# coding=utf-8
import logging
[docs]class ResourceCache(object):
"""A :class:`~oldman.management.cache.ResourceCache` object caches
:class:`~oldman.resource.Resource` objects.
It interfaces a :class:`dogpile.cache.region.CacheRegion` front-end object.
If not `None`, `cache_region` must be already configured, i.e. mapped to a back-end
(like `Memcache <http://memcached.org/>`_ or `Redis <http://redis.io/>`_).
See `the official list of back-ends
<http://dogpilecache.readthedocs.org/en/latest/api.html#module-dogpile.cache.backends.memory>`_ supported
by `dogpile.cache <https://bitbucket.org/zzzeek/dogpile.cache>`_.
When `cache_region` is None, no effective caching is done.
However, methods :func:`~oldman.management.cache.ResourceCache.get_resource`,
:func:`~oldman.management.cache.ResourceCache.set_resource`
and :func:`~oldman.management.cache.ResourceCache.remove_resource` can still safely be
called. They just have no effect.
:param cache_region: :class:`dogpile.cache.region.CacheRegion` object.
This object must already be configured.
Defaults to None (no cache).
"""
def __init__(self, cache_region):
self._region = cache_region
self._logger = logging.getLogger(__name__)
@property
[docs] def cache_region(self):
""":class:`dogpile.cache.region.CacheRegion` object. May be `None`."""
return self._region
[docs] def is_active(self):
""":return: `True` if the `cache_region` is active."""
return self._region is not None
[docs] def change_cache_region(self, cache_region):
"""Replaces the `cache_region` attribute.
:param cache_region: :class:`dogpile.cache.region.CacheRegion` object.
May be `None`.
"""
self._region = cache_region
[docs] def get_resource(self, id):
"""Gets a :class:`~oldman.resource.Resource` object from the cache.
:param id: IRI of the resource.
:return: :class:`~oldman.resource.Resource` object or `None` if not found.
"""
if id is None or self._region is None:
return None
resource = self._region.get(unicode(id))
if resource:
self._logger.debug(u"%s found in the cache." % resource.id)
return resource
return None
[docs] def set_resource(self, resource):
"""Adds or updates a :class:`~oldman.resource.Resource` object in the cache.
Its key is its `ìd`.
:param resource: :class:`~oldman.resource.Resource` object to add to the cache (or update).
"""
if self._region is not None:
self._region.set(unicode(resource.id), resource)
self._logger.debug(u"%s cached." % resource.id)
[docs] def remove_resource(self, resource):
"""Removes a :class:`~oldman.resource.Resource` object from the cache.
Indempotent (no problem if the :class:`~oldman.resource.Resource` object is not the
cache). Does nothing if `cache_region` is `None`.
:param resource: :class:`~oldman.resource.Resource` object to remove from the cache."""
if self._region is not None:
self._region.delete(unicode(resource.id))
self._logger.debug(u"%s removed from the cache." % resource.id)
[docs] def remove_resource_from_id(self, id):
""":func:`~oldman.management.cache.ResourceCache.remove_resource` is usually preferred.
Indempotent and does nothing if `cache_region` is `None`.
:param id: IRI of the resource to remove from the cache.
"""
if self._region is not None:
self._region.delete(unicode(id))
self._logger.debug(u"%s removed from the cache." % id)
[docs] def invalidate_cache(self):
"""See :func:`dogpile.cache.region.CacheRegion.invalidate`.
.. admonition:: Cache invalidation
Please note that this method is not supported by some :class:`dogpile.cache.api.CacheBackend`
objects. In such a case, this method has no effect so entries must be removed **explicitly**
from their keys.
"""
if self._region is not None:
self._region.invalidate()