MYSQL-使用mycat工具实现mysql主从读写分离

1. 读写分离原理介绍

生产环境架构：使用主从复制的方式同步数据，再通过读写分离来提高数据库的并发负载能力。

读写分离的优点：
①对于越来越大的访问压力，单台服务器的性能成为了瓶颈，需要分担负载。
②主库负责写，从库负责读，缓解了X锁(排他锁)和S锁(共享锁)的占用。
③从库可以使用myisam引擎，提升查询性能，节约系统开销。
④增加冗余，提高可用性。

读写分离的实现：
①应用程序层实现：在应用程序内部及连接器中实现读写分离。【内部实现读写分离、部署较易、访问能力不大时性能较好、架构调整代码也要调整、难以实现高级应用、无法适用大型应用场景】
②中间件实现：在外部中间件程序实现读写分离。【mycat，其他不多介绍】

2. mycat数据库分库分表中间件

2.1 mycat介绍

mycat是一款开源的、面向企业应用开发的数据库集群。支持事务、ACID，是一款新型的数据库中间件产品。

mysql实现读写分离拓扑图：
在这里插入图片描述
mycat可以在windows、linux、mac、solaris等系统上安装运行。

mycat官网： http://www.mycat.org.cn/

2.2 mycat中间件实现读写分离部署

主机名	IP地址	主从数据库类型	mysql版本	mycat安装主机
master	192.168.10.10	主库	mysql 5.7.31	192.168.10.10
slave	192.168.10.20	从库	mysql 5.7.31

①下载并解压mycat：

# 下载tar包并解压到/usr/local/mycat目录
[root@master ~]# ll Mycat-server-1.6.7.4-release-20200105164103-linux.tar.gz 
-rw-r--r--. 1 root root 21760812 9月  23 15:36 Mycat-server-1.6.7.4-release-20200105164103-linux.tar.gz
[root@master ~]# tar xzf Mycat-server-1.6.7.4-release-20200105164103-linux.tar.gz -C /usr/local/
[root@master ~]# ll /usr/local/mycat/
总用量 12
drwxr-xr-x. 2 root root  190 9月  23 15:37 bin
drwxrwxrwx. 2 root root    6 10月 22 2019 catlet
drwxrwxrwx. 4 root root 4096 9月  23 15:37 conf
drwxr-xr-x. 2 root root 4096 9月  23 15:37 lib
drwxrwxrwx. 2 root root    6 1月   5 2020 logs
-rwxrwxrwx. 1 root root  227 1月   5 2020 version.txt

# 创建mycat用户，并设置密码
[root@master ~]# useradd mycat
[root@master ~]# echo 123456 | passwd --stdin mycat
更改用户 mycat 的密码 。
passwd：所有的身份验证令牌已经成功更新。

# 设置/usr/local/mycat目录的所有者和所属组为mycat
[root@master ~]# chown -R mycat:mycat /usr/local/mycat/
[root@master ~]# ll /usr/local/mycat/
总用量 12
drwxr-xr-x. 2 mycat mycat  190 9月  23 15:37 bin
drwxrwxrwx. 2 mycat mycat    6 10月 22 2019 catlet
drwxrwxrwx. 4 mycat mycat 4096 9月  23 15:37 conf
drwxr-xr-x. 2 mycat mycat 4096 9月  23 15:37 lib
drwxrwxrwx. 2 mycat mycat    6 1月   5 2020 logs
-rwxrwxrwx. 1 mycat mycat  227 1月   5 2020 version.txt

bin程序目录
conf配置文件目录
lib目录主要存放mycat依赖的一些jar文件
logs目录存放日志

# 查看版本信息 1.6.7.4-release
[root@master ~]# cd /usr/local/mycat/
[root@master mycat]# cat version.txt
BuildTime  2020-01-05 08:41:01
GitVersion   f929f96a16852869bc9dc63f4c0f192ee02818e0
MavenVersion 1.6.7.4-release
GitUrl https://github.com/MyCATApache/Mycat-Server.git
MyCatSite http://www.mycat.org.cn

②安装高版本的JDK，至少高于JDK1.7版本：

# 卸载原来的openjdk,安装oracle-jdk
# oracle-jdk性能比openjdk好，兼容性大。
[root@master ~]# java -version
openjdk version "1.8.0_181"
OpenJDK Runtime Environment (build 1.8.0_181-b13)
OpenJDK 64-Bit Server VM (build 25.181-b13, mixed mode)
[root@master ~]# yum remove -y java-* 

