算法描述

深入分析分布式下的路由策略

算法实现

  1. public static void main(String[] args) {
  2.         ConsistanceHash hash = new ConsistanceHash(3);
  3.         hash.addIp("10.191.30.2");
  4.         hash.addIp("10.191.31.3");
  5.         hash.addIp("10.191.32.4");
  6.         for (int i = 0; i < 100; i++) {
  7.             System.out.println(hash.getIp(UUID.randomUUID().toString()));
  8.         }
  9.     }
  11. static class ConsistanceHash{
  12.         SortedMap<Integer, String> map = new TreeMap<>();
  13.         int size;
  15.         public ConsistanceHash(int size) {
  16.             this.size = size;
  17.         }
  19.         private String getIp(String request){
  20.             Integer key = map.firstKey();
  21.             SortedMap<Integer, String> temp = map.tailMap(hash(request));
  22.             if (!temp.isEmpty()){
  23.                 key = temp.firstKey();
  24.             }
  25.             return map.get(key);
  26.         }
  28.         private void addIp(String ip){
  29.             for (int i = 0; i < size; i++) {
  30.                 map.put(hash(ip + "_" + i), ip);
  31.             }
  32.         }
  34.         private int hash(String str){
  35.             final int p = 16777619;
  36.             int hash = (int) 2166136261L;
  37.             for (int i = 0; i < str.length(); i++)
  38.                 hash = (hash ^ str.charAt(i)) * p;
  39.             hash += hash << 13;
  40.             hash ^= hash >> 7;
  41.             hash += hash << 3;
  42.             hash ^= hash >> 17;
  43.             hash += hash << 5;
  45.             // 如果算出来的值为负数则取其绝对值
  46.             if (hash < 0)
  47.                 hash = Math.abs(hash);
  48.             return hash;
  49.         }
  50.     }