詳解spring cloud中使用Ribbon實現(xiàn)客戶端的軟負載均衡

更新時間：2018年01月15日 13:48:53 作者：牛奮lch

這篇文章主要介紹了詳解spring cloud中使用Ribbon實現(xiàn)客戶端的軟負載均衡，小編覺得挺不錯的，現(xiàn)在分享給大家，也給大家做個參考。一起跟隨小編過來看看吧

開篇

本例是在springboot整合H2內(nèi)存數(shù)據(jù)庫，實現(xiàn)單元測試與數(shù)據(jù)庫無關(guān)性和使用RestTemplate消費spring boot的Restful服務兩個示例的基礎(chǔ)上改造而來

在使用RestTemplate來消費spring boot的Restful服務示例中，我們提到，調(diào)用spring boot服務的時候，需要將服務的URL寫死或者是寫在配置文件中，但這兩種方式，無論哪一種，一旦ip地址發(fā)生了變化，都需要改動程序，并重新部署服務，使用Ribbon的時候，可以有效的避免這個問題。

前言：

軟負載均衡的實現(xiàn)方式有兩種，分別是服務端的負載均衡和客戶端的負載均衡

服務端負載均衡：當瀏覽器向后臺發(fā)出請求的時候，會首先向反向代理服務器發(fā)送請求，反向代理服務器會根據(jù)客戶端部署的ip：port映射表以及負載均衡策略，來決定向哪臺服務器發(fā)送請求，一般會使用到nginx反向代理技術(shù)。

客戶端負載均衡：當瀏覽器向后臺發(fā)出請求的時候，客戶端會向服務注冊器(例如：Eureka Server)，拉取注冊到服務器的可用服務信息，然后根據(jù)負載均衡策略，直接命中哪臺服務器發(fā)送請求。這整個過程都是在客戶端完成的，并不需要反向代理服務器的參與。

一、啟動Eureka Server

請參考該例：spring cloud中啟動Eureka Server

二、啟動微服務，并注冊到Eureka Server上

spring cloud-將spring boot服務注冊到Eureka Server上

為了演示負載均衡的效果，再啟動一個為服務，注意需要將端口號改成不一致

三、添加Ribbon支持

1、添加Ribbon的依賴

2、添加負載均衡支持

package com.chhliu.springboot.restful; 
import org.springframework.beans.factory.annotation.Autowired; 
import org.springframework.boot.SpringApplication; 
import org.springframework.boot.autoconfigure.SpringBootApplication; 
import org.springframework.boot.web.client.RestTemplateBuilder; 
import org.springframework.cloud.client.loadbalancer.LoadBalanced; 
import org.springframework.cloud.netflix.eureka.EnableEurekaClient; 
import org.springframework.context.annotation.Bean; 
import org.springframework.web.client.RestTemplate; 
@SpringBootApplication 
@EnableEurekaClient 
public class SpringbootRestTemplateApplication { 
   
  @Autowired 
  private RestTemplateBuilder builder; 
 
  @Bean 
  @LoadBalanced // 添加負載均衡支持，很簡單，只需要在RestTemplate上添加@LoadBalanced注解，那么RestTemplate即具有負載均衡的功能,如果不加@LoadBalanced注解的話，會報java.net.UnknownHostException:springboot-h2異常，此時無法通過注冊到Eureka Server上的服務名來調(diào)用服務，因為RestTemplate是無法從服務名映射到ip:port的，映射的功能是由LoadBalancerClient來實現(xiàn)的。 
  public RestTemplate restTemplate() { 
    return builder.build(); 
  } 
 
  public static void main(String[] args) { 
    SpringApplication.run(SpringbootRestTemplateApplication.class, args); 
  } 
}

3、修改調(diào)用微服務的URL

package com.chhliu.springboot.restful.controller; 
import org.springframework.beans.factory.annotation.Autowired; 
import org.springframework.web.bind.annotation.GetMapping; 
import org.springframework.web.bind.annotation.PathVariable; 
import org.springframework.web.bind.annotation.RestController; 
import org.springframework.web.client.RestTemplate;  
import com.chhliu.springboot.restful.vo.User; 
 
