I tried, same happened. it's related to how Postgres works internally with
the Django-ORM.
On Wednesday, August 21, 2019 at 3:07:47 PM UTC+2, mohamed habib wrote:
>
> Wild guess in the dark here, as I am unfamiliar with this API. you are
> doing:
>
> `payment.pay_request()`
>
> before creating the WeacceptTransaction object.
>
> Maybe this line needs to move below:
> `models.WeAcceptTransaction.objects.create(...)` ?
>
> At what point is the callback request triggered ?
>
> On Wed, Aug 21, 2019 at 3:36 PM Ahmed Shahwan <a...@shahwan.me
> <javascript:>> wrote:
>
>> Transaction model:
>>
>>
>> class WeacceptTransaction(Transaction):
>> """Weaccept's Transaction model"""
>>
>> # before frontend interaction
>> auth_token = models.TextField() # got from step 1
>> order_id = models.IntegerField(verbose_name="Accept's Order ID") #
>> id from step 2
>> order_url = models.CharField(max_length=255, null=True) # order_url
>> from step 2
>> billing_data = JSONField() # provided in request for paymet key,
>> step 3
>> payment_key = models.TextField() # payment_token from step 3
>> hmac = models.TextField(null=True)
>> # after (from callback)
>> success_status = models.BooleanField(default=False)
>> is_refunded = models.BooleanField(default=False)
>> reference_number = models.IntegerField(null=True)
>> processed_clbk_json = JSONField(null=True)
>>
>>
>> The cash_payment View:
>>
>> class CashPayment(APIView):
>> """Cash Payment endpoint"""
>>
>> serializer_class = serializers.CardPaymentSerializer
>> required_fields = ["amount_cents", "billing_data"]
>>
>> def post(self, request):
>> # Validate required fields
>> utils.validate(self.required_fields, request)
>> payment = utils.CashPayment(**request.data)
>> payment.prepare()
>> payment.pay_request()
>> # create a new transaction
>> models.WeacceptTransaction.objects.create(
>> merchant_order_id=payment.merchant_order_id,
>> amount=payment.amount_cents,
>> auth_token=payment.auth_res.get("token"),
>> order_id=payment.order_reg_res.get("id"),
>> order_url=payment.order_reg_res.get("order_url"),
>> billing_data=payment.billing_data,
>> payment_key=payment.payment_key_res.get("token"),
>> hmac=payment.pay_req_res.get("hmac"),
>> )
>>
>> return Response(
>> {
>> "message": "Our representative will go to the address you
>> provided "
>> "to collect the cash from you",
>> **payment.pay_req_res,
>> }
>> )
>>
>>
>> Please note: the first 3 steps are wrapped into the method `prepare()`
>> the 4th step is `pay_request()`
>>
>>
>> the callback-url endpoint (where the 5th step happens)
>>
>> class TransactionProcessedCallback(APIView):
>> """Processed callback that will recieve "TRANSACTION", "TOKEN", "ORDER
>> ",
>> "DELIVERY_STATUS" objects"""
>>
>> def post(self, request):
>> # XXX extend to handle TOKEN, DELIVERY_STATUS objects... later
>> t_obj = request.data.get("obj") # transaction object
>> incoming_hmac = request.query_params.get("hmac")
>> calculated_hmac = utils.calculate_hmac_transaction(t_obj)
>>
>> # if not equal hmac, not coming from Accept!
>> if incoming_hmac != calculated_hmac:
>> return Response(
>> {"message": "invalid data"}, status=status.
