224 lines
6.8 KiB
Python
224 lines
6.8 KiB
Python
# 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 collections import OrderedDict
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from typing import Any, Generic, Optional, TypeVar, Union, overload
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import attr
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from typing_extensions import Literal
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from twisted.internet import defer
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from synapse.config import cache as cache_config
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from synapse.metrics.background_process_metrics import run_as_background_process
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from synapse.util import Clock
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from synapse.util.caches import EvictionReason, register_cache
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logger = logging.getLogger(__name__)
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SENTINEL: Any = object()
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T = TypeVar("T")
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KT = TypeVar("KT")
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VT = TypeVar("VT")
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class ExpiringCache(Generic[KT, VT]):
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def __init__(
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self,
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cache_name: str,
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clock: Clock,
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max_len: int = 0,
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expiry_ms: int = 0,
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reset_expiry_on_get: bool = False,
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iterable: bool = False,
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):
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"""
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Args:
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cache_name: Name of this cache, used for logging.
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clock
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max_len: 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: 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: If true, will reset the expiry time for
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an item on access. Defaults to False.
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iterable: 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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"""
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self._cache_name = cache_name
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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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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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self._cache: OrderedDict[KT, _CacheEntry] = OrderedDict()
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self.iterable = iterable
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self.metrics = register_cache("expiring", cache_name, self)
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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() -> "defer.Deferred[None]":
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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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self._clock.looping_call(f, self._expiry_ms / 2)
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def __setitem__(self, key: KT, value: VT) -> None:
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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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def evict(self) -> None:
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# Evict if there are now too many items
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while self._max_size and len(self) > self._max_size:
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_key, value = self._cache.popitem(last=False)
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if self.iterable:
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self.metrics.inc_evictions(EvictionReason.size, len(value.value))
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else:
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self.metrics.inc_evictions(EvictionReason.size)
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def __getitem__(self, key: KT) -> VT:
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try:
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entry = self._cache[key]
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self.metrics.inc_hits()
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except KeyError:
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self.metrics.inc_misses()
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raise
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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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def pop(self, key: KT, default: T = SENTINEL) -> Union[VT, T]:
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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, SENTINEL)
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# The key was not found.
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if value is SENTINEL:
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if default is SENTINEL:
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raise KeyError(key)
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return default
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if self.iterable:
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self.metrics.inc_evictions(EvictionReason.invalidation, len(value.value))
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else:
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self.metrics.inc_evictions(EvictionReason.invalidation)
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return value.value
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def __contains__(self, key: KT) -> bool:
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return key in self._cache
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@overload
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def get(self, key: KT, default: Literal[None] = None) -> Optional[VT]:
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...
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@overload
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def get(self, key: KT, default: T) -> Union[VT, T]:
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...
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def get(self, key: KT, default: Optional[T] = None) -> Union[VT, Optional[T]]:
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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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def setdefault(self, key: KT, value: VT) -> VT:
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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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async def _prune_cache(self) -> None:
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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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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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value = self._cache.pop(k)
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if self.iterable:
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self.metrics.inc_evictions(EvictionReason.time, len(value.value))
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else:
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self.metrics.inc_evictions(EvictionReason.time)
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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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def __len__(self) -> int:
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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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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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@attr.s(slots=True, auto_attribs=True)
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class _CacheEntry:
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time: int
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value: Any
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