Java加权负载均衡策略

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