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1 读写分离原理

为了确保数据库产品的稳定性，很多数据库拥有双机热备功能，也就是，第一台数据库服务器对外提供增删改业务的生产服务器，第二台数据库服务器，主要进行读的操作。

原理：让主数据库（master）处理事务性增删改操作，而从数据库（slave）处理select 查询操作。

2 Mysql 配置主从复制

2.1 创建2个Mysql 数据库服务，并启动两个Mysql服务

2.2 配置Master库的/etc/my.cnf

[mysqld]basedir=/usr/local/mysqldatadir=/usr/local/mysql/datasocket=/tmp/mysql.sockuser=mysqlport=3306# Master# 开启日志log-bin = mysql-bin# 日志格式按行同步binlog-format = ROW# 设置服务id，主从不能一致server-id = 1# 设置需要同步的数据库binlog-do-db = user_db# 设置忽略系统库同步binlog-ignore-db = mysqlbinlog-ignore-db = information_schemabinlog-ignore-db = performance_schemabinlog-ignore-db = sys# Disabling symbolic-links is recommended to prevent assorted security riskssymbolic-links=0# character configcharacter_set_server=utf8mb4[mysqld_safe]log-error=/usr/local/mysql/data/mysql.logpid-file=/usr/local/mysql/data/mysql.pid# include all files from the config directory!includedir /etc/my.cnf.d

主要配置

# Master# 开启日志log-bin = mysql-bin# 日志格式按行同步binlog-format = ROW# 设置服务id，主从不能一致server-id = 1# 设置需要同步的数据库binlog-do-db = user_db# 设置忽略系统库同步binlog-ignore-db = mysqlbinlog-ignore-db = information_schemabinlog-ignore-db = performance_schemabinlog-ignore-db = sys

2.3 配置Slave库的/etc/my.cnf

[mysqld]basedir=/usr/local/mysqldatadir=/usr/local/mysql/datasocket=/tmp/mysql.sockuser=mysqlport=3306# Slave# 开启日志log-bin = mysql-bin# 日志按照行进行数据同步binlog-format = ROW# 设置服务id，主从不能一致server-id = 2# 设置需要同步的数据库replicate-do-db=user_db# 设置忽略系统库replicate-ignore-db = mysql replicate-ignore-db = information_schema replicate-ignore-db = performance_schema replicate-ignore-db = sys#replicate-wild-ignore_table = mysql.%#replicate-wild-ignore_table = information_schema.%#replicate-wildignore_table = performance_schema.%#replicate-wild-ignore_table = sys.%# Disabling symbolic-links is recommended to prevent assorted security riskssymbolic-links=0#character configcharacter_set_server=utf8mb4[mysqld_safe]log-error=/usr/local/mysql/data/mysql.logpid-file=/usr/local/mysql/data/mysql.pid## include all files from the config directory#!includedir /etc/my.cnf.d

主要配置

# Slave# 开启日志log-bin = mysql-bin# 日志按照行进行数据同步binlog-format = ROW# 设置服务id，主从不能一致server-id = 2# 设置需要同步的数据库replicate-do-db=user_db# 设置忽略系统库replicate-ignore-db = mysql replicate-ignore-db = information_schema replicate-ignore-db = performance_schema replicate-ignore-db = sys

2.4 Master上创建用于主从复置的账号

mysql -uroot -p123456 -h192.168.124.12

CREATE USER 'sync'@'%' IDENTIFIED WITH mysql_native_password BY '123456';# 授权主备复制专用账号GRANT REPLICATION SLAVE ON *.* TO 'sync'@'%';show grants for sync;# 刷新权限flush privileges;# 确认位点，记录下文件名及位点show master status;

mysql 数据库中查询user表获取文件名和点位

mysql-bin.0000011 156

2.5 Slave上设置从库向主库同步

首先切换到从库登录

mysql -uroot -p123456 -h192.168.124.11 -P3306

# 先停止同步stop slave;# 修改从库指向到主库，使用上一步记录的文件名以及位点CHANGE MASTER TO master_host='192.168.124.12',master_port=3306,master_user='sync',master_password='123456',master_log_file='mysql-bin.000011',master_log_pos=156;# 启动同步start slave;# 查看slave 的状态show slave status;

CREATE SCHEMA `testdb` DEFAULT CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci ;

CREATE TABLE `testdb`.`t_user` (  `id` BIGINT NOT NULL,  `name` VARCHAR(45) NOT NULL,  `age` INT NOT NULL,  PRIMARY KEY (`id`))ENGINE = InnoDBDEFAULT CHARACTER SET = utf8mb4COLLATE = utf8mb4_unicode_ci;

