585 lines
20 KiB
Python
585 lines
20 KiB
Python
# -*- coding: utf-8 -*-
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# Copyright 2015, 2016 OpenMarket Ltd
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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import logging
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from synapse.util.async import ObservableDeferred
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from synapse.util import unwrapFirstError, logcontext
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from synapse.util.caches.lrucache import LruCache
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from synapse.util.caches.treecache import TreeCache, iterate_tree_cache_entry
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from . import DEBUG_CACHES, register_cache
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from twisted.internet import defer
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from collections import namedtuple
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import os
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import functools
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import inspect
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import threading
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logger = logging.getLogger(__name__)
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_CacheSentinel = object()
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CACHE_SIZE_FACTOR = float(os.environ.get("SYNAPSE_CACHE_FACTOR", 0.1))
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class CacheEntry(object):
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__slots__ = [
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"deferred", "sequence", "callbacks", "invalidated"
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]
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def __init__(self, deferred, sequence, callbacks):
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self.deferred = deferred
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self.sequence = sequence
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self.callbacks = set(callbacks)
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self.invalidated = False
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def invalidate(self):
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if not self.invalidated:
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self.invalidated = True
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for callback in self.callbacks:
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callback()
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self.callbacks.clear()
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class Cache(object):
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__slots__ = (
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"cache",
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"max_entries",
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"name",
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"keylen",
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"sequence",
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"thread",
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"metrics",
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"_pending_deferred_cache",
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)
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def __init__(self, name, max_entries=1000, keylen=1, tree=False, iterable=False):
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cache_type = TreeCache if tree else dict
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self._pending_deferred_cache = cache_type()
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self.cache = LruCache(
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max_size=max_entries, keylen=keylen, cache_type=cache_type,
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size_callback=(lambda d: len(d.result)) if iterable else None,
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)
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self.name = name
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self.keylen = keylen
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self.sequence = 0
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self.thread = None
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self.metrics = register_cache(name, self.cache)
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def check_thread(self):
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expected_thread = self.thread
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if expected_thread is None:
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self.thread = threading.current_thread()
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else:
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if expected_thread is not threading.current_thread():
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raise ValueError(
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"Cache objects can only be accessed from the main thread"
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)
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def get(self, key, default=_CacheSentinel, callback=None):
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callbacks = [callback] if callback else []
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val = self._pending_deferred_cache.get(key, _CacheSentinel)
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if val is not _CacheSentinel:
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if val.sequence == self.sequence:
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val.callbacks.update(callbacks)
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self.metrics.inc_hits()
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return val.deferred
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val = self.cache.get(key, _CacheSentinel, callbacks=callbacks)
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if val is not _CacheSentinel:
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self.metrics.inc_hits()
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return val
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self.metrics.inc_misses()
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if default is _CacheSentinel:
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raise KeyError()
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else:
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return default
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def set(self, key, value, callback=None):
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callbacks = [callback] if callback else []
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self.check_thread()
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entry = CacheEntry(
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deferred=value,
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sequence=self.sequence,
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callbacks=callbacks,
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)
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entry.callbacks.update(callbacks)
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existing_entry = self._pending_deferred_cache.pop(key, None)
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if existing_entry:
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existing_entry.invalidate()
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self._pending_deferred_cache[key] = entry
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def shuffle(result):
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if self.sequence == entry.sequence:
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existing_entry = self._pending_deferred_cache.pop(key, None)
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if existing_entry is entry:
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self.cache.set(key, entry.deferred, entry.callbacks)
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else:
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entry.invalidate()
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else:
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entry.invalidate()
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return result
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entry.deferred.addCallback(shuffle)
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def prefill(self, key, value, callback=None):
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callbacks = [callback] if callback else []
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self.cache.set(key, value, callbacks=callbacks)
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def invalidate(self, key):
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self.check_thread()
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if not isinstance(key, tuple):
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raise TypeError(
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"The cache key must be a tuple not %r" % (type(key),)
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)
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# Increment the sequence number so that any SELECT statements that
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# raced with the INSERT don't update the cache (SYN-369)
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self.sequence += 1
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entry = self._pending_deferred_cache.pop(key, None)
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if entry:
