Custom Cache Backends

You are able to easily add your own custom cache backends by exposing a function that can instantiate and return a cache object. CACHE_TYPE will be the import string to your custom cache type. If not a subclass of BaseCache, Flask-Caching will call it with three arguments:

• app, the Flask application object the cache is being initialized for

• args, the value of the CACHE_ARGS configuration option

• kwargs, the value of the CACHE_OPTIONS configuration option

Note

args and kwargs are not expanded when instantiating the cache object, i.e. they are not passed in as *args and **kwargs, but they are the exact value of the CACHE_ARGS and CACHE_OPTIONS configuration options (CACHE_ARGS, however, is converted to a list).

Your custom cache should, however, subclass the BaseCache class so it provides all the necessary methods to be usable.

Changelog

Changed in version 1.9.1: If your custom cache type is a subclass of BaseCache, Flask-Caching will, instead of directly instantiating the class, call its factory class method with the same args as listed above. Unless overridden, BaseCache.factory simply instantiates the object without passing any arguments to it. Built-in cache classes have overridden this to mimic the old, function based cache isntantiation, so if you subclassed something that is not BaseCache, you may want to consult the source code to see if your class is still compatible.

An example implementation:

#: the_app/custom.py
class RedisCache(BaseCache):
    def __init__(self, servers, default_timeout=500):
        pass

    @classmethod
    def factory(cls, app, args, kwargs):
        args.append(app.config['REDIS_SERVERS'])

        return cls(*args, **kwargs)

With this example, your CACHE_TYPE might be the_app.custom.RedisCache

CACHE_TYPE doesn’t have to directly point to a cache class, though. An example PylibMC cache implementation to change binary setting and provide username/password if SASL is enabled on the library:

#: the_app/custom.py
def pylibmccache(app, config, args, kwargs):
    return pylibmc.Client(servers=config['CACHE_MEMCACHED_SERVERS'],
                          username=config['CACHE_MEMCACHED_USERNAME'],
                          password=config['CACHE_MEMCACHED_PASSWORD'],
                          binary=True)

With this example, your CACHE_TYPE might be the_app.custom.pylibmccache