SpringCloud客户端的负载均衡Ribbon的实现
作者：lfalex
微服务架构，不可避免的存在单个微服务有多个实例，这篇文章主要介绍了SpringCloud客户端的负载均衡Ribbon的实现，小编觉得挺不错的，现在分享给大家，也给大家做个参考。一起跟随小编过来看看吧
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
@SpringBootApplication
@EnableEurekaServer
public class ServerApplication {
public static void main(String[] args) {
SpringApplication.run(ServerApplication.class,args);
}
}
pom.xml
<?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
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/
EurekaClient1:
pom.xml
<?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>
server.port=8762 spring.application.name=client-8762 eureka.client.service-url.defaultZone=http://localhost:8761/eureka/
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 ：
@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();
}
}
创建Controller，注入RestTemplate、LoadBalancerClient实例：
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();
}
}
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);
}
}
EurekaClient2：
pom.xml与EurekaClient1中一致
application.xml:
server.port=8763 spring.application.name=client-87 eureka.client.service-url.defaultZone=http://localhost:8761/eureka
ClientController.java:
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";
}
}
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