mirror of https://github.com/morpheus65535/bazarr
216 lines
6.2 KiB
Python
216 lines
6.2 KiB
Python
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import operator
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from ..util.compat import py3k
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class NoValue(object):
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"""Describe a missing cache value.
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The :attr:`.NO_VALUE` module global
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should be used.
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"""
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@property
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def payload(self):
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return self
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def __repr__(self):
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"""Ensure __repr__ is a consistent value in case NoValue is used to
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fill another cache key.
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"""
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return '<dogpile.cache.api.NoValue object>'
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if py3k:
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def __bool__(self): # pragma NO COVERAGE
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return False
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else:
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def __nonzero__(self): # pragma NO COVERAGE
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return False
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NO_VALUE = NoValue()
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"""Value returned from ``get()`` that describes
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a key not present."""
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class CachedValue(tuple):
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"""Represent a value stored in the cache.
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:class:`.CachedValue` is a two-tuple of
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``(payload, metadata)``, where ``metadata``
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is dogpile.cache's tracking information (
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currently the creation time). The metadata
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and tuple structure is pickleable, if
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the backend requires serialization.
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"""
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payload = property(operator.itemgetter(0))
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"""Named accessor for the payload."""
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metadata = property(operator.itemgetter(1))
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"""Named accessor for the dogpile.cache metadata dictionary."""
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def __new__(cls, payload, metadata):
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return tuple.__new__(cls, (payload, metadata))
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def __reduce__(self):
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return CachedValue, (self.payload, self.metadata)
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class CacheBackend(object):
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"""Base class for backend implementations."""
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key_mangler = None
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"""Key mangling function.
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May be None, or otherwise declared
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as an ordinary instance method.
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"""
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def __init__(self, arguments): # pragma NO COVERAGE
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"""Construct a new :class:`.CacheBackend`.
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Subclasses should override this to
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handle the given arguments.
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:param arguments: The ``arguments`` parameter
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passed to :func:`.make_registry`.
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"""
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raise NotImplementedError()
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@classmethod
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def from_config_dict(cls, config_dict, prefix):
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prefix_len = len(prefix)
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return cls(
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dict(
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(key[prefix_len:], config_dict[key])
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for key in config_dict
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if key.startswith(prefix)
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)
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)
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def has_lock_timeout(self):
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return False
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def get_mutex(self, key):
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"""Return an optional mutexing object for the given key.
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This object need only provide an ``acquire()``
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and ``release()`` method.
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May return ``None``, in which case the dogpile
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lock will use a regular ``threading.Lock``
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object to mutex concurrent threads for
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value creation. The default implementation
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returns ``None``.
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Different backends may want to provide various
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kinds of "mutex" objects, such as those which
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link to lock files, distributed mutexes,
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memcached semaphores, etc. Whatever
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kind of system is best suited for the scope
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and behavior of the caching backend.
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A mutex that takes the key into account will
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allow multiple regenerate operations across
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keys to proceed simultaneously, while a mutex
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that does not will serialize regenerate operations
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to just one at a time across all keys in the region.
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The latter approach, or a variant that involves
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a modulus of the given key's hash value,
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can be used as a means of throttling the total
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number of value recreation operations that may
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proceed at one time.
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"""
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return None
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def get(self, key): # pragma NO COVERAGE
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"""Retrieve a value from the cache.
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The returned value should be an instance of
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:class:`.CachedValue`, or ``NO_VALUE`` if
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not present.
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"""
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raise NotImplementedError()
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def get_multi(self, keys): # pragma NO COVERAGE
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"""Retrieve multiple values from the cache.
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The returned value should be a list, corresponding
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to the list of keys given.
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.. versionadded:: 0.5.0
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"""
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raise NotImplementedError()
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def set(self, key, value): # pragma NO COVERAGE
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"""Set a value in the cache.
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The key will be whatever was passed
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to the registry, processed by the
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"key mangling" function, if any.
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The value will always be an instance
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of :class:`.CachedValue`.
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"""
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raise NotImplementedError()
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def set_multi(self, mapping): # pragma NO COVERAGE
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"""Set multiple values in the cache.
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``mapping`` is a dict in which
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the key will be whatever was passed
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to the registry, processed by the
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"key mangling" function, if any.
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The value will always be an instance
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of :class:`.CachedValue`.
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When implementing a new :class:`.CacheBackend` or cutomizing via
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:class:`.ProxyBackend`, be aware that when this method is invoked by
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:meth:`.Region.get_or_create_multi`, the ``mapping`` values are the
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same ones returned to the upstream caller. If the subclass alters the
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values in any way, it must not do so 'in-place' on the ``mapping`` dict
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-- that will have the undesirable effect of modifying the returned
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values as well.
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.. versionadded:: 0.5.0
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"""
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raise NotImplementedError()
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def delete(self, key): # pragma NO COVERAGE
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"""Delete a value from the cache.
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The key will be whatever was passed
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to the registry, processed by the
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"key mangling" function, if any.
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The behavior here should be idempotent,
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that is, can be called any number of times
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regardless of whether or not the
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key exists.
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"""
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raise NotImplementedError()
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def delete_multi(self, keys): # pragma NO COVERAGE
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"""Delete multiple values from the cache.
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The key will be whatever was passed
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to the registry, processed by the
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"key mangling" function, if any.
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The behavior here should be idempotent,
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that is, can be called any number of times
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regardless of whether or not the
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key exists.
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.. versionadded:: 0.5.0
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"""
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raise NotImplementedError()
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