​浅谈分布式唯一Id生成器之最佳实践

package com.bytearch.sequence.util;
/**
 * 唯一id生成器
 * 1bit + 39bit时间差 + 8bit机器号 + 8bit用户编号(库号) + 8bit自增序列
 *
 * @author yarw  www.bytearch.com
 */
public final class SeqIdUtil {
    /**
     * 毫秒级开始时间 2020-01-01   时间差 = 当前时间 - MillisecondStartTime
     */
    private static final long MILLISECOND_START_TIME = 1577808000000L;
    /**
     * 时间差所占位数
     */
    private final long timeBits = 39L;
    /**
     * 机器Id所占位数
     **/
    private final static long WORKER_ID_BITS = 8L;
    /**
     * 用户指定编号(比如库号)位数
     */
    private final static long EXTRA_BITS = 8L;
    /**
     * 唯一序列位数
     */
    private static final long SN_BITS = 8L;
    private static final long MAX_SN = ~(-1L << SN_BITS);
    /**
     * 最多的机器id数
     */
    private final static long MAX_WORKER_ID = ~(-1L << WORKER_ID_BITS);
    private final static long MAX_EXTRA_ID = ~(-1L << EXTRA_BITS);
    /**
     * 毫秒内序列(0~4095)
     */
    private static long sequence = 0L;
    /**
     * 上次生成ID的时间截
     */
    private static long lastTimestamp = -1L;
    private static int ipSuffix = 0;
    static {
        //获取ip后三位
        ipSuffix = IpUtil.getIpSuffix();
    }
    /**
     * 自动获取机器编号-- 获取唯一ID
     *
     * @param extraId
     * @return
     */
    public static long nextId(long extraId) {
        return nextId(ipSuffix, extraId);
    }
    /**
     * 指定机器编号获取唯一Id
     *
     * @param workerId 机器编号
     * @param extraId  用户标识
     * @return
     */
    public static long nextId(long workerId, long extraId) {
        if (workerId > MAX_WORKER_ID || workerId < 0) {
            throw new IllegalArgumentException(String.format("workerId:%d invalid,  Its range is 0 to %d", workerId, MAX_WORKER_ID));
        }
        if (extraId > MAX_EXTRA_ID || extraId < 0) {
            throw new IllegalArgumentException(String.format("extraId:%d invalid,  Its range is 0 to %d", extraId, MAX_EXTRA_ID));
        }
        synchronized (SeqIdUtil.class) {
            long timestamp = timeGen();
            //如果当前时间小于上一次ID生成的时间戳，说明系统时钟回退过这个时候应当抛出异常
            if (timestamp < lastTimestamp) {
                throw new RuntimeException(String.format("clock moved backwards, Refusing to generate id for %d milliseconds", lastTimestamp - timestamp));
            }
            if (lastTimestamp == timestamp) {
                sequence = (sequence + 1) & MAX_SN;
                if (sequence == 0) {
                    timestamp = nextMillis(lastTimestamp);
                }
            } else {
                sequence = 0L;
            }
            lastTimestamp = timestamp;
            return (timestamp - MILLISECOND_START_TIME) << (SN_BITS + EXTRA_BITS + WORKER_ID_BITS)
                    | workerId << (SN_BITS + EXTRA_BITS)
                    | extraId << SN_BITS
                    | sequence;
        }
    }
    /**
     * 反解id
     *
     * @param id
     * @return
     */
    public static IdEntity decodeId(long id) {
        IdEntity idEntity = new IdEntity();
        idEntity.setSequenceId(id & MAX_SN);
        idEntity.setExtraId((id >> SN_BITS) & MAX_EXTRA_ID);
        idEntity.setWorkerId((id >> (SN_BITS + EXTRA_BITS)) & MAX_WORKER_ID);
        idEntity.setCreateTime((id >> (SN_BITS + EXTRA_BITS + WORKER_ID_BITS)) + MILLISECOND_START_TIME);
        return idEntity;
    }
    /**
     * 返回以毫秒为单位的当前时间
     *
     * @return 当前时间(毫秒)
     */
    private static long timeGen() {
        return System.currentTimeMillis();
    }
    /**
     * 阻塞到下一个毫秒，直到获得新的时间戳
     *
     * @param lastTimestamp 上次生成ID的时间截
     * @return 当前时间戳
     */
    private static long nextMillis(long lastTimestamp) {
        long timestamp = timeGen();
        while (timestamp <= lastTimestamp) {
            timestamp = timeGen();
        }
        return timestamp;
    }
    public static void main(String[] args) {
        long id = nextId(123);
        System.out.println("生成的id为:" + id);
        IdEntity idEntity = decodeId(id);
        System.out.println("解析id为:" + idEntity);
    }
}

package com.bytearch.sequence.util;
/**
 * @author yarw
 */
public class IdEntity {
    private long createTime;
    private long workerId;
    private long extraId;
    private long sequenceId;
    public long getCreateTime() {
        return createTime;
    }
    public void setCreateTime(long createTime) {
        this.createTime = createTime;
    }
    public long getWorkerId() {
        return workerId;
    }
    public void setWorkerId(long workerId) {
        this.workerId = workerId;
    }
    public long getExtraId() {
        return extraId;
    }
    public void setExtraId(long extraId) {
        this.extraId = extraId;
    }
    public long getSequenceId() {
        return sequenceId;
    }
    public void setSequenceId(long sequenceId) {
        this.sequenceId = sequenceId;
    }
    @Override
    public String toString() {
        return "IpEntity{" +
                "createTime=" + createTime +
                ", workerId=" + workerId +
                ", extraId=" + extraId +
                ", sequenceId=" + sequenceId +
                '}';
    }
}

生成的id为:187611327051168512
解析id为:IdEntity{createTime=1588990506504, workerId=185, extraId=123, sequenceId=0}