php+redis消息队列实现抢购功能

• 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':
  $this->ordercheckMysqL($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 $this->_error;
  }
  /
• 基于MysqL验证库存信息
• @desc 高并发下会导致超卖
• @author liubin
• @date 2017-02-10
  */
  protected function ordercheckMysqL($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;
  }
  $key = 'goodslist'.$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'];
$<a href="https://www.jb51.cc/tag/sql/" target="_blank" class="keywords">sql</a>_inventory = 'UPDATE goods SET counts = counts - 1 WHERE id = '.$gid;
$result = $this->_goodsModel->exect($<a href="https://www.jb51.cc/tag/sql/" target="_blank" class="keywords">sql</a>_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();

$<a href="https://www.jb51.cc/tag/sql/" target="_blank" class="keywords">sql</a> = 'insert into orders (id,order_id,goods_id,uid,addtime) values ('.$data['id'].',"'.$data['order_id'].'","'.$data['goods_id'].'","'.$data['uid'].'","'.$data['addtime'].'")';   
$result = $pdo->exec($<a href="https://www.jb51.cc/tag/sql/" target="_blank" class="keywords">sql</a>);
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;
}
}