733 lines
24 KiB
Python
733 lines
24 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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import math
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import threading
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import weakref
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from enum import Enum
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from functools import wraps
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from typing import (
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TYPE_CHECKING,
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Any,
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Callable,
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Collection,
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Dict,
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Generic,
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List,
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Optional,
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Type,
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TypeVar,
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Union,
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cast,
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overload,
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)
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from typing_extensions import Literal
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from twisted.internet import reactor
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from twisted.internet.interfaces import IReactorTime
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from synapse.config import cache as cache_config
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from synapse.metrics.background_process_metrics import wrap_as_background_process
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from synapse.metrics.jemalloc import get_jemalloc_stats
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from synapse.util import Clock, caches
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from synapse.util.caches import CacheMetric, EvictionReason, register_cache
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from synapse.util.caches.treecache import TreeCache, iterate_tree_cache_entry
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from synapse.util.linked_list import ListNode
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if TYPE_CHECKING:
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from synapse.server import HomeServer
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logger = logging.getLogger(__name__)
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try:
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from pympler.asizeof import Asizer
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def _get_size_of(val: Any, *, recurse: bool = True) -> int:
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"""Get an estimate of the size in bytes of the object.
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Args:
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val: The object to size.
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recurse: If true will include referenced values in the size,
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otherwise only sizes the given object.
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"""
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# Ignore singleton values when calculating memory usage.
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if val in ((), None, ""):
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return 0
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sizer = Asizer()
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sizer.exclude_refs((), None, "")
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return sizer.asizeof(val, limit=100 if recurse else 0)
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except ImportError:
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def _get_size_of(val: Any, *, recurse: bool = True) -> int:
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return 0
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# Function type: the type used for invalidation callbacks
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FT = TypeVar("FT", bound=Callable[..., Any])
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# Key and Value type for the cache
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KT = TypeVar("KT")
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VT = TypeVar("VT")
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# a general type var, distinct from either KT or VT
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T = TypeVar("T")
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P = TypeVar("P")
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class _TimedListNode(ListNode[P]):
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"""A `ListNode` that tracks last access time."""
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__slots__ = ["last_access_ts_secs"]
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def update_last_access(self, clock: Clock) -> None:
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self.last_access_ts_secs = int(clock.time())
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# Whether to insert new cache entries to the global list. We only add to it if
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# time based eviction is enabled.
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USE_GLOBAL_LIST = False
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# A linked list of all cache entries, allowing efficient time based eviction.
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GLOBAL_ROOT = ListNode["_Node"].create_root_node()
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@wrap_as_background_process("LruCache._expire_old_entries")
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async def _expire_old_entries(
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clock: Clock, expiry_seconds: int, autotune_config: Optional[dict]
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) -> None:
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"""Walks the global cache list to find cache entries that haven't been
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accessed in the given number of seconds, or if a given memory threshold has been breached.
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"""
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if autotune_config:
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max_cache_memory_usage = autotune_config["max_cache_memory_usage"]
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target_cache_memory_usage = autotune_config["target_cache_memory_usage"]
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min_cache_ttl = autotune_config["min_cache_ttl"] / 1000
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now = int(clock.time())
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node = GLOBAL_ROOT.prev_node
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assert node is not None
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i = 0
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logger.debug("Searching for stale caches")
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evicting_due_to_memory = False
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# determine if we're evicting due to memory
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jemalloc_interface = get_jemalloc_stats()
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if jemalloc_interface and autotune_config:
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try:
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jemalloc_interface.refresh_stats()
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mem_usage = jemalloc_interface.get_stat("allocated")
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if mem_usage > max_cache_memory_usage:
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logger.info("Begin memory-based cache eviction.")
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evicting_due_to_memory = True
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except Exception:
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logger.warning(
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"Unable to read allocated memory, skipping memory-based cache eviction."
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)
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while node is not GLOBAL_ROOT:
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# Only the root node isn't a `_TimedListNode`.
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assert isinstance(node, _TimedListNode)
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# if node has not aged past expiry_seconds and we are not evicting due to memory usage, there's
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# nothing to do here
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if (
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node.last_access_ts_secs > now - expiry_seconds
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and not evicting_due_to_memory
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):
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break
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# if entry is newer than min_cache_entry_ttl then do not evict and don't evict anything newer
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if evicting_due_to_memory and now - node.last_access_ts_secs < min_cache_ttl:
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break
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cache_entry = node.get_cache_entry()
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next_node = node.prev_node
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# The node should always have a reference to a cache entry and a valid
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# `prev_node`, as we only drop them when we remove the node from the
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# list.
