Custom serializer.py Connection closed by server - django

Question

What i am trying to do - is to save post to the model with custom conditions. But each time im trying to save - i receive this error django.db.utils.IntegrityError: null value in column violates not-null constraint
So far, i have tried editing my models, and adding null=True in parameters, but it doesn't seem to help. So what is the best way to solve the problem here? Also have to mention that it doesnt save event_code at all. But even if i will enter that code by hand - it still will give me "Connection closed by server." Also i dont know what this exactly means: Exception Location: /usr/local/lib/python3.11/site-packages/redis/asyncio/connection.py,
serialier.py:
class EventSerializers(serializers.ModelSerializer):
class Meta:
model = Events
fields = ["cam_id", "vehicle_plate", "is_recognition", "is_confirmation", "vehicle_plate", "transit_block_time_min"]
def save(self, **kwargs):
instance = super().save(**kwargs)
is_recognition = instance.is_recognition
is_confirmation = instance.is_confirmation
vehicle_plate = instance.vehicle_plate
if CarParkItem.objects.filter(vehicle_plate=vehicle_plate).exists():
instance.event_code = 1008
elif BlackListItem.objects.filter(vehicle_plate=vehicle_plate).exists():
instance.event_code = 1004
elif is_recognition == False:
instance.event_code = 1003
elif is_recognition == True and is_confirmation == False:
instance.event_code = 1006
elif is_recognition == True and is_confirmation == True:
instance.event_code = 1007
instance.save()
return instance
I have read about different approaches, but still dont know where and how to do it the best.
models that are used for it:
class BlackListItem(models.Model):
vehicle_plate = models.CharField(max_length=999, db_index=True)
valid_until = models.DateTimeField(db_index=True)
description = models.CharField(max_length=999)
def __str__(self):
return self.vehicle_plate
class CarParkItem(models.Model):
vehicle_plate = models.CharField(max_length=999, db_index=True)
valid_until = models.DateTimeField(db_index=True)
description = models.CharField(max_length=999)
def __str__(self):
return self.vehicle_plate
class WorkingMode(models.Model):
PASSMODE_CHOICES = [
('pay_by_hour', 'pay_by_hour'),
('pay_by_interval', 'pay_by_interval'),
('closed', 'closed'),
]
time_lte_hour = models.IntegerField() # <
time_gte_hour = models.IntegerField() # > от
time_lte_min = models.IntegerField() # < до
time_gte_min = models.IntegerField() # >
pass_mode = models.CharField(max_length=999, choices=PASSMODE_CHOICES) # pay_by_hour | pay_by_interval | closed
free_time_min = models.IntegerField(default=0)
interval = models.IntegerField(default=0)
transit_block_time_min = models.IntegerField(default=0, null=True)
price = models.IntegerField(default=0)
entry_fee = models.IntegerField(default=0)
description = models.CharField(max_length=999)
def __str__(self):
return self.pass_mode
and views.py:
class EventModeSet(viewsets.ModelViewSet):
queryset = Events.objects.all()
serializer_class = EventSerializers

Answer 1

it appears that the method def save should have been async as well, because my consumers.py code is also async. So i just added this:
async def save(self, **kwargs):
instance = super().save(**kwargs)
is_recognition = instance.is_recognition
is_confirmation = instance.is_confirmation
vehicle_plate = instance.vehicle_plate
if CarParkItem.objects.filter(vehicle_plate=vehicle_plate).exists():
instance.event_code = 1008
elif BlackListItem.objects.filter(vehicle_plate=vehicle_plate).exists():
instance.event_code = 1004
elif is_recognition == False:
instance.event_code = 1003
elif is_recognition == True and is_confirmation == False:
instance.event_code = 1006
elif is_recognition == True and is_confirmation == True:
instance.event_code = 1007
await asyncio.sleep(0)
instance.save()
As i understand asyncio.sleep(0) is letting other coroutines (from consumers.py) to finish their job before going to next sten instance.save. The fact that other coroutines were not awaited and were not finished - was causing disconnect issue