeded; try restarting transactionmysql> commit;Query OK, 0 rows affected (0.00 sec)mysql> select * from test1; ---- -------- | id | name | ---- -------- | 1 | 1wdrt5 || 2 | 2edft6 || 3 | 3eft6 | ---- -------- 3 rows in set (0.00 sec)

c) 测试结果：

隔离级别REPEATABLE-READ & innodb_rollback_on_timeout =ON 的情况下，事务中有超时回滚报错时，超时前sql也会回滚。

2.4 隔离级别为READ-COMMITTED & innodb_rollback_on_timeout =ON

a) 参数调整

代码语言：javascript复制
mysql> set global  transaction_isolation='READ-COMMITTED';mysql> exit#  重新登录mysql> show global variables like 'transaction_isolation'; ----------------------- ---------------- | Variable_name         | Value          | ----------------------- ---------------- | transaction_isolation | READ-COMMITTED | ----------------------- ---------------- 1 row in set (0.00 sec)
mysql> show global variables like 'innodb_rollback_on_timeout'; ---------------------------- ------- | Variable_name              | Value | ---------------------------- ------- | innodb_rollback_on_timeout | ON    | ---------------------------- ------- 1 row in set (0.00 sec)

b) 测试过程

session A

session B

mysql> use testdb;Database changedmysql> begin;Query OK, 0 rows affected (0.00 sec)mysql> select * from test1; ---- -------- | id | name | ---- -------- | 1 | 1wdrt5 || 2 | 2edft6 || 3 | 3eft6 | ---- -------- 3 rows in set (0.00 sec)mysql> select * from test1 where id =1 for update; ---- -------- | id | name | ---- -------- | 1 | 1wdrt5 | ---- -------- 1 row in set (0.00 sec) mysql> commit;Query OK, 0 rows affected (0.00 sec)mysql> select * from test1; ---- -------- | id | name | ---- -------- | 1 | 1wdrt5 || 2 | 2edft6 || 3 | 3eft6 || 5 | 5thu8 | ---- -------- 4 rows in set (0.00 sec)

mysql> use testdb;Database changedmysql> select * from test1; ---- -------- | id | name | ---- -------- | 1 | 1wdrt5 || 2 | 2edft6 || 3 | 3eft6 | ---- -------- 3 rows in set (0.00 sec)mysql> insert into test1 values(5,'5thu8');Query OK, 1 row affected (0.01 sec)mysql> delete from test1 where id =1;ERROR 1205 (HY000): Lock wait timeout exceeded; try restarting transactionmysql> commit;Query OK, 0 rows affected (0.00 sec)mysql> select * from test1; ---- -------- | id | name | ---- -------- | 1 | 1wdrt5 || 2 | 2edft6 || 3 | 3eft6 || 5 | 5thu8 | ---- -------- 4 rows in set (0.00 sec)

c) 测试结果

隔离级别为READ-COMMITTED & innodb_rollback_on_timeout =ON的情况下，即使事务中有超时回滚报错，超时前的sql不会回滚，依旧执行成功，同2者均为默认值的情况。

3. 小结

在MySQL8.0 中,仅有在隔离级别为READ-COMMITTED & innodb_rollback_on_timeout =ON情况下，事务中有超时回滚报错时，超时前sql也会回滚。

隔离级别

innodb_rollback_on_timeout

结果

REPEATABLE-READ

OFF

超时回滚前的SQL不会自动回滚

READ-COMMITTED

OFF

超时回滚前的SQL不会自动回滚

REPEATABLE-READ

ON

超时回滚前的SQL会自动回滚

READ-COMMITTED

ON

超时回滚前的SQL不会自动回滚

TIPS：

1) 测试过程中可以查看information_schema.innodb_trx表观察事务情况，在不同的版本中事务情况不一样.例如，隔离级别REPEATABLE-READ & innodb_rollback_on_timeout=on的情况下，MySQL5.6 中整个事务回滚后会自动创建一个事务，而MySQL5.7则不会再自动创建事务。

2) 在生产环境使用中,建议将innodb_rollback_on_timeout 设置为ON。应用程序一定要做好事务控制，在一个事务出现异常时必须进行显式rollback

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