Spring Cloud之Ribbon实现负载均衡

Ribbon是基于Eureka，首先要保证Eureka服务启动，关于Eureka可以参考之前的文章，

Spring Cloud之Eureka

1. 项目结构

2. Spring Boot版本

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.2.5.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>

3. parent pom.xml 依赖

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <packaging>pom</packaging>
    <modules>
        <module>ribbon-demo</module>
    </modules>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.2.5.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>

    <groupId>com.yarm</groupId>
    <artifactId>ribbon</artifactId>
    <version>1.0-SNAPSHOT</version>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
        <java.version>1.8</java.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>

    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-dependencies</artifactId>
                <version>Hoxton.SR1</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>

</project>

4. ribbon依赖

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <parent>
        <artifactId>ribbon</artifactId>
        <groupId>com.yarm</groupId>
        <version>1.0-SNAPSHOT</version>
    </parent>
    <modelVersion>4.0.0</modelVersion>

    <artifactId>ribbon-demo</artifactId>


    <dependencies>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-ribbon</artifactId>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>
</project>

其中，3和4可以合并引入

5. Ribbon配置类

package com.yarm.config;

import com.netflix.loadbalancer.IRule;
import com.netflix.loadbalancer.RandomRule;
import org.springframework.cloud.client.loadbalancer.LoadBalanced;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.client.RestTemplate;

@Configuration
public class RibbonConfig {
    @Bean
    @LoadBalanced
    public RestTemplate restTemplate() {
        return new RestTemplate();
    }

    // 配置随机策略
    @Bean
    public IRule ribbonRandomRule() {
        return new RandomRule();
    }
}

配置两种路由策略：轮询和随机策略

6. 测试随机策略

6.1 配置文件

server.port=6000
spring.application.name=demo-service

# eureka服务地址
eureka.client.serviceUrl.defaultZone=http://180.76.159.196:8761/eureka/
# 开启健康检查
eureka.client.healthcheck.enabled=true
# eureka client发送心跳给server端的频率。如果在leaseExpirationDurationInSeconds后，server端没有收到client的心跳，则将摘除该instance
eureka.instance.lease-renewal-interval-in-seconds=3
# eureka server至上一次收到client的心跳之后，等待下一次心跳的超时时间，在这个时间内若没收到下一次心跳，则将移除该instance
eureka.instance.lease-expiration-duration-in-seconds=6

6.2 Ribbon请求服务代码

package com.yarm.controller;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.client.RestTemplate;

import javax.annotation.Resource;

@RestController
@RequestMapping("test")
public class TestRibbonController {

    @Resource
    private RestTemplate restTemplate;

    @RequestMapping("test")
    public String test(){
        restTemplate.getForObject("http://demo-service/demo/demo", String.class);
        return "ok";
    }
}

6.3 被请求的接口

package com.yarm.controller;

import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
@RequestMapping("demo")
public class DemoController {
    @RequestMapping("demo")
    public String demo(){
        System.out.println("request from demo");
        return "SUCCESS";
    }
}

6.4 启动函数

package com.yarm;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.netflix.eureka.EnableEurekaClient;

@SpringBootApplication
@EnableEurekaClient
public class RibbonDemoApplication {
    public static void main(String[] args) {
        SpringApplication.run(RibbonDemoApplication.class, args);
    }
}

6.5 模拟两个服务，分配两个端口6000和6001分别启动服务

6.6 请求http://127.0.0.1:6000/test/test 或 http://127.0.0.1:6001/test/test

结论：

会发现请求随机的转发到不同端口的服务，如下图

项目地址：

https://github.com/15902124763/spring-cloud/