/usr/lib/python2.7/dist-packages/beaker/cache.py is in python-beaker 1.6.4-2.
This file is owned by root:root, with mode 0o644.
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for Beaker caching.
Included are the :class:`.Cache` and :class:`.CacheManager` classes,
as well as the function decorators :func:`.region_decorate`,
:func:`.region_invalidate`.
"""
import warnings
import beaker.container as container
import beaker.util as util
from beaker.crypto.util import sha1
from beaker.exceptions import BeakerException, InvalidCacheBackendError
from beaker.synchronization import _threading
import beaker.ext.memcached as memcached
import beaker.ext.database as database
import beaker.ext.sqla as sqla
import beaker.ext.google as google
# Initialize the cache region dict
cache_regions = {}
"""Dictionary of 'region' arguments.
A "region" is a string name that refers to a series of cache
configuration arguments. An application may have multiple
"regions" - one which stores things in a memory cache, one
which writes data to files, etc.
The dictionary stores string key names mapped to dictionaries
of configuration arguments. Example::
from beaker.cache import cache_regions
cache_regions.update({
'short_term':{
'expire':'60',
'type':'memory'
},
'long_term':{
'expire':'1800',
'type':'dbm',
'data_dir':'/tmp',
}
})
"""
cache_managers = {}
class _backends(object):
initialized = False
def __init__(self, clsmap):
self._clsmap = clsmap
self._mutex = _threading.Lock()
def __getitem__(self, key):
try:
return self._clsmap[key]
except KeyError, e:
if not self.initialized:
self._mutex.acquire()
try:
if not self.initialized:
self._init()
self.initialized = True
return self._clsmap[key]
finally:
self._mutex.release()
raise e
def _init(self):
try:
import pkg_resources
# Load up the additional entry point defined backends
for entry_point in pkg_resources.iter_entry_points('beaker.backends'):
try:
namespace_manager = entry_point.load()
name = entry_point.name
if name in self._clsmap:
raise BeakerException("NamespaceManager name conflict,'%s' "
"already loaded" % name)
self._clsmap[name] = namespace_manager
except (InvalidCacheBackendError, SyntaxError):
# Ignore invalid backends
pass
except:
import sys
from pkg_resources import DistributionNotFound
# Warn when there's a problem loading a NamespaceManager
if not isinstance(sys.exc_info()[1], DistributionNotFound):
import traceback
from StringIO import StringIO
tb = StringIO()
traceback.print_exc(file=tb)
warnings.warn(
"Unable to load NamespaceManager "
"entry point: '%s': %s" % (
entry_point,
tb.getvalue()),
RuntimeWarning, 2)
except ImportError:
pass
# Initialize the basic available backends
clsmap = _backends({
'memory': container.MemoryNamespaceManager,
'dbm': container.DBMNamespaceManager,
'file': container.FileNamespaceManager,
'ext:memcached': memcached.MemcachedNamespaceManager,
'ext:database': database.DatabaseNamespaceManager,
'ext:sqla': sqla.SqlaNamespaceManager,
'ext:google': google.GoogleNamespaceManager,
})
def cache_region(region, *args):
"""Decorate a function such that its return result is cached,
using a "region" to indicate the cache arguments.
Example::
from beaker.cache import cache_regions, cache_region
# configure regions
cache_regions.update({
'short_term':{
'expire':'60',
'type':'memory'
}
})
@cache_region('short_term', 'load_things')
def load(search_term, limit, offset):
'''Load from a database given a search term, limit, offset.'''
return database.query(search_term)[offset:offset + limit]
The decorator can also be used with object methods. The ``self``
argument is not part of the cache key. This is based on the
actual string name ``self`` being in the first argument
position (new in 1.6)::
class MyThing(object):
@cache_region('short_term', 'load_things')
def load(self, search_term, limit, offset):
'''Load from a database given a search term, limit, offset.'''
return database.query(search_term)[offset:offset + limit]
Classmethods work as well - use ``cls`` as the name of the class argument,
and place the decorator around the function underneath ``@classmethod``
(new in 1.6)::
class MyThing(object):
@classmethod
@cache_region('short_term', 'load_things')
def load(cls, search_term, limit, offset):
'''Load from a database given a search term, limit, offset.'''
return database.query(search_term)[offset:offset + limit]
:param region: String name of the region corresponding to the desired
caching arguments, established in :attr:`.cache_regions`.
