读写分离应用方案
读写分离是通过主从的配置方式,将查询请求均匀的分散到多个数据副本,进一步的提升系统的处理能力。
主从架构:读写分离,目的是高可用、读写扩展。主从库内容相同,根据SQL语义进行路由。
分库分表架构:数据分片,目的读写扩展、存储扩容。库和表内容不同,根据分片配置进行路由。
将水平分片和读写分离联合使用,能够更加有效的提升系统性能, 下图展现了将分库分表与读写分离一同使用时,应用程序与数据库集群之间的复杂拓扑关系。
读写分离虽然可以提升系统的吞吐量和可用性,但同时也带来了数据不一致的问题,包括多个主库之间的数据一致性,以及主库与从库之间的数据一致性的问题。 并且,读写分离也带来了与数据分片同样的问题,它同样会使得应用开发和运维人员对数据库的操作和运维变得更加复杂。
读写分离
在数据量不是很多的情况下,我们可以将数据库进行读写分离,以应对高并发的需求,通过水平扩展从库,来缓解查询的压力。如下:
分表+读写分离
在数据量达到500万的时候,这时数据量预估千万级别,我们可以将数据进行分表存储。
分库分表+读写分离
在数据量继续扩大,这时可以考虑分库分表,将数据存储在不同数据库的不同表中,如下:
透明化读写分离所带来的影响,让使用方尽量像使用一个数据库一样使用主从数据库集群,是ShardingSphere读写分离模块的主要设计目标。
核心功能
- 提供一主多从的读写分离配置。仅支持单主库,可以支持独立使用,也可以配合分库分表使用
- 独立使用读写分离,支持SQL透传。不需要SQL改写流程
- 同一线程且同一数据库连接内,能保证数据一致性。如果有写入操作,后续的读操作均从主库读取
- 基于Hint的强制主库路由。可以强制路由走主库查询实时数据,避免主从同步数据延迟
不支持项
- 主库和从库的数据同步
- 主库和从库的数据同步延迟
- 主库双写或多写
- 跨主库和从库之间的事务的数据不一致。建议在主从架构中,事务中的读写均用主库操作
读写分离应用实战
我们的实战基于博文MySQL之Sharding-JDBC数据分片中的实战案例。
我们在sharding-jdbc-demo项目中新建配置文件application-master-slave.properties:
# datasource
spring.shardingsphere.datasource.names=master,slave0
spring.shardingsphere.datasource.master.type=com.zaxxer.hikari.HikariDataSource
spring.shardingsphere.datasource.master.driver-class-name=com.mysql.jdbc.Driver
spring.shardingsphere.datasource.master.jdbc-url=jdbc:mysql://127.0.0.1:3306/rubin_shard_1?characterEncoding=utf8&serverTimezone=Asia/Shanghai&useSSL=false&allowPublicKeyRetrieval=true
spring.shardingsphere.datasource.master.username=root
spring.shardingsphere.datasource.master.password=123456
spring.shardingsphere.datasource.slave0.type=com.zaxxer.hikari.HikariDataSource
spring.shardingsphere.datasource.slave0.driver-class-name=com.mysql.jdbc.Driver
spring.shardingsphere.datasource.slave0.jdbc-url=jdbc:mysql://127.0.0.1:3306/rubin_shard_2?characterEncoding=utf8&serverTimezone=Asia/Shanghai&useSSL=false&allowPublicKeyRetrieval=true
spring.shardingsphere.datasource.slave0.username=root
spring.shardingsphere.datasource.slave0.password=123456
# master-slave
spring.shardingsphere.masterslave.name=datasource
spring.shardingsphere.masterslave.master-data-source-name=master
spring.shardingsphere.masterslave.slave-data-source-names=slave0
spring.shardingsphere.masterslave.load-balance-algorithm-type=ROUND_ROBIN
spring.shardingsphere.sharding.tables.city.key-generator.column=id
spring.shardingsphere.sharding.tables.city.key-generator.type=SNOWFLAKE
修改配置文件application.properties中的profile:
#spring.profiles.active=sharding-database
spring.profiles.active=master-slave
spring.shardingsphere.props.sql.show=true
创建测试类:
package com.rubin.shardingjdbcdemo;
import com.rubin.shardingjdbcdemo.entity.City;
import com.rubin.shardingjdbcdemo.repository.CityRepository;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.context.junit4.SpringRunner;
import java.util.List;
@SpringBootTest(classes = ShardingJdbcDemoApplication.class)
@RunWith(SpringRunner.class)
public class TestMasterSlave {
@Autowired
private CityRepository cityRepository;
@Test
public void testAdd() {
City city = new City();
city.setName("shanghai");
city.setProvince("shanghai");
cityRepository.save(city);
}
@Test
public void testFind() {
List<City> list = cityRepository.findAll();
list.forEach(city -> {
System.out.println(city.getId() + " " + city.getName() + " " + city.getProvince());
});
}
}
运行上面测试案例我们会发现读会自动读取了从库,写会自动写入主库。
下面是一个使用sharding-jdbc的分库分表+读写分离的配置示例:
# 数据源
spring.shardingsphere.datasource.names=master0,slave0,slave1,master1,slave2,slave3
spring.shardingsphere.datasource.master0.type=com.zaxxer.hikari.HikariDataSource
