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，那麼客戶端如何將請求分攤到多個微服務的實例上呢？這裏咱們就須要使用負載均衡了

1、Ribbon簡介

　　Ribbon是Netflix發佈的負載均衡器，它有助於控制HTTP和TCP客戶端的行爲。爲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默認爲咱們提供了不少的負載均衡算法，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。

2、Ribbon實戰

​一、建立EurekaServer，EurekaClient1，EurekaClient2，以前已經說過了Eureka的使用，這裏直接上代碼：

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：這兩個配置eureka默認爲true，要改爲false，不然會報錯，connot connect server #表示是否將本身註冊在EurekaServer上 eureka.client.register-with-eureka=false #表示是否從EurekaServer獲取註冊信息 eureka.client.fetch-registry=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

而在啓動類中加入RestTemplate遠程調用實例到容器中，而且添加LoadBalanced註解，使RestTemplate具有負載均衡的能力：

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

建立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); } }

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("獲取用戶成功"); return "獲取用戶成功"; } }

二、啓動順序：

　　①、依次啓動EurekaServer =》 EurekaClient1 =》 EurekaClient2   ；

　　②、而後將EurekaClient2中的application.properties的server.port=8763改成server.port=8764，再次啓動該項目;

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

　　④、咱們在地址欄輸入http://localhost:8762/loadInstance，多刷新幾回，會發現每次調用的端口實例都不一樣，以下圖：

　　　　

　　　　

　　⑤、咱們在看控制檯，如圖：

　　　　

 

至此，Ribbon已經入門，是否是很簡單，可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