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547b1355d3
The get_entities_changed function was changed to return all changed entities since the given stream position, rather than only those changed from a given list of entities. This resulted in the function incorrectly returning large numbers of entities that, for example, caused large increases in database usage.
149 lines
5.1 KiB
Python
149 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 = {
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e for e in entities
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if e in changed_entities
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}
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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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