前言：微服務架構，不可避免的存在單個微服務有多個實例，那么客戶端如何將請求分攤到多個微服務的實例上呢？這里我們就需要使用負載均衡了
一、ribbon簡介
ribbon是netflix發布的負載均衡器，它有助于控制http和tcp客戶端的行為。為ribbon配置服務提供者地址列表后，ribbon就可基于某種負載均衡算法，自動地幫助服務消費者去請求。ribbon默認為我們提供了很多的負載均衡算法，例如：輪詢，隨機等，也可自定義；
ribbon的github： https://github.com/netflix/ribbon
而在springcloud中使用ribbon和eureka時，ribbon會自動從eurekaserver中獲取服務提供者地址列表，并基于負載均衡算法。
二、ribbon實戰
?1、創建eurekaserver，eurekaclient1，eurekaclient2，之前已經說過了eureka的使用，這里直接上代碼：
eurekaserver：
serverapplication.java
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@springbootapplication@enableeurekaserverpublic class serverapplication { public static void main(string[] args) { springapplication.run(serverapplication.class,args); }} |
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> |
application.properties
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server.port=8761#注意：這兩個配置eureka默認為true，要改成false，否則會報錯，connot connect server#表示是否將自己注冊在eurekaserver上eureka.client.register-with-eureka=false#表示是否從eurekaserver獲取注冊信息eureka.client.fetch-registry=falseeureka.client.service-url.defaultzone=http://localhost:8761/eureka/ |
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=8762spring.application.name=client-8762eureka.client.service-url.defaultzone=http://localhost:8761/eureka/ |
而在啟動類中加入resttemplate遠程調用實例到容器中，并且 添加loadbalanced注解，使resttemplate具備負載均衡的能力 ：
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@springbootapplication@enablediscoveryclientpublic class clientapplication { public static void main(string[] args) { springapplication.run(clientapplication.class, args); } /** * @description: 加入@loadbalanced注解，就可以為resttemplate加入負載均衡的能力 * @param: * @return: * @author: * @date: 2018/6/15 */ @bean @loadbalanced public resttemplate getresttemplate() { return new resttemplate(); }} |
創建controller，注入resttemplate、loadbalancerclient實例：
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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 **/@controllerpublic 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@enablediscoveryclientpublic class clientapplication { public static void main(string[] args) { springapplication.run(clientapplication.class, args); }} |
eurekaclient2：
pom.xml與eurekaclient1中一致
application.xml:
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server.port=8763spring.application.name=client-87eureka.client.service-url.defaultzone=http://localhost:8761/eureka |
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 **/@controllerpublic class clientcontroller { @getmapping("/getuser") @responsebody public string getuser() { system.out.println("獲取用戶成功"); return "獲取用戶成功"; }} |
2、啟動順序：
①、依次啟動eurekaserver =》 eurekaclient1 =》 eurekaclient2 ；
②、然后將eurekaclient2中的application.properties的server.port=8763改為server.port=8764，再次啟動該項目;
③、打開eurekaserver的配置頁面（http://localhost:8761/），如下：
④、我們在地址欄輸入http://localhost:8762/loadinstance，多刷新幾次，會發現每次調用的端口實例都不同，如下圖：
⑤、我們在看控制臺，如圖：
至此，ribbon已經入門，是不是很簡單，但是這只是最簡單的應用，九牛一毛爾...學無止境乎！
示例代碼：https://gitee.com/lfalex/springcloud-example
原文鏈接：http://www.cnblogs.com/lfalex0831/p/9188214.html