# 下载oracle-jdk,解压到/usr/local/下
[root@master ~]# tar xzvf /usr/local/src/jdk-8u191-linux-x64.tar.gz -C /usr/local/

# 在/usr/local目录下做一个软连接
[root@master ~]# cd /usr/local/
oot@master local]# ln -s jdk1.8.0_191 jdk1.8

# 配置环境变量
[root@master ~]# vim /etc/profile.d/jdk8.sh
[root@master ~]# cat /etc/profile.d/jdk8.sh 
export JAVA_HOME=/usr/local/jdk1.8.0_191
export CLASS_PATH=.:$JAVA_HOME/lib/dt.jar:$JAVA_HOME/jar/tools.jar:$JAVA_HOME/jre/lib
export PATH=$JAVA_HOME/bin:$JAVA_HOME/jre/bin:$PATH

# 使环境变量生效
[root@master ~]# chmod +x /etc/profile.d/jdk8.sh
[root@master ~]# /etc/profile.d/jdk8.sh
[root@master ~]# bash

# 查看jdk版本
# 不配置环境变量的话可以做一个软连接
[root@master local]# ln -s /usr/local/jdk1.8/bin/java /usr/bin/java
[root@master local]# java -version
java version "1.8.0_191"
Java(TM) SE Runtime Environment (build 1.8.0_191-b12)
Java HotSpot(TM) 64-Bit Server VM (build 25.191-b12, mixed mode)

③部署mycat启动：

# 配置环境变量，在/etc/profile.d目录下创建mycat.sh脚本，添加环境变量
[root@master ~]# vim /etc/profile.d/mycat.sh
[root@master ~]# cat /etc/profile.d/mycat.sh 
MYCAT_HOME=/usr/local/mycat
PATH=$MYCAT_HOME/bin:$PATH

# 使环境变量立即生效
[root@master ~]# chmod +x /etc/profile.d/mycat.sh
[root@master ~]# source /etc/profile.d/mycat.sh 

# 定义mycat集群中各服务器的IP地址和主机名的映射关系
[root@master ~]# vim /etc/hosts
192.168.10.10 master
192.168.10.20 slave

# 修改mycat的用户信息和授权信息
[root@master ~]# cd /usr/local/mycat/conf/
[root@master conf]# cp server.xml server.xml.bak
[root@master conf]# echo "" > server.xml
[root@master conf]# vim server.xml
# wabong用户用于写,rabong用户用于读
[root@master conf]# cat server.xml
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mycat:server SYSTEM "server.dtd">
<mycat:server xmlns:mycat="http://io.mycat/">
	<system>
	<property name="defaultSqlParser">druidparser</property>
	</system>
	<!--以下设置为应用访问帐号权限 -->
	<!--可写账号 -->
	<user name="wabong">
	<property name="password">123456</property>
	<property name="schemas">test</property>
	</user>
	<!--可读账号 -->
	<user name="rabong">    # 读库账号
	<property name="password">123456</property>
	<property name="schemas">test</property>
	<property name="readOnly">true</property>
	</user>
</mycat:server>

# 配置mycat架构
[root@master conf]# cp schema.xml schema.xml.bak
[root@master conf]# echo "" > schema.xml
[root@master conf]# vim schema.xml
[root@master conf]# cat schema.xml
<?xml version="1.0"?>
<!DOCTYPE mycat:schema SYSTEM "schema.dtd">
<mycat:schema xmlns:mycat="http://io.mycat/">
 <schema name="test" checkSQLschema="false" sqlMaxLimit="100" dataNode='dn1'> </schema>
 <dataNode name="dn1" dataHost="dthost" database="test"/>
 <dataHost name="dthost" maxCon="500" minCon="10" balance="1" writeType="0" dbType="mysql" dbDriver="native" switchType="-1" slaveThreshold="100">
 <heartbeat>select user()</heartbeat>
 <!--后端写库信息 -->
 <writeHost host="master" url="192.168.10.10:3306" user="mycat" password="Abong123.">
	 <!--后端读库信息 -->
	<readHost host="slave" url="192.168.10.20:3306" user="mycat" password="Abong123." />
 </writeHost>
 </dataHost>
</mycat:schema>

# 启动mycat
[root@master ~]# mycat 
Usage: /usr/local/mycat/bin/mycat {
    
     console | start | stop | restart | status | dump }
[root@master ~]# mycat start
Starting Mycat-server...
[root@master ~]# cat /usr/local/mycat/logs/wrapper.log     # 看到这个日志记录，就说明已经启动成功了。
INFO   | jvm 1    | 2020/09/23 16:23:27 | MyCAT Server startup successfully. see logs in logs/mycat.log
[root@master ~]# mycat status;
Mycat-server is running (9115).

