一致性hash算法Consistent Hashing

对于原有hash算法hash%n

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1.话不多说直接上代码,原理或详解自行百度即可

import cn.pheker.utils.UtilElapsedTime;
import cn.pheker.utils.UtilLogger;
import cn.pheker.utils.UtilMD5;import java.util.*;/*** <pre>* author    cn.pheker* date      2018/3/19 10:20* email     1176479642@qq.com* desc      一致性哈希算法** </pre>*/
public class ConsistentHashing {private static final long MIN_NODE_NUMBER = 0;private static final int MAX_NODE_NUMBER = Integer.MAX_VALUE;private static int VIRTUAL_NODE_NUMBER;//真实节点private List<Node> realNodes = new LinkedList<Node>();//虚拟节点,hash环private SortedMap<Integer, VNode> circle = new TreeMap<Integer, VNode>();private ConsistentHashing(int vnNumber) {VIRTUAL_NODE_NUMBER = vnNumber;}public static ConsistentHashing build(int vnNumber) {return new ConsistentHashing(vnNumber);}public ConsistentHashing addNode(Map<String,String> ipPorts) {Set<String> ips = ipPorts.keySet();Iterator<String> ipite = ips.iterator();while(ipite.hasNext()){String ip = ipite.next();addNode(ip, ipPorts.get(ip));}return this;}public ConsistentHashing addNode(String ip, int port) {addNode(ip, String.valueOf(port));return this;}public ConsistentHashing addNode(String ip, String port) {Node node = new Node(ip, port);if (!realNodes.contains(node)) {realNodes.add(node);UtilLogger.println("[Node]:"+node.toString()+" Hash:"+node.hashFNV1_32());//生成VIRTUAL_NODE_NUMBER个虚拟节点for (int i = 0; i < VIRTUAL_NODE_NUMBER; i++) {VNode vNode = node.createVNode(i);circle.put(vNode.hashFNV1_32(), vNode);UtilLogger.println("\t[VNode]:"+vNode.toString()+" Hash:"+vNode.hashFNV1_32());}}return this;}public void removeNode(String ip,String port) {Node node = new Node(ip, port);for(int i = 0;i<VIRTUAL_NODE_NUMBER;i++) {VNode vNode = node.createVNode(i);circle.remove(vNode.hashFNV1_32());}circle.remove(node.hashFNV1_32());}public VNode getNode(String ip, int port) {return getNode(ip, String.valueOf(port));}public VNode getNode(String ip, String port) {Node node = new Node(ip, port);int hash = node.hashFNV1_32();if(circle.isEmpty()) return null;SortedMap<Integer, VNode> tailMap = circle.tailMap(hash);int hashKey;if (tailMap.isEmpty()) {hashKey = circle.firstKey();}else {hashKey = tailMap.firstKey();}//顺时针最近节点VNode vNode = circle.get(hashKey);UtilLogger.println(String.format("[%s]:%s ==> [%s]:%s",node.hashFNV1_32(),node,vNode.hashFNV1_32(),vNode));return vNode;}/*** 第个节点都是一个服务器主机*/public class Node {String ip;String port;public Node(String ip, String port) {this.ip = ip;this.port = port;}public String getIp() {return ip;}public void setIp(String ip) {this.ip = ip;}public String getPort() {return port;}public void setPort(String port) {this.port = port;}public VNode createVNode(int vnNumber) {return new VNode(ip, port, vnNumber);}@Overridepublic boolean equals(Object o) {if (this == o) return true;if (o == null || getClass() != o.getClass()) return false;Node vNode = (Node) o;return Objects.equals(ip, vNode.ip) &&Objects.equals(port, vNode.port);}@Overridepublic String toString() {return ip + ":" + port;}/***使用FNV1_32_HASH算法计算服务器的Hash值,这里不能重写hashCode的方法*/public int hashFNV1_32(){String str = UtilMD5.MD5(this.toString());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;}}/*** 虚拟节点*/public class VNode extends Node{int number;public VNode(String ip, String port,int number) {super(ip, port);this.number = number;}public Node toNode() {return new Node(ip,port);}@Overridepublic boolean equals(Object o) {if (this == o) return true;if (o == null || getClass() != o.getClass()) return false;if (!super.equals(o)) return false;VNode vNode = (VNode) o;return number == vNode.number;}@Overridepublic int hashCode() {return Objects.hash(number);}@Overridepublic String toString() {return ip + ":" + port+"#"+number;}}/*** 校验hash分布均匀性* @return*/public float check() {Set<Integer> ks = circle.keySet();int size = ks.size();long sum = 0L;for (int hash : ks) {sum += hash;}double percent = size == MIN_NODE_NUMBER ? MIN_NODE_NUMBER :(100*2*sum/size)/MAX_NODE_NUMBER;return Float.valueOf(String.format("%.2f", percent));}public static void main(String[] args) {UtilElapsedTime.test(() -> {ConsistentHashing ch = ConsistentHashing.build(3);//添加节点UtilLogger.println("------------添加节点----------------");ch.addNode("10.96.74.187", 80);ch.addNode("127.0.0.1", 8080);ch.addNode("243.15.155.0", 2150);ch.addNode("243.15.155.1", 2150);UtilLogger.println("------------是否均匀----------------");UtilLogger.println(ch.check() + "%");//获取节点UtilLogger.println("------------获取节点----------------");ch.getNode("10.96.74.187", 80);ch.getNode("123.1.122.253", 44);ch.getNode("234.67.80.219", 3306);return "耗时计算完成";});}}

2.结果

------------添加节点----------------
[Node]:10.96.74.187:80 Hash:1695118842[VNode]:10.96.74.187:80#0 Hash:1661313686[VNode]:10.96.74.187:80#1 Hash:1283046442[VNode]:10.96.74.187:80#2 Hash:564332117
[Node]:127.0.0.1:8080 Hash:678080562[VNode]:127.0.0.1:8080#0 Hash:1731933288[VNode]:127.0.0.1:8080#1 Hash:1369405387[VNode]:127.0.0.1:8080#2 Hash:200594664
[Node]:243.15.155.0:2150 Hash:1175061629[VNode]:243.15.155.0:2150#0 Hash:134880260[VNode]:243.15.155.0:2150#1 Hash:1677894747[VNode]:243.15.155.0:2150#2 Hash:522817245
[Node]:243.15.155.1:2150 Hash:1305999210[VNode]:243.15.155.1:2150#0 Hash:1193457699[VNode]:243.15.155.1:2150#1 Hash:279279823[VNode]:243.15.155.1:2150#2 Hash:2115663065
------------是否均匀----------------
98.0%
------------获取节点----------------
[1695118842]:10.96.74.187:80 ==> [1731933288]:127.0.0.1:8080#0
[601034131]:123.1.122.253:44 ==> [1193457699]:243.15.155.1:2150#0
[508181784]:234.67.80.219:3306 ==> [522817245]:243.15.155.0:2150#2
[23.104187ms] 耗时计算完成Process finished with exit code 0

3.注意事项

代码中用到了几个工具类UtilMD5,UtilLogger换成自己的即可,UtilElapsedTime用于计算耗时,可以直接去掉。

4.参考链接

对一致性Hash算法，Java代码实现的深入研究
白话解析：一致性哈希算法 consistent hashing