104 lines
3.3 KiB
Python
104 lines
3.3 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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from synapse.util.caches.lrucache import LruCache
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from collections import namedtuple
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from . import caches_by_name, cache_counter
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import threading
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import logging
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logger = logging.getLogger(__name__)
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DictionaryEntry = namedtuple("DictionaryEntry", ("full", "value"))
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class DictionaryCache(object):
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"""Caches key -> dictionary lookups, supporting caching partial dicts, i.e.
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fetching a subset of dictionary keys for a particular key.
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"""
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def __init__(self, name, max_entries=1000):
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self.cache = LruCache(max_size=max_entries)
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self.name = name
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self.sequence = 0
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self.thread = None
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# caches_by_name[name] = self.cache
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class Sentinel(object):
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__slots__ = []
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self.sentinel = Sentinel()
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caches_by_name[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, dict_keys=None):
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entry = self.cache.get(key, self.sentinel)
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if entry is not self.sentinel:
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cache_counter.inc_hits(self.name)
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if dict_keys is None:
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return DictionaryEntry(entry.full, dict(entry.value))
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else:
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return DictionaryEntry(entry.full, {
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k: entry.value[k]
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for k in dict_keys
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if k in entry.value
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})
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cache_counter.inc_misses(self.name)
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return DictionaryEntry(False, {})
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def invalidate(self, key):
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self.check_thread()
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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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self.cache.pop(key, None)
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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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def update(self, sequence, key, value, full=False):
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self.check_thread()
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if self.sequence == sequence:
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# Only update the cache if the caches sequence number matches the
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# number that the cache had before the SELECT was started (SYN-369)
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if full:
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self._insert(key, value)
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else:
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self._update_or_insert(key, value)
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def _update_or_insert(self, key, value):
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entry = self.cache.setdefault(key, DictionaryEntry(False, {}))
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entry.value.update(value)
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def _insert(self, key, value):
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self.cache[key] = DictionaryEntry(True, value)
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