package com.kidgrow.common.utils;
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import cn.hutool.core.date.SystemClock;
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import cn.hutool.core.lang.Assert;
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import cn.hutool.core.util.StrUtil;
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import com.baomidou.mybatisplus.core.toolkit.StringPool;
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import lombok.extern.slf4j.Slf4j;
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import java.lang.management.ManagementFactory;
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import java.net.InetAddress;
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import java.net.NetworkInterface;
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import java.util.concurrent.ThreadLocalRandom;
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/**
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* 石家庄喜高科技有限责任公司 版权所有 © Copyright 2020<br>
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*
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* @Description: 分布式ID生成算法<br>
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* @Project: <br>
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* @CreateDate: Created in 2020/2/3 15:48 <br>
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* @Author: <a href="4345453@kidgrow.com">liuke</a>
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*/
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@Slf4j
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public class Sequence {
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/**
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* 时间起始标记点，作为基准，一般取系统的最近时间（一旦确定不能变动）
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*/
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private final long twepoch = 1288834974657L;
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/**
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* 机器标识位数
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*/
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private final long workerIdBits = 5L;
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private final long datacenterIdBits = 5L;
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private final long maxWorkerId = -1L ^ (-1L << workerIdBits);
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private final long maxDatacenterId = -1L ^ (-1L << datacenterIdBits);
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/**
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* 毫秒内自增位
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*/
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private final long sequenceBits = 12L;
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private final long workerIdShift = sequenceBits;
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private final long datacenterIdShift = sequenceBits + workerIdBits;
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/**
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* 时间戳左移动位
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*/
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private final long timestampLeftShift = sequenceBits + workerIdBits + datacenterIdBits;
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private final long sequenceMask = -1L ^ (-1L << sequenceBits);
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private final long workerId;
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/**
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* 数据标识 ID 部分
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*/
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private final long datacenterId;
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/**
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* 并发控制
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*/
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private long sequence = 0L;
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/**
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* 上次生产 ID 时间戳
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*/
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private long lastTimestamp = -1L;
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/**
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* 时间回拨最长时间(ms)，超过这个时间就抛出异常
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*/
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private long timestampOffset = 5L;
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public Sequence() {
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this.datacenterId = getDatacenterId(maxDatacenterId);
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this.workerId = getMaxWorkerId(datacenterId, maxWorkerId);
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}
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/**
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* <p>
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* 有参构造器
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* </p>
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*
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* @param workerId 工作机器 ID
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* @param datacenterId 序列号
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*/
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public Sequence(long workerId, long datacenterId) {
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Assert.isFalse(workerId > maxWorkerId || workerId < 0,
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String.format("worker Id can't be greater than %d or less than 0", maxWorkerId));
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Assert.isFalse(datacenterId > maxDatacenterId || datacenterId < 0,
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String.format("datacenter Id can't be greater than %d or less than 0", maxDatacenterId));
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this.workerId = workerId;
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this.datacenterId = datacenterId;
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}
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/**
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* <p>
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* 获取 maxWorkerId
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* </p>
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*/
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protected static long getMaxWorkerId(long datacenterId, long maxWorkerId) {
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StringBuilder mpid = new StringBuilder();
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mpid.append(datacenterId);
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String name = ManagementFactory.getRuntimeMXBean().getName();
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if (StrUtil.isNotEmpty(name)) {
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/*
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* GET jvmPid
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*/
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mpid.append(name.split(StringPool.AT)[0]);
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}
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/*
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* MAC + PID 的 hashcode 获取16个低位
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*/
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return (mpid.toString().hashCode() & 0xffff) % (maxWorkerId + 1);
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}
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/**
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* <p>
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* 数据标识id部分
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* </p>
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*/
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protected static long getDatacenterId(long maxDatacenterId) {
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long id = 0L;
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try {
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InetAddress ip = InetAddress.getLocalHost();
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NetworkInterface network = NetworkInterface.getByInetAddress(ip);
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if (network == null) {
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id = 1L;
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} else {
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byte[] mac = network.getHardwareAddress();
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if (null != mac) {
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id = ((0x000000FF & (long) mac[mac.length - 1]) | (0x0000FF00 & (((long) mac[mac.length - 2]) << 8))) >> 6;
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id = id % (maxDatacenterId + 1);
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}
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}
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} catch (Exception e) {
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log.warn(" getDatacenterId: " + e.getMessage());
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}
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return id;
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}
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/**
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* 获取下一个ID
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*
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* @return
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*/
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public synchronized long nextId() {
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long timestamp = timeGen();
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//闰秒
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if (timestamp < lastTimestamp) {
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long offset = lastTimestamp - timestamp;
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if (offset <= timestampOffset) {
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try {
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wait(offset << 1);
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timestamp = timeGen();
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if (timestamp < lastTimestamp) {
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throw new RuntimeException(String.format("Clock moved backwards. Refusing to generate id for %d milliseconds", offset));
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}
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} catch (Exception e) {
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throw new RuntimeException(e);
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}
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} else {
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throw new RuntimeException(String.format("Clock moved backwards. Refusing to generate id for %d milliseconds", offset));
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}
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}
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if (lastTimestamp == timestamp) {
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// 相同毫秒内，序列号自增
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sequence = (sequence + 1) & sequenceMask;
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if (sequence == 0) {
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// 同一毫秒的序列数已经达到最大
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timestamp = tilNextMillis(lastTimestamp);
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}
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} else {
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// 不同毫秒内，序列号置为 1 - 3 随机数
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sequence = ThreadLocalRandom.current().nextLong(1, 3);
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}
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lastTimestamp = timestamp;
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// 时间戳部分 | 数据中心部分 | 机器标识部分 | 序列号部分
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return ((timestamp - twepoch) << timestampLeftShift)
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| (datacenterId << datacenterIdShift)
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| (workerId << workerIdShift)
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| sequence;
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}
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protected long tilNextMillis(long lastTimestamp) {
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long timestamp = timeGen();
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while (timestamp <= lastTimestamp) {
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timestamp = timeGen();
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}
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return timestamp;
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}
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protected long timeGen() {
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return SystemClock.now();
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}
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public static void main(String[] args) {
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System.out.println(new Sequence().nextId());
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}
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}
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