Use redis to deduct inventory for flash sales, limiting each account to only one snap-up. This simple demo uses three basic types: string, hash, and list.

• Use string Type int value to store the remaining inventory, and reduce it by 1 after the snap-up is successful

• Use hash to store the id of the "sold-in" member (you can ensure that the user id is the only one in the field property). Note: The uid corresponding to the field of this hash may not necessarily be a successful purchase.

• Use list to save the list of member IDs that are actually successful in the purchase, as a queue for subsequent order processing

When I first wrote it, I tried to use string bitmap to save whether the member has successfully purchased, but this will cause problems when concurrency is high, so I later changed it to unique Field hash

2 files:

• init.php: initialized inventory, statistical data, list of successful members, etc.

• buy.php: rush purchase

Initialization

ini.php:

$m_redis = new YourRedisClass(); //redis类很多, 可以自己写, 也可以用predis等
$m_redis->set('rush_stock', 20);//int, 可抢购的商品总数
$m_redis->set('rush_success', 0); //int, 成功的数量
$m_redis->set('rush_fail', 0); //int, 失败的数量
$m_redis->expire('rush_queue_h', 0); //hash, 已加入抢购队列的会员的hash记录表(field是唯一的, 可限制每个uid只有一次), 不一定抢购成功
$m_redis->set('rush_got_uid', ''); //string, 抢购成功的会员uid记录, 只是为了能简单的显示抢到的会员.
$m_redis->del('rush_got_uid_l'); //list, 抢购成功的会员uid(方便抢购后的订单批次处理)
echo 'success, '.date('Y-m-d H:i:s');

Execute this file and initialize the quantity.

Execute "mget rush_stock rush_fail rush_success rush_got_uid" under redis-cli to confirm the initialization data

Instakill

Judgment logic:

• 
  

1. Whether the inventory is 0, if the inventory is >0, it will enter the rush buying queue

• 
  

1. ##The rush buying queue data (hash) is written successfully, and the inventory is ready to be deducted

• 
  

##If the inventory deduction is successful (remainder >= 0), the rush purchase is successful and the order processing queue (list) is entered.
1. Currently, string int is used to store inventory, and list items can also be used. Number to count, but initialization is not as simple as string type.

   
   

buy.php

//随机生成会员id
$uid = rand(1,200);

$m_redis = new YourRedisClass(); //redis类很多, 可以自己写, 也可以用predis等

$key = 'rush_stock';
$q = $m_redis->get($key);

//1. 先判断库存数量
//库存为0, 直接无法进入抢购队列
if($q < 1){
    $m_redis->incr(&#39;rush_fail&#39;);//记录失败的数量
    die($uid.&#39;:OutOfStock&#39;);
}

//2. 判断该会员是否购买过 => 是否进入过队列
$queued = $m_redis->hSet(&#39;rush_queue_h&#39;, $uid, $uid);//这里只能判断是否进入了抢购的队列. 如果库存为0则无法进入. 进入了队列后才能抢购
if(!$queued){
    $m_redis->incr(&#39;rush_fail&#39;);//记录失败的数量
    die($uid.&#39;:queue failed&#39;);
}

//让cpu飞一会
$n = rand(20000,100000);
for($i=0; $i < $n; $i++){
    $a = rand(1,20000);
    $a = rand(1,30000);
    $a = rand(1,40000);
    $a = rand(1,50000);
    $a = rand(1,60000);
    $a = rand(1,70000);
    $a = rand(1,80000);
    $a = rand(1,90000);
}


//3. 扣减数量
$q = $m_redis->decr($key, 1);//扣减数量后会返回结果值
echo $q.&#39; left:&#39;;


////region 如果不判断操作后返回的结果,则可能会造成超发
//$m_redis->incr(&#39;q_success&#39;);//记录成功的数量  ==>这个是有bug的, 不可取
//die(&#39;:success&#39;);
////endregion

if($q < 0){
    $m_redis->incr(&#39;rush_fail&#39;);//记录失败的数量
    die($uid.&#39;:decrease fail&#39;);
}else{
    //记录成功的数量
    $m_redis->incr(&#39;rush_success&#39;);
    //记录该会员已购买
    $m_redis->append(&#39;rush_got_uid&#39;, $uid.&#39;,&#39;); //字符串追加
    $m_redis->rPush(&#39;rush_got_uid_l&#39;, $uid); //list
    die($uid.&#39;:success&#39;);
}

The hash in the above code saves the member uid, The member uid that just enters the rush purchase queue may not necessarily be successful in the rush purchase. Those who have not entered the rush purchase queue at all will not be in this hash and will be rejected directly because the inventory is 0.

AB stress test: Make a simple 500 concurrent requests and try a total of 2,000 requests (during testing, Nginx hangs up after 600 concurrent requests under win10)

Apache路径bin>ab -n 2000 -c 500 http://xxx.com/buy.php

Execute "mget rush_stock rush_fail rush_success rush_got_uid" under redis-cli to confirm the result, Check the number of possible over-issuances through the value of rush_stock

Execute "hvals rush_queue_h" to check the user IDs entering the rush purchase queue. This number >= the number of users who have successfully rushed to buy.

For the list queue For data operations, you can use the

command, which can implement the FIFO data processing sequence.

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