package com.aps.common.core.utils.uuid;
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import com.aps.common.core.enums.SystemClock;
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import org.slf4j.Logger;
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import org.slf4j.LoggerFactory;
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import org.springframework.stereotype.Component;
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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.Enumeration;
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import java.util.concurrent.ThreadLocalRandom;
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import java.util.regex.Pattern;
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/**
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* 基于Twitter的Snowflake算法实现分布式高效有序ID生产黑科技(sequence)——升级版Snowflake
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*
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* <br>
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* SnowFlake的结构如下(每部分用-分开):<br>
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* <br>
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* 0 - 0000000000 0000000000 0000000000 0000000000 0 - 00000 - 00000 - 000000000000 <br>
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* <br>
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* 1位标识，由于long基本类型在Java中是带符号的，最高位是符号位，正数是0，负数是1，所以id一般是正数，最高位是0<br>
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* <br>
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* 41位时间截(毫秒级)，注意，41位时间截不是存储当前时间的时间截，而是存储时间截的差值（当前时间截 - 开始时间截)
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* 得到的值），这里的的开始时间截，一般是我们的id生成器开始使用的时间，由我们程序来指定的（如下START_TIME属性）。41位的时间截，可以使用69年，年T = (1L << 41) / (1000L * 60 * 60 * 24 * 365) = 69<br>
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* <br>
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* 10位的数据机器位，可以部署在1024个节点，包括5位dataCenterId和5位workerId<br>
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* <br>
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* 12位序列，毫秒内的计数，12位的计数顺序号支持每个节点每毫秒(同一机器，同一时间截)产生4096个ID序号<br>
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* <br>
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* <br>
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* 加起来刚好64位，为一个Long型。<br>
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* SnowFlake的优点是，整体上按照时间自增排序，并且整个分布式系统内不会产生ID碰撞(由数据中心ID和机器ID作区分)，并且效率较高，经测试，SnowFlake每秒能够产生26万ID左右。
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* <p>
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* <p>
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* 特性：
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* 1.支持自定义允许时间回拨的范围<p>
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* 2.解决跨毫秒起始值每次为0开始的情况（避免末尾必定为偶数，而不便于取余使用问题）<p>
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* 3.解决高并发场景中获取时间戳性能问题<p>
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* 4.支撑根据IP末尾数据作为workerId
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* 5.时间回拨方案思考：1024个节点中分配10个点作为时间回拨序号（连续10次时间回拨的概率较小）
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* <p>
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* 常见问题:
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* 1.时间回拨问题
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* 2.机器id的分配和回收问题
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* 3.机器id的上限问题
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*
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* @author lry
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* @version 3.0
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*/
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@Component
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public class Sequence {
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private static final Logger log = LoggerFactory.getLogger(Sequence.class);
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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 = 1519740777809L;
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/**
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* 5位的机房id
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*/
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private final long datacenterIdBits = 5L;
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/**
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* 5位的机器id
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*/
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private final long workerIdBits = 5L;
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/**
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* 每毫秒内产生的id数: 2的12次方个
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*/
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private final long sequenceBits = 12L;
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protected final long maxDatacenterId = -1L ^ (-1L << datacenterIdBits);
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protected final long maxWorkerId = -1L ^ (-1L << workerIdBits);
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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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/**
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* 所属机房id
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*/
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private final long datacenterId;
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/**
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* 所属机器id
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*/
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private final long workerId;
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/**
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* 并发控制序列
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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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private static volatile InetAddress LOCAL_ADDRESS = null;
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private static final Pattern IP_PATTERN = Pattern.compile("\\d{1,3}(\\.\\d{1,3}){3,5}$");
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public Sequence() {
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this.datacenterId = getDatacenterId();
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this.workerId = getMaxWorkerId(datacenterId);
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}
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/**
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* 有参构造器
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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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if (workerId > maxWorkerId || workerId < 0) {
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throw new IllegalArgumentException(String.format("Worker Id can't be greater than %d or less than 0", maxWorkerId));
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}
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if (datacenterId > maxDatacenterId || datacenterId < 0) {
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throw new IllegalArgumentException(String.format("Datacenter Id can't be greater than %d or less than 0", maxDatacenterId));
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}
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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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* 基于网卡MAC地址计算余数作为数据中心
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* <p>
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* 可自定扩展
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*/
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protected long getDatacenterId() {
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long id = 0L;
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try {
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NetworkInterface network = NetworkInterface.getByInetAddress(getLocalAddress());
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if (null == network) {
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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 - 2]) | (0x0000FF00 & (((long) mac[mac.length - 1]) << 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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* 基于 MAC + PID 的 hashcode 获取16个低位
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* <p>
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* 可自定扩展
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*/
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protected long getMaxWorkerId(long datacenterId) {
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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 (name != null && name.length() > 0) {
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// GET jvmPid
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mpId.append(name.split("@")[0]);
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}
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// MAC + PID 的 hashcode 获取16个低位
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return (mpId.toString().hashCode() & 0xffff) % (maxWorkerId + 1);
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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 next id
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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 <= 5) {
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try {
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// 休眠双倍差值后重新获取，再次校验
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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.INSTANCE.currentTimeMillis();
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}
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/**
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* Find first valid IP from local network card
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*
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* @return first valid local IP
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*/
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public static InetAddress getLocalAddress() {
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if (LOCAL_ADDRESS != null) {
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return LOCAL_ADDRESS;
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}
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LOCAL_ADDRESS = getLocalAddress0();
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return LOCAL_ADDRESS;
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}
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private static InetAddress getLocalAddress0() {
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InetAddress localAddress = null;
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try {
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localAddress = InetAddress.getLocalHost();
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if (isValidAddress(localAddress)) {
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return localAddress;
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}
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} catch (Throwable e) {
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log.warn("Failed to retrieving ip address, " + e.getMessage(), e);
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}
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try {
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Enumeration<NetworkInterface> interfaces = NetworkInterface.getNetworkInterfaces();
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if (interfaces != null) {
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while (interfaces.hasMoreElements()) {
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try {
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NetworkInterface network = interfaces.nextElement();
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Enumeration<InetAddress> addresses = network.getInetAddresses();
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while (addresses.hasMoreElements()) {
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try {
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InetAddress address = addresses.nextElement();
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if (isValidAddress(address)) {
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return address;
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}
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} catch (Throwable e) {
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log.warn("Failed to retrieving ip address, " + e.getMessage(), e);
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}
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}
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} catch (Throwable e) {
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log.warn("Failed to retrieving ip address, " + e.getMessage(), e);
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}
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}
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}
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} catch (Throwable e) {
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log.warn("Failed to retrieving ip address, " + e.getMessage(), e);
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}
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log.error("Could not get local host ip address, will use 127.0.0.1 instead.");
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return localAddress;
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}
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private static boolean isValidAddress(InetAddress address) {
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if (address == null || address.isLoopbackAddress()) {
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return false;
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}
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String name = address.getHostAddress();
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return (name != null && !"0.0.0.0".equals(name) && !"127.0.0.1".equals(name) && IP_PATTERN.matcher(name).matches());
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}
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}
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