Go语言实现权重抽奖系统的项目实践

package main

import (
    "crypto/rand"
    "encoding/json"
    "fmt"
    "math/big"
    "net/http"
    "sync"
)

// 奖品配置
type Prize struct {
    ID     int    `json:"id"`
    Name   string `json:"name"`
    Weight int    `json:"weight"` // 权重值（非百分比）
}

// 抽奖系统
type LotterySystem struct {
    prizes       []Prize
    totalWeight  int
    issuedPrizes map[int]bool
    mu           sync.Mutex
}

// 初始化抽奖系统
func NewLotterySystem(prizes []Prize) *LotterySystem {
    total := 0
    for _, p := range prizes {
        total += p.Weight
    }
    return &LotterySystem{
        prizes:       prizes,
        totalWeight:  total,
        issuedPrizes: make(map[int]bool),
    }
}

// 安全随机数生成
func secureRandom(max int) (int, error) {
    n, err := rand.Int(rand.Reader, big.NewInt(int64(max)))
    if err != nil {
        return 0, err
    }
    return int(n.Int64()), nil
}

// 执行抽奖
func (ls *LotterySystem) Draw() (*Prize, error) {
    ls.mu.Lock()
    defer ls.mu.Unlock()

    if ls.totalWeight == 0 {
        return nil, fmt.Errorf("no available prizes")
    }

    // 生成随机数
    randomNum, err := secureRandom(ls.totalWeight)
    if err != nil {
        return nil, err
    }

    // 权重选择
    current := 0
    for _, p := range ls.prizes {
        current += p.Weight
        if randomNum < current {
            if ls.issuedPrizes[p.ID] {
                continue // 已发放的奖品跳过
            }
            ls.issuedPrizes[p.ID] = true
            return &p, nil
        }
    }

    return nil, fmt.Errorf("draw failed")
}

// HTTP服务
func main() {
    // 初始化奖品池
    prizes := []Prize{
        {ID: 1, Name: "一等奖", Weight: 1},
        {ID: 2, Name: "二等奖", Weight: 5},
        {ID: 3, Name: "三等奖", Weight: 20},
        {ID: 4, Name: "参与奖", Weight: 74},
    }

    lottery := NewLotterySystem(prizes)

    http.HandleFunc("/draw", func(w http.ResponseWriter, r *http.Request) {
        prize, err := lottery.Draw()
        if err != nil {
            http.Error(w, err.Error(), http.StatusInternalServerError)
            return
        }

        w.Header().Set("Content-Type", "application/json")
        json.NewEncoder(w).Encode(prize)
    })

    fmt.Println("抽奖服务已启动，监听端口 8080")
    http.ListenAndServe(":8080", nil)
}

// 权重选择逻辑
current := 0
for _, p := range ls.prizes {
    current += p.Weight
    if randomNum < current {
        return &p
    }
}

// 使用crypto/rand生成安全随机数
func secureRandom(max int) (int, error) {
    n, err := rand.Int(rand.Reader, big.NewInt(int64(max)))
    // ...
}

var mu sync.Mutex

func (ls *LotterySystem) Draw() {
    ls.mu.Lock()
    defer ls.mu.Unlock()
    // ...
}

issuedPrizes map[int]bool

// 添加测试端点验证概率分布
http.HandleFunc("/test", func(w http.ResponseWriter, r *http.Request) {
    results := make(map[int]int)
    for i := 0; i < 10000; i++ {
        tempLottery := NewLotterySystem(prizes)
        prize, _ := tempLottery.Draw()
        results[prize.ID]++
    }
    json.NewEncoder(w).Encode(results)
})

// 使用Redis分布式锁
func (ls *LotterySystem) DistributedDraw() {
    lock := redis.NewLock("lottery_lock")
    err := lock.Lock()
    // ...抽奖逻辑...
    lock.Unlock()
}

type Prize struct {
    // ...
    Stock     int // 新增库存字段
}
func (ls *LotterySystem) Draw() {
    // 检查库存
    if p.Stock <= 0 {
        continue
    }
    // 扣减库存
    p.Stock--
}

go run main.go

curl http://localhost:8080/draw
# 示例返回：{"id":3,"name":"三等奖","weight":20}

curl http://localhost:8080/test
# 返回万次抽奖结果分布