:param \*args: Optional ``str()``-compatible arguments which will uniquely
identify the key used by this decorated function, in addition
to the positional arguments passed to the function itself at call time.
This is recommended as it is needed to distinguish between any two functions
or methods that have the same name (regardless of parent class or not).
.. note::
The function being decorated must only be called with
positional arguments, and the arguments must support
being stringified with ``str()``. The concatenation
of the ``str()`` version of each argument, combined
with that of the ``*args`` sent to the decorator,
forms the unique cache key.
.. note::
When a method on a class is decorated, the ``self`` or ``cls``
argument in the first position is
not included in the "key" used for caching. New in 1.6.
"""
return _cache_decorate(args, None, None, region)
def region_invalidate(namespace, region, *args):
"""Invalidate a cache region corresponding to a function
decorated with :func:`.cache_region`.
:param namespace: The namespace of the cache to invalidate. This is typically
a reference to the original function (as returned by the :func:`.cache_region`
decorator), where the :func:`.cache_region` decorator applies a "memo" to
the function in order to locate the string name of the namespace.
:param region: String name of the region used with the decorator. This can be
``None`` in the usual case that the decorated function itself is passed,
not the string name of the namespace.
:param args: Stringifyable arguments that are used to locate the correct
key. This consists of the ``*args`` sent to the :func:`.cache_region`
decorator itself, plus the ``*args`` sent to the function itself
at runtime.
Example::
from beaker.cache import cache_regions, cache_region, region_invalidate
# configure regions
cache_regions.update({
'short_term':{
'expire':'60',
'type':'memory'
}
})
@cache_region('short_term', 'load_data')
def load(search_term, limit, offset):
'''Load from a database given a search term, limit, offset.'''
return database.query(search_term)[offset:offset + limit]
def invalidate_search(search_term, limit, offset):
'''Invalidate the cached storage for a given search term, limit, offset.'''
region_invalidate(load, 'short_term', 'load_data', search_term, limit, offset)
Note that when a method on a class is decorated, the first argument ``cls``
or ``self`` is not included in the cache key. This means you don't send
it to :func:`.region_invalidate`::
class MyThing(object):
@cache_region('short_term', 'some_data')
def load(self, search_term, limit, offset):
'''Load from a database given a search term, limit, offset.'''
return database.query(search_term)[offset:offset + limit]
def invalidate_search(self, search_term, limit, offset):
'''Invalidate the cached storage for a given search term, limit, offset.'''
region_invalidate(self.load, 'short_term', 'some_data', search_term, limit, offset)
"""
if callable(namespace):
if not region:
region = namespace._arg_region
namespace = namespace._arg_namespace
if not region:
raise BeakerException("Region or callable function "
"namespace is required")
else:
region = cache_regions[region]
cache = Cache._get_cache(namespace, region)
_cache_decorator_invalidate(cache, region['key_length'], args)
class Cache(object):
"""Front-end to the containment API implementing a data cache.