INSERT INTO `testdb`.`t_user` (`id`, `name`, `age`) VALUES ('1', 'zhangsan', '3');

需要注意的是数据库的字符集编码必须一致

3 ShardingSphere实现读写分离

3.1 配置properties

# sharding-JDBC分片策略（主从复制配置）# 配置数据源，给数据源命名spring.shardingsphere.datasource.names=m0,s0# 配置数据源具体内容，连接池、驱动、地址、用户名和密码# testdb 主服务器spring.shardingsphere.datasource.m0.type=com.alibaba.druid.pool.DruidDataSourcespring.shardingsphere.datasource.m0.driver-class-name=com.mysql.cj.jdbc.Driverspring.shardingsphere.datasource.m0.url=jdbc:mysql://192.168.124.12:3306/testdb?serverTimezone=GMT%2B8spring.shardingsphere.datasource.m0.username=rootspring.shardingsphere.datasource.m0.password=123456# 配置数据源具体内容，连接池、驱动、地址、用户名和密码# testdb 从服务器spring.shardingsphere.datasource.s0.type=com.alibaba.druid.pool.DruidDataSourcespring.shardingsphere.datasource.s0.driver-class-name=com.mysql.cj.jdbc.Driverspring.shardingsphere.datasource.s0.url=jdbc:mysql://192.168.124.11:3306/testdb?serverTimezone=GMT%2B8spring.shardingsphere.datasource.s0.username=rootspring.shardingsphere.datasource.s0.password=123456# 一个实体类对应两张表，覆盖spring.main.allow-bean-definition-overriding=true# 主从库逻辑数据源定义 ds0 为testdbspring.shardingsphere.sharding.master-slave-rules.ds0.master-data-source-name=m0spring.shardingsphere.sharding.master-slave-rules.ds0.slave-data-source-names=s0# t_user 分表策略，固定分配至ds0的t_user真实表spring.shardingsphere.sharding.tables.t_user.actual-data-nodes=ds$->{0}.t_userspring.shardingsphere.sharding.tables.t_user.key-generator.column=idspring.shardingsphere.sharding.tables.t_user.key-generator.type=SNOWFLAKE# 打印sql输出日志spring.shardingsphere.props.sql.show=true

3.2 编写po

package com.ccb.sharding.po;import com.baomidou.mybatisplus.annotation.TableId;import com.baomidou.mybatisplus.annotation.TableName;@TableName("t_user")public class Student {       @TableId("id")    private Long id;    private String name;    private int age;    public Long getId() {           return id;    }    public void setId(Long id) {           this.id = id;    }    public String getName() {           return name;    }    public void setName(String name) {           this.name = name;    }    public int getAge() {           return age;    }    public void setAge(int age) {           this.age = age;    }    @Override    public String toString() {           return "Student{" +                "id=" + id +                ", name='" + name + '\'' +                ", age=" + age +                '}';    }}

3.3 编写mapper

package com.ccb.sharding.mapper;import com.baomidou.mybatisplus.core.mapper.BaseMapper;import com.ccb.sharding.po.Student;import com.ccb.sharding.po.User;import org.springframework.stereotype.Repository;@Repositorypublic interface StudentMapper extends BaseMapper
   
     {   }
   

3.4 编写Test

package com.ccb.sharding;import com.baomidou.mybatisplus.core.conditions.query.QueryWrapper;import com.ccb.sharding.mapper.StudentMapper;import com.ccb.sharding.po.Student;import org.junit.jupiter.api.Test;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.boot.test.context.SpringBootTest;@SpringBootTestclass ShardingApplicationTests {       @Autowired    StudentMapper studentMapper;    // ================= 测试读写分离 ======================    @Test    public void addStudentMaster() {           Student student = new Student();        student.setName("Lily");        student.setAge(23);        studentMapper.insert(student);    }    @Test    public void getStudentSlave(){           QueryWrapper queryWrapper = new QueryWrapper();        queryWrapper.eq("id",1278468912563892226L);        Student student = studentMapper.selectOne(queryWrapper);        System.out.println(student);    }}

3.5 TestRest

3.5.1 主库

3.5.2 从库

Result

3.5.3 写入时

3.5.4 读取时

以上可以看到主从都有数据，并且写入时是主库master，读取时是从库slave，实现了目标主从复制、读写分离

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