spring cloud之ribbon复习回顾

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 {

    @Override
    public void initWithNiwsConfig(IClientConfig iClientConfig) {

    }

    @Override
    public 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 {

    @Autowired
    private 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.