java实现一致性hash算法实例代码

一致性hash算法java版本简单实现

package com.java4all.grouth.consistent;

import java.util.linkedList;
import java.util.List;
import java.util.SortedMap;
import java.util.TreeMap;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;


public class ConsistentHash {

 private static final Logger LOGGER = LoggerFactory.getLogger(ConsistentHash.class);

 
 private static final int VIRTUAL_NUM = 5;

 
 private static SortedMap shards = new TreeMap<>();

 
 private static List realNodes = new linkedList<>();

 
 private static String[] servers = {"116.116.1.1", "116.116.1.2", "116.116.1.3", "116.116.1.5", "116.116.1.6"};


 
 static {
  for (String server : servers) {
   realNodes.add(server);
   LOGGER.info("添加真实节点{}",server);
   for(int i = 0;i < VIRTUAL_NUM; i ++){
    String virtualNode = server + "&&VN" + i;
    int hash = getHash(virtualNode);
    shards.put(hash,virtualNode);
    LOGGER.info("添加虚拟节点{}，hash为{}",virtualNode,hash);
   }
  }
 }


 public static void main(String[]args){
  test2();
 }

 public static void test2(){
  //测试定位node
  LOGGER.info(getSever("aa"));
  LOGGER.info(getSever("涨三"));
  LOGGER.info(getSever("num_19120000"));
  LOGGER.info(getSever("num_19120000"));
  LOGGER.info("------------------");
  //测试添加节点
  addNode("192.192.116.1");
  addNode("192.192.116.2");
  LOGGER.info("------------------");
  //测试删除节点
  delNode("116.116.1.1");
 }
 
 public static String getSever(String str){
  //计算hash
  int hash = getHash(str);
  Integer key = null;
  //寻找最近的虚拟node
  SortedMap tailMap = shards.tailMap(hash);
  //获取在hash环上 右侧最近的虚拟节点的key
  key = tailMap.isEmpty() ? shards.lastKey() : tailMap.firstKey();
  //根据hash获取虚拟节点
  String virtualNode = shards.get(key);
  //返回虚拟节点的真实ip
  return virtualNode.substring(0,virtualNode.indexOf("&&"));
 }



 
 public static void addNode(String node){
  if(!realNodes.contains(node)){
   realNodes.add(node);
   LOGGER.info("新增真实节点上线，{}",node);
   for(int i = 0;i < VIRTUAL_NUM;i ++){
    String virtualNode = node + "&&VN" + i;
    int hash = getHash(virtualNode);
    shards.put(hash,virtualNode);
    LOGGER.info("新增虚拟节点{}，hash为{}",virtualNode,hash);
   }
  }

 }

 
 public static void delNode(String node){
  if(realNodes.contains(node)){
   //下线真实节点
   realNodes.remove(node);
   LOGGER.info("真实节点下线，{}",node);
   for(int i = 0;i < VIRTUAL_NUM; i++){
    String virtualNode = node + "&&VN" + i;
    int hash = getHash(virtualNode);
    //移除虚拟节点
    shards.remove(hash);
    LOGGER.info("下线虚拟节点{}，hash为{}",virtualNode,hash);
   }
  }
 }

 
 private static int getHash(String str) {
  final int p = 16777619;
  int hash = (int) 2166136261L;
  for (int i = 0; i < str.length(); i++) {
   hash = (hash ^ str.charAt(i)) * p;
  }
  hash += hash << 13;
  hash ^= hash >> 7;
  hash += hash << 3;
  hash ^= hash >> 17;
  hash += hash << 5;
  // 如果算出来的值为负数则取其绝对值
  if (hash < 0) {
   hash = Math.abs(hash);
  }
  return hash;
 }
}

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