权重轮询调度算法(WeightedRound-RobinScheduling)-Java实现2

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


与上一遍博客 http://www.cnblogs.com/huligong1234/p/3819979.html 中实现方式不同，
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。
本篇文章也加上了动态添加服务器，和动态down掉服务器的演示实例。 由于研究本算法的目的是在其他方面的应用，故涉及服务器请求超时时间等因素，并未考虑。

 

  1 import java.util.ArrayList;
  2 import java.util.Date;
  3 import java.util.HashMap;
  4 import java.util.List;
  5 import java.util.Map;
  6 import java.util.Map.Entry;
  7 
  8 /**
  9  * 权重轮询调度算法(WeightedRound-RobinScheduling)-Java实现
 10  * @author huligong
 11  * */
 12 public class WeightedRoundRobinScheduling {
 13 
 14     private List serverList; //服务器集合
 15 
 16     public Server GetBestServer() {
 17         Server server = null;
 18         Server best = null;
 19         int total = 0;
 20         for(int i=0,len=serverList.size();i){
 21             //当前服务器对象
 22             server = serverList.get(i);
 23 
 24             //当前服务器已宕机，排除
 25             if(server.down){
 26                 continue;
 27             }
 28 
 29             server.currentWeight += server.effectiveWeight;
 30             total += server.effectiveWeight;
 31             
 32             if(server.effectiveWeight < server.weight){
 33                 server.effectiveWeight++;
 34             }
 35             
 36             if(best == null || server.currentWeight>best.currentWeight){
 37                 best = server;
 38             }
 39             
 40         }
 41 
 42         if (best == null) {
 43             return null;
 44         }
 45 
 46         best.currentWeight -= total;
 47         best.checkedDate = new Date();
 48         return best;
 49     }
 50     
 51     
 52 
 53     class Server {
 54         public String ip;
 55         public int weight;
 56         public int effectiveWeight;
 57         public int currentWeight;
 58         public boolean down = false;
 59         public Date checkedDate;
 60         public Server(String ip, int weight) {
 61             super();
 62             this.ip = ip;
 63             this.weight = weight;
 64             this.effectiveWeight = this.weight;
 65             this.currentWeight = 0;
 66             if(this.weight < 0){
 67                 this.down = true;
 68             }else{
 69                 this.down = false;
 70             }
 71         }
 72         public String getIp() {
 73             return ip;
 74         }
 75         public void setIp(String ip) {
 76             this.ip = ip;
 77         }
 78         public int getWeight() {
 79             return weight;
 80         }
 81         public void setWeight(int weight) {
 82             this.weight = weight;
 83         }
 84         public int getEffectiveWeight() {
 85             return effectiveWeight;
 86         }
 87         public void setEffectiveWeight(int effectiveWeight) {
 88             this.effectiveWeight = effectiveWeight;
 89         }
 90         public int getCurrentWeight() {
 91             return currentWeight;
 92         }
 93         public void setCurrentWeight(int currentWeight) {
 94             this.currentWeight = currentWeight;
 95         }
 96         public boolean isDown() {
 97             return down;
 98         }
 99         public void setDown(boolean down) {
100             this.down = down;
101         }
102         public Date getCheckedDate() {
103             return checkedDate;
104         }
105         public void setCheckedDate(Date checkedDate) {
106             this.checkedDate = checkedDate;
107         }
108         
109     }
110     
111 
112     public void init() {
113         Server s1 = new Server("192.168.0.100", 3);//3
114         Server s2 = new Server("192.168.0.101", 2);//2
115         Server s3 = new Server("192.168.0.102", 6);//6
116         Server s4 = new Server("192.168.0.103", 4);//4
117         Server s5 = new Server("192.168.0.104", 1);//1
118         Server s6 = new Server("192.168.0.105", 0);//0
119         Server s7 = new Server("192.168.0.106", 0);//0
120         Server s8 = new Server("192.168.0.107", 0);//0
121         Server s9 = new Server("192.168.0.108", 0);//0
122         serverList = new ArrayList();
123         serverList.add(s1);
124         serverList.add(s2);
125         serverList.add(s3);
126         serverList.add(s4);
127         serverList.add(s5);
128         serverList.add(s6);
129         serverList.add(s7);
130         serverList.add(s8);
131         serverList.add(s9);
132     }
133     
134     public void add(int i) {
135         Server s = new Server("192.168.0.1"+i, i-15);
136         serverList.add(s);
137     }
138     
139     public Server getServer(int i) {
140         if(i<serverList.size()){
141             return serverList.get(i);
142         }
143        return null;
144     }
145     
146     
147     public static void main(String[] args) {
148         WeightedRoundRobinScheduling obj = new WeightedRoundRobinScheduling();
149         obj.init();
150         
151         Map countResult = new HashMap();
152         
153         for (int i = 0; i < 100; i++) {
154             Server s = obj.GetBestServer();
155             String log = "ip:"+s.ip+";weight:"+s.weight;
156             if(countResult.containsKey(log)){
157                 countResult.put(log,countResult.get(log)+1);
158             }else{
159                 countResult.put(log,1);
160             }
161             System.out.println(log);
162         
163             //动态添加服务器
164             if(i==20 || i==22){
165                   obj.add(i);
166             }
167             
168             //动态停止服务器
169             if(i==30){
170                 obj.getServer(2).setDown(true);
171                 obj.getServer(3).setDown(true);
172           }
173         }
174         
175         for(Entry map : countResult.entrySet()){
176             System.out.println("服务器 "+map.getKey()+" 请求次数： "+map.getValue());
177         }
178     }
179 
180 }

currentweight用于记录本次请求时服务器参与计算后的的权值，这样才能保证每次请求都不是同一台机器，effectiveweight，由于每台机器的配置或响应能力不一样，所以需要给其一个权值，确保高配置或响应快的机器多分配到请求。

权值大小和获得的请求次数是对应的，当前程序中有模拟动态停止服务器的代码，所以会影响整体结果。真实项目中，如果有服务器动态被停掉，所有的currentWeight都有重置的，这样才能保证后面运行的结果符合权重比值。示例代码中的15之类值无特别含义，仅是为了计算后产生的权值与之前的权值相差不大。