(七)spring cloud微服务分布式云架构-服务消费者(rest+ribbon)

一、ribbon简介

Ribbon is a client side load balancer which gives you a lot of control over the behaviour of HTTP and TCP clients. Feign already uses Ribbon, so if you are using @FeignClient then this section also applies.

—–摘自官网 Spring Cloud大型企业分布式微服务云架构源码请加一七九一七四三三八零

ribbon是一个负载均衡客户端,可以很好的控制htt和tcp的一些行为。Feign默认集成了ribbon。

ribbon 已经默认实现了这些配置bean:

IClientConfig ribbonClientConfig: DefaultClientConfigImpl

IRule ribbonRule: ZoneAvoidanceRule

IPing ribbonPing: NoOpPing

ServerList ribbonServerList: ConfigurationBasedServerList

ServerListFilter ribbonServerListFilter: ZonePreferenceServerListFilter

ILoadBalancer ribbonLoadBalancer: ZoneAwareLoadBalancer

二、建一个服务消费者

重新新建一个spring-boot工程,取名为:service-ribbon;

在它的pom.xml文件分别引入起步依赖spring-cloud-starter-eureka、spring-cloud-starter-ribbon、spring-boot-starter-web,代码如下:



    4.0.0
 
    com.forezp
    service-ribbon
    0.0.1-SNAPSHOT
    jar
 
    service-ribbon
    Demo project for Spring Boot
 
    
        org.springframework.boot
        spring-boot-starter-parent
        1.5.2.RELEASE
         
    
 
    
        UTF-8
        UTF-8
        1.8
    
 
    
        
            org.springframework.cloud
            spring-cloud-starter-eureka
        
        
            org.springframework.cloud
            spring-cloud-starter-ribbon
        
        
            org.springframework.boot
            spring-boot-starter-web
        
 
        
            org.springframework.boot
            spring-boot-starter-test
            test
        
    
 
    
        
            
                org.springframework.cloud
                spring-cloud-dependencies
                Dalston.RC1
                pom
                import
            
        
    
 
    
        
            
                org.springframework.boot
                spring-boot-maven-plugin
            
        
    
 
    
        
            spring-milestones
            Spring Milestones
            https://repo.spring.io/milestone
            
                false
            
        
    

在工程的配置文件指定服务的注册中心地址为http:/ /localhost:8761/eureka/,程序名称为 service-ribbon,程序端口为8764。配置文件application.yml如下:

eureka:
  client:
    serviceUrl:
      defaultZone: http://localhost:8761/eureka/
server:
  port: 8764
spring:
  application:
    name: service-ribbon

在工程的启动类中,通过@EnableDiscoveryClient向服务中心注册;并且向程序的ioc注入一个bean: restTemplate;并通过@LoadBalanced注解表明这个restRemplate开启负载均衡的功能。

@SpringBootApplication
@EnableDiscoveryClient
public class ServiceRibbonApplication {
 
    public static void main(String[] args) {
        SpringApplication.run(ServiceRibbonApplication.class, args);
    }
 
    @Bean
    @LoadBalanced
    RestTemplate restTemplate() {
        return new RestTemplate();
    }
 
}

写一个测试类HelloService,通过之前注入ioc容器的restTemplate来消费service-hi服务的“/hi”接口,在这里我们直接用的程序名替代了具体的url地址,在ribbon中它会根据服务名来选择具体的服务实例,根据服务实例在请求的时候会用具体的url替换掉服务名,代码如下:

@Service
public class HelloService {
 
    @Autowired
    RestTemplate restTemplate;
 
    public String hiService(String name) {
        return restTemplate.getForObject("http://SERVICE-HI/hi?name="+name,String.class);
    }
 
}

写一个controller,在controller中用调用HelloService 的方法,代码如下:

/**
 * Created by fangzhipeng on 2017/4/6.
 */
@RestController
public class HelloControler {
 
    @Autowired
    HelloService helloService;
    @RequestMapping(value = "/hi")
    public String hi(@RequestParam String name){
        return helloService.hiService(name);
    }
 
 
}

在浏览器上多次访问http:/ /localhost:8764/hi?name=forezp,浏览器交替显示:

hi forezp,i am from port:8762
 
hi forezp,i am from port:8763

这说明当我们通过调用restTemplate.getForObject(“http:/ /SERVICE-HI/hi?name=“+name,String.class)方法时,已经做了负载均衡,访问了不同的端口的服务实例。

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