架构师训练营第 1 期 week5

import java.util.*;
public class ConsistantHash {
    public static String[] ip;//物理节点
    public static int virtualIp = 200;//虚拟ip的数量
    //用来虚拟节点的标识
    public static String flag = "@#!";
    //虚拟节点到IP的映射关系
    public static TreeMap<Long,String> vituralToIp = new TreeMap<Long,String>();
    //记录每个ip存储的key的数量
    public static Map<String,Integer> ipValueCount = new HashMap<String,Integer>();
    //添加物理节点
    public static void addNode(String ip){
        ipValueCount.put(ip,0);
        //long ipHash  = FNVHash(ip);
        for(int i=0;i<virtualIp;i++){
            Long hash  = FNVHash(ip+flag+i);
            vituralToIp.put(hash,ip);
        }
    }
    //删除物理节点
    public static void removeNode(String ip){
        for(int i=0;i<virtualIp;i++){
            vituralToIp.remove(FNVHash(ip+flag+i));
        }
    }
    //插入对象映射的ip,暂时先按key是字符串处理
    public static String valueToNode(String key){
        long hash = FNVHash(key);
        //获取比hash值大的数的集合
        SortedMap<Long, String> gtHash = vituralToIp.tailMap(hash);
        Long resultKey = gtHash.isEmpty()?vituralToIp.firstKey():gtHash.firstKey();
        return vituralToIp.get(resultKey);
    }
    // 32位的 Fowler-Noll-Vo 哈希算法
    private static Long FNVHash(String key) {
        final int p = 16777619;
        Long hash = 2166136261L;
        for (int idx = 0, num = key.length(); idx < num; ++idx) {
            hash = (hash ^ key.charAt(idx)) * p;
        }
        hash += hash << 13;
        hash ^= hash >> 7;
        hash += hash << 3;
        hash ^= hash >> 17;
        hash += hash << 5;
        if (hash < 0) {
            hash = Math.abs(hash);
        }
        return hash;
    }
    public static void main(String[] args) {
        ip = new String[]{"192.168.1.1","192.168.1.2","192.168.1.3","192.168.1.4"};
        for(String s:ip){
            addNode(s);
        }
        //for(Map.Entry<Long,String> entry:vituralToIp.entrySet()){
            //System.out.println(entry.getValue());
        //}
        int num = 1000000;
        bzcValueToIp(num);
    }
    //测试指定数据在不同IP的分配情况,以标准差的形式体现
    public static void bzcValueToIp(int num){
        String key ="";
        String ip ="";
        for(int i=0;i<num;i++){
            key = UUID.randomUUID().toString()+flag+num;
            ip = valueToNode(key);
            ipValueCount.put(ip,ipValueCount.get(ip)+1);
        }
        System.out.println("随机key的数量："+num);
        System.out.println("虚拟节点的的数量为："+virtualIp);
       // double bzc = 0;
        List<Integer> resultList = new ArrayList<Integer>();
        for (Map.Entry<String,Integer> entry:ipValueCount.entrySet()){
            System.out.println("ip为"+entry.getKey()+"的主机存储数量为："+entry.getValue());
            resultList.add(entry.getValue());
        }
        int iplength = ip.length();
        double avg = num/iplength;//平均值
        double bzc = Math.sqrt(resultList.stream().mapToDouble(a->Math.pow((a-avg),2)).sum()/iplength);
        System.out.println("标准差为："+bzc);
    }
}