Huangzj
97 lines
2.5 KiB
Go
97 lines
2.5 KiB
Go
/*
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* @Author : huangzj
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* @Time : 2020/12/16 9:32
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* @Description：
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*/
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package snowflake
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import (
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"errors"
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"sync"
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"time"
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)
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const (
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workerBits uint8 = 10
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numberBits uint8 = 12
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workerMax int64 = -1 ^ (-1 << workerBits)
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numberMax int64 = -1 ^ (-1 << numberBits)
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timeShift uint8 = workerBits + numberBits
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workerShift uint8 = numberBits
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startTime int64 = 1525705533000 // 如果在程序跑了一段时间修改了epoch这个值 可能会导致生成相同的ID
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)
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const (
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workerIDBits = uint64(5) // 10bit 工作机器ID中的 5bit workerID
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dataCenterIDBits = uint64(5) // 10 bit 工作机器ID中的 5bit dataCenterID
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sequenceBits = uint64(12)
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maxWorkerID = int64(-1) ^ (int64(-1) << workerIDBits) //节点ID的最大值 用于防止溢出
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maxDataCenterID = int64(-1) ^ (int64(-1) << dataCenterIDBits)
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maxSequence = int64(-1) ^ (int64(-1) << sequenceBits)
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timeLeft = uint8(22) // timeLeft = workerIDBits + sequenceBits // 时间戳向左偏移量
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dataLeft = uint8(17) // dataLeft = dataCenterIDBits + sequenceBits
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workLeft = uint8(12) // workLeft = sequenceBits // 节点IDx向左偏移量
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// 2020-05-20 08:00:00 +0800 CST
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twepoch = int64(1589923200000) // 常量时间戳(毫秒)
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)
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type Worker struct {
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mu sync.Mutex
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LastStamp int64 // 记录上一次ID的时间戳
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WorkerID int64 // 该节点的ID
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DataCenterID int64 // 该节点的 数据中心ID
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Sequence int64 // 当前毫秒已经生成的ID序列号(从0 开始累加) 1毫秒内最多生成4096个ID
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}
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//分布式情况下,我们应通过外部配置文件或其他方式为每台机器分配独立的id
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func NewWorker(workerID, dataCenterID int64) *Worker {
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return &Worker{
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WorkerID: workerID,
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LastStamp: 0,
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Sequence: 0,
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DataCenterID: dataCenterID,
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}
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}
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func (w *Worker) getMilliSeconds() int64 {
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return time.Now().UnixNano() / 1e6
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}
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func (w *Worker) NextID() (uint64, error) {
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w.mu.Lock()
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defer w.mu.Unlock()
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return w.nextID()
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}
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func (w *Worker) nextID() (uint64, error) {
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timeStamp := w.getMilliSeconds()
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if timeStamp < w.LastStamp {
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return 0, errors.New("time is moving backwards,waiting until")
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}
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if w.LastStamp == timeStamp {
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w.Sequence = (w.Sequence + 1) & maxSequence
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if w.Sequence == 0 {
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for timeStamp <= w.LastStamp {
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timeStamp = w.getMilliSeconds()
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}
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}
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} else {
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w.Sequence = 0
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}
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w.LastStamp = timeStamp
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id := ((timeStamp - twepoch) << timeLeft) |
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(w.DataCenterID << dataLeft) |
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(w.WorkerID << workLeft) |
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w.Sequence
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return uint64(id), nil
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}
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