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entry.invalidate()
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self.cache.pop(key, None)
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def invalidate_many(self, key):
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self.check_thread()
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if not isinstance(key, tuple):
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raise TypeError(
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"The cache key must be a tuple not %r" % (type(key),)
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)
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self.sequence += 1
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self.cache.del_multi(key)
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entry_dict = self._pending_deferred_cache.pop(key, None)
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if entry_dict is not None:
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for entry in iterate_tree_cache_entry(entry_dict):
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entry.invalidate()
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def invalidate_all(self):
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self.check_thread()
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self.sequence += 1
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self.cache.clear()
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class _CacheDescriptorBase(object):
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def __init__(self, orig, num_args, inlineCallbacks, cache_context=False):
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self.orig = orig
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if inlineCallbacks:
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self.function_to_call = defer.inlineCallbacks(orig)
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else:
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self.function_to_call = orig
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arg_spec = inspect.getargspec(orig)
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all_args = arg_spec.args
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if "cache_context" in all_args:
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if not cache_context:
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raise ValueError(
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"Cannot have a 'cache_context' arg without setting"
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" cache_context=True"
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)
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elif cache_context:
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raise ValueError(
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"Cannot have cache_context=True without having an arg"
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" named `cache_context`"
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)
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if num_args is None:
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num_args = len(all_args) - 1
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if cache_context:
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num_args -= 1
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if len(all_args) < num_args + 1:
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raise Exception(
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"Not enough explicit positional arguments to key off for %r: "
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"got %i args, but wanted %i. (@cached cannot key off *args or "
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"**kwargs)"
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% (orig.__name__, len(all_args), num_args)
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)
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self.num_args = num_args
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# list of the names of the args used as the cache key
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self.arg_names = all_args[1:num_args + 1]
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# self.arg_defaults is a map of arg name to its default value for each
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# argument that has a default value
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if arg_spec.defaults:
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self.arg_defaults = dict(zip(
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all_args[-len(arg_spec.defaults):],
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arg_spec.defaults
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))
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else:
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self.arg_defaults = {}
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if "cache_context" in self.arg_names:
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raise Exception(
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"cache_context arg cannot be included among the cache keys"
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)
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self.add_cache_context = cache_context
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class CacheDescriptor(_CacheDescriptorBase):
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""" A method decorator that applies a memoizing cache around the function.
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This caches deferreds, rather than the results themselves. Deferreds that
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fail are removed from the cache.
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The function is presumed to take zero or more arguments, which are used in
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a tuple as the key for the cache. Hits are served directly from the cache;
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misses use the function body to generate the value.
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The wrapped function has an additional member, a callable called
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"invalidate". This can be used to remove individual entries from the cache.
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The wrapped function has another additional callable, called "prefill",
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which can be used to insert values into the cache specifically, without
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calling the calculation function.
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Cached functions can be "chained" (i.e. a cached function can call other cached
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functions and get appropriately invalidated when they called caches are
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invalidated) by adding a special "cache_context" argument to the function
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and passing that as a kwarg to all caches called. For example::
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@cachedInlineCallbacks(cache_context=True)
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def foo(self, key, cache_context):
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r1 = yield self.bar1(key, on_invalidate=cache_context.invalidate)
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r2 = yield self.bar2(key, on_invalidate=cache_context.invalidate)
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defer.returnValue(r1 + r2)
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Args:
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num_args (int): number of positional arguments (excluding ``self`` and
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``cache_context``) to use as cache keys. Defaults to all named
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args of the function.
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"""
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def __init__(self, orig, max_entries=1000, num_args=None, tree=False,
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inlineCallbacks=False, cache_context=False, iterable=False):
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super(CacheDescriptor, self).__init__(
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orig, num_args=num_args, inlineCallbacks=inlineCallbacks,
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cache_context=cache_context)
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max_entries = int(max_entries * CACHE_SIZE_FACTOR)
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self.max_entries = max_entries
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self.tree = tree
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self.iterable = iterable
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def __get__(self, obj, objtype=None):
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cache = Cache(
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name=self.orig.__name__,
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max_entries=self.max_entries,
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keylen=self.num_args,
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tree=self.tree,
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iterable=self.iterable,
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)
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def get_cache_key(args, kwargs):
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"""Given some args/kwargs return a generator that resolves into
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the cache_key.
