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
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、准备工作
这一篇文章基于上一篇文章的工程，启动eureka-server 工程；启动service-hi工程，它的端口为8762；将service-hi的配置文件的端口改为8763,并启动，这时你会发现：service-hi在eureka-server注册了2个实例，这就相当于一个小的集群。访问localhost:8761如图所示：
三、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：| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 | <?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.forezp</groupId> <artifactId>service-ribbon</artifactId> <version> 0.0 . 1 -SNAPSHOT</version> <packaging>jar</packaging> <name>service-ribbon</name> <description>Demo project for Spring Boot</description> <parent> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-parent</artifactId> <version> 1.5 . 2 .RELEASE</version> <relativePath/> <!-- lookup parent from repository --> </parent> <properties> <project.build.sourceEncoding>UTF- 8 </project.build.sourceEncoding> <project.reporting.outputEncoding>UTF- 8 </project.reporting.outputEncoding> <java.version> 1.8 </java.version> </properties> <dependencies> <dependency> <groupId>org.springframework.cloud</groupId> <artifactId>spring-cloud-starter-eureka</artifactId> </dependency> <dependency> <groupId>org.springframework.cloud</groupId> <artifactId>spring-cloud-starter-ribbon</artifactId> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-web</artifactId> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-test</artifactId> <scope>test</scope> </dependency> </dependencies> <dependencyManagement> <dependencies> <dependency> <groupId>org.springframework.cloud</groupId> <artifactId>spring-cloud-dependencies</artifactId> <version>Dalston.RC1</version> <type>pom</type> <scope> import </scope> </dependency> </dependencies> </dependencyManagement> <build> <plugins> <plugin> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-maven-plugin</artifactId> </plugin> </plugins> </build> <repositories> <repository> <id>spring-milestones</id> <name>Spring Milestones</name> <url>https: //repo.spring.io/milestone</url> <snapshots> <enabled> false </enabled> </snapshots> </repository> </repositories> </project> |
在工程的配置文件指定服务的注册中心地址为，程序名称为 service-ribbon，程序端口为8764。配置文件application.yml如下：
| 1 2 3 4 5 6 7 8 9 | 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。
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 | @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：
| 1 2 3 4 5 6 7 8 9 10 11 | @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：
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 | /** * 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，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(““+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。
架构代码如下:
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