配置mysql主从同步复制：

# 配置主库/etc/my.cnf
[root@master ~]# vim /etc/my.cnf
log-bin=mysql-bin-master
server-id=1
binlog-do-db=test
binlog-ignore-db=mysql
[root@master ~]# systemctl restart mysqld

# 在主库上创建用户mycat，并授予all privileges的权限，允许在所有主机的客户端上使用mycat用户进行登录。
[root@master ~]# mysql -uroot -p
Enter password: 

mysql> grant all privileges on *.* to mycat@'%' identified by 'Abong123.';   # 用于读写分离的用户
Query OK, 0 rows affected, 1 warning (0.04 sec)

mysql> grant replication slave on *.* to [email protected] identified by 'Abong123.';   # 用于主从复制的用户
Query OK, 0 rows affected, 1 warning (0.03 sec)

mysql> flush privileges;
Query OK, 0 rows affected (0.02 sec)

mysql> exit
Bye

# 主库上导出test数据库，并导入到从库。保持主从数据一致性。
[root@master ~]# mysqldump -uroot -p test > test.sql
Enter password: 
[root@master ~]# ll test.sql 
-rw-r--r--. 1 root root 6815 9月  24 11:24 test.sql
[root@master ~]# scp test.sql [email protected]:/root/

[root@slave ~]# mysql -uroot -p     # 导入test到从库前的检测
Enter password: 
mysql> show databases;    # 从库上没有test数据库，要先创建。
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| sys                |
+--------------------+
4 rows in set (0.00 sec)

mysql> create database test;
Query OK, 1 row affected (0.00 sec)

mysql> exit
Bye
[root@slave ~]# mysql -uroot -p test < test.sql
Enter password: 

# 配置从库上的/etc/my.cnf
[root@slave ~]# vim /etc/my.cnf
[mysqld]
server-id=2
[root@slave ~]# systemctl restart mysqld

# 在从库上创建用户mycat，并授予all privileges的权限，允许在所有主机的客户端上使用mycat用户进行登录。
[root@slave ~]# mysql -uroot -p
Enter password: 

mysql> grant all privileges on *.* to mycat@'%' identified by 'Abong123.';
Query OK, 0 rows affected, 1 warning (0.04 sec)

mysql> flush privileges;
Query OK, 0 rows affected (0.02 sec)

mysql> exit
Bye

# 开放主库上的3306端口号
[root@master ~]# firewall-cmd --permanent --zone=public --add-port=3306/tcp
success
[root@master ~]# firewall-cmd --reload 
success

# 建立主从关系
mysql> show master status\G;    # 主库信息
*************************** 1. row ***************************
             File: mysql-bin-master.000001
         Position: 154
     Binlog_Do_DB: test
 Binlog_Ignore_DB: mysql
Executed_Gtid_Set: 
1 row in set (0.00 sec)

ERROR: 
No query specified

# 配置从库对应主库信息：
mysql> stop slave;
Query OK, 0 rows affected, 1 warning (0.00 sec)

mysql> change master to master_host='192.168.10.10',master_port=3306,master_user='slave',master_password='Abong123.',master_log_file='mysql-bin-master.000001',master_log_pos= 154;
Query OK, 0 rows affected, 2 warnings (0.06 sec)

mysql> start slave;
Query OK, 0 rows affected (0.02 sec)

mysql> show slave status\G;    # 可以看到主从同步复制的关系已经建立起来。
             Slave_IO_Running: Yes
            Slave_SQL_Running: Yes
      Slave_SQL_Running_State: Slave has read all relay log; waiting for more updates

2.3 mycat读写分离测试

登录格式：mysql -urabong -p123456 -h 192.168.10.10 -P8066
mycat是装在192.168.10.10上的，所以-h也是192.168.10.10
对mycat来说，8066是数据端口，9066是管理端口
客户端登录mysql数据库，用8066端口。
客户端管理mycat，用9066端口。
①只读用户rabong通过mycat登录mysql数据库：

[root@master ~]# mysql -urabong -p123456 -h 192.168.10.10 -P8066
mysql: [Warning] Using a password on the command line interface can be insecure.
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 10
Server version: 5.6.29-mycat-1.6.7.4-release-20200105164103 MyCat Server (OpenCloudDB)   # 可以看到是通过中间件mycat登录的

