本文已收录于专栏 《中间件合集》

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概念说明

什么是Ribbon

  Ribbon 是一个客户端负载均衡器，它是Spring Cloud Netflix开源的一个组件，用于在分布式系统中实现对服务实例的负载均衡。它可以作为一个独立的组件使用，也可以与 Spring Cloud 等微服务框架集成使用。
  Ribbon 的主要功能是根据一定的负载均衡策略，将客户端请求分配到可用的服务实例上，以提高系统的可用性和性能。它通过周期性地从服务注册中心（如 Eureka）获取可用的服务实例列表，并根据配置的负载均衡策略选择合适的实例来处理请求。Ribbon 支持多种负载均衡策略，如轮询、随机、加权随机、加权轮询等。

Ribbon和Nginx负载均衡的区别

工作流程

1. 客户端发起请求到 Ribbon。
2. Ribbon 从服务注册中心获取可用的服务实例列表。
3. 根据配置的负载均衡策略，选择一个合适的服务实例。
4. 将请求转发给选中的服务实例进行处理。
5. 如果请求失败或超时，Ribbon 会尝试选择其他的服务实例进行重试。
   

代码实现

RibbonSDK

sdk是每个使用ribbon的服务中需要引入的jar包，需要借助jar包中的功能来完成ribbon的使用。

package com.example.ribbonsdk.config.test;import com.example.client.Controller.SDKController;
import org.springframework.beans.BeansException;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.context.annotation.Bean;
import org.springframework.core.env.Environment;
import org.springframework.http.*;
import org.springframework.http.client.ClientHttpRequestExecution;
import org.springframework.http.client.ClientHttpRequestInterceptor;
import org.springframework.http.client.ClientHttpResponse;
import org.springframework.stereotype.Component;
import org.springframework.web.client.RestTemplate;
import org.springframework.web.util.UriComponentsBuilder;import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.URI;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Random;/*** @BelongsProject: ribbonDemo* @BelongsPackage: com.example.ribbonsdk.config* @Author: Wuzilong* @Description: RibbonSDK* @CreateTime: 2023-07-31 22:47* @Version: 1.0*/
@Component
public class RequestInterceptor implements ClientHttpRequestInterceptor, ApplicationContextAware {public static ApplicationContext applicationContext;int index = 0;// 目前是写死的，应该放到注册中心中去，动态的添加注册服务和权重public Map<String,Integer> serverList = new HashMap<>(){{put("localhost:9002",7); // 权重值为7put("localhost:9005",3); // 权重值为3}};@Overridepublic void setApplicationContext(ApplicationContext applicationContext) throws BeansException {if (this.applicationContext == null) {this.applicationContext = applicationContext;}}/*** @Author:Wuzilong* @Description: 手动注入AnnotationConfigApplicationContext用于判断* @CreateTime: 2023/6/19 17:36* @param:* @return:**/@Beanpublic AnnotationConfigApplicationContext annotationConfigApplicationContext() {return new AnnotationConfigApplicationContext();}@Overridepublic ClientHttpResponse intercept(HttpRequest request, byte[] body, ClientHttpRequestExecution execution) throws IOException {System.out.println("拦截器拦截进来了，拦截的地址是："+request.getURI());RestTemplate restTemplate = new RestTemplate();//获取服务名String serveName = request.getURI().getAuthority();String newAuthority = null;Environment environment = applicationContext.getBean(Environment.class);String loadBalanceName = environment.getProperty("ribbon.loadBalanceName");if (loadBalanceName.equals("polling")){newAuthority = this.polling(serveName);System.out.println("采用的是负载均衡策略————轮询");}else if (loadBalanceName.equals("weight")){newAuthority = this.weight();System.out.println("采用的是负载均衡策略————权重");}String newHost= newAuthority.split(":")[0];String newPort= newAuthority.split(":")[1];URI newUri = UriComponentsBuilder.fromUri(request.getURI()).host(newHost).port(newPort).build().toUri();RequestEntity tRequestEntity = new RequestEntity(HttpMethod.GET, newUri);ResponseEntity<String> exchange = restTemplate.exchange(tRequestEntity, String.class);System.out.println("请求的服务是"+exchange.getBody());// 创建一个ClientHttpResponse对象，并将实际的响应内容传递给它ClientHttpResponse response = new ClientHttpResponse() {@Overridepublic HttpStatus getStatusCode() {return exchange.getStatusCode();}@Overridepublic int getRawStatusCode() {return exchange.getStatusCodeValue();}@Overridepublic String getStatusText() {return exchange.getBody();}@Overridepublic void close() {}@Overridepublic InputStream getBody() {return new ByteArrayInputStream(exchange.getBody().getBytes());}@Overridepublic HttpHeaders getHeaders() {return exchange.getHeaders();}};return response;}//轮询获取服务的IP地址public  String polling(String serverName){List<String> pollingList = applicationContext.getBean(SDKController.class).getList(serverName);String ipContext = pollingList.get(index);index=(index+1)%pollingList.size();return ipContext;}//权重获取服务的IP地址public String weight() {int totalWeight = serverList.values().stream().mapToInt(Integer::intValue).sum();int randomWeight = new Random().nextInt(totalWeight); // 生成一个随机权重值int cumulativeWeight = 0; // 累计权重值for (Map.Entry<String,Integer> server : serverList.entrySet()) {cumulativeWeight += server.getValue();if (randomWeight < cumulativeWeight) {return server.getKey();}}return null; // 没有找到合适的服务器}}

