权重轮询调度算法(WeightedRound-RobinScheduling)

权重轮询调度算法(WeightedRound-RobinScheduling)-Java实现
                                      ----参考Nginx中负载均衡算法实现

这里主要参考这篇文章的实现： Nginx 负载均衡-加权轮询策略剖析 http://www.cnblogs.com/dyllove98/archive/2013/07/13/3188450.html，
与上一遍中实现比起来，效果比较好，权重比较低的服务器，也比较容易背获取到，但请求数量比较大的时候，两个实现方式中，每个服务器分担的请求数基本无差别，区别主要是顺序上。

import java.util.ArrayList;
import java.util.Date;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;

/**
 * 权重轮询调度算法(WeightedRound-RobinScheduling)-Java实现
 * @author huligong
 * */
public class WeightedRoundRobinScheduling {

    private List<Server> serverList; //服务器集合

    public Server GetBestServer() {
        Server server = null;
        Server best = null;
        int total = 0;
        for(int i=0,len=serverList.size();i<len;i++){
            //当前服务器对象
            server = serverList.get(i);

            //当前服务器已宕机，排除
            if(server.down){
                continue;
            }

            server.currentWeight += server.effectiveWeight;
            total += server.effectiveWeight;

            if(server.effectiveWeight < server.weight){
                server.effectiveWeight++;
            }

            if(best == null || server.currentWeight>best.currentWeight){
                best = server;
            }

        }

        if (best == null) {
            return null;
        }

        best.currentWeight -= total;
        best.checkedDate = new Date();
        return best;
    }

    class Server {
        public String ip;
        public int weight;
        public int effectiveWeight;
        public int currentWeight;
        public boolean down = false;
        public Date checkedDate;
        public Server(String ip, int weight) {
            super();
            this.ip = ip;
            this.weight = weight;
            this.effectiveWeight = this.weight;
            this.currentWeight = 0;
            if(this.weight < 0){
                this.down = true;
            }else{
                this.down = false;
            }
        }
        public String getIp() {
            return ip;
        }
        public void setIp(String ip) {
            this.ip = ip;
        }
        public int getWeight() {
            return weight;
        }
        public void setWeight(int weight) {
            this.weight = weight;
        }
        public int getEffectiveWeight() {
            return effectiveWeight;
        }
        public void setEffectiveWeight(int effectiveWeight) {
            this.effectiveWeight = effectiveWeight;
        }
        public int getCurrentWeight() {
            return currentWeight;
        }
        public void setCurrentWeight(int currentWeight) {
            this.currentWeight = currentWeight;
        }
        public boolean isDown() {
            return down;
        }
        public void setDown(boolean down) {
            this.down = down;
        }
        public Date getCheckedDate() {
            return checkedDate;
        }
        public void setCheckedDate(Date checkedDate) {
            this.checkedDate = checkedDate;
        }

    }

    public void init() {
        Server s1 = new Server("192.168.0.100", 3);//
        Server s2 = new Server("192.168.0.101", 2);//
        Server s3 = new Server("192.168.0.102", 6);//
        Server s4 = new Server("192.168.0.103", 4);//
        Server s5 = new Server("192.168.0.104", 1);//
        Server s6 = new Server("192.168.0.105", 0);//
        Server s7 = new Server("192.168.0.106", 0);//
        Server s8 = new Server("192.168.0.107", 0);//
        Server s9 = new Server("192.168.0.108", 0);//
        serverList = new ArrayList<Server>();
        serverList.add(s1);
        serverList.add(s2);
        serverList.add(s3);
        serverList.add(s4);
        serverList.add(s5);
        serverList.add(s6);
        serverList.add(s7);
        serverList.add(s8);
        serverList.add(s9);
    }

    public void add(int i) {
        Server s = new Server("192.168.0.1"+i, i-15);
        serverList.add(s);
    }

    public Server getServer(int i) {
        if(i<serverList.size()){
            return serverList.get(i);
        }
       return null;
    }

    public static void main(String[] args) {
        WeightedRoundRobinScheduling obj = new WeightedRoundRobinScheduling();
        obj.init();

        Map<String,Integer> countResult = new HashMap<String,Integer>();

        for (int i = 0; i < 100; i++) {
            Server s = obj.GetBestServer();
            String log = "ip:"+s.ip+";weight:"+s.weight;
            if(countResult.containsKey(log)){
                countResult.put(log,countResult.get(log)+1);
            }else{
                countResult.put(log,1);
            }
            System.out.println(log);

            //动态添加服务器
            if(i==20 || i==22){
                  obj.add(i);
            }

            //动态停止服务器
            if(i==30){
                obj.getServer(2).setDown(true);
                obj.getServer(3).setDown(true);
          }
        }

        for(Entry<String, Integer> map : countResult.entrySet()){
            System.out.println("服务器 "+map.getKey()+" 请求次数： "+map.getValue());
        }
    }

}