加权轮询

后端集群每台机器都分配一个权重，权重高得会承担更多的流量，相反权重低的分配的流量也会少，这种策略允许后端集群机器配置差异化

java实现

import java.util.ArrayList;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Set;import org.springframework.stereotype.Controller;@Controller
public class IpMapController extends LogBaseController implements Runnable {private static Integer pos = 0;// 待scp的Ip列表，Key代表Ip，Value代表该Ip的权重public static HashMap<String, Integer> serverWeightMap = new HashMap<String, Integer>();static {serverWeightMap.put("127.0.0.1", 1);serverWeightMap.put("127.0.0.2", 1);serverWeightMap.put("127.0.0.3", 1);serverWeightMap.put("127.0.0.4", 1);}public void run() {// 重建一个Map，避免服务器的上下线导致的并发问题Map<String, Integer> serverMap = new HashMap<String, Integer>();serverMap.putAll(serverWeightMap);// 取得Ip地址ListSet<String> keySet = serverMap.keySet();Iterator<String> iterator = keySet.iterator();// 根据权重组成iplistList<String> serverList = new ArrayList<String>();while (iterator.hasNext()) {String server = iterator.next();int weight = serverMap.get(server);for (int i = 0; i < weight; i++)serverList.add(server);}String server = null;synchronized (pos) {if (pos >= keySet.size()){pos = 0;}server = serverList.get(pos);System.out.println("server:" + server + ",pos=" + pos);pos++;}}public static void main(String[] args) {IpMapController ipRunnable = new IpMapController();for (int i = 0; i <= 10; i++) {System.out.println("t" + i);new Thread(ipRunnable).start();}}}

多线程输出结果

t0
t1
t2
t3
t4
t5
t6
server:127.0.0.4,pos=0
server:127.0.0.3,pos=1
server:127.0.0.2,pos=2
server:127.0.0.2,pos=2
t7
server:127.0.0.4,pos=0
server:127.0.0.3,pos=1
t8
server:127.0.0.2,pos=2
server:127.0.0.2,pos=2
t9
server:127.0.0.4,pos=0
t10
server:127.0.0.3,pos=1
server:127.0.0.2,pos=2