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assert next_node is not None
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assert cache_entry is not None
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cache_entry.drop_from_cache()
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# Check mem allocation periodically if we are evicting a bunch of caches
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if jemalloc_interface and evicting_due_to_memory and (i + 1) % 100 == 0:
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try:
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jemalloc_interface.refresh_stats()
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mem_usage = jemalloc_interface.get_stat("allocated")
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if mem_usage < target_cache_memory_usage:
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evicting_due_to_memory = False
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logger.info("Stop memory-based cache eviction.")
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except Exception:
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logger.warning(
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"Unable to read allocated memory, this may affect memory-based cache eviction."
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)
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# If we've failed to read the current memory usage then we
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# should stop trying to evict based on memory usage
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evicting_due_to_memory = False
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# If we do lots of work at once we yield to allow other stuff to happen.
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if (i + 1) % 10000 == 0:
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logger.debug("Waiting during drop")
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if node.last_access_ts_secs > now - expiry_seconds:
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await clock.sleep(0.5)
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else:
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await clock.sleep(0)
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logger.debug("Waking during drop")
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node = next_node
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# If we've yielded then our current node may have been evicted, so we
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# need to check that its still valid.
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if node.prev_node is None:
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break
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i += 1
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logger.info("Dropped %d items from caches", i)
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def setup_expire_lru_cache_entries(hs: "HomeServer") -> None:
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"""Start a background job that expires all cache entries if they have not
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been accessed for the given number of seconds, or if a given memory usage threshold has been
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breached.
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"""
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if not hs.config.caches.expiry_time_msec and not hs.config.caches.cache_autotuning:
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return
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if hs.config.caches.expiry_time_msec:
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expiry_time = hs.config.caches.expiry_time_msec / 1000
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logger.info("Expiring LRU caches after %d seconds", expiry_time)
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else:
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expiry_time = math.inf
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global USE_GLOBAL_LIST
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USE_GLOBAL_LIST = True
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clock = hs.get_clock()
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clock.looping_call(
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_expire_old_entries,
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30 * 1000,
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clock,
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expiry_time,
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hs.config.caches.cache_autotuning,
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)
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class _Node(Generic[KT, VT]):
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__slots__ = [
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"_list_node",
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"_global_list_node",
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"_cache",
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"key",
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"value",
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"callbacks",
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"memory",
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]
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def __init__(
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self,
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root: "ListNode[_Node]",
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key: KT,
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value: VT,
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cache: "weakref.ReferenceType[LruCache[KT, VT]]",
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clock: Clock,
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callbacks: Collection[Callable[[], None]] = (),
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prune_unread_entries: bool = True,
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):
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self._list_node = ListNode.insert_after(self, root)
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self._global_list_node: Optional[_TimedListNode] = None
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if USE_GLOBAL_LIST and prune_unread_entries:
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self._global_list_node = _TimedListNode.insert_after(self, GLOBAL_ROOT)
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self._global_list_node.update_last_access(clock)
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# We store a weak reference to the cache object so that this _Node can
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# remove itself from the cache. If the cache is dropped we ensure we
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# remove our entries in the lists.
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self._cache = cache
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self.key = key
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self.value = value
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# Set of callbacks to run when the node gets deleted. We store as a list
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# rather than a set to keep memory usage down (and since we expect few
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# entries per node, the performance of checking for duplication in a
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# list vs using a set is negligible).
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#
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# Note that we store this as an optional list to keep the memory
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# footprint down. Storing `None` is free as its a singleton, while empty
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# lists are 56 bytes (and empty sets are 216 bytes, if we did the naive
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# thing and used sets).
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self.callbacks: Optional[List[Callable[[], None]]] = None
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self.add_callbacks(callbacks)
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self.memory = 0
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if caches.TRACK_MEMORY_USAGE:
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self.memory = (
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_get_size_of(key)
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+ _get_size_of(value)
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+ _get_size_of(self._list_node, recurse=False)
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+ _get_size_of(self.callbacks, recurse=False)
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+ _get_size_of(self, recurse=False)
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)
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self.memory += _get_size_of(self.memory, recurse=False)
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if self._global_list_node:
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self.memory += _get_size_of(self._global_list_node, recurse=False)
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self.memory += _get_size_of(self._global_list_node.last_access_ts_secs)
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def add_callbacks(self, callbacks: Collection[Callable[[], None]]) -> None:
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"""Add to stored list of callbacks, removing duplicates."""