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We loop through each arg name, looking up if its in the `kwargs`,
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otherwise using the next argument in `args`. If there are no more
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args then we try looking the arg name up in the defaults
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"""
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pos = 0
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for nm in self.arg_names:
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if nm in kwargs:
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yield kwargs[nm]
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elif pos < len(args):
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yield args[pos]
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pos += 1
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else:
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yield self.arg_defaults[nm]
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@functools.wraps(self.orig)
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def wrapped(*args, **kwargs):
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# If we're passed a cache_context then we'll want to call its invalidate()
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# whenever we are invalidated
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invalidate_callback = kwargs.pop("on_invalidate", None)
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cache_key = tuple(get_cache_key(args, kwargs))
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# Add our own `cache_context` to argument list if the wrapped function
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# has asked for one
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if self.add_cache_context:
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kwargs["cache_context"] = _CacheContext(cache, cache_key)
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try:
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cached_result_d = cache.get(cache_key, callback=invalidate_callback)
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observer = cached_result_d.observe()
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if DEBUG_CACHES:
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@defer.inlineCallbacks
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def check_result(cached_result):
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actual_result = yield self.function_to_call(obj, *args, **kwargs)
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if actual_result != cached_result:
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logger.error(
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"Stale cache entry %s%r: cached: %r, actual %r",
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self.orig.__name__, cache_key,
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cached_result, actual_result,
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)
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raise ValueError("Stale cache entry")
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defer.returnValue(cached_result)
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observer.addCallback(check_result)
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except KeyError:
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ret = defer.maybeDeferred(
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logcontext.preserve_fn(self.function_to_call),
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obj, *args, **kwargs
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)
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def onErr(f):
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cache.invalidate(cache_key)
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return f
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ret.addErrback(onErr)
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result_d = ObservableDeferred(ret, consumeErrors=True)
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cache.set(cache_key, result_d, callback=invalidate_callback)
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observer = result_d.observe()
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if isinstance(observer, defer.Deferred):
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return logcontext.make_deferred_yieldable(observer)
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else:
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return observer
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wrapped.invalidate = cache.invalidate
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wrapped.invalidate_all = cache.invalidate_all
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wrapped.invalidate_many = cache.invalidate_many
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wrapped.prefill = cache.prefill
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wrapped.cache = cache
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obj.__dict__[self.orig.__name__] = wrapped
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return wrapped
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class CacheListDescriptor(_CacheDescriptorBase):
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"""Wraps an existing cache to support bulk fetching of keys.
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Given a list of keys it looks in the cache to find any hits, then passes
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the list of missing keys to the wrapped function.
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Once wrapped, the function returns either a Deferred which resolves to
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the list of results, or (if all results were cached), just the list of
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results.
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"""
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def __init__(self, orig, cached_method_name, list_name, num_args=None,
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inlineCallbacks=False):
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"""
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Args:
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orig (function)
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cached_method_name (str): The name of the chached method.
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list_name (str): Name of the argument which is the bulk lookup list
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num_args (int): number of positional arguments (excluding ``self``,
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but including list_name) to use as cache keys. Defaults to all
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named args of the function.
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inlineCallbacks (bool): Whether orig is a generator that should
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be wrapped by defer.inlineCallbacks
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"""
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super(CacheListDescriptor, self).__init__(
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orig, num_args=num_args, inlineCallbacks=inlineCallbacks)
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self.list_name = list_name
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self.list_pos = self.arg_names.index(self.list_name)
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self.cached_method_name = cached_method_name
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self.sentinel = object()
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if self.list_name not in self.arg_names:
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raise Exception(
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"Couldn't see arguments %r for %r."
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% (self.list_name, cached_method_name,)
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)
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def __get__(self, obj, objtype=None):
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cache = getattr(obj, self.cached_method_name).cache
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@functools.wraps(self.orig)
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def wrapped(*args, **kwargs):
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# If we're passed a cache_context then we'll want to call its invalidate()
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# whenever we are invalidated
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invalidate_callback = kwargs.pop("on_invalidate", None)
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arg_dict = inspect.getcallargs(self.orig, obj, *args, **kwargs)
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keyargs = [arg_dict[arg_nm] for arg_nm in self.arg_names]
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list_args = arg_dict[self.list_name]
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# cached is a dict arg -> deferred, where deferred results in a
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# 2-tuple (`arg`, `result`)
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results = {}
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cached_defers = {}
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missing = []
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for arg in list_args:
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key = list(keyargs)
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key[self.list_pos] = arg
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try:
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res = cache.get(tuple(key), callback=invalidate_callback)
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if not res.has_succeeded():
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res = res.observe()
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res.addCallback(lambda r, arg: (arg, r), arg)
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cached_defers[arg] = res
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else:
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results[arg] = res.get_result()
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except KeyError:
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missing.append(arg)
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if missing:
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args_to_call = dict(arg_dict)
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args_to_call[self.list_name] = missing
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ret_d = defer.maybeDeferred(
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logcontext.preserve_fn(self.function_to_call),
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**args_to_call
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)
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ret_d = ObservableDeferred(ret_d)
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# We need to create deferreds for each arg in the list so that
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# we can insert the new deferred into the cache.
