golang 实现雪花Id-Go服务器开发

雪花Id是Twitter提出的一种分布式唯一ID生成算法，可以使用golang实现。

具体实现如下：

package main
import (
    "fmt"
    "math/rand"
    "strconv"
    "sync"
    "time"
)
// 定义常量
const (
    workerIdBits     = 5
    datacenterIdBits = 5
    sequenceBits     = 12
    maxWorkerId     = -1 ^ (-1 << workerIdBits)     // 31
    maxDatacenterId = -1 ^ (-1 << datacenterIdBits) // 31
    timeLeftShift  = sequenceBits + workerIdBits + datacenterIdBits
    workerLeftShift  = sequenceBits
    datacenterLeftShift  = sequenceBits + workerIdBits
    sequenceMask = -1 ^ (-1 << sequenceBits) // 4095
)
type Snowflake struct {
    mutex         sync.Mutex
    startTime     int64
    datacenterId  int64
    workerId      int64
    sequence      int64
}
func NewSnowflake(datacenterId, workerId int64) *Snowflake {
    if datacenterId < 0 || datacenterId > maxDatacenterId {
        panic(fmt.Sprintf("datacenter Id can't be greater than %d or less than 0", maxDatacenterId))
    }
    if workerId < 0 || workerId > maxWorkerId {
        panic(fmt.Sprintf("worker Id can't be greater than %d or less than 0", maxWorkerId))
    }
    return &Snowflake{
        startTime:     getTime(),
        datacenterId:  datacenterId,
        workerId:      workerId,
        sequence:      0,
    }
}
func (sf *Snowflake) GetId() int64 {
    sf.mutex.Lock()
    defer sf.mutex.Unlock()
    now := getTime()
    if now < sf.startTime {
        panic(fmt.Sprintf("Clock moved backwards.  Refusing to generate id for %d milliseconds", sf.startTime-now))
    }
    if now == sf.startTime {
        sf.sequence = (sf.sequence + 1) & sequenceMask
        if sf.sequence == 0 {
            now = getNextTime(sf.startTime)
        }
    } else {
        sf.sequence = 0
    }
    sf.startTime = now
    return (now-sf.startTime)<<timeLeftShift | sf.datacenterId<<datacenterLeftShift |
        sf.workerId<<workerLeftShift | sf.sequence
}
func getTime() int64 {
    return time.Now().UnixNano() / int64(time.Millisecond)
}
func getNextTime(startTime int64) int64 {
    timestamp := getTime()
    for timestamp <= startTime {
        timestamp = getTime()
    }
    return timestamp
}
func main() {
    rand.Seed(time.Now().UnixNano())
    datacenterId := rand.Int63n(maxDatacenterId)
    workerId := rand.Int63n(maxWorkerId)
    snowflake := NewSnowflake(datacenterId, workerId)
    for i := 0; i < 10; i++ {
        fmt.Println(strconv.FormatInt(snowflake.GetId(), 10))
    }
}