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flaskcache.py
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"Flask-Caching compatible disk and file backed cache."
from flask_caching.backends.cache import BaseCache
from .fanout import FanoutCache, FanoutMixin
class FlaskCache(BaseCache, FanoutMixin):
def __init__(self, directory, params=None, default_timeout=300):
"""Initialize FlaskCache instance.
:param str directory: cache directory
:param dict params: cache parameters
"""
super().__init__(default_timeout=default_timeout)
params = {} if params is None else params
shards = params.get('SHARDS', 8)
timeout = params.get('DATABASE_TIMEOUT', 0.010)
options = params.get('OPTIONS', {})
self._cache = FanoutCache(directory, shards, timeout, **options)
# TODO: Complete the methods below and add tests.
def get(self, key):
"""Look up key in the cache and return the value for it.
:param key: the key to be looked up.
:returns: The value if it exists and is readable, else ``None``.
"""
return None
def delete(self, key):
"""Delete `key` from the cache.
:param key: the key to delete.
:returns: Whether the key existed and has been deleted.
:rtype: boolean
"""
return True
def get_many(self, *keys):
"""Returns a list of values for the given keys.
For each key an item in the list is created::
foo, bar = cache.get_many("foo", "bar")
Has the same error handling as :meth:`get`.
:param keys: The function accepts multiple keys as positional
arguments.
"""
return [self.get(k) for k in keys]
def get_dict(self, *keys):
"""Like :meth:`get_many` but return a dict::
d = cache.get_dict("foo", "bar")
foo = d["foo"]
bar = d["bar"]
:param keys: The function accepts multiple keys as positional
arguments.
"""
return dict(zip(keys, self.get_many(*keys)))
def set(self, key, value, timeout=None):
"""Add a new key/value to the cache (overwrites value, if key already
exists in the cache).
:param key: the key to set
:param value: the value for the key
:param timeout: the cache timeout for the key in seconds (if not
specified, it uses the default timeout). A timeout of
0 indicates that the cache never expires.
:returns: ``True`` if key has been updated, ``False`` for backend
errors. Pickling errors, however, will raise a subclass of
``pickle.PickleError``.
:rtype: boolean
"""
return True
def add(self, key, value, timeout=None):
"""Works like :meth:`set` but does not overwrite the values of already
existing keys.
:param key: the key to set
:param value: the value for the key
:param timeout: the cache timeout for the key in seconds (if not
specified, it uses the default timeout). A timeout of
0 idicates that the cache never expires.
:returns: Same as :meth:`set`, but also ``False`` for already
existing keys.
:rtype: boolean
"""
return True
def set_many(self, mapping, timeout=None):
"""Sets multiple keys and values from a mapping.
:param mapping: a mapping with the keys/values to set.
:param timeout: the cache timeout for the key in seconds (if not
specified, it uses the default timeout). A timeout of
0 idicates that the cache never expires.
:returns: Whether all given keys have been set.
:rtype: boolean
"""
rv = True
for key, value in iteritems_wrapper(mapping):
if not self.set(key, value, timeout):
rv = False
return rv
def delete_many(self, *keys):
"""Deletes multiple keys at once.
:param keys: The function accepts multiple keys as positional
arguments.
:returns: Whether all given keys have been deleted.
:rtype: boolean
"""
if self.ignore_errors:
return all([self.delete(key) for key in keys])
return all(self.delete(key) for key in keys)
def has(self, key):
"""Checks if a key exists in the cache without returning it. This is a
cheap operation that bypasses loading the actual data on the backend.
This method is optional and may not be implemented on all caches.
:param key: the key to check
"""
raise NotImplementedError(
"%s doesn't have an efficient implementation of `has`. That "
"means it is impossible to check whether a key exists without "
"fully loading the key's data. Consider using `self.get` "
"explicitly if you don't care about performance."
)
def clear(self):
"""Clears the cache. Keep in mind that not all caches support
completely clearing the cache.
:returns: Whether the cache has been cleared.
:rtype: boolean
"""
return True
def inc(self, key, delta=1):
"""Increments the value of a key by `delta`. If the key does
not yet exist it is initialized with `delta`.
For supporting caches this is an atomic operation.
:param key: the key to increment.
:param delta: the delta to add.
:returns: The new value or ``None`` for backend errors.
"""
value = (self.get(key) or 0) + delta
return value if self.set(key, value) else None
def dec(self, key, delta=1):
"""Decrements the value of a key by `delta`. If the key does
not yet exist it is initialized with `-delta`.
For supporting caches this is an atomic operation.
:param key: the key to increment.
:param delta: the delta to subtract.
:returns: The new value or `None` for backend errors.
"""
value = (self.get(key) or 0) - delta
return value if self.set(key, value) else None
def make_cache(app, config, args, kwargs):
return FlaskCache(*args, **kwargs)