mirror of
https://mau.dev/maunium/synapse.git
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![Erik Johnston](/assets/img/avatar_default.png)
Instead of calculating the size of the cache repeatedly, which can take a long time now that it can use a callback, instead cache the size and update that on insertion and deletion. This requires changing the cache descriptors to have two caches, one for pending deferreds and the other for the actual values. There's no reason to evict from the pending deferreds as they won't take up any more memory.
546 lines
18 KiB
Python
546 lines
18 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
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from synapse.util.caches.lrucache import LruCache
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from synapse.util.caches.treecache import TreeCache, popped_to_iterator
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from synapse.util.logcontext import (
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PreserveLoggingContext, preserve_context_over_deferred, preserve_context_over_fn
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)
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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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val = self._pending_deferred_cache.pop(key, None)
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if val is not None:
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entry_dict, _ = val
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for entry in popped_to_iterator(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 CacheDescriptor(object):
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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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"""
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def __init__(self, orig, max_entries=1000, num_args=1, tree=False,
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inlineCallbacks=False, cache_context=False, iterable=False):
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max_entries = int(max_entries * CACHE_SIZE_FACTOR)
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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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self.max_entries = max_entries
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self.num_args = num_args
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self.tree = tree
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self.iterable = iterable
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all_args = inspect.getargspec(orig)
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self.arg_names = all_args.args[1:num_args + 1]
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if "cache_context" in all_args.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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try:
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self.arg_names.remove("cache_context")
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except ValueError:
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pass
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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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self.add_cache_context = cache_context
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if len(self.arg_names) < self.num_args:
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raise Exception(
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"Not enough explicit positional arguments to key off of for %r."
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" (@cached cannot key off of *args or **kwargs)"
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% (orig.__name__,)
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)
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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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@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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# Add temp cache_context so inspect.getcallargs doesn't explode
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if self.add_cache_context:
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kwargs["cache_context"] = None
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arg_dict = inspect.getcallargs(self.orig, obj, *args, **kwargs)
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cache_key = tuple(arg_dict[arg_nm] for arg_nm in self.arg_names)
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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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return preserve_context_over_deferred(observer)
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except KeyError:
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ret = defer.maybeDeferred(
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preserve_context_over_fn,
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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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ret = ObservableDeferred(ret, consumeErrors=True)
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cache.set(cache_key, ret, callback=invalidate_callback)
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return preserve_context_over_deferred(ret.observe())
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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(object):
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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 fucntion.
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"""
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def __init__(self, orig, cached_method_name, list_name, num_args=1,
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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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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)
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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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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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self.num_args = num_args
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self.list_name = list_name
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self.arg_names = inspect.getargspec(orig).args[1:num_args + 1]
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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 len(self.arg_names) < self.num_args:
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raise Exception(
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"Not enough explicit positional arguments to key off of for %r."
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" (@cached cannot key off of *args or **kwars)"
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% (orig.__name__,)
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)
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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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preserve_context_over_fn,
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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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with PreserveLoggingContext():
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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 preserve_context_over_deferred(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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def invalidate(self):
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self.cache.invalidate(self.key)
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def cached(max_entries=1000, num_args=1, 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=1, 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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inlineCallbacks=True,
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cache_context=cache_context,
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iterable=iterable,
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)
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def cachedList(cached_method_name, list_name, num_args=1, inlineCallbacks=False):
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"""Creates a descriptor that wraps a function in a `CacheListDescriptor`.
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Used to do batch lookups for an already created cache. A single argument
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is specified as a list that is iterated through to lookup keys in the
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original cache. A new list consisting of the keys that weren't in the cache
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get passed to the original function, the result of which is stored in the
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cache.
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Args:
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cache (Cache): The underlying cache to use.
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list_name (str): The name of the argument that is the list to use to
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do batch lookups in the cache.
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num_args (int): Number of arguments to use as the key in the cache.
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inlineCallbacks (bool): Should the function be wrapped in an
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`defer.inlineCallbacks`?
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Example:
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class Example(object):
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@cached(num_args=2)
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def do_something(self, first_arg):
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...
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@cachedList(do_something.cache, list_name="second_args", num_args=2)
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def batch_do_something(self, first_arg, second_args):
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...
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|
"""
|
|
return lambda orig: CacheListDescriptor(
|
|
orig,
|
|
cached_method_name=cached_method_name,
|
|
list_name=list_name,
|
|
num_args=num_args,
|
|
inlineCallbacks=inlineCallbacks,
|
|
)
|