1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
|
# -*- 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)
|
