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SpringCloud-客户端的负载均衡Ribbon（三）

前言：微服务架构，不可避免的存在单个微服务有多个实例，那么客户端如何将请求分摊到多个微服务的实例上呢？这里我们就需要使用负载均衡了

一、Ribbon简介

　　Ribbon是Netflix发布的负载均衡器，它有助于控制HTTP和TCP客户端的行为。为Ribbon配置服务提供者地址列表后，Ribbon就可基于某种负载均衡算法，自动地帮助服务消费者去请求。Ribbon默认为我们提供了很多的负载均衡算法，例如：轮询，随机等，也可自定义；

　　而在SpringCloud中使用Ribbon和Eureka时，Ribbon会自动从EurekaServer中获取服务提供者地址列表，并基于负载均衡算法。

二、Ribbon实战

​1、创建EurekaServer，EurekaClient1，EurekaClient2，之前已经说过了Eureka的使用，这里直接上代码：

EurekaServer：

@SpringBootApplication

@EnableEurekaServer

public class ServerApplication {

    public static void main(String[] args) {

        SpringApplication.run(ServerApplication.class,args);

    }

}

ServerApplication.java

<?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>

  <groupId>com.cn</groupId>

  <artifactId>eureka-ribbon-server</artifactId>

  <version>1.0-SNAPSHOT</version>

  <properties>

    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>

    <java.version>1.8</java.version>

  </properties>

  <parent>

    <groupId>org.springframework.boot</groupId>

    <artifactId>spring-boot-starter-parent</artifactId>

    <version>1.5.13.RELEASE</version>

  </parent>

  <dependencies>

    <dependency>

      <groupId>org.springframework.</groupId>

      <artifactId></artifactId>

    </dependency>

    <dependency>

      <groupId>org.springframework.cloud</groupId>

      <artifactId>spring-cloud-starter-eureka-server</artifactId>

    </dependency>

  </dependencies>

  <dependencyManagement>

    <dependencies>

      <dependency>

        <groupId>org.springframework.cloud</groupId>

        <artifactId>spring-cloud-dependencies</artifactId>

        <version>Edgware.SR3</version>

        <type>pom</type>

        <scope>import</scope>

      </dependency>

    </dependencies>

  </dependencyManagement>

  <!-- 添加spring-boot的maven插件 -->

  <build>

    <plugins>

      <plugin>

        <groupId>org.springframework.boot</groupId>

        <artifactId>spring-boot-maven-plugin</artifactId>

      </plugin>

    </plugins>

  </build>

</project>

pom.xml

server.port=8761

#注意：这两个配置eureka默认为true，要改成false，否则会报错，connot connect server

#表示是否将自己注册在EurekaServer上

eureka.client.register-with-eureka=false

#表示是否从EurekaServer获取注册信息

eureka.client.fetch-registry=false

eureka.client.service-url.defaultZone=http://localhost:8761/eureka/

application.properties

EurekaClient1:

<?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>

  <groupId>com.cn</groupId>

  <artifactId>eureka-ribbon-client</artifactId>

  <version>1.0-SNAPSHOT</version>

  <properties>

    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>

    <java.version>1.8</java.version>

  </properties>

  <parent>

    <groupId>org.springframework.boot</groupId>

    <artifactId>spring-boot-starter-parent</artifactId>

    <version>1.5.13.RELEASE</version>

  </parent>

  <dependencies>

    <dependency>

      <groupId>org.springframework.cloud</groupId>

      <artifactId>spring-cloud-starter-ribbon</artifactId>

    </dependency>

    <dependency>

      <groupId>org.springframework.cloud</groupId>

      <artifactId>spring-cloud-starter-eureka</artifactId>

    </dependency>

  </dependencies>

  <dependencyManagement>

    <dependencies>

      <dependency>

        <groupId>org.springframework.cloud</groupId>

        <artifactId>spring-cloud-dependencies</artifactId>

        <version>Edgware.SR3</version>

        <type>pom</type>

        <scope>import</scope>

      </dependency>

    </dependencies>

  </dependencyManagement>

  <!-- 添加spring-boot的maven插件 -->

  <build>

    <plugins>

      <plugin>

        <groupId>org.springframework.boot</groupId>

        <artifactId>spring-boot-maven-plugin</artifactId>

      </plugin>

    </plugins>

  </build>

</project>

pom.xml

server.port=8762

spring.application.name=client-8762

eureka.client.service-url.defaultZone=http://localhost:8761/eureka/

application.properties

而在启动类中加入RestTemplate远程调用实例到容器中，并且添加LoadBalanced注解，使RestTemplate具备负载均衡的能力：

@SpringBootApplication

@EnableDiscoveryClient

public class ClientApplication {

    public static void main(String[] args) {

        SpringApplication.run(ClientApplication.class, args);

