Detailed explanation of the steps to implement rush buying using php+redis message queue (with code)

This time I will bring you a detailed explanation of the steps to implement rush buying using the php redis message queue (with code). What are the precautions for implementing rush buying using the php redis message queue? The following is a practical case, let’s take a look.

Implementation functions:

1. Based on redis queue to prevent high concurrency overselling

2. Based on mysql transaction adding exclusive lock to prevent high concurrency overselling

Based on the redis queue workflow:

1. The administrator creates a redis product inventory queue based on the inventory in the goods table

2. The client accesses the flash sale API
3. The web server first starts from Key points of querying the remaining inventory in the redis product inventory queue
4. If there is remaining inventory in the redis queue, create an order in mysql, remove the inventory, and the snap-up is successful
5. If there is no remaining inventory in the redis queue, it will prompt that the inventory is insufficient. Key content of failed rush purchase

Based on mysql transaction and exclusive lock workflow:

1. Open the transaction

2. Query the inventory and set the write lock (exclusive lock) displayed: SELECT * FROM goods WHERE id = 1 FOR UPDATE
3. Generate order
4. Destock, implicitly set write lock (exclusive lock): UPDATE goods SET counts = counts – 1 WHERE id = 1
5. Commit and release the lock

Note: You can set the shared lock in the second step, otherwise it may cause a deadlock.

Code:

