一致性hash算法java版本簡單實(shí)現(xiàn)

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;/** * 一致性hash算法java簡易實(shí)現(xiàn) * @author IT云清 * 參考：https://blog.csdn.net/zhanglu0223/article/details/100579254 */public class ConsistentHash { private static final Logger LOGGER = LoggerFactory.getLogger(ConsistentHash.class); /** * 虛擬節(jié)點(diǎn)個數(shù) * 每個真實(shí)節(jié)點(diǎn)對應(yīng)的虛擬節(jié)點(diǎn)個數(shù) */ private static final int VIRTUAL_NUM = 5; /** * 虛擬節(jié)點(diǎn) * eg:<656715414,192.168.1.1&&VN3> * 真實(shí)節(jié)點(diǎn)數(shù)量一般偏少，引入虛擬節(jié)點(diǎn)來平衡 * 每個真實(shí)節(jié)點(diǎn)對應(yīng)多個虛擬節(jié)點(diǎn)，這樣每個節(jié)點(diǎn)盡可能在hash環(huán)上均勻分布，可以根據(jù)虛擬節(jié)點(diǎn)找到真實(shí)節(jié)點(diǎn) */ private static SortedMap<Integer,String> shards = new TreeMap<>(); /** * 真實(shí)節(jié)點(diǎn) */ private static List<String> realNodes = new LinkedList<>(); /** * 模擬初始節(jié)點(diǎn) */ private static String[] servers = {'116.116.1.1', '116.116.1.2', '116.116.1.3', '116.116.1.5', '116.116.1.6'}; /** * 初始化虛擬節(jié)點(diǎn) */ static { for (String server : servers) { realNodes.add(server); LOGGER.info('添加真實(shí)節(jié)點(diǎn){}',server); for(int i = 0;i < VIRTUAL_NUM; i ++){ String virtualNode = server + '&&VN' + i; int hash = getHash(virtualNode); shards.put(hash,virtualNode); LOGGER.info('添加虛擬節(jié)點(diǎn){}，hash為{}',virtualNode,hash); } } } public static void main(String[]args){ test2(); } public static void test2(){ //測試定位node LOGGER.info(getSever('aa')); LOGGER.info(getSever('漲三')); LOGGER.info(getSever('num_19120000')); LOGGER.info(getSever('num_19120000')); LOGGER.info('------------------'); //測試添加節(jié)點(diǎn) addNode('192.192.116.1'); addNode('192.192.116.2'); LOGGER.info('------------------'); //測試刪除節(jié)點(diǎn) delNode('116.116.1.1'); } /** * 獲取真實(shí)節(jié)點(diǎn)ip * @param str 字符串 * @return */ public static String getSever(String str){ //計(jì)算hash int hash = getHash(str); Integer key = null; //尋找最近的虛擬node SortedMap<Integer, String> tailMap = shards.tailMap(hash); //獲取在hash環(huán)上 右側(cè)最近的虛擬節(jié)點(diǎn)的key key = tailMap.isEmpty() ? shards.lastKey() : tailMap.firstKey(); //根據(jù)hash獲取虛擬節(jié)點(diǎn) String virtualNode = shards.get(key); //返回虛擬節(jié)點(diǎn)的真實(shí)ip return virtualNode.substring(0,virtualNode.indexOf('&&')); } /** * 添加節(jié)點(diǎn) * @param node */ public static void addNode(String node){ if(!realNodes.contains(node)){ realNodes.add(node); LOGGER.info('新增真實(shí)節(jié)點(diǎn)上線，{}',node); for(int i = 0;i < VIRTUAL_NUM;i ++){ String virtualNode = node + '&&VN' + i; int hash = getHash(virtualNode); shards.put(hash,virtualNode); LOGGER.info('新增虛擬節(jié)點(diǎn){}，hash為{}',virtualNode,hash); } } } /** * 刪除節(jié)點(diǎn) * @param node */ public static void delNode(String node){ if(realNodes.contains(node)){ //下線真實(shí)節(jié)點(diǎn) realNodes.remove(node); LOGGER.info('真實(shí)節(jié)點(diǎn)下線，{}',node); for(int i = 0;i < VIRTUAL_NUM; i++){ String virtualNode = node + '&&VN' + i; int hash = getHash(virtualNode); //移除虛擬節(jié)點(diǎn) shards.remove(hash); LOGGER.info('下線虛擬節(jié)點(diǎn){}，hash為{}',virtualNode,hash); } } } /** * FNV1_32_HASH算法 * @param str 任意字符串 * @return 返回int類型的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; // 如果算出來的值為負(fù)數(shù)則取其絕對值 if (hash < 0) { hash = Math.abs(hash); } return hash; }}

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