Go语言中的分布式ID生成器设计与实现

package main

import (
	"sync"
	"time"
)

const (
	timeBits   = 41
	nodeBits   = 10
	sequenceBits = 12
)

type Snowflake struct {
	mu      sync.Mutex
	nodeId  uint64
	sequence uint64
	lastTime uint64
}

func NewSnowflake(nodeId uint64) *Snowflake {
	return &Snowflake{
		nodeId: nodeId,
	}
}

func (s *Snowflake) Generate() uint64 {
	s.mu.Lock()
	defer s.mu.Unlock()

	now := time.Now().UnixNano() / int64(time.Millisecond)
	if now <= s.lastTime {
		panic("clock moved backwards")
	}

	s.sequence = (s.sequence + 1) & ((1 << sequenceBits) - 1)
	if s.sequence == 0 {
		for now <= s.lastTime {
			now = time.Now().UnixNano() / int64(time.Millisecond)
		}
		s.lastTime = now
		s.nodeId = (s.nodeId + 1) & ((1 << nodeBits) - 1)
	}

	id := uint64(now-s.baseTime)<<timeBits | s.nodeId<<sequenceBits | s.sequence
	return id
}