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php+redis消息队列实现抢购功能

实现功能:

1. 基于redis队列,防止高并发的超卖
2. 基于mysql的事务加排它锁,防止高并发的超卖

基于redis队列工作流程:

1. 管理员根据goods表中的库存,创建redis商品库存队列
2. 客户端访问秒杀API
3. web服务器先从redis的商品库存队列中查询剩余库存重点内容
4. redis队列中有剩余,则在mysql中创建订单,去库存,抢购成功
5. redis队列中没有剩余,则提示库存不足,抢购失败重点内容

基于mysql事务和排它锁工作流程:

1. 开启事务
2. 查询库存,并显示的设置写锁(排他锁):SELECT * FROM goods WHERE id = 1 FOR UPDATE
3. 生成订单
4. 去库存,隐示的设置写锁(排他锁):UPDATE goods SET counts = counts – 1 WHERE id = 1
5. commit,释放锁

注意:第二步步可以设置共享锁,不然有可能会造成死锁。

代码

 

_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
  *
 */
 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
  *
 */
 public function getError(){
  return $this->_error;
 }
 /*
  * 基于mysql验证库存信息
  * @desc 高并发下会导致超卖
  *
 */
 protected function order_check_mysql($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
  *
 */
 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
 
 
  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;
 }
}
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