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。
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());
}
}
}