PHP+redis realizes snap-up function

<?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 = '';

 /**

  * 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;

 }

}