Django model generates hundreds of files in a saving loop-CodePudding

I'm using Django 3.8.2 on Ubuntu 18.04, I'm generating a PDF file upon saving a django model but files are generated in a loop endlessly.

I have this django model:

class Fattura(models.Model):
   ordine = models.ForeignKey(Ordine, on_delete=models.CASCADE, related_name="fatture", null=False)
   pdf = models.FileField(upload_to='archivio/fatture/%Y/%m')

the pdf field is generated when an instance is saved, based on the information contained in the related "ordine" field which is a ForeignKey to this other model:

class Ordine(models.Model):

   utente = models.ForeignKey(User, on_delete=models.CASCADE, related_name="ordini", null=False)
   data = models.DateField(auto_now_add=True)
   abbonamento = models.ForeignKey(Abbonamento, on_delete=models.PROTECT, null=False)
   importo = models.DecimalField(max_digits = 5, decimal_places = 2, null=False)

I declared every instructions for the generation of the PDF inside the save() method of my Fattura model. I'm using the library that is recommended by Django's documentation: reportlab. Here is the custom save method:

    def save(self, *args, **kwargs):

       self.count_save  = 1 # I defined this attribute which I increment to understand what is actually looping
       print("COUNT SAVE: "   str(self.count_save)) # it always grows, that's the save method being re-called

       if self.pdf._file == None:

          try:
             buffer = io.BytesIO()

             p = canvas.Canvas(buffer)

             p.drawString(100,100, str(self.ordine))
             p.showPage()
             p.save()

             buffer.seek(0)

             utente = self.ordine.utente

             num_questa_fattura = utente.ordini.count()

             nome_file = "{}_{}-{}.pdf".format(
                self.ordine.utente.first_name.lower(),
                self.ordine.utente.last_name.lower(),
                num_questa_fattura)
            
             percorso = '{}/upload/archivio/fatture/{}/{}/{}'.format(
                BASE_DIR, # from settings.py
                self.ordine.data.year,
                self.ordine.data.month,
                nome_file)

             file_temporaneo = NamedTemporaryFile(delete=True)


             file_temporaneo.write(buffer.getbuffer())

             file_temporaneo.flush()

             temp_file = File(file_temporaneo, name = nome_file)

             print(nome_file)
             print(file_temporaneo)
             print("--------------------- SAVE")

             self.pdf.save(nome_file, file_temporaneo, save=True) # saving the field
             file_temporaneo.close()


           except:

             raise ValidationError("Invoice could not be saved")

       super().save(*args, **kwargs) # saving the object to the database

When I save a Fattura object with my Django admin panel hundreds of PDF files are generated inside the folder I declared, in a loop, and no database saving really completes. No Django model object is available afterward so nothing is finally saved to the database and precisely 499 files are generated each time.

I'm not sure what is causing this loop, maybe the pdf field save method in the try statement? Or the final super().save(*args, **kwargs)? I can't remove it though, otherwise nothing would be saved if a PDF file is actually associated with one instance and I'm updating the other field ordine

Here's an excerpt from my logs

[Tue Nov 02 15:25:06.974768 2021] [wsgi:error] [pid 10050] [remote 95.x.x.x:36048] COUNT SAVE: 262
[Tue Nov 02 15:25:07.010584 2021] [wsgi:error] [pid 10050] [remote 95.x.x.x:36048] maria_rosselli-1.pdf
[Tue Nov 02 15:25:07.015778 2021] [wsgi:error] [pid 10050] [remote 95.x.x.x:36048] <tempfile._TemporaryFileWrapper object at 0x7f7b07ac0390>
[Tue Nov 02 15:25:07.020944 2021] [wsgi:error] [pid 10050] [remote 95.x.x.x:36048] --------------------- SAVE
[Tue Nov 02 15:25:07.124451 2021] [wsgi:error] [pid 10050] [remote 95.x.x.x:36048] COUNT SAVE: 263
[Tue Nov 02 15:25:07.164934 2021] [wsgi:error] [pid 10050] [remote 95.x.x.x:36048] maria_rosselli-1.pdf
[Tue Nov 02 15:25:07.170144 2021] [wsgi:error] [pid 10050] [remote 95.x.x.x:36048] <tempfile._TemporaryFileWrapper object at 0x7f7b07ac0e48>
[Tue Nov 02 15:25:07.175250 2021] [wsgi:error] [pid 10050] [remote 95.x.x.x:36048] --------------------- SAVE
[Tue Nov 02 15:25:07.253426 2021] [wsgi:error] [pid 10050] [remote 95.x.x.x:36048] COUNT SAVE: 264
[Tue Nov 02 15:25:07.286589 2021] [wsgi:error] [pid 10050] [remote 95.x.x.x:36048] maria_rosselli-1.pdf
[Tue Nov 02 15:25:07.291734 2021] [wsgi:error] [pid 10050] [remote 95.x.x.x:36048] <tempfile._TemporaryFileWrapper object at 0x7f7b07ac0e10>
[Tue Nov 02 15:25:07.296894 2021] [wsgi:error] [pid 10050] [remote 95.x.x.x:36048] --------------------- SAVE

CodePudding user response：

you need to set save to False to call the model instance's save methid again when saving the pdf:

self.pdf.save(nome_file, file_temporaneo, save=False)