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![Erik Johnston](/assets/img/avatar_default.png)
Instead of calculating the size of the cache repeatedly, which can take a long time now that it can use a callback, instead cache the size and update that on insertion and deletion. This requires changing the cache descriptors to have two caches, one for pending deferreds and the other for the actual values. There's no reason to evict from the pending deferreds as they won't take up any more memory.
229 lines
6.8 KiB
Python
229 lines
6.8 KiB
Python
# -*- coding: utf-8 -*-
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# 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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from functools import wraps
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import threading
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from synapse.util.caches.treecache import TreeCache
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def enumerate_leaves(node, depth):
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if depth == 0:
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yield node
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else:
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for n in node.values():
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for m in enumerate_leaves(n, depth - 1):
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yield m
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class _Node(object):
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__slots__ = ["prev_node", "next_node", "key", "value", "callbacks"]
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def __init__(self, prev_node, next_node, key, value, callbacks=set()):
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self.prev_node = prev_node
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self.next_node = next_node
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self.key = key
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self.value = value
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self.callbacks = callbacks
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class LruCache(object):
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"""
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Least-recently-used cache.
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Supports del_multi only if cache_type=TreeCache
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If cache_type=TreeCache, all keys must be tuples.
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Can also set callbacks on objects when getting/setting which are fired
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when that key gets invalidated/evicted.
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"""
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def __init__(self, max_size, keylen=1, cache_type=dict, size_callback=None):
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cache = cache_type()
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self.cache = cache # Used for introspection.
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list_root = _Node(None, None, None, None)
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list_root.next_node = list_root
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list_root.prev_node = list_root
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lock = threading.Lock()
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def evict():
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while cache_len() > max_size:
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todelete = list_root.prev_node
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delete_node(todelete)
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cache.pop(todelete.key, None)
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def synchronized(f):
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@wraps(f)
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def inner(*args, **kwargs):
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with lock:
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return f(*args, **kwargs)
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return inner
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cached_cache_len = [0]
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if size_callback is not None:
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def cache_len():
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return cached_cache_len[0]
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else:
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def cache_len():
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return len(cache)
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self.len = synchronized(cache_len)
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def add_node(key, value, callbacks=set()):
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prev_node = list_root
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next_node = prev_node.next_node
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node = _Node(prev_node, next_node, key, value, callbacks)
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prev_node.next_node = node
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next_node.prev_node = node
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cache[key] = node
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if size_callback:
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cached_cache_len[0] += size_callback(node.value)
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def move_node_to_front(node):
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prev_node = node.prev_node
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next_node = node.next_node
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prev_node.next_node = next_node
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next_node.prev_node = prev_node
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prev_node = list_root
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next_node = prev_node.next_node
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node.prev_node = prev_node
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node.next_node = next_node
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prev_node.next_node = node
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next_node.prev_node = node
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def delete_node(node):
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prev_node = node.prev_node
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next_node = node.next_node
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prev_node.next_node = next_node
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next_node.prev_node = prev_node
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if size_callback:
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cached_cache_len[0] -= size_callback(node.value)
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for cb in node.callbacks:
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cb()
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node.callbacks.clear()
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@synchronized
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def cache_get(key, default=None, callbacks=[]):
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node = cache.get(key, None)
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if node is not None:
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move_node_to_front(node)
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node.callbacks.update(callbacks)
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return node.value
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else:
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return default
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@synchronized
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def cache_set(key, value, callbacks=[]):
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node = cache.get(key, None)
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if node is not None:
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if value != node.value:
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for cb in node.callbacks:
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cb()
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node.callbacks.clear()
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if size_callback:
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cached_cache_len[0] -= size_callback(node.value)
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cached_cache_len[0] += size_callback(value)
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node.callbacks.update(callbacks)
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move_node_to_front(node)
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node.value = value
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else:
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add_node(key, value, set(callbacks))
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evict()
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@synchronized
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def cache_set_default(key, value):
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node = cache.get(key, None)
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if node is not None:
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evict() # As the new node may be bigger than the old node.
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return node.value
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else:
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add_node(key, value)
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evict()
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return value
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@synchronized
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def cache_pop(key, default=None):
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node = cache.get(key, None)
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if node:
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delete_node(node)
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cache.pop(node.key, None)
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return node.value
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else:
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return default
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@synchronized
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def cache_del_multi(key):
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"""
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This will only work if constructed with cache_type=TreeCache
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"""
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popped = cache.pop(key)
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if popped is None:
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return
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for leaf in enumerate_leaves(popped, keylen - len(key)):
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delete_node(leaf)
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@synchronized
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def cache_clear():
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list_root.next_node = list_root
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list_root.prev_node = list_root
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for node in cache.values():
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for cb in node.callbacks:
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cb()
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cache.clear()
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@synchronized
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def cache_contains(key):
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return key in cache
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self.sentinel = object()
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self.get = cache_get
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self.set = cache_set
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self.setdefault = cache_set_default
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self.pop = cache_pop
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if cache_type is TreeCache:
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self.del_multi = cache_del_multi
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self.len = synchronized(cache_len)
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self.contains = cache_contains
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self.clear = cache_clear
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def __getitem__(self, key):
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result = self.get(key, self.sentinel)
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if result is self.sentinel:
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raise KeyError()
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else:
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return result
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def __setitem__(self, key, value):
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self.set(key, value)
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def __delitem__(self, key, value):
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result = self.pop(key, self.sentinel)
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if result is self.sentinel:
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raise KeyError()
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def __len__(self):
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return self.len()
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def __contains__(self, key):
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return self.contains(key)
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