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if not callbacks:
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return
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if not self.callbacks:
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self.callbacks = []
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for callback in callbacks:
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if callback not in self.callbacks:
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self.callbacks.append(callback)
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def run_and_clear_callbacks(self) -> None:
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"""Run all callbacks and clear the stored list of callbacks. Used when
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the node is being deleted.
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"""
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if not self.callbacks:
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return
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for callback in self.callbacks:
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callback()
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self.callbacks = None
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def drop_from_cache(self) -> None:
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"""Drop this node from the cache.
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Ensures that the entry gets removed from the cache and that we get
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removed from all lists.
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"""
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cache = self._cache()
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if (
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cache is None
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or cache.pop(self.key, _Sentinel.sentinel) is _Sentinel.sentinel
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):
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# `cache.pop` should call `drop_from_lists()`, unless this Node had
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# already been removed from the cache.
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self.drop_from_lists()
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def drop_from_lists(self) -> None:
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"""Remove this node from the cache lists."""
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self._list_node.remove_from_list()
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if self._global_list_node:
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self._global_list_node.remove_from_list()
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def move_to_front(self, clock: Clock, cache_list_root: ListNode) -> None:
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"""Moves this node to the front of all the lists its in."""
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self._list_node.move_after(cache_list_root)
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if self._global_list_node:
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self._global_list_node.move_after(GLOBAL_ROOT)
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self._global_list_node.update_last_access(clock)
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class _Sentinel(Enum):
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# defining a sentinel in this way allows mypy to correctly handle the
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# type of a dictionary lookup.
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sentinel = object()
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class LruCache(Generic[KT, VT]):
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"""
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Least-recently-used cache, supporting prometheus metrics and invalidation callbacks.
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If cache_type=TreeCache, all keys must be tuples.
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"""
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def __init__(
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self,
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max_size: int,
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cache_name: Optional[str] = None,
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cache_type: Type[Union[dict, TreeCache]] = dict,
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size_callback: Optional[Callable[[VT], int]] = None,
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metrics_collection_callback: Optional[Callable[[], None]] = None,
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apply_cache_factor_from_config: bool = True,
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clock: Optional[Clock] = None,
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prune_unread_entries: bool = True,
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):
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"""
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Args:
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max_size: The maximum amount of entries the cache can hold
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cache_name: The name of this cache, for the prometheus metrics. If unset,
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no metrics will be reported on this cache.
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cache_type (type):
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type of underlying cache to be used. Typically one of dict
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or TreeCache.
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size_callback (func(V) -> int | None):
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metrics_collection_callback:
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metrics collection callback. This is called early in the metrics
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collection process, before any of the metrics registered with the
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prometheus Registry are collected, so can be used to update any dynamic
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metrics.
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Ignored if cache_name is None.
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apply_cache_factor_from_config (bool): If true, `max_size` will be
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multiplied by a cache factor derived from the homeserver config
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clock:
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prune_unread_entries: If True, cache entries that haven't been read recently
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will be evicted from the cache in the background. Set to False to
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opt-out of this behaviour.
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"""
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# Default `clock` to something sensible. Note that we rename it to
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# `real_clock` so that mypy doesn't think its still `Optional`.
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if clock is None:
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real_clock = Clock(cast(IReactorTime, reactor))
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else:
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real_clock = clock
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cache: Union[Dict[KT, _Node[KT, VT]], TreeCache] = cache_type()
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self.cache = cache # Used for introspection.
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self.apply_cache_factor_from_config = apply_cache_factor_from_config
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# Save the original max size, and apply the default size factor.
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self._original_max_size = max_size
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# We previously didn't apply the cache factor here, and as such some caches were
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# not affected by the global cache factor. Add an option here to disable applying
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# the cache factor when a cache is created
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if apply_cache_factor_from_config:
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self.max_size = int(max_size * cache_config.properties.default_factor_size)
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else:
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self.max_size = int(max_size)
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# register_cache might call our "set_cache_factor" callback; there's nothing to
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# do yet when we get resized.
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self._on_resize: Optional[Callable[[], None]] = None
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if cache_name is not None:
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metrics: Optional[CacheMetric] = register_cache(
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"lru_cache",
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cache_name,
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self,
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collect_callback=metrics_collection_callback,
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)
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else:
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metrics = None
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# this is exposed for access from outside this class
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self.metrics = metrics
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# We create a single weakref to self here so that we don't need to keep
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# creating more each time we create a `_Node`.
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weak_ref_to_self = weakref.ref(self)
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list_root = ListNode[_Node[KT, VT]].create_root_node()
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lock = threading.Lock()
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def evict() -> None:
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while cache_len() > self.max_size:
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# Get the last node in the list (i.e. the oldest node).
