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;@Controllerpublic 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List Set<String> keySet = serverMap.keySet(); Iterator<String> iterator = keySet.iterator(); // 根据权重组成iplist List<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

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