  RequestInterceptor 类实现了两个接口，一个是ClientHttpRequestInterceptor用来重写intercept方法，也就是说重写了拦截器中的业务逻辑，我们可以把拦截到的请求进行处理，处理的过程可以写到intercept方法中，另一个是ApplicationContextAware这个接口是用来获取bean容器中对象的。

发送请求端

引入RibbonSDK和Nacos的依赖

        <dependency><groupId>com.example</groupId><artifactId>RibbonSDK</artifactId><version>1.0-SNAPSHOT</version></dependency>

        <!-- 手写nacos的sdk，用来获取注册列表--><dependency><groupId>com.example</groupId><artifactId>Client</artifactId><version>2.5-20230615.123611-1</version></dependency>

Nacos的其他配置可参考：手写Naocs注册中心基本原理  手写Nacos配置中心基本原理

配置文件中填写负载均衡策略

ribbon:loadBalanceName: polling

调用代码

import com.example.ribbonsdk.config.test.RequestInterceptor;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.web.client.RestTemplateBuilder;
import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.stereotype.Service;
import org.springframework.web.client.RestTemplate;/*** @BelongsProject: ribbonDemo* @BelongsPackage: com.example.ribbonsdk.service* @Author: Wuzilong* @Description: 请求端* @CreateTime: 2023-08-28 08:20* @Version: 1.0*/
@Service
public class ServiceA {@Autowiredprivate RequestInterceptor requestInterceptor;public void getServiceInfo(){String url = "http://"+"localhost"+"/B/receiveMessage/";RestTemplate restTemplate=new RestTemplateBuilder().build();restTemplate.getInterceptors().add(requestInterceptor);ResponseEntity<String> forEntity = restTemplate.getForEntity(url, String.class);if (forEntity.getStatusCode() == HttpStatus.OK) {System.out.println("调用B服务成功！");}}
}

import com.example.ribbonsdk.service.ServiceA;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RestController;/*** @BelongsProject: ribbonDemo* @BelongsPackage: com.example.ribbonsdk.Controller* @Author: Wuzilong* @Description: 描述什么人干什么事儿* @CreateTime: 2023-07-31 22:54* @Version: 1.0*/
@RestController
@RequestMapping("/ribbonsdk")
public class ServiceAController {@Autowiredprivate ServiceA serviceA;@RequestMapping(value="getInfo",method= RequestMethod.GET)public void getInfo(){serviceA.getServiceInfo();}
}

接收请求端

import org.springframework.beans.factory.annotation.Value;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;import java.net.InetAddress;
import java.net.UnknownHostException;/*** @BelongsProject: ServiceB* @BelongsPackage: com.example.serviceb.Controller* @Author: Wuzilong* @Description: B服务* @CreateTime: 2023-06-07 19:08* @Version: 1.0*/
@RestController
@RequestMapping("/B")
public class ServiceBController {@Value("${server.port}")private String serverPort;@GetMapping("/receiveMessage")public String receiveMessage() throws UnknownHostException {System.out.println("B：我被调用了");//返回的内容是ip地址和端口号return InetAddress.getLocalHost().getHostAddress()+":"+serverPort;}
}

执行效果

发送请求端

接收请求端

总结提升

  Ribbon 是一个强大的客户端负载均衡器，可以帮助构建可靠和高性能的分布式系统。它通过负载均衡策略将请求分发到多个服务实例上，提供了灵活的配置选项和额外的功能。

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