前言：微服务架构，不可避免的存在单个微服务有多个实例，那么客户端如何将请求分摊到多个微服务的实例上呢？这里我们就需要使用负载均衡了
一、ribbon简介
ribbon是netflix发布的负载均衡器，它有助于控制http和tcp客户端的行为。为ribbon配置服务提供者地址列表后，ribbon就可基于某种负载均衡算法，自动地帮助服务消费者去请求。ribbon默认为我们提供了很多的负载均衡算法，例如：轮询，随机等，也可自定义；
ribbon的github： https://github.com/netflix/ribbon
而在springcloud中使用ribbon和eureka时，ribbon会自动从eurekaserver中获取服务提供者地址列表，并基于负载均衡算法。
二、ribbon实战
1、创建eurekaserver，eurekaclient1，eurekaclient2，之前已经说过了eureka的使用，这里直接上代码：
eurekaserver：
serverapplication.java
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@springbootapplication
@enableeurekaserver
public class serverapplication {
public static void main(string[] args) {
springapplication.run(serverapplication.class,args);
}
}
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pom.xml
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<?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.cn</groupid>
<artifactid>eureka-ribbon-server</artifactid>
<version>1.0-snapshot</version>
<properties>
<project.build.sourceencoding>utf-8</project.build.sourceencoding>
<java.version>1.8</java.version>
</properties>
<parent>
<groupid>org.springframework.boot</groupid>
<artifactid>spring-boot-starter-parent</artifactid>
<version>1.5.13.release</version>
</parent>
<dependencies>
<dependency>
<groupid>org.springframework.</groupid>
<artifactid></artifactid>
</dependency>
<dependency>
<groupid>org.springframework.cloud</groupid>
<artifactid>spring-cloud-starter-eureka-server</artifactid>
</dependency>
</dependencies>
<dependencymanagement>
<dependencies>
<dependency>
<groupid>org.springframework.cloud</groupid>
<artifactid>spring-cloud-dependencies</artifactid>
<version>edgware.sr3</version>
<type>pom</type>
<scope>import</scope>
</dependency>
</dependencies>
</dependencymanagement>
<!-- 添加spring-boot的maven插件 -->
<build>
<plugins>
<plugin>
<groupid>org.springframework.boot</groupid>
<artifactid>spring-boot-maven-plugin</artifactid>
</plugin>
</plugins>
</build>
</project>
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application.properties
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server.port=8761
#注意：这两个配置eureka默认为true，要改成false，否则会报错，connot connect server
#表示是否将自己注册在eurekaserver上
eureka.client.register-with-eureka=false
#表示是否从eurekaserver获取注册信息
eureka.client.fetch-registry=false
eureka.client.service-url.defaultzone=http://localhost:8761/eureka/
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eurekaclient1:
pom.xml
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<?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.cn</groupid>
<artifactid>eureka-ribbon-client</artifactid>
<version>1.0-snapshot</version>
<properties>
<project.build.sourceencoding>utf-8</project.build.sourceencoding>
<java.version>1.8</java.version>
</properties>
<parent>
<groupid>org.springframework.boot</groupid>
<artifactid>spring-boot-starter-parent</artifactid>
<version>1.5.13.release</version>
</parent>
<dependencies>
<dependency>
<groupid>org.springframework.cloud</groupid>
<artifactid>spring-cloud-starter-ribbon</artifactid>
</dependency>
<dependency>
<groupid>org.springframework.cloud</groupid>
<artifactid>spring-cloud-starter-eureka</artifactid>
</dependency>
</dependencies>
<dependencymanagement>
<dependencies>
<dependency>
<groupid>org.springframework.cloud</groupid>
<artifactid>spring-cloud-dependencies</artifactid>
<version>edgware.sr3</version>
<type>pom</type>
<scope>import</scope>
</dependency>
</dependencies>
</dependencymanagement>
<!-- 添加spring-boot的maven插件 -->
<build>
<plugins>
<plugin>
<groupid>org.springframework.boot</groupid>
<artifactid>spring-boot-maven-plugin</artifactid>
</plugin>
</plugins>
</build>
</project>
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server.port=8762
