SpringCloud-客戶端的負載均衡Ribbon（三）

前言：微服務架構，不可避免的存在單個微服務有多個實例，那么客戶端如何將請求分攤到多個微服務的實例上呢？這里我們就需要使用負載均衡了

一、Ribbon簡介

　　Ribbon是Netflix發布的負載均衡器，它有助於控制HTTP和TCP客戶端的行為。為Ribbon配置服務提供者地址列表后，Ribbon就可基於某種負載均衡算法，自動地幫助服務消費者去請求。Ribbon默認為我們提供了很多的負載均衡算法，例如：輪詢，隨機等，也可自定義；

Ribbon的GitHub：https://github.com/Netflix/ribbon

　　而在SpringCloud中使用Ribbon和Eureka時，Ribbon會自動從EurekaServer中獲取服務提供者地址列表，並基於負載均衡算法。

二、Ribbon實戰

​1、創建EurekaServer，EurekaClient1，EurekaClient2，之前已經說過了Eureka的使用，這里直接上代碼：

EurekaServer：

@SpringBootApplication
@EnableEurekaServer
public class ServerApplication {

    public static void main(String[] args) {
        SpringApplication.run(ServerApplication.class,args);
    }

}

<?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>

server.port=8761
#注意：這兩個配置eureka默認為true，要改成false，否則會報錯，connot connect server
#表示是否將自己注冊在EurekaServer上
eureka.client.register-with-eureka=false
#表示是否從EurekaServer獲取注冊信息
eureka.client.fetch-registry=false

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

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>

server.port=8762
spring.application.name=client-8762
eureka.client.service-url.defaultZone=http://localhost:8761/eureka/

而在啟動類中加入RestTemplate遠程調用實例到容器中，並且添加LoadBalanced注解，使RestTemplate具備負載均衡的能力：

@SpringBootApplication
@EnableDiscoveryClient
public class ClientApplication {

    public static void main(String[] args) {
        SpringApplication.run(ClientApplication.class, args);
    }

    /** 
     * @Description: 加入@LoadBalanced注解，就可以為RestTemplate加入負載均衡的能力 
     * @Param:
     * @return:  
     * @Author:  
     * @Date: 2018/6/15 
     */ 
    @Bean
    @LoadBalanced
    public RestTemplate getRestTemplate() {
        return new RestTemplate();
    }

}

創建Controller，注入RestTemplate、LoadBalancerClient實例：

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與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);
    }

}

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("獲取用戶成功");
        return "獲取用戶成功";
    }

}

2、啟動順序：

　　①、依次啟動EurekaServer =》 EurekaClient1 =》 EurekaClient2   ；

　　②、然后將EurekaClient2中的application.properties的server.port=8763改為server.port=8764，再次啟動該項目;

　　③、打開EurekaServer的配置頁面（http://localhost:8761/），如下：

　　④、我們在地址欄輸入http://localhost:8762/loadInstance，多刷新幾次，會發現每次調用的端口實例都不同，如下圖：

　　　　

　　　　

　　⑤、我們在看控制台，如圖：

　　　　

 

至此，Ribbon已經入門，是不是很簡單，但是這只是最簡單的應用，九牛一毛爾...學無止境乎！

 

 

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