145 lines
4.8 KiB
Python
145 lines
4.8 KiB
Python
# -*- 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.
|
|
|
|
import logging
|
|
import threading
|
|
from collections import namedtuple
|
|
|
|
from synapse.util.caches.lrucache import LruCache
|
|
|
|
from . import register_cache
|
|
|
|
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, fetched_keys=None):
|
|
"""Updates the entry in the cache
|
|
|
|
Args:
|
|
sequence
|
|
key (K)
|
|
value (dict[X,Y]): The value to update the cache with.
|
|
fetched_keys (None|set[X]): All of the dictionary keys which were
|
|
fetched from the database.
|
|
|
|
If None, this is the complete value for key K. Otherwise, it
|
|
is used to infer a list of keys which 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 fetched_keys is None:
|
|
self._insert(key, value, set())
|
|
else:
|
|
self._update_or_insert(key, value, fetched_keys)
|
|
|
|
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)
|