146 lines
5.1 KiB
Python
146 lines
5.1 KiB
Python
# -*- coding: utf-8 -*-
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# Copyright 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 sortedcontainers import SortedDict
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from synapse.util import caches
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logger = logging.getLogger(__name__)
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class StreamChangeCache(object):
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"""Keeps track of the stream positions of the latest change in a set of entities.
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Typically the entity will be a room or user id.
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Given a list of entities and a stream position, it will give a subset of
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entities that may have changed since that position. If position key is too
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old then the cache will simply return all given entities.
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"""
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def __init__(self, name, current_stream_pos, max_size=10000, prefilled_cache=None):
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self._max_size = int(max_size * caches.CACHE_SIZE_FACTOR)
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self._entity_to_key = {}
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self._cache = SortedDict()
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self._earliest_known_stream_pos = current_stream_pos
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self.name = name
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self.metrics = caches.register_cache("cache", self.name, self._cache)
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if prefilled_cache:
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for entity, stream_pos in prefilled_cache.items():
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self.entity_has_changed(entity, stream_pos)
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def has_entity_changed(self, entity, stream_pos):
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"""Returns True if the entity may have been updated since stream_pos
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"""
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assert type(stream_pos) is int or type(stream_pos) is long
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if stream_pos < self._earliest_known_stream_pos:
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self.metrics.inc_misses()
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return True
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latest_entity_change_pos = self._entity_to_key.get(entity, None)
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if latest_entity_change_pos is None:
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self.metrics.inc_hits()
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return False
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if stream_pos < latest_entity_change_pos:
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self.metrics.inc_misses()
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return True
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self.metrics.inc_hits()
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return False
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def get_entities_changed(self, entities, stream_pos):
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"""
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Returns subset of entities that have had new things since the given
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position. Entities unknown to the cache will be returned. If the
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position is too old it will just return the given list.
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"""
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assert type(stream_pos) is int
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if stream_pos >= self._earliest_known_stream_pos:
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changed_entities = {
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self._cache[k] for k in self._cache.islice(
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start=self._cache.bisect_right(stream_pos),
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)
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}
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result = changed_entities.intersection(entities)
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self.metrics.inc_hits()
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else:
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result = set(entities)
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self.metrics.inc_misses()
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return result
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def has_any_entity_changed(self, stream_pos):
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"""Returns if any entity has changed
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"""
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assert type(stream_pos) is int
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if not self._cache:
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# If we have no cache, nothing can have changed.
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return False
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if stream_pos >= self._earliest_known_stream_pos:
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self.metrics.inc_hits()
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return self._cache.bisect_right(stream_pos) < len(self._cache)
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else:
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self.metrics.inc_misses()
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return True
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def get_all_entities_changed(self, stream_pos):
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"""Returns all entites that have had new things since the given
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position. If the position is too old it will return None.
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"""
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assert type(stream_pos) is int
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if stream_pos >= self._earliest_known_stream_pos:
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return [self._cache[k] for k in self._cache.islice(
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start=self._cache.bisect_right(stream_pos))]
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else:
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return None
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def entity_has_changed(self, entity, stream_pos):
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"""Informs the cache that the entity has been changed at the given
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position.
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"""
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assert type(stream_pos) is int
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if stream_pos > self._earliest_known_stream_pos:
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old_pos = self._entity_to_key.get(entity, None)
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if old_pos is not None:
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stream_pos = max(stream_pos, old_pos)
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self._cache.pop(old_pos, None)
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self._cache[stream_pos] = entity
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self._entity_to_key[entity] = stream_pos
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while len(self._cache) > self._max_size:
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k, r = self._cache.popitem(0)
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self._earliest_known_stream_pos = max(
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k, self._earliest_known_stream_pos,
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)
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self._entity_to_key.pop(r, None)
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def get_max_pos_of_last_change(self, entity):
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"""Returns an upper bound of the stream id of the last change to an
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entity.
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"""
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return self._entity_to_key.get(entity, self._earliest_known_stream_pos)
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