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todelete = list_root.prev_node
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# The list root should always have a valid `prev_node` if the
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# cache is not empty.
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assert todelete is not None
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# The node should always have a reference to a cache entry, as
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# we only drop the cache entry when we remove the node from the
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# list.
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node = todelete.get_cache_entry()
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assert node is not None
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evicted_len = delete_node(node)
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cache.pop(node.key, None)
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if metrics:
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metrics.inc_evictions(EvictionReason.size, evicted_len)
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def synchronized(f: FT) -> FT:
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@wraps(f)
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def inner(*args: Any, **kwargs: Any) -> Any:
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with lock:
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return f(*args, **kwargs)
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|
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return cast(FT, inner)
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|
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cached_cache_len = [0]
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if size_callback is not None:
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|
|
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def cache_len() -> int:
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return cached_cache_len[0]
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else:
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def cache_len() -> int:
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return len(cache)
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self.len = synchronized(cache_len)
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|
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def add_node(
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key: KT, value: VT, callbacks: Collection[Callable[[], None]] = ()
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) -> None:
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node: _Node[KT, VT] = _Node(
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list_root,
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key,
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value,
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weak_ref_to_self,
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real_clock,
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callbacks,
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prune_unread_entries,
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)
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cache[key] = node
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|
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if size_callback:
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cached_cache_len[0] += size_callback(node.value)
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if caches.TRACK_MEMORY_USAGE and metrics:
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metrics.inc_memory_usage(node.memory)
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|
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def move_node_to_front(node: _Node[KT, VT]) -> None:
|
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node.move_to_front(real_clock, list_root)
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|
|
def delete_node(node: _Node[KT, VT]) -> int:
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node.drop_from_lists()
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|
|
|
deleted_len = 1
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if size_callback:
|
|
deleted_len = size_callback(node.value)
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cached_cache_len[0] -= deleted_len
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|
|
node.run_and_clear_callbacks()
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|
|
if caches.TRACK_MEMORY_USAGE and metrics:
|
|
metrics.dec_memory_usage(node.memory)
|
|
|
|
return deleted_len
|
|
|
|
@overload
|
|
def cache_get(
|
|
key: KT,
|
|
default: Literal[None] = None,
|
|
callbacks: Collection[Callable[[], None]] = ...,
|
|
update_metrics: bool = ...,
|
|
) -> Optional[VT]:
|
|
...
|
|
|
|
@overload
|
|
def cache_get(
|
|
key: KT,
|
|
default: T,
|
|
callbacks: Collection[Callable[[], None]] = ...,
|
|
update_metrics: bool = ...,
|
|
) -> Union[T, VT]:
|
|
...
|
|
|
|
@synchronized
|
|
def cache_get(
|
|
key: KT,
|
|
default: Optional[T] = None,
|
|
callbacks: Collection[Callable[[], None]] = (),
|
|
update_metrics: bool = True,
|
|
) -> Union[None, T, VT]:
|
|
node = cache.get(key, None)
|
|
if node is not None:
|
|
move_node_to_front(node)
|
|
node.add_callbacks(callbacks)
|
|
if update_metrics and metrics:
|
|
metrics.inc_hits()
|
|
return node.value
|
|
else:
|
|
if update_metrics and metrics:
|
|
metrics.inc_misses()
|
|
return default
|
|
|
|
@synchronized
|
|
def cache_set(
|
|
key: KT, value: VT, callbacks: Collection[Callable[[], None]] = ()
|
|
) -> None:
|
|
node = cache.get(key, None)
|
|
if node is not None:
|
|
# We sometimes store large objects, e.g. dicts, which cause
|
|
# the inequality check to take a long time. So let's only do
|
|
# the check if we have some callbacks to call.
|
|
if value != node.value:
|
|
node.run_and_clear_callbacks()
|
|
|
|
# We don't bother to protect this by value != node.value as
|
|
# generally size_callback will be cheap compared with equality
|
|
# checks. (For example, taking the size of two dicts is quicker
|
|
# than comparing them for equality.)
|
|
if size_callback:
|
|
cached_cache_len[0] -= size_callback(node.value)
|
|
cached_cache_len[0] += size_callback(value)
|
|
|
|
node.add_callbacks(callbacks)
|
|
|
|
move_node_to_front(node)
|
|
node.value = value
|
|
else:
|
|
add_node(key, value, set(callbacks))
|
|
|
|
evict()
|
|
|
|
@synchronized
|
|
def cache_set_default(key: KT, value: VT) -> VT:
|
|
node = cache.get(key, None)
|
|
if node is not None:
|
|
return node.value
|
|
else:
|
|
add_node(key, value)
|
|
evict()
|
|
return value
|
|
|
|
@overload
|
|
def cache_pop(key: KT, default: Literal[None] = None) -> Optional[VT]:
|
|
...
