springcloud-Ribbon 客户端负载均衡

• Ribbon 基础
• Ribbon 引入项目改造

 

一般来说，提到负载均衡，大家一般很容易想到浏览器 -> NGINX -> 反向代理多个 Tomcat 这样的架构图——业界管这种负载均衡模式叫”服务器端负载均衡”，因为此种模式下，负载均衡算法是 NGINX 提供的，而 NGINX 部署在服务器端。

Ribbon 则是一个客户端侧负载均衡组件——通俗地说，就是集成在客户端（服务消费者一侧），并提供负载均衡算法的一个组件。

 

Ribbon 是 Netflix 发布的负载均衡器，它可以帮我们控制 HTTP 和 TCP 客户端的行为。只需为 Ribbon 配置服务提供者地址列表，Ribbon 就可基于负载均衡算法计算出要请求的目标服务地址。

Ribbon 默认为我们提供了很多的负载均衡算法，例如轮询、随机、响应时间加权等——当然，为 Ribbon 自定义负载均衡算法也非常容易，只需实现IRule 接口即可。

TIPS Ribbon 的仓库地址（Github）: https://github.com/Netflix/ribbon

 

在 Spring Cloud 中，当 Ribbon 与 Eureka 配合使用时，Ribbon 可自动从 Eureka Server 获取服务提供者地址列表，并基于负载均衡算法，选择其中一个服务提供者实例。下图展示了 Ribbon 与 Eureka 配合使用时的大致架构。

 

 

创建ribon服务,microservice-consumer-movie-ribbon

pom.xml 

 Maven 引入依赖：由于 spring-cloud-starter-netflix-eureka-client 已经包含 spring-cloud-starter-netfilx-ribbon，故而无需额外添加依赖

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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.lzj1234</groupId>     <artifactId>microservice-consumer-movie-ribbon</artifactId>     <version>1.0-SNAPSHOT</version>     <parent>         <groupId>org.springframework.boot</groupId>         <artifactId>spring-boot-starter-parent</artifactId>         <version>2.0.7.RELEASE</version>         <relativePath/>     </parent>       <properties>         <java.version>1.8</java.version> <!--        <maven.compiler.source>8</maven.compiler.source>--> <!--        <maven.compiler.target>8</maven.compiler.target>-->     </properties>     <dependencies>         <!-- https://mvnrepository.com/artifact/org.springframework.boot/spring-boot-starter-data-jpa -->         <dependency>             <groupId>org.springframework.boot</groupId>             <artifactId>spring-boot-starter-data-jpa</artifactId>         </dependency>           <!-- https://mvnrepository.com/artifact/org.springframework.boot/spring-boot-starter-web -->         <dependency>             <groupId>org.springframework.boot</groupId>             <artifactId>spring-boot-starter-web</artifactId>             <!--            <version>2.4.2</version>-->         </dependency>           <!-- 引入H2数据库，一种内嵌的数据库，语法类似MySQL -->         <!-- https://mvnrepository.com/artifact/com.h2database/h2 -->         <dependency>             <groupId>com.h2database</groupId>             <artifactId>h2</artifactId>             <version>1.4.200</version>             <!--            <scope>test</scope>-->         </dependency>           <!-- https://mvnrepository.com/artifact/org.projectlombok/lombok -->         <dependency>             <groupId>org.projectlombok</groupId>             <artifactId>lombok</artifactId>             <version>1.18.18</version>             <scope>provided</scope>         </dependency>           <!-- https://mvnrepository.com/artifact/org.springframework.boot/spring-boot-starter-test -->         <dependency>             <groupId>org.springframework.boot</groupId>             <artifactId>spring-boot-starter-test</artifactId>             <!--            <version>2.4.2</version>-->             <scope>test</scope>         </dependency>         <!-- https://mvnrepository.com/artifact/org.apache.maven.plugins/maven-clean-plugin -->         <dependency>             <groupId>org.apache.maven.plugins</groupId>             <artifactId>maven-clean-plugin</artifactId>             <version>2.5</version>         </dependency>         <!-- 新增依赖 -->         <dependency>             <groupId>org.springframework.cloud</groupId>             <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>         </dependency>     </dependencies>       <!-- 引入spring cloud的依赖，不能少，主要用来管理Spring Cloud生态各组件的版本 -->     <dependencyManagement>         <dependencies>             <dependency>                 <groupId>org.springframework.cloud</groupId>                 <artifactId>spring-cloud-dependencies</artifactId>                 <version>Finchley.SR2</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>             <plugin>                 <groupId>org.apache.maven.plugins</groupId>                 <artifactId>maven-compiler-plugin</artifactId>                 <version>2.5.1</version>                 <configuration>                     <source>1.8</source>                     <target>1.8</target>                 </configuration>             </plugin>         </plugins>     </build> </project>

　　

 

org.springframework.boot:spring-boot-maven-plugin:2.0.7.RELEASE:repackage failed: Unable to find mai

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<plugin>                 <groupId>org.springframework.boot</groupId>                 <artifactId>spring-boot-maven-plugin</artifactId>             </plugin>

　　

这是因为springboot默认没有启动类，需要手动添加启动类：springboot

 

创建启动类，App.java

package com.lzj1234;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
import org.springframework.cloud.client.loadbalancer.LoadBalanced;
import org.springframework.context.annotation.Bean;
import org.springframework.web.client.RestTemplate;

@SpringBootApplication
@EnableDiscoveryClient
public class App {
    public static void main(String[] args) {
        SpringApplication.run(App.class,args);
    }
    
    @Bean
    @LoadBalanced
    public RestTemplate restTemplate(){
        return new RestTemplate();
    }
// 只需在 RestTemplate 上添加 LoadBalanced 注解，即可让 RestTemplate 整合 Ribbon！
}

　　

再次执行mvn install 命令，安装依赖包，就不会出错了

 

MovieController

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package com.lzj1234;     import org.springframework.beans.factory.annotation.Autowired; import org.springframework.cloud.client.loadbalancer.LoadBalanced; import org.springframework.web.bind.annotation.GetMapping; import org.springframework.web.bind.annotation.PathVariable; import org.springframework.web.bind.annotation.RequestMapping; import org.springframework.web.bind.annotation.RestController; import org.springframework.web.client.RestTemplate;   @RequestMapping("/movies") @RestController public class MovieController {       @Autowired     RestTemplate restTemplate;       @GetMapping("/users/{id}")     public User findById(@PathVariable Long id){         // 这里用到了RestTemplate的占位符能力  microservice-provider-user         User user=this.restTemplate.getForObject("http://microservice-provider-user/users/{id}",User.class,id);         return user;     } }

 

配置文件

 

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server:   port: 8010 spring:   application:     name: microservice-consumer-movie-ribbon logging:   level:     root: INFO     # 配置日志级别，让hibernate打印出执行的SQL参数     org.hibernate: INFO     org.hibernate.type.descriptor.sql.BasicBinder: TRACE     org.hibernate.type.descriptor.sql.BasicExtractor: TRACE   # 新增配置 eureka:   client:     serviceUrl:       defaultZone: http://localhost:8080/eureka/   instance:     prefer-ip-address: true

　　

 

mvn spring-boot:run 

 

 

 

 

 

 

 

 

 

在项目中引用 Ribbon 来实现了客户端的负载均衡。Ribbon 是一个客户端侧负载均衡组件——通俗地说，就是集成在客户端（服务消费者一侧），并提供负载均衡算法的一个组件。