2015-02-16 17:16:47 +01:00
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# -*- coding: utf-8 -*-
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2016-01-07 05:26:29 +01:00
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# Copyright 2015, 2016 OpenMarket Ltd
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2015-02-16 17:16:47 +01:00
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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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2018-07-09 08:09:20 +02:00
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from collections import OrderedDict
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2015-02-16 17:16:47 +01:00
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2020-05-11 19:45:23 +02:00
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from synapse.config import cache as cache_config
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2018-07-18 15:35:24 +02:00
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from synapse.metrics.background_process_metrics import run_as_background_process
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2018-07-09 08:09:20 +02:00
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from synapse.util.caches import register_cache
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2015-02-16 17:16:47 +01:00
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logger = logging.getLogger(__name__)
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2018-09-21 15:55:47 +02:00
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SENTINEL = object()
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2020-09-04 12:54:56 +02:00
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class ExpiringCache:
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2019-06-20 11:32:02 +02:00
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def __init__(
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self,
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cache_name,
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clock,
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max_len=0,
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expiry_ms=0,
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reset_expiry_on_get=False,
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iterable=False,
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):
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2015-02-16 17:16:47 +01:00
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"""
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Args:
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cache_name (str): Name of this cache, used for logging.
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clock (Clock)
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max_len (int): Max size of dict. If the dict grows larger than this
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then the oldest items get automatically evicted. Default is 0,
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which indicates there is no max limit.
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expiry_ms (int): How long before an item is evicted from the cache
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in milliseconds. Default is 0, indicating items never get
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evicted based on time.
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reset_expiry_on_get (bool): If true, will reset the expiry time for
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an item on access. Defaults to False.
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2017-01-16 14:48:04 +01:00
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iterable (bool): If true, the size is calculated by summing the
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sizes of all entries, rather than the number of entries.
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2015-02-16 17:16:47 +01:00
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"""
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self._cache_name = cache_name
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2020-05-11 19:45:23 +02:00
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self._original_max_size = max_len
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self._max_size = int(max_len * cache_config.properties.default_factor_size)
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2015-02-16 17:16:47 +01:00
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self._clock = clock
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self._expiry_ms = expiry_ms
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self._reset_expiry_on_get = reset_expiry_on_get
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2017-01-16 16:33:22 +01:00
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self._cache = OrderedDict()
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self.iterable = iterable
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2016-02-23 12:54:48 +01:00
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2018-05-22 02:47:37 +02:00
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self.metrics = register_cache("expiring", cache_name, self)
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2015-02-16 17:16:47 +01:00
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if not self._expiry_ms:
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# Don't bother starting the loop if things never expire
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return
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def f():
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return run_as_background_process(
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"prune_cache_%s" % self._cache_name, self._prune_cache
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)
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2015-02-16 17:16:47 +01:00
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2016-02-02 18:18:50 +01:00
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self._clock.looping_call(f, self._expiry_ms / 2)
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2015-02-16 17:16:47 +01:00
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def __setitem__(self, key, value):
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now = self._clock.time_msec()
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self._cache[key] = _CacheEntry(now, value)
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self.evict()
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2020-05-11 19:45:23 +02:00
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def evict(self):
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# Evict if there are now too many items
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2020-05-11 19:45:23 +02:00
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while self._max_size and len(self) > self._max_size:
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2017-01-17 12:18:13 +01:00
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_key, value = self._cache.popitem(last=False)
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if self.iterable:
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2018-09-21 17:25:42 +02:00
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self.metrics.inc_evictions(len(value.value))
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2018-02-01 18:57:51 +01:00
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else:
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self.metrics.inc_evictions()
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def __getitem__(self, key):
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try:
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entry = self._cache[key]
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2016-06-02 12:29:44 +02:00
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self.metrics.inc_hits()
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2016-03-01 11:59:17 +01:00
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except KeyError:
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self.metrics.inc_misses()
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2016-03-01 12:00:10 +01:00
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raise
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2015-02-16 17:16:47 +01:00
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if self._reset_expiry_on_get:
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entry.time = self._clock.time_msec()
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return entry.value
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2018-10-01 13:25:27 +02:00
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def pop(self, key, default=SENTINEL):
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"""Removes and returns the value with the given key from the cache.
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If the key isn't in the cache then `default` will be returned if
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specified, otherwise `KeyError` will get raised.
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Identical functionality to `dict.pop(..)`.
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"""
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value = self._cache.pop(key, default)
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if value is SENTINEL:
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raise KeyError(key)
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2018-09-21 15:55:47 +02:00
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return value
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2017-06-29 15:08:33 +02:00
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def __contains__(self, key):
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return key in self._cache
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2015-02-16 17:16:47 +01:00
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def get(self, key, default=None):
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try:
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return self[key]
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except KeyError:
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return default
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2017-03-10 11:30:38 +01:00
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def setdefault(self, key, value):
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try:
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return self[key]
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except KeyError:
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self[key] = value
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return value
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2015-02-17 16:44:41 +01:00
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def _prune_cache(self):
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if not self._expiry_ms:
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# zero expiry time means don't expire. This should never get called
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# since we have this check in start too.
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return
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begin_length = len(self)
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now = self._clock.time_msec()
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keys_to_delete = set()
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2020-06-15 13:03:36 +02:00
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for key, cache_entry in self._cache.items():
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if now - cache_entry.time > self._expiry_ms:
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keys_to_delete.add(key)
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for k in keys_to_delete:
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2017-01-17 12:18:13 +01:00
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value = self._cache.pop(k)
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if self.iterable:
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2018-09-21 17:25:42 +02:00
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self.metrics.inc_evictions(len(value.value))
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else:
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self.metrics.inc_evictions()
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2015-02-16 17:16:47 +01:00
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logger.debug(
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"[%s] _prune_cache before: %d, after len: %d",
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self._cache_name,
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begin_length,
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len(self),
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)
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2016-02-23 12:54:48 +01:00
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def __len__(self):
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if self.iterable:
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return sum(len(entry.value) for entry in self._cache.values())
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else:
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return len(self._cache)
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2016-02-23 12:54:48 +01:00
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2020-05-11 19:45:23 +02:00
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def set_cache_factor(self, factor: float) -> bool:
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"""
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Set the cache factor for this individual cache.
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This will trigger a resize if it changes, which may require evicting
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items from the cache.
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Returns:
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bool: Whether the cache changed size or not.
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"""
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new_size = int(self._original_max_size * factor)
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if new_size != self._max_size:
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self._max_size = new_size
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self.evict()
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return True
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return False
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2015-02-16 17:16:47 +01:00
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2020-09-04 12:54:56 +02:00
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class _CacheEntry:
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2018-09-21 15:52:21 +02:00
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__slots__ = ["time", "value"]
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2015-02-16 17:16:47 +01:00
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def __init__(self, time, value):
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self.time = time
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self.value = value
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