电商库存超卖常见方案总结
字段设计
Snipaste_2021-07-03_15-07-00错误示例
function test1()
{
//商品id
$id = request()->input('id');
$product = Product::where('id', $id)->firstOrFail();
if ($product->num <= 0) {
return "卖光啦！！";
}
//库存减1
$product->decrement('num');
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()
}
在数据库中查看库存
redis原子锁
function test2()
{
//商品id
$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！！";
}
//库存减1
$product->decrement('num');
return 'success';
}catch (LockTimeoutException $e) {
return '当前人数过多';
} finally {
optional($lock)->release();
}
}
Snipaste_2021-07-03_15-07-26MySQL悲观锁
function test3()
{
//商品id
$id = request()->input('id');
try {
\DB::beginTransaction();
$product = Product::where('id', $id)->lockForUpdate()->first();
if ($product->num <= 0) {
return "卖光啦！！";
}
//库存减1
$product->decrement('num');
\DB::commit();
return "success";
} catch (\Exception $exception) {
}
}
Snipaste_2021-07-03_15-07-36MySQL乐观锁
function test4()
{
//商品id
$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';
}
优化
\DB::update('UPDATE `product` SET num = num -1 WHERE id = ? AND num-1 >= 0', [$id]);
适用Redis存储库存
function test5()
{
//商品id
$id = request()->input('id');
$num = Redis::command('get', ['product_' . $id]);
if ($num <= 0) {
return "卖完啦！";
}
//减库存
$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';
}
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