laravel解决超卖的几个方法

发布于：2022-06-23 12:43:51  栏目：技术文档

数据库字段

1 错误的示范

function test1()
{
    $id = request()->input('id');
    $product = Product::where('id', $id)->firstOrFail();
    if ($product->num <= 0) return "卖光啦！！";
    $product->decrement('num');      //库存减1
    return "success";
}

使用 go 模拟并发

package main
import (
    "fmt"
    "github.com/PeterYangs/tools/http"
    "sync"
)
func main() {
    client := http.Client()
    wait := sync.WaitGroup{}
    for i := 0; i < 50; i++ {
        wait.Add(1)
        go func(w *sync.WaitGroup) {
            defer w.Done()
            res, _ := client.Request().GetToString("http://www.api/test1?id=1")
            fmt.Println(res)
        }(&wait)
    }
    wait.Wait()
}

2 方案1 redis 原子锁

function test2()
{
    $id = request()->input('id');
    $lock = \Cache::lock("product_" . $id, 10);
    try {
        //最多等待5秒，5秒后未获取到锁，则抛出异常
        $lock->block(5);
        $product = Product::where('id', $id)->firstOrFail();
        if ($product->num <= 0) {
            return "卖光啦！！";
        }
        $product->decrement('num');
        return 'success';
    }catch (LockTimeoutException $e) {
        return '当前人数过多';
    } finally {
        optional($lock)->release();
    }
}

3 方案2 mysql 悲观锁

function test3()
{
    $id = request()->input('id');
    try {
        \DB::beginTransaction();
        $product = Product::where('id', $id)->lockForUpdate()->first();
        if ($product->num <= 0) {
            return "卖光啦！！";
        }
        $product->decrement('num');
        \DB::commit();
        return "success";
    } catch (\Exception $exception) {
    }
}

库存正常

4 方案3 mysql 乐观锁

function test4()
{
    $id = request()->input('id');
    $product = Product::where('id', $id)->first();
    if ($product->num <= 0) {
        return "卖光啦！！";
    }
    //修改前检查库存和之前是否一致，不一致说明已经有变动，则放弃更改
    $res = \DB::update('UPDATE `product` SET num = num -1 WHERE id = ? AND num=?', [$id, $product->num]);
    if (!$res) {
        return '当前人数过多';
    }
    return 'success';
}

库存正常优化乐观锁修改库存的 sql 修改为\DB::update(‘UPDATE product SET num = num -1 WHERE id = ? AND num-1 >= 0’, [$id]);

5 方案4 redis 存储库存

function test5()
{
    $id = request()->input('id');
    $num = Redis::command('get', ['product_' . $id]);
    if ($num <= 0) {
        return "卖完啦！";
    }
    $re = Redis::command('decrby', ['product_' . $id, 1]);
    //减多了回滚
    if ($re < 0) {
        Redis::command('incrby', ['product_' . $id, 1]);
        return "卖完啦！";
    }
    return 'success';
}

库存正常原文链接：https://blog.csdn.net/weixin_41882200/article/details/119249367欢迎补充

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