问题
I am using Django's native Authorization/Authentication model to manage logins for my WebApp. This creates instances of the User model.
I would like to write a simple class-based-APIView that can tell me if a specific email is already used (IE: Is there already a user with the given email in my database?). The first time this API is called, it should get the matching User object from the DB. But subsequent times it is called, it should return it from the Memcache (if and only if, the underlying row in the database is unchanged). How can I do that??
Should I inherit from generic.APIView? Why or why not? What would the view look like? In particular I want to understand how to properly do the memcaching and cache-coherency checking. Furthermore, how would this memcaching scheme work if I had another API that modified the User object?
Thanks. I was unable to find detailed idiot-proof manual on using memcaching properly in Django.
回答1:
Caching is perhaps the simplest part of django - so I'll leave that discussion to the last. The bigger problem is figuring out when your model changed.
You can decide what constitutes an update. For example, you might consider that only when a particular field is updated, then the cache is updated. Your cache update process should be limited to the writing/updating code or view. If you go about this method, then I would recommend django-model-utils and its StatusField - you can add this logic in save() method by overriding it; or implement it at the code that is updating models.
You can also do a simpler approach, that is, no matter what is updated - as long as save() is called, expire the cache and repopulate it.
The rest of the code is very simple.
Attempt to fetch the item from the cache, if the item doesn't exist (called a cache miss), then you populate the cache by fetching from the database. Otherwise, you'll get the item from the cache and then you save yourself a database hit.
The cache interface is very simple, you set('somekey', 'somevalue') you can optionally tell it when to expire the item. Then you try to get('somekey'), if this returns None, then its a cache miss (perhaps the item expired), and you have to fetch it and populate the cache. Otherwise, you'll get the cached object.
来源：https://stackoverflow.com/questions/25490194/how-to-implement-memcached-with-django-apis-while-underlying-database-objects