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- # -*- coding: utf-8 -*-
- # Copyright 2015, 2016 OpenMarket Ltd
- #
- # Licensed under the Apache License, Version 2.0 (the "License");
- # you may not use this file except in compliance with the License.
- # You may obtain a copy of the License at
- #
- # http://www.apache.org/licenses/LICENSE-2.0
- #
- # Unless required by applicable law or agreed to in writing, software
- # distributed under the License is distributed on an "AS IS" BASIS,
- # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- # See the License for the specific language governing permissions and
- # limitations under the License.
- from synapse.util.caches.lrucache import LruCache
- from collections import namedtuple
- from . import register_cache
- import threading
- import logging
- logger = logging.getLogger(__name__)
- class DictionaryEntry(namedtuple("DictionaryEntry", ("full", "known_absent", "value"))):
- """Returned when getting an entry from the cache
- Attributes:
- full (bool): Whether the cache has the full or dict or just some keys.
- If not full then not all requested keys will necessarily be present
- in `value`
- known_absent (set): Keys that were looked up in the dict and were not
- there.
- value (dict): The full or partial dict value
- """
- def __len__(self):
- return len(self.value)
- class DictionaryCache(object):
- """Caches key -> dictionary lookups, supporting caching partial dicts, i.e.
- fetching a subset of dictionary keys for a particular key.
- """
- def __init__(self, name, max_entries=1000):
- self.cache = LruCache(max_size=max_entries, size_callback=len)
- self.name = name
- self.sequence = 0
- self.thread = None
- # caches_by_name[name] = self.cache
- class Sentinel(object):
- __slots__ = []
- self.sentinel = Sentinel()
- self.metrics = register_cache("dictionary", name, self.cache)
- def check_thread(self):
- expected_thread = self.thread
- if expected_thread is None:
- self.thread = threading.current_thread()
- else:
- if expected_thread is not threading.current_thread():
- raise ValueError(
- "Cache objects can only be accessed from the main thread"
- )
- def get(self, key, dict_keys=None):
- """Fetch an entry out of the cache
- Args:
- key
- dict_key(list): If given a set of keys then return only those keys
- that exist in the cache.
- Returns:
- DictionaryEntry
- """
- entry = self.cache.get(key, self.sentinel)
- if entry is not self.sentinel:
- self.metrics.inc_hits()
- if dict_keys is None:
- return DictionaryEntry(entry.full, entry.known_absent, dict(entry.value))
- else:
- return DictionaryEntry(entry.full, entry.known_absent, {
- k: entry.value[k]
- for k in dict_keys
- if k in entry.value
- })
- self.metrics.inc_misses()
- return DictionaryEntry(False, set(), {})
- def invalidate(self, key):
- self.check_thread()
- # Increment the sequence number so that any SELECT statements that
- # raced with the INSERT don't update the cache (SYN-369)
- self.sequence += 1
- self.cache.pop(key, None)
- def invalidate_all(self):
- self.check_thread()
- self.sequence += 1
- self.cache.clear()
- def update(self, sequence, key, value, full=False, known_absent=None):
- """Updates the entry in the cache
- Args:
- sequence
- key
- value (dict): The value to update the cache with.
- full (bool): Whether the given value is the full dict, or just a
- partial subset there of. If not full then any existing entries
- for the key will be updated.
- known_absent (set): Set of keys that we know don't exist in the full
- dict.
- """
- self.check_thread()
- if self.sequence == sequence:
- # Only update the cache if the caches sequence number matches the
- # number that the cache had before the SELECT was started (SYN-369)
- if known_absent is None:
- known_absent = set()
- if full:
- self._insert(key, value, known_absent)
- else:
- self._update_or_insert(key, value, known_absent)
- def _update_or_insert(self, key, value, known_absent):
- # We pop and reinsert as we need to tell the cache the size may have
- # changed
- entry = self.cache.pop(key, DictionaryEntry(False, set(), {}))
- entry.value.update(value)
- entry.known_absent.update(known_absent)
- self.cache[key] = entry
- def _insert(self, key, value, known_absent):
- self.cache[key] = DictionaryEntry(True, known_absent, value)
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