java实现hash一致性算法

import org.apache.commons.lang3.RandomUtils;
import org.apache.commons.lang3.StringUtils;

import java.util.*;

/**
 * 一致性hash
 */
public class ConsistentHashWithVirtualNode {

    /**
     * 待添加入Hash环的服务器列表
     */

    private static String[] SERVERS = {"192.168.1.2:6379", "192.168.1.3:6379"};

    /**
     * key表示服务器的hash值，value表示虚拟节点的名称
     */
    private static SortedMap<Integer, String> HASH_CIRCLE = new TreeMap<Integer, String>();
    /**
     * 用于结果统计
     */
    private static Map<String, Integer> result = new HashMap<String, Integer>();
    /**
     * 每个真实节点对应虚拟节点数
     */
    private static Integer VIRTUAL_NODES_NUM = 150;

    /**
     * 使用FNV1_32_HASH算法计算服务器的Hash值
     */
    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;

        // 如果值为负数则取其绝对值
        if (hash < 0)
            hash = Math.abs(hash);
        return hash;
    }

    static {
        for (int i = 0; i < SERVERS.length; i++) {
            for (Integer j = 0; j < VIRTUAL_NODES_NUM; j++) {
                setServer(SERVERS[i] + "vn" + j);
            }
        }
    }

    private static void setServer(String ip) {
        setServer(ip, null);
    }

    private static void setServer(String ip, Integer hash) {
        hash = hash != null ? getHash(hash.toString()) : getHash(ip);
        if (StringUtils.isBlank(HASH_CIRCLE.get(hash))) {
            HASH_CIRCLE.put(hash, ip);
            System.out.println("[" + ip + "]加入sortedMap中, 其Hash值为" + hash);
        } else {
            //解决hash碰撞
            setServer(ip, hash);
        }
    }

    public static void main(String[] args) {
        for (int i = 0; i < 50; i++) {
            long nodes = RandomUtils.nextLong();
            String server = getServer(nodes);
            String realServer = server.split("vn")[0];
            System.out.println("[" + nodes + "]的hash值为" + getHash("" + nodes) + ", 被路由到虚拟结点[" + server + "], 真实结点[" + realServer + "]");
            result.put(realServer, (result.get(realServer) == null ? 0 : result.get(realServer)) + 1);
        }
        result.forEach((k, v) -> {
            System.out.println("结点[" + k + "]上有" + v);
        });
    }

    public static String getServer(Object node) {
        String ip = HASH_CIRCLE.get(HASH_CIRCLE.firstKey());
        // 得到带路由的结点的Hash值
        int hash = getHash(node.toString());
        // 得到大于该Hash值的所有Map
        SortedMap<Integer, String> subMap = HASH_CIRCLE.tailMap(hash);

        if (!subMap.isEmpty()) {
            // 第一个Key就是顺时针过去离node最近的那个结点
            Integer i = subMap.firstKey();
            ip = subMap.get(i);
        }
        // 返回对应的服务器名称
        return ip;
    }
}