SpringCloud客戶端的負載均衡Ribbon的實現

前言：微服務架構，不可避免的存在單個微服務有多個實例，那麼客戶端如何將請求分攤到多個微服務的實例上呢？這裡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後，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，這裡直接上代碼：

EurekaServer：

ServerApplication.java

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

pom.xml

 <?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>

application.properties

 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#表示是否將自己註冊在EurekaServer上eureka.client.register-with-eureka=false#表示是否從EurekaServer獲取註冊信息eureka.client.fetch-registry=falseeureka.client.service-url.defaultZone=http://localhost:8761/eureka/

EurekaClient1:

pom.xml

 <?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=8762spring.application.name=client-8762eureka.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註解，使RestTemplate具備負載均衡的能力：

 @SpringBootApplication@EnableDiscoveryClientpublic class ClientApplication { public static void main(String[] args) { SpringApplication.run(ClientApplication.class, args); } /** * @Description: 加入@LoadBalanced註解，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 **/@Controllerpublic 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(); }}

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

EurekaClient2：

pom.xml與EurekaClient1中一致

application.xml:

 server.port=8763spring.application.name=client-87eureka.client.service-url.defaultZone=http://localhost:8761/eureka

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 **/@Controllerpublic 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、然後將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