|
|
|
|
@overload
|
|
def cache_pop(key: KT, default: T) -> Union[T, VT]:
|
|
...
|
|
|
|
@synchronized
|
|
def cache_pop(key: KT, default: Optional[T] = None) -> Union[None, T, VT]:
|
|
node = cache.get(key, None)
|
|
if node:
|
|
evicted_len = delete_node(node)
|
|
cache.pop(node.key, None)
|
|
if metrics:
|
|
metrics.inc_evictions(EvictionReason.invalidation, evicted_len)
|
|
return node.value
|
|
else:
|
|
return default
|
|
|
|
@synchronized
|
|
def cache_del_multi(key: KT) -> None:
|
|
"""Delete an entry, or tree of entries
|
|
|
|
If the LruCache is backed by a regular dict, then "key" must be of
|
|
the right type for this cache
|
|
|
|
If the LruCache is backed by a TreeCache, then "key" must be a tuple, but
|
|
may be of lower cardinality than the TreeCache - in which case the whole
|
|
subtree is deleted.
|
|
"""
|
|
popped = cache.pop(key, None)
|
|
if popped is None:
|
|
return
|
|
# for each deleted node, we now need to remove it from the linked list
|
|
# and run its callbacks.
|
|
for leaf in iterate_tree_cache_entry(popped):
|
|
delete_node(leaf)
|
|
|
|
@synchronized
|
|
def cache_clear() -> None:
|
|
for node in cache.values():
|
|
node.run_and_clear_callbacks()
|
|
node.drop_from_lists()
|
|
|
|
assert list_root.next_node == list_root
|
|
assert list_root.prev_node == list_root
|
|
|
|
cache.clear()
|
|
if size_callback:
|
|
cached_cache_len[0] = 0
|
|
|
|
if caches.TRACK_MEMORY_USAGE and metrics:
|
|
metrics.clear_memory_usage()
|
|
|
|
@synchronized
|
|
def cache_contains(key: KT) -> bool:
|
|
return key in cache
|
|
|
|
# make sure that we clear out any excess entries after we get resized.
|
|
self._on_resize = evict
|
|
|
|
self.get = cache_get
|
|
self.set = cache_set
|
|
self.setdefault = cache_set_default
|
|
self.pop = cache_pop
|
|
self.del_multi = cache_del_multi
|
|
# `invalidate` is exposed for consistency with DeferredCache, so that it can be
|
|
# invalidated by the cache invalidation replication stream.
|
|
self.invalidate = cache_del_multi
|
|
self.len = synchronized(cache_len)
|
|
self.contains = cache_contains
|
|
self.clear = cache_clear
|
|
|
|
def __getitem__(self, key: KT) -> VT:
|
|
result = self.get(key, _Sentinel.sentinel)
|
|
if result is _Sentinel.sentinel:
|
|
raise KeyError()
|
|
else:
|
|
return result
|
|
|
|
def __setitem__(self, key: KT, value: VT) -> None:
|
|
self.set(key, value)
|
|
|
|
def __delitem__(self, key: KT, value: VT) -> None:
|
|
result = self.pop(key, _Sentinel.sentinel)
|
|
if result is _Sentinel.sentinel:
|
|
raise KeyError()
|
|
|
|
def __len__(self) -> int:
|
|
return self.len()
|
|
|
|
def __contains__(self, key: KT) -> bool:
|
|
return self.contains(key)
|
|
|
|
def set_cache_factor(self, factor: float) -> bool:
|
|
"""
|
|
Set the cache factor for this individual cache.
|
|
|
|
This will trigger a resize if it changes, which may require evicting
|
|
items from the cache.
|
|
|
|
Returns:
|
|
bool: Whether the cache changed size or not.
|
|
"""
|
|
if not self.apply_cache_factor_from_config:
|
|
return False
|
|
|
|
new_size = int(self._original_max_size * factor)
|
|
if new_size != self.max_size:
|
|
self.max_size = new_size
|
|
if self._on_resize:
|
|
self._on_resize()
|
|
return True
|
|
return False
|
|
|
|
def __del__(self) -> None:
|
|
# We're about to be deleted, so we make sure to clear up all the nodes
|
|
# and run callbacks, etc.
|
|
#
|
|
# This happens e.g. in the sync code where we have an expiring cache of
|
|
# lru caches.
|
|
self.clear()
|