https://github.com/yuanyu90221/go-snowflake-id-service

https://github.com/yuanyu90221/go-snowflake-id-service

Last synced: 16 days ago
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• Host: GitHub
• URL: https://github.com/yuanyu90221/go-snowflake-id-service
• Owner: yuanyu90221
• Created: 2023-01-14T15:51:22.000Z (about 2 years ago)
• Default Branch: master
• Last Pushed: 2023-01-16T05:34:32.000Z (about 2 years ago)
• Last Synced: 2024-06-21T18:52:41.018Z (7 months ago)
• Language: Go
• Size: 4.88 KB
• Stars: 3
• Watchers: 3
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: README.md

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README

        
# go-snowflake-id-service

This is a snowflake-id service implemented by golang

## [snowflake id](https://zh.wikipedia.org/zh-tw/%E9%9B%AA%E8%8A%B1%E7%AE%97%E6%B3%95)

A distributed monotone incremented Identifier generate algorithm

## format

| timestamp       | shardId        |  seqId     |               

|-----------------|----------------|------------|

| timestamp difference in millisecond(41bit) | shardId(10bit)| seqId(12bit)|

## functionality

1. in 1 millisecond could generate 2^12 different id 

2. if more than 2^12 request in 1 millisecond, this service will block this request

## for atomic operation

use golang mutex lock for generate seqId operation

```go

type Shard struct {

	mulock   sync.Mutex

	epoch    int64

	lastTime int64

	shardId  int64

	seqId    int64

}

```

first get current timestamp

check current == lastTime then mean in same millisecond, then increase seqId

if current == lastTime and seqId > seqMax then mean need to wait until next millisecond

current > lastTime mean recount the seqId to 0

```go

func (s *Shard) NextID() int64 {

	s.mulock.Lock()

	defer s.mulock.Unlock()

	now := currentMillisecond()

	if s.lastTime == now {

		s.seqId++

		// seqId over the max , then loop until next millisecond

		if s.seqId > seqIdMax {

			for now <= s.lastTime {

				now = currentMillisecond()

			}

		}

	} else {

		s.seqId = 0

		s.lastTime = now

	}

	id := int64((now-s.epoch)<