详解springcloud中使用Ribbon实现客户端的软负载均衡
开篇
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本例是在springboot整合H2内存数据库,实现单元测试与数据库无关性和使用RestTemplate消费spring boot的Restful服务两个示例的基础上改造而来
在使用RestTemplate来消费spring boot的Restful服务示例中,我们提到,调用spring boot服务的时候,需要将服务的URL写死或者是写在配置文件中,但这两种方式,无论哪一种,一旦ip地址发生了变化,都需要改动程序,并重新部署服务,使用Ribbon的时候,可以有效的避免这个问题。
前言:
软负载均衡的实现方式有两种,分别是服务端的负载均衡和客户端的负载均衡
服务端负载均衡:当浏览器向后台发出请求的时候,会首先向反向代理服务器发送请求,反向代理服务器会根据客户端部署的ip:port映射表以及负载均衡策略,来决定向哪台服务器发送请求,一般会使用到nginx反向代理技术。
客户端负载均衡:当浏览器向后台发出请求的时候,客户端会向服务注册器(例如:Eureka Server),拉取注册到服务器的可用服务信息,然后根据负载均衡策略,直接命中哪台服务器发送请求。这整个过程都是在客户端完成的,并不需要反向代理服务器的参与。
一、启动Eureka Server
请参考该例:spring cloud中启动Eureka Server
二、启动微服务,并注册到Eureka Server上
spring cloud-将spring boot服务注册到Eureka Server上
为了演示负载均衡的效果,再启动一个为服务,注意需要将端口号改成不一致
三、添加Ribbon支持
1、添加Ribbon的依赖
2、添加负载均衡支持
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 // 添加负载均衡支持,很简单,只需要在RestTemplate上添加@LoadBalanced注解,那么RestTemplate即具有负载均衡的功能,如果不加@LoadBalanced注解的话,会报java.net.UnknownHostException:springboot-h3异常,此时无法通过注册到Eureka Server上的服务名来调用服务,因为RestTemplate是无法从服务名映射到ip:port的,映射的功能是由LoadBalancerClient来实现的。 public RestTemplate restTemplate() { return builder.build(); } public static void main(String[] args) { SpringApplication.run(SpringbootRestTemplateApplication.class, args); } }
3、修改调用微服务的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) {// 将原来的ip:port的形式,改成注册到Eureka Server上的应用名即可 User u = this.restTemplate.getForObject("http://springboot-h3/user/" + id, User.class); System.out.println(u); return u; } }
四、查看Eureka Server状态
五,在浏览器中,多次刷新http://localhost:7904/template/2地址
六、测试结果
7900端口服务:
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端口服务:
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端口服务:
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-h3.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]
从上面的测试结果可以看出,总共调了7904端口服务9次,其中7904端口服务调7900端口服务4次,调7901端口5次,刚好是9次
经过上面的几个步骤,就基本使用Ribbon实现了客户端负载均衡的功能
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