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README
Apache-2.0

❄️ GO-Snowflake

Build Status

Snowflake简介

在单机系统中我们会使用自增id作为数据的唯一id,自增id在数据库中有利于排序和索引,但是在分布式系统中如果还是利用数据库的自增id会引起冲突,自增id非常容易被爬虫爬取数据。在分布式系统中有使用uuid作为数据唯一id的,但是uuid是一串随机字符串,所以它无法被排序。

Twitter设计了Snowflake算法为分布式系统生成ID,Snowflake的id是int64类型,它通过datacenterId和workerId来标识分布式系统,下面看下它的组成:

1bit 41bit 5bit 5bit 12bit
符号位(保留字段) 时间戳(当前时间-纪元时间) 数据中心id 机器id 自增序列

算法简介

在使用Snowflake生成id时,首先会计算时间戳timestamp(当前时间 - 纪元时间),如果timestamp数据超过41bit则异常。同样需要判断datacenterId和workerId不能超过5bit(0-31),在处理自增序列时,如果发现自增序列超过12bit时需要等待,因为当前毫秒下12bit的自增序列被用尽,需要进入下一毫秒后自增序列继续从0开始递增。


🚀 快速开始

🕹 克隆 & 运行

git clone https://github.com/GUAIK-ORG/go-snowflake.git

go run main.go

💾 安装 & 导入

go get github.com/GUAIK-ORG/go-snowflake

// 在项目中导入模块
import "github.com/GUAIK-ORG/go-snowflake/snowflake"

⚠️注意事项

  • 在多实例(多个snowflake对象)的并发环境下,请确保每个实例(datacenterid,workerid)的唯一性,否则生成的ID可能冲突。

📊 测试

本机测试:

参数 配置
OS MacBook Pro (13-inch, Late 2016, Four Thunderbolt 3 Ports)
CPU 2.9 GHz 双核Intel Core i5
RAM 8 GB 2133 MHz LPDDR3

测试代码

func TestLoad() {
    var wg sync.WaitGroup
    s, err := snowflake.NewSnowflake(int64(0), int64(0))
    if err != nil {
        glog.Error(err)
        return
    }
    var check sync.Map
    t1 := time.Now()
    for i := 0; i < 200000; i++ {
        wg.Add(1)
        go func() {
            defer wg.Done()
            val := s.NextVal()
            if _, ok := check.Load(val); ok {
                // id冲突检查
                glog.Error(fmt.Errorf("error#unique: val:%v", val))
                return
            }
            check.Store(val, 0)
            if val == 0 {
                glog.Error(fmt.Errorf("error"))
                return
            }
        }()
    }
    wg.Wait()
    elapsed := time.Since(t1)
    glog.Infof("generate 20k ids elapsed: %v", elapsed)
}

运行结果

load

🗂 使用说明

创建Snowflake对象

// NewSnowflake(datacenterid, workerid int64) (*Snowflake, error)
// 参数1 (int64): 数据中心ID (可用范围:0-31)
// 参数2 (int64): 机器ID    (可用范围:0-31)
// 返回1 (*Snowflake): Snowflake对象 | nil
// 返回2 (error): 错误码
s, err := snowflake.NewSnowflake(int64(0), int64(0))
if err != nil {
    glog.Error(err)
    return
}

生成唯一ID

s, err := snowflake.NewSnowflake(int64(0), int64(0))
// ......
// (s *Snowflake) NextVal() int64
// 返回1 (int64): 唯一ID
id := s.NextVal()
// ......

通过ID获取数据中心ID与机器ID

// ......
// GetDeviceID(sid int64) (datacenterid, workerid int64)
// 参数1 (int64): 唯一ID
// 返回1 (int64): 数据中心ID
// 返回2 (int64): 机器ID
datacenterid, workerid := snowflake.GetDeviceID(id))

通过ID获取时间戳(创建ID时的时间戳 - epoch)

// ......
// GetTimestamp(sid int64) (timestamp int64)
// 参数1 (int64): 唯一ID
// 返回1 (int64): 从epoch开始计算的时间戳
t := snowflake.GetTimestamp(id)

通过ID获取生成ID时的时间戳

// ......
// GetGenTimestamp(sid int64) (timestamp int64)
// 参数1 (int64): 唯一ID
// 返回1 (int64): 唯一ID生成时的时间戳
t := snowflake.GetGenTimestamp(id)

通过ID获取生成ID时的时间(精确到:秒)

// ......
// GetGenTime(sid int64)
// 参数1 (int64): 唯一ID
// 返回1 (string): 唯一ID生成时的时间
tStr := snowflake.GetGenTime(id)

查看时间戳字段使用占比(41bit能存储的范围:从epoch开始往后69年)

// ......
// GetTimestampStatus() (state float64)
// 返回1 (float64): 时间戳字段使用占比(范围 0.0 - 1.0)
status := snowflake.GetTimestampStatus()
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简介

Go 语言实现的 Snowflake 算法,为分布式系统生成唯一ID,单机测试1秒可生成20万ID。 展开 收起
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