Copyright (c) 2000, 2020, 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> 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> desc emp;     # 可以看到rabong是没有写权限的，即只能执行select语句。
ERROR 1495 (HY000): User readonly
mysql> select * from emp;
+----+------+--------+
| id | name | deptno |
+----+------+--------+
|  1 | haha |     20 |
|  2 | xixi |     20 |
|  3 | ohoh |     20 |
|  5 | yeye |     20 |
+----+------+--------+
4 rows in set (0.10 sec)

②可写用户wabong通过mycat登录mysql数据库：

[root@master ~]# mysql -uwabong -p123456 -h 192.168.10.10 -P8066
mysql: [Warning] Using a password on the command line interface can be insecure.
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 11
Server version: 5.6.29-mycat-1.6.7.4-release-20200105164103 MyCat Server (OpenCloudDB)   # 可以看到是通过中间件mycat登录的

Copyright (c) 2000, 2020, 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> 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> desc emp;      # 可以看到用户wabong是具有读写权限的
+--------+-------------+------+-----+---------+-------+
| Field  | Type        | Null | Key | Default | Extra |
+--------+-------------+------+-----+---------+-------+
| id     | int(11)     | NO   | PRI | NULL    |       |
| name   | varchar(10) | YES  |     | NULL    |       |
| deptno | int(11)     | YES  | MUL | NULL    |       |
+--------+-------------+------+-----+---------+-------+
3 rows in set (0.40 sec)

mysql> select  * from emp;
+----+------+--------+
| id | name | deptno |
+----+------+--------+
|  1 | haha |     20 |
|  2 | xixi |     20 |
|  3 | ohoh |     20 |
|  5 | yeye |     20 |
+----+------+--------+
4 rows in set (0.01 sec)

③测试主库或从库故障，对用户访问数据库的影响：

主库正常运行，停止从库：

[root@slave ~]# systemctl stop mysqld

[root@master ~]# mysql -uwabong -p123456 -h 192.168.10.10 -P8066
mysql: [Warning] Using a password on the command line interface can be insecure.
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 12
Server version: 5.6.29-mycat-1.6.7.4-release-20200105164103 MyCat Server (OpenCloudDB)

Copyright (c) 2000, 2020, 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> 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> desc emp;
+--------+-------------+------+-----+---------+-------+
| Field  | Type        | Null | Key | Default | Extra |
+--------+-------------+------+-----+---------+-------+
| id     | int(11)     | NO   | PRI | NULL    |       |
| name   | varchar(10) | YES  |     | NULL    |       |
| deptno | int(11)     | YES  | MUL | NULL    |       |
+--------+-------------+------+-----+---------+-------+
3 rows in set (1.66 sec)

mysql> select * from emp;
+----+------+--------+
| id | name | deptno |
+----+------+--------+
|  1 | haha |     20 |
|  2 | xixi |     20 |
|  3 | ohoh |     20 |
|  5 | yeye |     20 |
+----+------+--------+
4 rows in set (0.32 sec)

mysql> insert into emp values(4,'lala',20);
Query OK, 1 row affected (0.08 sec)

mysql> select * from emp;
+----+------+--------+
| id | name | deptno |
+----+------+--------+
|  1 | haha |     20 |
|  2 | xixi |     20 |
|  3 | ohoh |     20 |
|  4 | lala |     20 |
|  5 | yeye |     20 |
+----+------+--------+
5 rows in set (0.00 sec)

测试结果：主库上仍然可以进行读写操作。对主库的写操作会在从库恢复后再次进行同步复制，保证主从数据的一致性。

主库挂了，从库正常运行：

[root@master ~]# systemctl stop mysqld

[root@master ~]# mysql -uwabong -p123456 -h 192.168.10.10 -P8066
mysql: [Warning] Using a password on the command line interface can be insecure.
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 13
Server version: 5.6.29-mycat-1.6.7.4-release-20200105164103 MyCat Server (OpenCloudDB)

Copyright (c) 2000, 2020, 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> 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> desc emp;
ERROR 1184 (HY000): java.net.ConnectException: 拒绝连接
mysql> select * from emp;
+----+------+--------+
| id | name | deptno |
+----+------+--------+
|  1 | haha |     20 |
|  2 | xixi |     20 |
|  3 | ohoh |     20 |
|  4 | lala |     20 |
|  5 | yeye |     20 |
+----+------+--------+
5 rows in set (0.00 sec)

测试结果：由于主库挂了，故不再对主库进行写操作，为保持主从数据库的一致性，从库上也不能进行写操作，但是还可以进行读操作。