youknowone / ring

Python cache interface with clean API and built-in memcache & redis + asyncio support.
http://ring-cache.readthedocs.io/en/latest/
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Can't access ring-specific attributes on a cached property #180

Open striveforbest opened 3 years ago

striveforbest commented 3 years ago

I am writing a reports/calculations module and using ring to store the results of expensive calculations in redis. I started with using classmethods and it worked as expected, I was able to access ring-specific attributes (has, key, etc) but with property I cannot seem to be able to.

Here is a simplified example:


from django_redis import get_redis_connection

redis_connection = get_redis_connection('default')

class ProductCalculations:
    """
    Generate business intelligence from an organizations Product data.
    """

    def __init__(self, organization):
        self.organization = organization

    def __ring_key__(self):
        """ Required for setting a correct cache key. """
        return self.organization

    @ring.redis(redis_connection, coder='pickle')
    @property
    def products(self) -> 'QuerySet[Product]':
        return Product.objects.filter(organization=self.organization)

    @ring.redis(redis_connection, coder='pickle')
    @property
    def product_count(self) -> int:
        return self.products.count()

Upon inspecting the results, I can't seem to be able to access ring-specific attributes:

org = Organization.objects.all()[0]

calc = ProductCalculations(org)
calc.products

calc.products.has(o)

AttributeError: 'QuerySet' object has no attribute 'has'

Is this an expected behavior? How can I access ring-specific attributes on the cached property?

youknowone commented 3 years ago

Yes, it is an expected behavior. We need Ring object to access to the ring attributes, but property returns the result of function instead of ring object.

Not very neat, but I sometimes used this kind of workaround for development:

class ProductCalculations:
    @ring.redis(redis_connection, coder='pickle')
    def _products(self) -> 'QuerySet[Product]':
        return Product.objects.filter(organization=self.organization)

    @property
    def products(self):
        return self._products()

There is no way to access there for now. Maybe we need a tool like, ring.obtain(ProductCalculations, calc, 'products')

striveforbest commented 3 years ago

That's what I suspected. Thanks for the proposed workaround @youknowone . Something like obtain_ring function would be really handy. Hoping to see it in the future.

striveforbest commented 3 years ago

@youknowone so if it's a property and I don't have access to ring methods, how do I force the recache? I do need access to .update() and, potentially, .delete(). Sometimes I know the code/logic changed and I need to recache otherwise i'd be getting stale results. But Ring just returns stored/stale results because the key exists.