Django view html to pdf executed twice - django

Question

I have following Class to generate a pdf file where I use django-renderpdf to generate a pdf from a html template. But the view is executed twice and an error is thrown.
My class:
class WeeklyMetre(PDFView):
template_name = 'reports/invoice/weekly_metre.html'
allow_force_html = True
prompt_download = True
#property
def download_name(self) -> str:
invoice = Invoice.objects.get(pk=self.kwargs['pk'])
return f"WeeklyMetre_{invoice.invoice_number}.pdf"
def get_context_data(self, *args, **kwargs):
context = super().get_context_data(*args, **kwargs)
invoice = Invoice.objects.get(pk=self.kwargs.get('pk'))
market_labor_specifications = _getWeeklyMetreData(invoice=invoice)
# calculate reported items: reported market_labor_specifications
# invoiced specifications which are validated in invoice-period
# but labor_date before invoice-period
reported_mls = MarketLaborSpecification.objects.filter(invoice_id=self.kwargs.get('pk'), market_labor__labor_date__lt=invoice.period_from) \
.values('market_labor__labor_date', 'specification__position', 'specification__name') \
.order_by('market_labor__labor_date', 'specification__position', 'specification__name') \
.annotate(sum_pos=Sum('validated_quantity'))
context.update({
'invoice': invoice,
'market_labor_specifications': market_labor_specifications,
'reported_mlss': reported_mls
})
print('context data', datetime.datetime.now())
return context
Between the two excutions I have following error:
[01/Feb/2021 07:16:38] "GET /reports/invoice/select/17/ HTTP/1.1" 200 1414
context data 2021-02-01 07:16:44.835695
[01/Feb/2021 07:16:45] "GET /reports/weekly/metre/17/ HTTP/1.1" 200 58063
----------------------------------------
Exception happened during processing of request from ('127.0.0.1', 60114)
Traceback (most recent call last):
File "/usr/lib/python3.6/socketserver.py", line 654, in process_request_thread
self.finish_request(request, client_address)
File "/usr/lib/python3.6/socketserver.py", line 364, in finish_request
self.RequestHandlerClass(request, client_address, self)
File "/usr/lib/python3.6/socketserver.py", line 724, in __init__
self.handle()
File "/home/t3tr4ktys/python-virtual-environments/BillOfQuantities/lib/python3.6/site-packages/django/core/servers/basehttp.py", line 174, in handle
self.handle_one_request()
File "/home/t3tr4ktys/python-virtual-environments/BillOfQuantities/lib/python3.6/site-packages/django/core/servers/basehttp.py", line 182, in handle_one_request
self.raw_requestline = self.rfile.readline(65537)
File "/usr/lib/python3.6/socket.py", line 586, in readinto
return self._sock.recv_into(b)
ConnectionResetError: [Errno 104] Connection reset by peer
----------------------------------------
context data 2021-02-01 07:16:47.544189
[01/Feb/2021 07:16:48] "GET /reports/weekly/metre/17/ HTTP/1.1" 200 58063
First of all I don't know why it is executed twice and on the second execution the user is no more authenticated. At the end the pdf is generated well but I cannot apply the LoginRequiredMixin. More informations will be provided if needed and thank you for any help.

Answer 1

Looks like you closed tab in browser or browser stopped to accept response from server in some another way. But web server haven't stopped it's renderring and still generates response, but do not have whom to response. That's why you see:
ConnectionResetError: [Errno 104] Connection reset by peer
After that browser does retry with page reload and you see the second request in logs.
So, you need to understand why it happens. See what browser logs and Dev.Tools will show you (statuses, response and etc.).
P.S. About LoginRequiredMixin - don't know probably some internal things of browser caused with that "retry", but I believe it still should send cookies and session_id.

Answer 2

I believe I've experienced something like this.
The problem is that when you call your endpoint you call it in the URL without a '/' at the end causing DRF to return 301
that redirects you to the same path but with '/' at the end. The problem with that, that after the redirect you lose your headers and cookies and thus become unauthenticated.
That also explains why you can see 2 calls.
So basically if you have a call like this:
api/viewset/dosomethngs
to:
api/viewset/dosomethngs/