    }

    /**

     * @Description: 加入@LoadBalanced注解，就可以为RestTemplate加入负载均衡的能力

     * @Param:

     * @return:

     * @Author:

     * @Date: 2018/6/15

     */

    @Bean

    @LoadBalanced

    public RestTemplate getRestTemplate() {

        return new RestTemplate();

    }

}

创建Controller，注入RestTemplate、LoadBalancerClient实例：

package com.cn.controller;

import org.springframework.beans.factory.annotation.Autowired;

import org.springframework.cloud.client.ServiceInstance;

import org.springframework.cloud.client.loadbalancer.LoadBalancerClient;

import org.springframework.stereotype.Controller;

import org.springframework.web.bind.annotation.GetMapping;

import org.springframework.web.bind.annotation.ResponseBody;

import org.springframework.web.client.RestTemplate;

/**

 * @program: springcloud-example

 * @description:

 * @author:

 * @create: 2018-06-15 15:55

 **/

@Controller

public class RibbonController {

    @Autowired

    private LoadBalancerClient loadBalancerClient;

    @Autowired

    private RestTemplate restTemplate;

    @GetMapping("/loadInstance")

    @ResponseBody

    public String loadInstance() {

        ServiceInstance choose = this.loadBalancerClient.choose("client-87");

        System.out.println(choose.getServiceId()+":"+choose.getHost()+":"+choose.getPort());

        return choose.getServiceId() + ":" + choose.getHost() + ":" + choose.getPort();

    }

}

EurekaClient2：

pom.xml与EurekaClient1中一致

application.xml:

server.port=8763

spring.application.name=client-87

eureka.client.service-url.defaultZone=http://localhost:8761/eureka
package com.cn;

import org.springframework.boot.SpringApplication;

import org.springframework.boot.autoconfigure.SpringBootApplication;

import org.springframework.cloud.client.discovery.EnableDiscoveryClient;

/**

 * @program: springcloud-example

 * @description:

 * @author: 535504

 * @create: 2018-06-15 16:05

 **/

@SpringBootApplication

@EnableDiscoveryClient

public class ClientApplication {

    public static void main(String[] args) {

        SpringApplication.run(ClientApplication.class, args);

    }

}

ClientApplication

ClientController.java:

package com.cn.contorller;

import org.springframework.stereotype.Controller;

import org.springframework.web.bind.annotation.GetMapping;

import org.springframework.web.bind.annotation.ResponseBody;

/**

 * @program: springcloud-example

 * @description:

 * @author:

 * @create: 2018-06-15 16:12

 **/

@Controller

public class ClientController {

    @GetMapping("/getUser")

    @ResponseBody

    public String getUser() {

        System.out.println("获取用户成功");

        return "获取用户成功";

    }

}

2、启动顺序：

　　①、依次启动EurekaServer =》 EurekaClient1 =》 EurekaClient2   ；

　　②、然后将EurekaClient2中的application.properties的server.port=8763改为server.port=8764，再次启动该项目;

　　③、打开EurekaServer的配置页面（http://localhost:8761/），如下：

SpringCloud-客户端的负载均衡Ribbon（三）-LMLPHP

　　④、我们在地址栏输入http://localhost:8762/loadInstance，多刷新几次，会发现每次调用的端口实例都不同，如下图：

　　　　SpringCloud-客户端的负载均衡Ribbon（三）-LMLPHP

　　　　SpringCloud-客户端的负载均衡Ribbon（三）-LMLPHP

　　⑤、我们在看控制台，如图：

　　　　SpringCloud-客户端的负载均衡Ribbon（三）-LMLPHP

至此，Ribbon已经入门，是不是很简单，但是这只是最简单的应用，九牛一毛尔...学无止境乎！

示例代码：https://gitee.com/lfalex/springcloud-example

05-20 14:30
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