PHP高并发测试|防止库存超卖的案例讲解

<?php$redis =new Redis();$redis->connect("127.0.0.1", 6379);$redis->auth('PASSWORD');$redis->watch('sales');//乐观锁 监视作用 set()  初始值0$sales = $redis->get('sales');//var_dump($sales); exit;
db();global $con;// 查询商品信息//$product_id = 1;//$sql = "select * from products where id={$product_id}";//$result = mysqli_query($con, $sql);//$row = mysqli_fetch_assoc($result);//$store = $row['store'];// 库存$n = 15;if ($sales >= $n) {    insertLog('库存为0 秒杀失败');    exit('秒杀结束');}
//redis开启事务$redis->multi();$redis->incr('sales'); //将 key 中储存的数字值增一 ,如果 key 不存在，那么 key 的值会先被初始化为 0 ，然后再执行 INCR 操作。$res = $redis->exec(); //成功1 失败0
if ($res) {    //秒杀成功    $con = new mysqli('localhost','root','PASSWORD','dev');    if (!$con) {        echo "数据库连接失败";    }
    $product_id = 1;// 商品ID    $buy_num = 1;// 购买数量    sleep(1);
    $sql = "update products set store=store-{$buy_num} where id={$product_id}";
    if (mysqli_query($con, $sql)) {        echo "秒杀完成";        insertLog('恭喜 秒杀成功');    }
} else {    insertLog('抱歉 秒杀失败');    exit('抢购失败');}
function db(){    global $con;    $con = new mysqli('localhost','root','WOrd1234.*','dev');    if (!$con) {        echo "数据库连接失败";    }}
/** * 记录日志 */function insertLog($content){    global $con;    $sql = "INSERT INTO `order_log` (content) values('$content')";    mysqli_query($con, $sql);}

ab -n 30 -c 10 http://xxxxxx.top/code/the_limit/optimistic\ _redis_lock.php