相信熟悉过Nginx的都知道,Nginx其中有一个功能是负载均衡。
Nginx的负载均衡里可以配置一个服务器列表,如:
- upstream detecotr_server {
- #ip_hash;
- #这里指定多个源服务器,ip:端口,80端口的话可写可不写
- server 192.168.154.1:8080 weight=1;# max_fails=2 fails_time=2;
- server 192.168.154.2:8088 weight=2;# max_fail2=2 fails_time=2;
- }
当负载均衡策略为加权轮询,如果的3个请求,则会有1个请求分发到192.168.154.1服务器上,2个请求分发到192.168.154.2服务器上。
现在使用加权随机数来模拟来加权轮询算法,当一个请求过来的时候,根据不同服务器对应的的权值,随机返回处理请求的服务器。
- public class WeightRandom {
- public static Map<String, Integer> servers = new HashMap<String, Integer>();
- static{
- servers.put("192.168.20.101", 1);
- servers.put("192.168.20.102", 2);
- servers.put("192.168.20.103", 3);
- servers.put("192.168.20.104", 4);
- }
- public static String selectServer(Map<String, Integer> servers){
- if(servers == null || servers.size() == 0) return null;
- Integer sum = 0;
- Set<Map.Entry<String, Integer>> entrySet = servers.entrySet();
- Iterator<Map.Entry<String, Integer>> iterator = entrySet.iterator();
- while(iterator.hasNext()){
- sum += iterator.next().getValue();
- }
- Integer rand = new Random().nextInt(sum) + 1;
- for(Map.Entry<String, Integer> entry : entrySet){
- rand -= entry.getValue();
- if(rand <=0){
- return entry.getKey();
- }
- }
- return null;
- }
- public static void main(String[] args){
- Map<String, Integer> map = new HashMap<String, Integer>();
- String key = null;
- for(int i = 0; i < 1000; i++){
- key = selectServer(servers);
- if(map.containsKey(key)){
- map.put(key, map.get(key) + 1);
- }else{
- map.put(key, 1);
- }
- }
- for(String key1 : map.keySet()){
- System.out.println(key1 + " " + map.get(key1));
- }
- }
- }
结果:
192.168.20.104 408
192.168.20.101 97
192.168.20.102 208
192.168.20.103 287
对服务器:192.168.20.101 192.168.20.102 192.168.20.103 192.168.20.104
接近 1 2 3 4 的比率
转