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for arg in missing:
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observer = ret_d.observe()
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observer.addCallback(lambda r, arg: r.get(arg, None), arg)
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observer = ObservableDeferred(observer)
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key = list(keyargs)
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key[self.list_pos] = arg
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cache.set(
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tuple(key), observer,
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callback=invalidate_callback
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)
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def invalidate(f, key):
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cache.invalidate(key)
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return f
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observer.addErrback(invalidate, tuple(key))
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res = observer.observe()
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res.addCallback(lambda r, arg: (arg, r), arg)
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cached_defers[arg] = res
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if cached_defers:
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def update_results_dict(res):
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results.update(res)
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return results
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return logcontext.make_deferred_yieldable(defer.gatherResults(
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cached_defers.values(),
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consumeErrors=True,
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).addCallback(update_results_dict).addErrback(
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unwrapFirstError
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))
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else:
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return results
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obj.__dict__[self.orig.__name__] = wrapped
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return wrapped
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class _CacheContext(namedtuple("_CacheContext", ("cache", "key"))):
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# We rely on _CacheContext implementing __eq__ and __hash__ sensibly,
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# which namedtuple does for us (i.e. two _CacheContext are the same if
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# their caches and keys match). This is important in particular to
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# dedupe when we add callbacks to lru cache nodes, otherwise the number
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# of callbacks would grow.
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def invalidate(self):
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self.cache.invalidate(self.key)
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def cached(max_entries=1000, num_args=None, tree=False, cache_context=False,
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iterable=False):
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return lambda orig: CacheDescriptor(
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orig,
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max_entries=max_entries,
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num_args=num_args,
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tree=tree,
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cache_context=cache_context,
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iterable=iterable,
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)
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def cachedInlineCallbacks(max_entries=1000, num_args=None, tree=False,
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cache_context=False, iterable=False):
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return lambda orig: CacheDescriptor(
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orig,
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max_entries=max_entries,
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num_args=num_args,
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tree=tree,
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inlineCallbacks=True,
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cache_context=cache_context,
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iterable=iterable,
|
|
)
|
|
|
|
|
|
def cachedList(cached_method_name, list_name, num_args=None, inlineCallbacks=False):
|
|
"""Creates a descriptor that wraps a function in a `CacheListDescriptor`.
|
|
|
|
Used to do batch lookups for an already created cache. A single argument
|
|
is specified as a list that is iterated through to lookup keys in the
|
|
original cache. A new list consisting of the keys that weren't in the cache
|
|
get passed to the original function, the result of which is stored in the
|
|
cache.
|
|
|
|
Args:
|
|
cache (Cache): The underlying cache to use.
|
|
list_name (str): The name of the argument that is the list to use to
|
|
do batch lookups in the cache.
|
|
num_args (int): Number of arguments to use as the key in the cache
|
|
(including list_name). Defaults to all named parameters.
|
|
inlineCallbacks (bool): Should the function be wrapped in an
|
|
`defer.inlineCallbacks`?
|
|
|
|
Example:
|
|
|
|
class Example(object):
|
|
@cached(num_args=2)
|
|
def do_something(self, first_arg):
|
|
...
|
|
|
|
@cachedList(do_something.cache, list_name="second_args", num_args=2)
|
|
def batch_do_something(self, first_arg, second_args):
|
|
...
|
|
"""
|
|
return lambda orig: CacheListDescriptor(
|
|
orig,
|
|
cached_method_name=cached_method_name,
|
|
list_name=list_name,
|
|
num_args=num_args,
|
|
inlineCallbacks=inlineCallbacks,
|
|
)
|