>> HTTP_400_BAD_REQUEST
>> )
>>
>> import ipdb
>>
>> ipdb.set_trace()
>> # XXX: The error happens here
>> transaction = models.WeacceptTransaction.objects.get(
>> merchant_order_id=t_obj.get("order").get("merchant_order_id")
>> )
>> transaction.success_status = bool(t_obj.get("success"))
>> transaction.is_refunded = bool(t_obj.get("is_refunded"))
>> transaction.reference_number = int(t_obj.get("data").get(
>> "transaction_no") or 1)
>> transaction.processed_clbk_json = t_obj
>> transaction.save(
>> update_fields=[
>> "success_status",
>> "is_refunded",
>> "reference_number",
>> "processed_clbk_json",
>> ]
>> )
>>
>> email = t_obj.get("order").get("shipping_data").get("email")
>> # TODO: send mail based upon success status
>> try:
>> send_mail(
>> "Transaction Processed",
>> "Your transaction is processed",
>> "SERNDER MAIL",
>> [email],
>> fail_silently=False,
>> )
>> except Exception as ex:
>> print(">>>>>>>>>>FAILED TO SEND MAIL")
>> print(ex)
>>
>> return Response({"message": "Transaction Updated!"}, status=
>> status.HTTP_200_OK)
>>
>>
>> The 6th step (redirect-url) is irrelevant here, and not included in the
>> XPAY's service for this payment option.
>>
>>
>> On Wednesday, August 21, 2019 at 2:03:20 PM UTC+2, mohammed habib wrote:
>>>
>>> Are you sure the callback request passes the right parameters ?
>>>
>>> Could you share some of your views code from the 6 steps, and your
>>> Transaction model ?
>>>
>>> Sent from my iPhone
>>>
>>> On 21 Aug 2019, at 14:46, Ahmed Shahwan <a...@shahwan.me> wrote:
>>>
>>> Hi,
>>>
>>> I have a very strange problem that I don't know why it happens.
>>> I'm creating a REST API service that wraps another REST API payment
>>> service, let's call the other services XPAY. It has various payment options
>>> (Card, eWallet, Kiosk, and Cash). The steps required to use the services
>>> (to make a transaction)
>>>
>>> 1. authentication 2. order registration 3. payment key 4. prepare
>>> frontend based on payment type 5. Callback URL 6. Redirect URL
>>>
>>> and each step depends on its predecessor. The first 4 steps are
>>> performed through HTTP Requests that I issue from my service. I store some
>>> of the information I receive in those steps in a Model called Transaction.
>>> 5th and 6th steps are Callback endpoints that I create to receive further
>>> information about the status of the transaction that I started in the first
>>> 4 steps.
>>>
>>> My endpoints design is:
>>>
>>> myservice/payment/card
>>> myservice/payment/wallet
>>> myservice/payment/kiosk
>>> myservice/payment/cash
>>>
>>> myservice/payment/callback-url
>>> myservice/payment/redirect-url
>>>
>>> These endpoints are wrappers for the payment methods available in XPAY's
>>> service that my frontend apps will use to provide those payment options for
>>> users.
>>>
>>> I implemented the first 3 endpoints with no problem. inside those
>>> endpoints, I create a transaction object with a unique id and then update
>>> it from inside the *callback-url endpoint* after I receive the
>>> information from XPAY's service. Note that it takes some time between
>>> creating the Transaction object and saving it into the database from inside
>>> my endpoint, and updating it from inside the callback url endpoint.
>>>
>>> The weird thing happens in the 4th endpoint `cash` endpoint. XPAY's
>>> service responds very quickly on my *callback-url endpoint* and when it
>>> gets to the updating step, I get *Transaction.DoesNotExist *Exception while
>>> getting the transaction object using Transaction.objects.get(id=id).
>>>
>>> After some debugging time using ipdb I found that the instance has
>>> already been saved to the database! and I can retrieve it with its id. but
>>> when I let it run ordinarily the saving operation doesn't finish until that
>>> time (I got to know that using some print() statements), which is very
>>> strange, it's impossible that my laptop is that slow!
>>>
>>> Solutions I tried:
>>> 1. atomic transaction
>>> 2. time.sleep some time after making the request and saving the
>>> transaction object to the db
>>> 3. time.sleep in the callback-url before getting the transaction from DB
>>>
>>> I checked any possible logic error related to it and there's nothing
>>> illogical.
>>>
>>> the issue is related to Postgres and how it operates, and also with
>>> Django's ORM. I don't know.
>>>
>>> Main technologies I use:
>>> Django 2.2
>>> Postgres Docker container
>>> DRF
>>>
>>> I hope someone gives me an insight into why this is happening and how to
>>> work around it.
>>>
>>> Thanks
>>>
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>>> .
>>>
>>> --
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>> .
>>
>
>
> --
> Best regards,
> *Mohammed M. Habib, PhD*
>
>
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