KeyError exception on retrieving cached model

[mmoallemi99]

Hi People,

I have this model called Palette and I'm using Django 2.2 latest patch, Django Cacheops 4.2
and once a week I have this exception breaking my API:

KeyError: 'palette'
File "django/db/models/fields/related_descriptors.py", line 164, in get
rel_obj = self.field.get_cached_value(instance)
File "django/db/models/fields/mixins.py", line 13, in get_cached_value
return instance._state.fields_cache[cache_name]
Palette.DoesNotExist: Palette matching query does not exist.
File "django/core/handlers/exception.py", line 34, in inner
response = get_response(request)
File "django/core/handlers/base.py", line 115, in _get_response
response = self.process_exception_by_middleware(e, request)
File "django/core/handlers/base.py", line 113, in _get_response
response = wrapped_callback(request, *callback_args, **callback_kwargs)
File "django/views/decorators/csrf.py", line 54, in wrapped_view
return view_func(*args, **kwargs)
File "rest_framework/viewsets.py", line 114, in view
return self.dispatch(request, *args, **kwargs)
File "rest_framework/views.py", line 505, in dispatch
response = self.handle_exception(exc)
File "rest_framework/views.py", line 465, in handle_exception
self.raise_uncaught_exception(exc)
File "rest_framework/views.py", line 476, in raise_uncaught_exception
raise exc
File "rest_framework/views.py", line 502, in dispatch
response = handler(request, *args, **kwargs)
File "palettes/views.py", line 190, in list
return super(PaletteViewSet, self).list(request, *args, **kwargs)
File "rest_framework/mixins.py", line 43, in list
return self.get_paginated_response(serializer.data)
File "rest_framework/serializers.py", line 760, in data
ret = super().data
File "rest_framework/serializers.py", line 260, in data
self._data = self.to_representation(self.instance)
File "rest_framework/serializers.py", line 678, in to_representation
self.child.to_representation(item) for item in iterable
File "rest_framework/serializers.py", line 678, in
self.child.to_representation(item) for item in iterable
File "rest_framework/serializers.py", line 529, in to_representation
ret[field.field_name] = field.to_representation(attribute)
File "rest_framework/fields.py", line 1905, in to_representation
return method(value)
File "palettes/serializers.py", line 367, in get_colors
return ColorsUsedInPaletteSerializer(qs, many=True, context=self.context).data[:5]
File "rest_framework/serializers.py", line 760, in data
ret = super().data
File "rest_framework/serializers.py", line 260, in data
self._data = self.to_representation(self.instance)
File "palettes/serializers.py", line 76, in to_representation
return super(PaletteItemListSerializer, self).to_representation(data)
File "rest_framework/serializers.py", line 678, in to_representation
self.child.to_representation(item) for item in iterable
File "rest_framework/serializers.py", line 678, in
self.child.to_representation(item) for item in iterable
File "rest_framework/serializers.py", line 529, in to_representation
ret[field.field_name] = field.to_representation(attribute)
File "rest_framework/fields.py", line 1905, in to_representation
return method(value)
File "cacheops/query.py", line 115, in wrapper
cache_key = prefix + 'as:' + key_func(func, args, kwargs, key_extra)
File "cacheops/utils.py", line 92, in func_cache_key
return md5hex(json.dumps(factors, sort_keys=True, default=obj_key))
File "init.py", line 238, in dumps
**kw).encode(obj)
File "json/encoder.py", line 199, in encode
chunks = self.iterencode(o, _one_shot=True)
File "json/encoder.py", line 257, in iterencode
return _iterencode(o, 0)
File "cacheops/utils.py", line 85, in obj_key
return str(obj)
File "rest_framework/serializers.py", line 537, in repr
return representation.serializer_repr(self, indent=1)
File "rest_framework/utils/representation.py", line 71, in serializer_repr
ret = field_repr(serializer, force_many) + ':'
File "rest_framework/utils/representation.py", line 54, in field_repr
arg_string = ', '.join([smart_repr(val) for val in field._args])
File "rest_framework/utils/representation.py", line 54, in
arg_string = ', '.join([smart_repr(val) for val in field._args])
File "rest_framework/utils/representation.py", line 33, in smart_repr
value = repr(value)
File "django/db/models/query.py", line 253, in repr
return '<%s %r>' % (self.class.name, data)
File "django/db/models/base.py", line 519, in repr
return '<%s: %s>' % (self.class.name, self)
File "palettes/models.py", line 140, in str
return f'{self.color} in {self.palette}'
File "django/db/models/fields/related_descriptors.py", line 178, in get
rel_obj = self.get_object(instance)
File "django/db/models/fields/related_descriptors.py", line 145, in get_object
return qs.get(self.field.get_reverse_related_filter(instance))
File "cacheops/query.py", line 359, in get
return qs._no_monkey.get(qs, *args, **kwargs)
File "django/db/models/query.py", line 408, in get
self.model._meta.object_name

And when I apply invalidate_model on Palette model, the issue is fixed.
I would deeply appreciate any help on this.

[Suor]

Can you try latest casheops?

[mmoallemi99]

Updated to django-cacheops 5.0.1

[Suor]

The error itself is not in casheops code, judging by your stack trace. Do you use other caching solution with it?

[Suor]

If not can you write a test illustrating your issue? The instruction is at the end of README.

[Suor]

Looks like a dup of #348 after some though. Bad stack trace conceals it.