事務具有ACID特性，本篇對Sequoia DB巨杉數據庫的分佈式事務進行介紹，並對當前數據庫版本支持的RU（讀未提交）、RC（讀已提交）和RS（讀穩定性）三種隔離級別進行設置和驗證。
1 部署架構
本實驗Sequoia DB巨杉數據庫集羣拓撲結構爲單副本三分區，包括1個SequoiaSQL-MySQL數據庫實例節點、1個存儲引擎節點、1個編目節點和3個數據節點。
2 MySQL實例層創建庫和表
2.1 連接MySQL
[sdbadmin@sdbserver1 mysql]$ mysql -h 127.0.0.1 -uroot
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 4
Server version: 5.7.25 Source distribution
Copyright (c) 2000, 2019, Oracle and/or its affiliates. All rights reserved.
Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.
Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
2.2 查看數據庫和表
mysql> use test;
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A
Database changed
mysql> show create table emp\G;
*************************** 1. row ***************************
Table: emp
Create Table: CREATE TABLE `emp` (
`empno` int(11) NOT NULL AUTO_INCREMENT,
`ename` varchar(200) COLLATE utf8mb4_bin DEFAULT NULL,
`age` int(11) DEFAULT NULL,
PRIMARY KEY (`empno`)
) ENGINE=SEQUOIADB AUTO_INCREMENT=1002 DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_bin
1 row in set (0.00 sec)
ERROR:
No query specified
mysql> select * from emp;
+-------+-------+------+
| empno | ename | age |
+-------+-------+------+
| 1 | Alen | 23 |
| 2 | Lucy | 25 |
| 3 | Tom | 30 |
| 4 | Jack | 35 |
+-------+-------+------+
4 rows in set (0.01 sec)
在SequoiaSQL-MySQL實例中創建的表將會默認使用SEQUOIADB存儲引擎，包含主鍵或唯一鍵的表將會默認以唯一鍵作爲分區鍵自動分區。
3 查看SequoiaDB事務隔離級別
1）進入SequoiaDB Shell交互界面並獲取數據庫連接
[sdbadmin@sdbserver1 mysql]$ sdb
Welcome to SequoiaDB shell!
help() for help, Ctrl+c or quit to exit
> var db=new Sdb('localhost',11810)
Takes 0.005610s
2）查看事務的隔離級別
> db.snapshot(SDB_SNAP_CONFIGS,{},{NodeName:'',transactionon:'',transisolation:''})
{
"NodeName": "sdbserver1:11800",
"transactionon": "TRUE",
"transisolation": 0
}
{
"NodeName": "sdbserver1:11810",
"transactionon": "TRUE",
"transisolation": 0
}
{
"NodeName": "sdbserver1:11820",
"transactionon": "TRUE",
"transisolation": 0
}
{
"NodeName": "sdbserver1:11830",
"transactionon": "TRUE",
"transisolation": 0
}
{
"NodeName": "sdbserver1:11840",
"transactionon": "TRUE",
"transisolation": 0
}
Return 5 row(s).
Takes 0.002294s.
transisolation參數指定隔離結拜，0表示隔離級別爲讀未提交。
transactionon爲true表示開啓事務功能。
4 驗證事務隔離級別
4.1 驗證RU讀未提交隔離級別
1）開啓會話1
[sdbadmin@sdbserver1 mysql]$ mysql -h 127.0.0.1 -uroot
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 5
Server version: 5.7.25 Source distribution
Copyright (c) 2000, 2019, Oracle and/or its affiliates. All rights reserved.
Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.
Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
mysql> begin;
Query OK, 0 rows affected (0.00 sec)
mysql> update test.emp set age=30 where empno=1;
Query OK, 1 row affected (0.01 sec)
Rows matched: 1 Changed: 1 Warnings: 0
mysql> select * from test.emp;
+-------+-------+------+
| empno | ename | age |
+-------+-------+------+
| 1 | Alen | 30 |
| 2 | Lucy | 25 |
| 3 | Tom | 30 |
| 4 | Jack | 35 |
+-------+-------+------+
4 rows in set (0.00 sec)
可看到empno=1的年齡已更改爲30.
2）開啓會話2
[sdbadmin@sdbserver1 ~]$ mysql -h127.0.0.1 -uroot
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 6
Server version: 5.7.25 Source distribution
Copyright (c) 2000, 2013, Oracle and/or its affiliates. All rights reserved.
Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.
Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
mysql> select * from test.emp;
+-------+-------+------+
| empno | ename | age |
+-------+-------+------+
| 1 | Alen | 30 |
| 2 | Lucy | 25 |
| 3 | Tom | 30 |
| 4 | Jack | 35 |
+-------+-------+------+
4 rows in set (0.01 sec)
mysql> begin;
Query OK, 0 rows affected (0.00 sec)
mysql> select * from test.emp;
+-------+-------+------+
| empno | ename | age |
+-------+-------+------+
| 1 | Alen | 30 |
| 2 | Lucy | 25 |
| 3 | Tom | 30 |
| 4 | Jack | 35 |
+-------+-------+------+
4 rows in set (0.01 sec)
可以看到，即使會話1沒有提交，會話2都可以看到已修改過的數據。
3）會話1和會話2提交事務
mysql> commit;
Query OK, 0 rows affected (0.00 sec)
4.2 驗證RC讀已提交隔離級別
1）修改事務隔離級別爲RC
[sdbadmin@sdbserver1 ~]$ sdb
Welcome to SequoiaDB shell!
help() for help, Ctrl+c or quit to exit
> var db=new Sdb('localhost',11810)
Takes 0.005333s.
> db.updateConf({transisolation:1},{Global:true})
Takes 0.034368s.
2）查看節點事務隔離級別
> db.snapshot(SDB_SNAP_CONFIGS,{},{NodeName:'',transactionon:'',transisolation:''})
{
"NodeName": "sdbserver1:11800",
"transactionon": "TRUE",
"transisolation": 1
}
{
"NodeName": "sdbserver1:11810",
"transactionon": "TRUE",
"transisolation": 1
}
{
"NodeName": "sdbserver1:11820",
"transactionon": "TRUE",
"transisolation": 1
}
{
"NodeName": "sdbserver1:11830",
"transactionon": "TRUE",
"transisolation": 1
}
{
"NodeName": "sdbserver1:11840",
"transactionon": "TRUE",
"transisolation": 1
}
Return 5 row(s).
Takes 0.005910s.
transisolation爲1 表示隔離級別爲讀已提交。
3）開啓會話1
mysql> begin ;
Query OK, 0 rows affected (0.00 sec)
mysql> update test.emp set age=25 where empno=1;
Query OK, 1 row affected (0.01 sec)
Rows matched: 1 Changed: 1 Warnings: 0
將age從30改爲25。
mysql> select * from test.emp;
+-------+-------+------+
| empno | ename | age |
+-------+-------+------+
| 1 | Alen | 25 |
| 2 | Lucy | 25 |
| 3 | Tom | 30 |
| 4 | Jack | 35 |
+-------+-------+------+
4 rows in set (0.00 sec)
4）開啓會話2
mysql> begin;
Query OK, 0 rows affected (0.00 sec)
mysql> select * from test.emp;
+-------+-------+------+
| empno | ename | age |
+-------+-------+------+
| 1 | Alen | 30 |
| 2 | Lucy | 25 |
| 3 | Tom | 30 |
| 4 | Jack | 35 |
+-------+-------+------+
4 rows in set (0.01 sec)
可以看到，會話2無法看到修改後的數據。
5）會話1提交
mysql> commit;
Query OK, 0 rows affected (0.00 sec)
6）會話2可以看到修改後的數據
mysql> select * from test.emp;
+-------+-------+------+
| empno | ename | age |
+-------+-------+------+
| 1 | Alen | 25 |
| 2 | Lucy | 25 |
| 3 | Tom | 30 |
| 4 | Jack | 35 |
+-------+-------+------+
4 rows in set (0.00 sec)
7）會話2提交
mysql> commit;
Query OK, 0 rows affected (0.00 sec)
4.3 驗證RS讀穩定性隔離級別
1）修改事務隔離級別爲RS
> db.updateConf({transisolation:2},{Global:true})
Takes 0.028669s.
2）查看節點事務隔離級別
> db.snapshot(SDB_SNAP_CONFIGS,{},{NodeName:'',transactionon:'',transisolation:''})
{
"NodeName": "sdbserver1:11800",
"transactionon": "TRUE",
"transisolation": 2
}
{
"NodeName": "sdbserver1:11810",
"transactionon": "TRUE",
"transisolation": 2
}
{
"NodeName": "sdbserver1:11820",
"transactionon": "TRUE",
"transisolation": 2
}
{
"NodeName": "sdbserver1:11830",
"transactionon": "TRUE",
"transisolation": 2
}
{
"NodeName": "sdbserver1:11840",
"transactionon": "TRUE",
"transisolation": 2
}
Return 5 row(s).
Takes 0.004875s.
transisolation爲2 表示隔離級別爲讀穩定性。
3）開啓會話1
mysql> begin;
Query OK, 0 rows affected (0.00 sec)
mysql> select * from test.emp;
+-------+-------+------+
| empno | ename | age |
+-------+-------+------+
| 1 | Alen | 25 |
| 2 | Lucy | 25 |
| 3 | Tom | 30 |
| 4 | Jack | 35 |
+-------+-------+------+
4 rows in set (0.00 sec)
4）開啓會話2更新數據
mysql> begin;
Query OK, 0 rows affected (0.00 sec)
mysql> update test.emp set age=30 where ename='Alen';
會話2的update操作發生等待，只有等會話1執行commit或rollback後，會話2才能執行成功。
5）會話1執行提交操作
mysql> commit;
Query OK, 0 rows affected (0.00 sec)
以上就是對Sequoia DB巨杉數據庫分佈式事務管理的演示。