:param namespace: the namespace of this Cache
:param type: type of cache to use
:param expire: seconds to keep cached data
:param expiretime: seconds to keep cached data (legacy support)
:param starttime: time when cache was cache was
"""
def __init__(self, namespace, type='memory', expiretime=None,
starttime=None, expire=None, **nsargs):
try:
cls = clsmap[type]
if isinstance(cls, InvalidCacheBackendError):
raise cls
except KeyError:
raise TypeError("Unknown cache implementation %r" % type)
self.namespace_name = namespace
self.namespace = cls(namespace, **nsargs)
self.expiretime = expiretime or expire
self.starttime = starttime
self.nsargs = nsargs
@classmethod
def _get_cache(cls, namespace, kw):
key = namespace + str(kw)
try:
return cache_managers[key]
except KeyError:
cache_managers[key] = cache = cls(namespace, **kw)
return cache
def put(self, key, value, **kw):
self._get_value(key, **kw).set_value(value)
set_value = put
def get(self, key, **kw):
"""Retrieve a cached value from the container"""
return self._get_value(key, **kw).get_value()
get_value = get
def remove_value(self, key, **kw):
mycontainer = self._get_value(key, **kw)
mycontainer.clear_value()
remove = remove_value
def _get_value(self, key, **kw):
if isinstance(key, unicode):
key = key.encode('ascii', 'backslashreplace')
if 'type' in kw:
return self._legacy_get_value(key, **kw)
kw.setdefault('expiretime', self.expiretime)
kw.setdefault('starttime', self.starttime)
return container.Value(key, self.namespace, **kw)
@util.deprecated("Specifying a "
"'type' and other namespace configuration with cache.get()/put()/etc. "
"is deprecated. Specify 'type' and other namespace configuration to "
"cache_manager.get_cache() and/or the Cache constructor instead.")
def _legacy_get_value(self, key, type, **kw):
expiretime = kw.pop('expiretime', self.expiretime)
starttime = kw.pop('starttime', None)
createfunc = kw.pop('createfunc', None)
kwargs = self.nsargs.copy()
kwargs.update(kw)
c = Cache(self.namespace.namespace, type=type, **kwargs)
return c._get_value(key, expiretime=expiretime, createfunc=createfunc,
starttime=starttime)
def clear(self):
"""Clear all the values from the namespace"""
self.namespace.remove()
# dict interface
def __getitem__(self, key):
return self.get(key)
def __contains__(self, key):
return self._get_value(key).has_current_value()
def has_key(self, key):
return key in self
def __delitem__(self, key):
self.remove_value(key)
def __setitem__(self, key, value):
self.put(key, value)
class CacheManager(object):
def __init__(self, **kwargs):
"""Initialize a CacheManager object with a set of options
Options should be parsed with the
:func:`~beaker.util.parse_cache_config_options` function to
ensure only valid options are used.
"""
self.kwargs = kwargs
self.regions = kwargs.pop('cache_regions', {})
# Add these regions to the module global
cache_regions.update(self.regions)
def get_cache(self, name, **kwargs):
kw = self.kwargs.copy()
kw.update(kwargs)
return Cache._get_cache(name, kw)
def get_cache_region(self, name, region):
if region not in self.regions:
raise BeakerException('Cache region not configured: %s' % region)
kw = self.regions[region]
return Cache._get_cache(name, kw)
def region(self, region, *args):
"""Decorate a function to cache itself using a cache region
The region decorator requires arguments if there are more than
two of the same named function, in the same module. This is
because the namespace used for the functions cache is based on
the functions name and the module.
Example::
# Assuming a cache object is available like:
cache = CacheManager(dict_of_config_options)
def populate_things():
@cache.region('short_term', 'some_data')
def load(search_term, limit, offset):
return load_the_data(search_term, limit, offset)
return load('rabbits', 20, 0)
.. note::
The function being decorated must only be called with
positional arguments.
"""
return cache_region(region, *args)
def region_invalidate(self, namespace, region, *args):
"""Invalidate a cache region namespace or decorated function
This function only invalidates cache spaces created with the
cache_region decorator.
