手写ribbon负载均衡

通过观察负载均衡规则源码可知，负载均衡器都继承了AbstractLoadBalancerRule抽象父类(负载均衡规则类)，我们手写自定义负载均衡器时，可参照源码进行修改

自定义(端口号大于25)的负载均衡器

package com.ssm.ribbon.rule;

import com.netflix.client.config.IClientConfig;
import com.netflix.loadbalancer.AbstractLoadBalancerRule;
import com.netflix.loadbalancer.ILoadBalancer;
import com.netflix.loadbalancer.Server;

import java.util.List;
import java.util.concurrent.ThreadLocalRandom;

public class SsmRule extends AbstractLoadBalancerRule {
    public SsmRule() {
    }

    @SuppressWarnings({"RCN_REDUNDANT_NULLCHECK_OF_NULL_VALUE"})
    public Server choose(ILoadBalancer lb, Object key) {
        if (lb == null) {
            return null;
        } else {
            Server server = null;

            while(server == null) {
                if (Thread.interrupted()) { //如果线程被中断，则返回null
                    return null;
                }

                List<Server> upList = lb.getReachableServers(); //当前可访问的服务器列表
                List<Server> allList = lb.getAllServers(); //所有服务器的列表
                int serverCount = allList.size();
                if (serverCount == 0) {
                    return null;
                }

                //int index = this.chooseRandomInt(serverCount); 修改随机算法
                //server = (Server)upList.get(index);

                //如果当前服务端口号大于25，就使用它
                for(Server upServer : upList) {
                    int port = upServer.getPort();
                    if(port > 25) {
                        server = upServer;
                        break;
                    }
                }
                if (server == null) {
                    Thread.yield(); //把资源倾斜给其他线程
                } else {
                    if (server.isAlive()) { //如果线程是活的，则返回它
                        return server;
                    }

                    server = null;
                    Thread.yield();
                }
            }

            return server;
        }
    }

    protected int chooseRandomInt(int serverCount) {
        return ThreadLocalRandom.current().nextInt(serverCount);
    }

    public Server choose(Object key) {
        return this.choose(this.getLoadBalancer(), key);
    }

    public void initWithNiwsConfig(IClientConfig clientConfig) {
    }
}

package com.ssm.ribbon.rule;

import com.netflix.loadbalancer.IRule;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

@Configuration
public class SsmRuleConfig {

    @Bean
    public IRule ssmRule() {
        return new SsmRule();
    }
}

指定该负载均衡器

package com.ssm.home;

import com.ssm.ribbon.rule.SsmRuleConfig;
import org.mybatis.spring.annotation.MapperScan;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.netflix.ribbon.RibbonClient;
import org.springframework.context.annotation.ComponentScan;

@SpringBootApplication
@MapperScan(value = "com.ssm.*.mapper")
@ComponentScan(value = "com.ssm")
@RibbonClient(name = "ape-cloud-sku", configuration = SsmRuleConfig.class)
public class HomeApplication {
    public static void main(String[] args) {
        System.setProperty("Log4jContextSelector", "org.apache.logging.log4j.core.async.AsyncLoggerContextSelector");
        SpringApplication.run(HomeApplication.class, args);
    }
}

当home微服务调用sku微服务时，使用自定义的负载均衡器