问题复现

客户端并发请求扣费接口，导致重复扣费；
服务端的加锁逻辑不正确，锁加到了非核心逻辑上，即加到了消费记录表，而不是加到了核心业务表。

有问题的代码

1. 首次进入聊天房则扣费，再次进入不重复扣费
2. 这个思路无法规避并发问题

    public function agoraToken(Request $request)
    {
        .
        .
        .
            try {
                DB::connection('footprint')->beginTransaction();
                if ($this->_userid == $appointmentInfo->userid) {
                    //如果已经存在则不重复扣费 但是并发问题会导致重复扣费
                    if (!AppointmentAction::existAction($this->_userid, $request->appointmentId, AppointmentAction::TYPE_ACTION_ENTER)) {
                        $propCount = UserConsume::getAppointmentSendConsumeCouponCount($this->_userid, $request->otherUserid);
                        $userConsume = new UserConsume($this->_userid);
                        Log::error("营业中约会 \n消费啤酒个数：" . $propCount . " \n用户id：" . $this->_userid . " \n对方id：" . $request->otherUserid . " \n时间戳:" . time());
                        $userConsume->consumeCommon(CouponInfo::PROP_COUPON_CHAMPAGNE_ID, PropInfo::PROP_CHAMPAGNE_ID, $propCount);
                        DB::connection('footprint')->commit();
                    }
                }
                
                //记录进入房间
                AppointmentAction::record($this->_userid, $request->appointmentId, AppointmentAction::TYPE_ACTION_ENTER);
            } catch (\Exception $exception) {
                Log::error("扣费失败：" . $exception);
                DB::connection('footprint')->rollBack();
            }
        .
        .
        .
    }

优化后的代码

1. 引入事务，引入try catch
2. 查询约会数据加锁，当未扣费时扣费，已扣费则修改扣费状态
3. 修改扣费状态成功提交事务，释放锁
4. 扣费失败回滚事务

    public function agoraToken(Request $request)
    {
        .
        .
        .
        //try catch 捕获异常，避免崩溃
            try {
                //开启事务 因为只是事务中的锁才生效 锁包括lockForUpdate()和sharedLock()
                DB::connection('footprint')->beginTransaction();
                //校验获取token的合法性
                $appointmentInfo = AppointmentInfo::query()->selectRaw('id,userid,"inviteeUserid","prepareId",status,"isConsume"')
                    ->where('id', $request->appointmentId)->lockForUpdate()->first();
                if (empty($appointmentInfo) || !in_array($this->_userid, [$appointmentInfo->inviteeUserid, $appointmentInfo->userid])) {
                    return ErrorCode::TYPE_ILLEGAL_REQUEST;
                }
   
                //这里是关键 根据isConsume标记是否扣费了
                if ($appointmentInfo->isConsume == AppointmentInfo::TYPE_IS_NOT_CONSUME) {
                    $propCount = UserConsume::getAppointmentSendConsumeCouponCount($this->_userid, $request->otherUserid);
                    $userConsume = new UserConsume($this->_userid);
                    Log::error("营业中约会,个数：" . $propCount . " 用户id：" . $this->_userid . ' 对方id：' . $request->otherUserid);
                    $userConsume->consumeCommon(CouponInfo::PROP_COUPON_CHAMPAGNE_ID, PropInfo::PROP_CHAMPAGNE_ID, $propCount);
                    //消费成功后修改isConsume的值，提交事务
                    $appointmentInfo->isConsume = AppointmentInfo::TYPE_IS_CONSUME;
                    $appointmentInfo->save();
                    DB::connection('footprint')->commit();
                }
                .
                .
                .
            } catch (\Exception $exception) {
                //异常情况打印log 回滚事务
                Log::error("约会扣费异常:" . \GuzzleHttp\json_encode($exception));
                DB::connection('footprint')->rollBack();
            }
        .
        .
        .
    }

期间的尝试和思考

1. 要给核心逻辑加锁，进入聊天房只是一种记录，而不是核心逻辑，不能作为锁定条件