:param namespace: Either the namespace of the result to invalidate, or the
cached function
:param region: The region the function was cached to. If the function was
cached to a single region then this argument can be None
:param args: Arguments that were used to differentiate the cached
function as well as the arguments passed to the decorated
function
Example::
# Assuming a cache object is available like:
cache = CacheManager(dict_of_config_options)
def populate_things(invalidate=False):
@cache.region('short_term', 'some_data')
def load(search_term, limit, offset):
return load_the_data(search_term, limit, offset)
# If the results should be invalidated first
if invalidate:
cache.region_invalidate(load, None, 'some_data',
'rabbits', 20, 0)
return load('rabbits', 20, 0)
"""
return region_invalidate(namespace, region, *args)
def cache(self, *args, **kwargs):
"""Decorate a function to cache itself with supplied parameters
:param args: Used to make the key unique for this function, as in region()
above.
:param kwargs: Parameters to be passed to get_cache(), will override defaults
Example::
# Assuming a cache object is available like:
cache = CacheManager(dict_of_config_options)
def populate_things():
@cache.cache('mycache', expire=15)
def load(search_term, limit, offset):
return load_the_data(search_term, limit, offset)
return load('rabbits', 20, 0)
.. note::
The function being decorated must only be called with
positional arguments.
"""
return _cache_decorate(args, self, kwargs, None)
def invalidate(self, func, *args, **kwargs):
"""Invalidate a cache decorated function
This function only invalidates cache spaces created with the
cache decorator.
:param func: Decorated function to invalidate
:param args: Used to make the key unique for this function, as in region()
above.
:param kwargs: Parameters that were passed for use by get_cache(), note that
this is only required if a ``type`` was specified for the
function
Example::
# Assuming a cache object is available like:
cache = CacheManager(dict_of_config_options)
def populate_things(invalidate=False):
@cache.cache('mycache', type="file", expire=15)
def load(search_term, limit, offset):
return load_the_data(search_term, limit, offset)
# If the results should be invalidated first
if invalidate:
cache.invalidate(load, 'mycache', 'rabbits', 20, 0, type="file")
return load('rabbits', 20, 0)
"""
namespace = func._arg_namespace
cache = self.get_cache(namespace, **kwargs)
if hasattr(func, '_arg_region'):
key_length = cache_regions[func._arg_region]['key_length']
else:
key_length = kwargs.pop('key_length', 250)
_cache_decorator_invalidate(cache, key_length, args)
def _cache_decorate(deco_args, manager, kwargs, region):
"""Return a caching function decorator."""
cache = [None]
def decorate(func):
namespace = util.func_namespace(func)
skip_self = util.has_self_arg(func)
def cached(*args):
if not cache[0]:
if region is not None:
if region not in cache_regions:
raise BeakerException(
'Cache region not configured: %s' % region)
reg = cache_regions[region]
if not reg.get('enabled', True):
return func(*args)
cache[0] = Cache._get_cache(namespace, reg)
elif manager:
cache[0] = manager.get_cache(namespace, **kwargs)
else:
raise Exception("'manager + kwargs' or 'region' "
"argument is required")
if skip_self:
try:
cache_key = " ".join(map(str, deco_args + args[1:]))
except UnicodeEncodeError:
cache_key = " ".join(map(unicode, deco_args + args[1:]))
else:
try:
cache_key = " ".join(map(str, deco_args + args))
except UnicodeEncodeError:
cache_key = " ".join(map(unicode, deco_args + args))
if region:
key_length = cache_regions[region]['key_length']
else:
key_length = kwargs.pop('key_length', 250)
if len(cache_key) + len(namespace) > int(key_length):
cache_key = sha1(cache_key).hexdigest()
def go():
return func(*args)
return cache[0].get_value(cache_key, createfunc=go)
cached._arg_namespace = namespace
if region is not None:
cached._arg_region = region
return cached
return decorate
def _cache_decorator_invalidate(cache, key_length, args):
"""Invalidate a cache key based on function arguments."""
try:
cache_key = " ".join(map(str, args))
except UnicodeEncodeError:
cache_key = " ".join(map(unicode, args))
if len(cache_key) + len(cache.namespace_name) > key_length:
cache_key = sha1(cache_key).hexdigest()
cache.remove_value(cache_key)
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