<?php
/**********************************************
* 抢购模块
*
* @author liubin
* @date 2016-02-10
*
* ab -n 1000 -c 100 http://192.168.16.73/Seckill/buy.php
*
*/
class seckill extends common
{
 private $_orderModel = null;
 private $_goodsModel = null;
 private $_redis = null;
 /*
  * 错误信息
 */
 protected $_error = &#39;&#39;;
 /**
  * 构造器
  *
 */
 public function construct()
 {
  if($this->_orderModel === null){
   $this->_orderModel = new OrderModel();
  }
  if($this->_goodsModel === null){
   $this->_goodsModel = new GoodsModel();
  }
  if($this->_redis === null){
   $this->_redis = new QRedis(); 
  }
 }
 /*
  * 秒杀API
  * 
  * @author liubin
  * @date 2017-02-10
 */
 public function addQsec(){
  $gid = intval($_GET['gid']);
  $type = isset($_GET['type']) ? $_GET['type'] : 'mysql';
  switch ($type) {
   case 'mysql':
    $this->order_check_mysql($gid);
    echo $this->getError();
    break;
   case 'redis':
    $this->order_check_redis($gid);
    echo $this->getError();
    break;
   case 'transaction':
    $this->order_check_transaction($gid);
    echo $this->getError();
    break;
   default:
    echo '类型错误';
    break;
  }
 }
 /*
  * 获取错误信息
  * 
  * @author liubin
  * @date 2017-02-10
 */
 public function getError(){
  return $this->_error;
 }
 /*
  * 基于mysql验证库存信息
  * @desc 高并发下会导致超卖
  *
  * @author liubin
  * @date 2017-02-10
 */
 protected function order_check_mysql($gid){
  $model = $this->_goodsModel;
  $pdo = $model->getHandler();
  $gid = intval($gid);
  /*
   * 1：$sql_forlock如果不加事务，不加写锁：
   * 超卖非常严重，就不说了
   * 
   * 2：$sql_forlock如果不加事务，只加写锁：
   * 第一个会话读$sql_forlock时加写锁，第一个会话$sql_forlock查询结束会释放该行锁.
   * 第二个会话在第一个会话释放后读$sql_forlock的写锁时，会再次$sql_forlock查库存
   * 导致超卖现象产生
   *
  */
  $sql_forlock = 'select * from goods where id = '.$gid .' limit 1 for update';
  //$sql_forlock = 'select * from goods where id = '.$gid .' limit 1';
  $result = $pdo->query($sql_forlock,PDO::FETCH_ASSOC);
  $goodsInfo = $result->fetch();
  if($goodsInfo['counts']>0){
   //去库存
   $gid = $goodsInfo['id'];
   $sql_inventory = 'UPDATE goods SET counts = counts - 1 WHERE id = '.$gid;
   $result = $this->_goodsModel->exect($sql_inventory);
   if($result){
    //创订单
    $data    = [];
    $data['order_id'] = $this->_orderModel->buildOrderNo();
    $data['goods_id'] = $goodsInfo['id'];
    $data['addtime'] = time();
    $data['uid']  = 1;
    $order_rs = $this->_orderModel->create_order($data);
    if($order_rs){
     $this->_error = '购买成功';
     return true;
    }
   }
  }
  $this->_error = '库存不足';
  return false;
 }
 /*
  * 基于redis队列验证库存信息
  * @desc Redis是底层是单线程的,命令执行是原子操作,包括lpush,lpop等.高并发下不会导致超卖
  *
  * @author liubin
  * @date 2017-02-10
 */
 protected function order_check_redis($gid){
  $goodsInfo = $this->_goodsModel->getGoods($gid);
  if(!$goodsInfo){
   $this->_error = '商品不存在';
   return false;
  }
  $key = 'goods_list_'.$goodsInfo['id'];
  $count = $this->_redis->getHandel()->lpop($key);
  if(!$count){
   $this->_error = '库存不足';
   return false;
  }
  //生成订单
  $data    = [];
  $data['order_id'] = $this->_orderModel->buildOrderNo();
  $data['goods_id'] = $goodsInfo['id'];
  $data['addtime'] = time();
  $data['uid']  = 1;
  $order_rs = $this->_orderModel->create_order($data);
  //库存减少
  $gid = $goodsInfo['id'];
  $sql = 'UPDATE goods SET counts = counts - 1 WHERE id = '.$gid;
  $result = $this->_goodsModel->exect($sql);
  $this->_error = '购买成功';
  return true;
 }
 /*
  * 基于mysql事务验证库存信息
  * @desc 事务 和 行锁 模式,高并发下不会导致超卖，但效率会慢点
  * @author liubin
  * @date 2017-02-10
  说明：
  如果$sql_forlock不加写锁，并发时，$sql_forlock查询的记录存都大于0，可以减库存操作.
  如果$sql_forlock加了写锁，并发时，$sql_forlock查询是等待第一次链接释放后查询.所以库存最多就是5
 */
 protected function order_check_transaction($gid){
  $model = $this->_goodsModel;
  $pdo = $model->getHandler();
  $gid = intval($gid);
  try{
   $pdo->beginTransaction();//开启事务处理
   /*
    * 1：$sql_forlock如果只加事务，不加写锁：
    * 开启事务
    * 因为没有加锁，读$sql_forlock后，并发时$sql_inventory之前还可以再读。
    * $sql_inventory之后和commit之前才会锁定
    * 出现超卖跟事务的一致性不冲突
    * 
    *
    * 2：$sql_forlock如果加了事务，又加读锁：
    * 开启事务
    * 第一个会话读$sql_forlock时加读锁，并发时，第二个会话也允许获得$sql_forlock的读锁，
    * 但是在第一个会话执行去库存操作时（写锁），写锁便会等待第二个会话的读锁，第二个会话执行写操作时，写锁便会等待第一个会话的读锁，
    * 出现死锁
    * 3：$sql_forlock如果加了事务，又加写锁：
    * 开启事务
    * 第一个会话读$sql_forlock时加写锁，直到commit才会释放写锁，并发查询不会出现超卖现象。
    *
   */
   $sql_forlock = 'select * from goods where id = '.$gid .' limit 1 for update';
   //$sql_forlock = 'select * from goods where id = '.$gid .' limit 1 LOCK IN SHARE MODE';
   //$sql_forlock = 'select * from goods where id = '.$gid .' limit 1';
   $result = $pdo->query($sql_forlock,PDO::FETCH_ASSOC);
   $goodsInfo = $result->fetch();
   if($goodsInfo['counts']>0){
    //去库存
    $gid = $goodsInfo['id'];
    $sql_inventory = 'UPDATE goods SET counts = counts - 1 WHERE id = '.$gid;
    $result = $this->_goodsModel->exect($sql_inventory);
    if(!$result){
     $pdo->rollBack();
     $this->_error = '库存减少失败';
     return false;
    }
    //创订单
    $data    = [];
    $data['id']   = 'null';
    $data['order_id'] = $this->_orderModel->buildOrderNo();
    $data['goods_id'] = $goodsInfo['id'];
    $data['uid']  = 'abc';
    $data['addtime'] = time();
    $sql = 'insert into orders (id,order_id,goods_id,uid,addtime) values ('.$data['id'].',"'.$data['order_id'].'","'.$data['goods_id'].'","'.$data['uid'].'","'.$data['addtime'].'")';   
    $result = $pdo->exec($sql);
    if(!$result){
     $pdo->rollBack();
     $this->_error = '订单创建失败';
     return false;
    }
    $pdo->commit();//提交
    $this->_error = '购买成功';
    return true;
   }else{
    $this->_error = '库存不足';
    return false;
   }
  }catch(PDOException $e){
   echo $e->getMessage();
   $pdo->rollBack();
  }
 }
 /*
  * 创建订单
  * mysql 事物处理，也可以用存储过程
  *
 */
 private function create_order($goodsInfo){
  //生成订单
  $data    = [];
  $data['order_id'] = $this->_orderModel->buildOrderNo();
  $data['goods_id'] = $goodsInfo['id'];
  $data['addtime'] = time();
  $data['uid']  = 1;
  $order_rs = $this->_orderModel->create_order($data);
  //库存减少
  $gid = $goodsInfo['id'];
  $sql = 'UPDATE goods SET counts = counts - 1 WHERE id = '.$gid;
  $result = $this->_goodsModel->exect($sql);
  return true;
 }
}

I believe you have mastered the method after reading the case in this article. For more exciting information, please pay attention to other related articles on the php Chinese website!

Recommended reading:

Detailed explanation of how php handles high-concurrency requests for rush purchases

How does php obtain cpu memory in windows? Real-time usage

The above is the detailed content of Detailed explanation of the steps to implement rush buying using php+redis message queue (with code). For more information, please follow other related articles on the PHP Chinese website!