一、ribbon簡介

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.

—–摘自官網

ribbon是一個負載均衡客戶端，可以很好的控制htt和tcp的一些行為。Feign預設集成了ribbon。

ribbon 已經預設實現了這些配置bean：

• IClientConfig ribbonClientConfig: DefaultClientConfigImpl

• IRule ribbonRule: ZoneAvoidanceRule

• IPing ribbonPing: NoOpPing

• ServerList ribbonServerList: ConfigurationBasedServerList

• ServerListFilter ribbonServerListFilter: ZonePreferenceServerListFilter

• ILoadBalancer ribbonLoadBalancer: ZoneAwareLoadBalancer

二、準備工作

這一篇文章基於上一篇文章的工程，啟動eureka-server 工程；啟動service-hi工程，它的埠為8762；將service-hi的配置檔案的埠改為8763,並啟動，這時你會發現：service-hi在eureka-server註冊了2個例項，這就相當於一個小的叢集。訪問localhost:8761如圖所示：

三、建一個服務消費者

重新新建一個spring-boot工程，取名為：service-ribbon; 
在它的pom.xml檔案分別引入起步依賴spring-cloud-starter-eureka、spring-cloud-starter-ribbon、spring-boot-starter-web，程式碼如下：

<?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-hi</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>jar</packaging>
 
    <name>service-hi</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.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>

通過註解@EnableEurekaClient 表明自己是一個eurekaclient.

@SpringBootApplication
@EnableEurekaClient
@RestController
public class ServiceHiApplication {
 
    public static void main(String[] args) {
        SpringApplication.run(ServiceHiApplication.class, args);
    }
 
    @Value("${server.port}")
    String port;
    @RequestMapping("/hi")
    public String home(@RequestParam String name) {
        return "hi "+name+",i am from port:" +port;
    }
 
}

僅僅@EnableEurekaClient是不夠的，還需要在配置檔案中註明自己的服務註冊中心的地址，application.yml配置檔案如下：

eureka:
  client:
    serviceUrl:
      defaultZone: http://localhost:8761/eureka/
server:
  port: 8762
spring:
  application:
    name: service-hi

需要指明spring.application.name,這個很重要，這在以後的服務與服務之間相互呼叫一般都是根據這個name 。 
啟動工程，開啟http://localhost:8761 ，即eureka server 的網址：

你會發現一個服務已經註冊在服務中了，服務名為SERVICE-HI ,埠為7862

這時開啟 http://localhost:8762/hi?name=forezp ，你會在瀏覽器上看到 :

hi forezp,i am from port:8762

架構程式碼如下:

資料和原始碼來源地址

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