spring.application.name=client-8762
eureka.client.service-url.defaultzone=http://localhost:8761/eureka/
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而在启动类中加入resttemplate远程调用实例到容器中，并且 添加loadbalanced注解，使resttemplate具备负载均衡的能力 ：
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@springbootapplication
@enablediscoveryclient
public class clientapplication {
public static void main(string[] args) {
springapplication.run(clientapplication.class, args);
}
/**
* @description: 加入@loadbalanced注解，就可以为resttemplate加入负载均衡的能力
* @param:
* @return:
* @author:
* @date: 2018/6/15
*/
@bean
@loadbalanced
public resttemplate getresttemplate() {
return new resttemplate();
}
}
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创建controller，注入resttemplate、loadbalancerclient实例：
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package com.cn.controller;
import org.springframework.beans.factory.annotation.autowired;
import org.springframework.cloud.client.serviceinstance;
import org.springframework.cloud.client.loadbalancer.loadbalancerclient;
import org.springframework.stereotype.controller;
import org.springframework.web.bind.annotation.getmapping;
import org.springframework.web.bind.annotation.responsebody;
import org.springframework.web.client.resttemplate;
/**
* @program: springcloud-example
* @description:
* @author:
* @create: 2018-06-15 15:55
**/
@controller
public class ribboncontroller {
@autowired
private loadbalancerclient loadbalancerclient;
@autowired
private resttemplate resttemplate;
@getmapping("/loadinstance")
@responsebody
public string loadinstance() {
serviceinstance choose = this.loadbalancerclient.choose("client-87");
system.out.println(choose.getserviceid()+":"+choose.gethost()+":"+choose.getport());
return choose.getserviceid() + ":" + choose.gethost() + ":" + choose.getport();
}
}
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package com.cn;
import org.springframework.boot.springapplication;
import org.springframework.boot.autoconfigure.springbootapplication;
import org.springframework.cloud.client.discovery.enablediscoveryclient;
/**
* @program: springcloud-example
* @description:
* @author: 535504
* @create: 2018-06-15 16:05
**/
@springbootapplication
@enablediscoveryclient
public class clientapplication {
public static void main(string[] args) {
springapplication.run(clientapplication.class, args);
}
}
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eurekaclient2：
pom.xml与eurekaclient1中一致
application.xml:
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server.port=8763
spring.application.name=client-87
eureka.client.service-url.defaultzone=http://localhost:8761/eureka
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clientcontroller.java:
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package com.cn.contorller;
import org.springframework.stereotype.controller;
import org.springframework.web.bind.annotation.getmapping;
import org.springframework.web.bind.annotation.responsebody;
/**
* @program: springcloud-example
* @description:
* @author:
* @create: 2018-06-15 16:12
**/
@controller
public class clientcontroller {
@getmapping("/getuser")
@responsebody
public string getuser() {
system.out.println("获取用户成功");
return "获取用户成功";
}
}
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2、启动顺序：
①、依次启动eurekaserver =》 eurekaclient1 =》 eurekaclient2 ；
②、然后将eurekaclient2中的application.properties的server.port=8763改为server.port=8764，再次启动该项目;
③、打开eurekaserver的配置页面（http://localhost:8761/），如下：
④、我们在地址栏输入http://localhost:8762/loadinstance，多刷新几次，会发现每次调用的端口实例都不同，如下图：
⑤、我们在看控制台，如图：
至此，ribbon已经入门，是不是很简单，但是这只是最简单的应用，九牛一毛尔...学无止境乎！
示例代码：https://gitee.com/lfalex/springcloud-example
原文链接：http://www.cnblogs.com/lfalex0831/p/9188214.html