spring.shardingsphere.datasource.master0.driver-class-name=com.mysql.jdbc.Driver
spring.shardingsphere.datasource.master0.jdbc-url=jdbc:mysql://127.0.0.1:3306/master0?characterEncoding=utf8&serverTimezone=Asia/Shanghai&useSSL=false&allowPublicKeyRetrieval=true
spring.shardingsphere.datasource.master0.username=root
spring.shardingsphere.datasource.master0.password=123456
spring.shardingsphere.datasource.slave0.type=com.zaxxer.hikari.HikariDataSource
spring.shardingsphere.datasource.slave0.driver-class-name=com.mysql.jdbc.Driver
spring.shardingsphere.datasource.slave0.jdbc-url=jdbc:mysql://127.0.0.1:3306/slave0?characterEncoding=utf8&serverTimezone=Asia/Shanghai&useSSL=false&allowPublicKeyRetrieval=true
spring.shardingsphere.datasource.slave0.username=root
spring.shardingsphere.datasource.slave0.password=123456
spring.shardingsphere.datasource.slave1.type=com.zaxxer.hikari.HikariDataSource
spring.shardingsphere.datasource.slave1.driver-class-name=com.mysql.jdbc.Driver
spring.shardingsphere.datasource.slave1.jdbc-url=jdbc:mysql://127.0.0.1:3306/slave1?characterEncoding=utf8&serverTimezone=Asia/Shanghai&useSSL=false&allowPublicKeyRetrieval=true
spring.shardingsphere.datasource.slave1.username=root
spring.shardingsphere.datasource.slave1.password=123456
spring.shardingsphere.datasource.master1.type=com.zaxxer.hikari.HikariDataSource
spring.shardingsphere.datasource.master1.driver-class-name=com.mysql.jdbc.Driver
spring.shardingsphere.datasource.master1.jdbc-url=jdbc:mysql://127.0.0.1:3306/master1?characterEncoding=utf8&serverTimezone=Asia/Shanghai&useSSL=false&allowPublicKeyRetrieval=true
spring.shardingsphere.datasource.master1.username=root
spring.shardingsphere.datasource.master1.password=123456
spring.shardingsphere.datasource.slave2.type=com.zaxxer.hikari.HikariDataSource
spring.shardingsphere.datasource.slave2.driver-class-name=com.mysql.jdbc.Driver
spring.shardingsphere.datasource.slave2.jdbc-url=jdbc:mysql://127.0.0.1:3306/slave2?characterEncoding=utf8&serverTimezone=Asia/Shanghai&useSSL=false&allowPublicKeyRetrieval=true
spring.shardingsphere.datasource.slave2.username=root
spring.shardingsphere.datasource.slave2.password=123456
spring.shardingsphere.datasource.slave3.type=com.zaxxer.hikari.HikariDataSource
spring.shardingsphere.datasource.slave3.driver-class-name=com.mysql.jdbc.Driver
spring.shardingsphere.datasource.slave3.jdbc-url=jdbc:mysql://127.0.0.1:3306/slave3?characterEncoding=utf8&serverTimezone=Asia/Shanghai&useSSL=false&allowPublicKeyRetrieval=true
spring.shardingsphere.datasource.slave3.username=root
spring.shardingsphere.datasource.slave3.password=123456
# 分库分表
spring.shardingsphere.sharding.tables.b_order.database-strategy.inline.sharding-column=company_id
spring.shardingsphere.sharding.tables.b_order.database-strategy.inline.algorithm-expression=master$->{company_id % 2}
spring.shardingsphere.sharding.tables.b_order.actual-data-nodes=master$->{0..1}.b_order$->{0..1}
spring.shardingsphere.sharding.tables.b_order.table-strategy.inline.sharding-column=id
spring.shardingsphere.sharding.tables.b_order.table-strategy.inline.algorithm-expression=b_order$->{id % 2}
# 读写分离
spring.shardingsphere.sharding.master-slave-rules.master0.master-data-source-name=master0
spring.shardingsphere.sharding.master-slave-rules.master0.slave-data-source-names=slave0, slave1
spring.shardingsphere.sharding.master-slave-rules.master1.master-data-source-name=master1
spring.shardingsphere.sharding.master-slave-rules.master1.slave-data-source-names=slave2, slave3
以上就是本博文的全部内容。欢迎小伙伴们积极留言交流~~~
文章评论