其实在项目中直接使用ribbon时不多，大多是使用feign的，其实feign底层也是通过ribbon构建的，主要记忆一下计算规则，ribbon的源码还是很不错的，还是值得学习的。
1、添加pom
<dependency><groupId>org.springframework.cloud</groupId><artifactId>spring-cloud-starter-netflix-ribbon</artifactId>
</dependency>
2、启动类注解
我没有在启动类添加注解，直接另外一个配置类@Configuration添加
3、添加配置
# 默认是轮训，都有随机、加权响应时间、重试，看具体业务和服务器搭配
#eureka-client.ribbon.NFLoadBalancerRuleClassName=com.netflix.loadbalancer.RoundRobinRule
4、参照源码规则，自己编写规则
这里是通过hashcode在hash闭环定义的，当每台服务器hashcode在hash闭环的对应位置后，每次请求直接定位到hash中顺时针寻找最近的服务器
package com.xl.ribbon.consumer.rules;import com.netflix.client.config.IClientConfig;
import com.netflix.loadbalancer.AbstractLoadBalancerRule;
import com.netflix.loadbalancer.IRule;
import com.netflix.loadbalancer.Server;
import lombok.NoArgsConstructor;
import org.springframework.util.CollectionUtils;
import org.springframework.web.context.request.RequestContextHolder;
import org.springframework.web.context.request.ServletRequestAttributes;
import org.springframework.web.servlet.mvc.condition.RequestConditionHolder;import javax.servlet.http.HttpServletRequest;
import java.io.UnsupportedEncodingException;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.List;
import java.util.SortedMap;
import java.util.TreeMap;@NoArgsConstructor
public class MyRule extends AbstractLoadBalancerRule implements IRule {@Overridepublic void initWithNiwsConfig(IClientConfig iClientConfig) {}@Overridepublic Server choose(Object key) {HttpServletRequest request = ((ServletRequestAttributes)RequestContextHolder.getRequestAttributes()).getRequest();String uri = request.getServletPath() + "?" + request.getQueryString();return route(uri.hashCode(), getLoadBalancer().getAllServers());}public Server route(int hashId, List<Server> servers) {if (CollectionUtils.isEmpty(servers)) {return null;}TreeMap<Long, Server> serverMap = new TreeMap<>();servers.forEach(server -> {// 虚化若干个服务节点，到环上for (int i = 0; i < 8; i++) {long hash = hash(server.getId() + i);serverMap.put(hash, server);}});long hash = hash(String.valueOf(hashId));SortedMap<Long, Server> last = serverMap.tailMap(hash);// 当request URL的hash值大于任意一个服务器对应的hashKey，// 取serverMap中的第一个节点if (last.isEmpty()) {Server value = serverMap.firstEntry().getValue();last.put(hash, value);}return last.get(last.firstKey());}public long hash(String key) {MessageDigest md5;try {md5 = MessageDigest.getInstance("MD5");} catch (NoSuchAlgorithmException e) {throw new RuntimeException(e);}byte[] keyBytes = null;try {keyBytes = key.getBytes("UTF-8");} catch (UnsupportedEncodingException e) {throw new RuntimeException(e);}md5.update(keyBytes);byte[] digest = md5.digest();long hash = (digest[2] & 0xFF << 16) | (digest[1] & 0xFF) << 8 | (digest[0] & 0xFF);return hash & 0xffffffffL;}
}5、规则配置
其实直接配置在application.properties也可以，这里我是在一个配置文件
package com.xl.ribbon.consumer;import com.netflix.loadbalancer.IRule;
import com.netflix.loadbalancer.RandomRule;
import com.xl.ribbon.consumer.rules.MyRule;
import org.springframework.cloud.netflix.ribbon.RibbonClient;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;/*** Created by lig on 2024/10/12.*/
@Configuration
//@RibbonClient(name = "eureka-client", configuration = com.netflix.loadbalancer.RandomRule.class)
@RibbonClient(name = "eureka-client", configuration = MyRule.class)
public class RibbonConfiguration {
//
// @Bean
// public IRule defaultLBStrategy() {
// return new RandomRule();
// }}6、接口
package com.xl.ribbon.consumer;import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.client.RestTemplate;/*** Created by lig on 2024/10/12.*/
@RestController
public class RibbonController {@Autowiredprivate RestTemplate restTemplate;@GetMapping("/sayHi")public String sayHi() {return restTemplate.getForObject("http://eureka-client/sayHi", String.class);}}总结
其实在实际项目中ribbon编写符合自己业务的规则还是挺复杂的，用途还是挺广的.