@RestController 
public class RestTemplateController { 
  @Autowired 
  private RestTemplate restTemplate; 
   
  @GetMapping("/template/{id}") 
  public User findById(@PathVariable Long id) {// 將原來的ip:port的形式，改成注冊到Eureka Server上的應用名即可 
    User u = this.restTemplate.getForObject("http://springboot-h2/user/" + id, User.class); 
    System.out.println(u); 
    return u; 
  } 
}

四、查看Eureka Server狀態(tài)

五，在瀏覽器中，多次刷新http://localhost:7904/template/2地址

六、測試結(jié)果

7900端口服務：

Hibernate: select user0_.id as id1_0_0_, user0_.age as age2_0_0_, user0_.balance as balance3_0_0_, user0_.name as name4_0_0_, user0_.username as username5_0_0_ from user user0_ where user0_.id=? 
Hibernate: select user0_.id as id1_0_0_, user0_.age as age2_0_0_, user0_.balance as balance3_0_0_, user0_.name as name4_0_0_, user0_.username as username5_0_0_ from user user0_ where user0_.id=? 
Hibernate: select user0_.id as id1_0_0_, user0_.age as age2_0_0_, user0_.balance as balance3_0_0_, user0_.name as name4_0_0_, user0_.username as username5_0_0_ from user user0_ where user0_.id=? 
Hibernate: select user0_.id as id1_0_0_, user0_.age as age2_0_0_, user0_.balance as balance3_0_0_, user0_.name as name4_0_0_, user0_.username as username5_0_0_ from user user0_ where user0_.id=?

7901端口服務：

Hibernate: select user0_.id as id1_0_0_, user0_.age as age2_0_0_, user0_.balance as balance3_0_0_, user0_.name as name4_0_0_, user0_.username as username5_0_0_ from user user0_ where user0_.id=? 
Hibernate: select user0_.id as id1_0_0_, user0_.age as age2_0_0_, user0_.balance as balance3_0_0_, user0_.name as name4_0_0_, user0_.username as username5_0_0_ from user user0_ where user0_.id=? 
Hibernate: select user0_.id as id1_0_0_, user0_.age as age2_0_0_, user0_.balance as balance3_0_0_, user0_.name as name4_0_0_, user0_.username as username5_0_0_ from user user0_ where user0_.id=? 
Hibernate: select user0_.id as id1_0_0_, user0_.age as age2_0_0_, user0_.balance as balance3_0_0_, user0_.name as name4_0_0_, user0_.username as username5_0_0_ from user user0_ where user0_.id=? 
Hibernate: select user0_.id as id1_0_0_, user0_.age as age2_0_0_, user0_.balance as balance3_0_0_, user0_.name as name4_0_0_, user0_.username as username5_0_0_ from user user0_ where user0_.id=?

7904端口服務：

User [id=2, username=user2, name=李四, age=20, balance=100.00] 
2017-01-23 09:58:05.682 INFO 7436 --- [erListUpdater-0] c.netflix.config.ChainedDynamicProperty : Flipping property: springboot-h2.ribbon.ActiveConnectionsLimit to use NEXT property: niws.loadbalancer.availabilityFilteringRule.activeConnectionsLimit = 2147483647 
User [id=2, username=user2, name=李四, age=20, balance=100.00] 
User [id=2, username=user2, name=李四, age=20, balance=100.00] 
User [id=2, username=user2, name=李四, age=20, balance=100.00] 
User [id=2, username=user2, name=李四, age=20, balance=100.00] 
User [id=2, username=user2, name=李四, age=20, balance=100.00] 
User [id=2, username=user2, name=李四, age=20, balance=100.00] 
User [id=2, username=user2, name=李四, age=20, balance=100.00] 
User [id=2, username=user2, name=李四, age=20, balance=100.00]

從上面的測試結(jié)果可以看出，總共調(diào)了7904端口服務9次，其中7904端口服務調(diào)7900端口服務4次，調(diào)7901端口5次，剛好是9次

經(jīng)過上面的幾個步驟，就基本使用Ribbon實現(xiàn)了客戶端負載均衡的功能

以上就是本文的全部內(nèi)容，希望對大家的學習有所幫助，也希望大家多多支持腳本之家。

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