分布式唯一键生成

分布式唯一键生成

/**
 * @author pengpan
 * @date 2021/2/6 17:20
 * @description 分布式唯一键生成
 */
@Slf4j
public class UniqueKeyUtils {
    
    

    /**
     * 时间搓格式化
     */
    private static final DateTimeFormatter TIME_FORMATTER = DateTimeFormatter.ofPattern("yyMMddHHmmssSSS");

    /**
     * 数字标识位数
     */
    private final long numberBitsMast = 26L;

    /**
     * 数据中心识位数
     */
    private final long dataCenterIdBits = 3L;

    /**
     * 机器标识位数
     */
    private final long workerIdBits = 11L;
    /**
     * 毫秒内自增位
     */
    private final long sequenceBits = numberBitsMast - dataCenterIdBits - workerIdBits;

    /**
     * 最大序列号
     */
    private final long sequenceMask = ~(-1L << sequenceBits);

    private final long workerIdShift = sequenceBits;

    private final long dataCenterIdShift = workerIdShift + workerIdBits;

    private long sequence = 0L;

    /**
     * 8个数字字符标识段左补齐
     */
    private final String numberFullLeft = "%08d";

    private long lastTimestamp = -1L;

    /**
     * 当前数据中心
     */
    private final long dataCenterId;

    /**
     * 当前机器节点
     */
    private final long workerId;

    private UniqueKeyUtils() {
    
    
        // 最大数据中心数
        long maxDataCenterId = ~(-1L << dataCenterIdBits);
        this.dataCenterId = getDataCenterId(maxDataCenterId);

        // 最大机器节点数
        long maxWorkerId = ~(-1L << workerIdBits);
        this.workerId = getMaxWorkerId(dataCenterId, maxWorkerId);
    }

    /**
     * 获取唯一键
     *
     * @return code
     */
    public static String generateNo() {
    
    
        return getSingleton().nextCode();
    }

    //内部类单例模式
    private static UniqueKeyUtils getSingleton() {
    
    
        return SingletonHolder.SINGLETON;
    }

    private static final class SingletonHolder {
    
    
        static final UniqueKeyUtils SINGLETON = new UniqueKeyUtils();
    }

    /**
     * next code
     *
     * @return code
     */
    private synchronized String nextCode() {
    
    
        long timestamp = timeGen();
        //闰秒
        if (timestamp < lastTimestamp) {
    
    
            long offset = lastTimestamp - timestamp;
            if (offset <= 5) {
    
    
                try {
    
    
                    wait(offset << 1);
                    timestamp = timeGen();
                    if (timestamp < lastTimestamp) {
    
    
                        throw new RuntimeException(String.format("Clock moved backwards.  Refusing to generate id for %d milliseconds", offset));
                    }
                } catch (Exception e) {
    
    
                    throw new RuntimeException(e);
                }
            } else {
    
    
                throw new RuntimeException(String.format("Clock moved backwards.  Refusing to generate id for %d milliseconds", offset));
            }
        }

        if (lastTimestamp == timestamp) {
    
    
            // 相同毫秒内，序列号自增
            sequence = (sequence + 1) & sequenceMask;
            if (sequence == 0) {
    
    
                // 同一毫秒的序列数已经达到最大
                timestamp = tilNextMillis(lastTimestamp);
            }
        } else {
    
    
            // 新增的毫秒，序列号置为 1 - 1000 随机数
            sequence = ThreadLocalRandom.current().nextLong(1, 1000);
        }

        lastTimestamp = timestamp;

        // 时间戳格式化 + (数据中心标识 | 机器标识部分 | 序列号部分)
        return TIME_FORMATTER.format(LocalDateTime.ofInstant(new Date(timestamp).toInstant(), ZoneId.systemDefault()))
                // 左补齐
                + String.format(numberFullLeft, ((dataCenterId << dataCenterIdShift)
                | (workerId << workerIdShift)
                | sequence));
    }

    /**
     * 数据标识id部分
     */
    private static long getDataCenterId(long maxDataCenterId) {
    
    
        long id = 0L;
        try {
    
    
            InetAddress ip = InetAddress.getLocalHost();
            NetworkInterface network = NetworkInterface.getByInetAddress(ip);
            if (network == null) {
    
    
                id = 1L;
            } else {
    
    
                byte[] mac = network.getHardwareAddress();
                if (null != mac) {
    
    
                    id = ((0x000000FF & (long) mac[mac.length - 2]) | (0x0000FF00 & (((long) mac[mac.length - 1]) << 8))) >> 6;
                    id = id % (maxDataCenterId + 1);
                }
            }
        } catch (Exception e) {
    
    
            log.info(" getDataCenterId: " + e.getMessage());
        }
        return id;
    }

    /**
     * 获取 maxWorkerId
     */
    private static long getMaxWorkerId(long maxDataCenterId, long maxWorkerId) {
    
    
        StringBuilder mpId = new StringBuilder();
        mpId.append(maxDataCenterId);
        String name = ManagementFactory.getRuntimeMXBean().getName();
        if (null != name && name.trim().length() > 0) {
    
    
            /*
             * GET jvmPid
             */
            mpId.append(name.split("@")[0]);
        }
        /*
         * MAC + PID 的 hashcode 获取16个低位
         */
        return (mpId.toString().hashCode() & 0xffff) % (maxWorkerId + 1);
    }

    /**
     * tilNextMillis
     *
     * @param lastTimestamp stamp
     * @return l
     */
    private long tilNextMillis(long lastTimestamp) {
    
    
        long timestamp = timeGen();
        while (timestamp <= lastTimestamp) {
    
    
            timestamp = timeGen();
        }
        return timestamp;
    }

    /**
     * 获取毫秒
     *
     * @return l
     */
    private long timeGen() {
    
    
        return SystemClock.now();
    }

    public static void main(String[] args) {
    
    
        long t = System.currentTimeMillis();
        for (int i = 0; i < 1000; i++) {
    
    
            System.out.println(generateNo());
        }
        System.out.println(System.currentTimeMillis() - t);
    }

}