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- # -*- coding: utf-8 -*-
- # Copyright 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.
- from synapse.util.caches import register_cache, CACHE_SIZE_FACTOR
- from blist import sorteddict
- import logging
- logger = logging.getLogger(__name__)
- class StreamChangeCache(object):
- """Keeps track of the stream positions of the latest change in a set of entities.
- Typically the entity will be a room or user id.
- Given a list of entities and a stream position, it will give a subset of
- entities that may have changed since that position. If position key is too
- old then the cache will simply return all given entities.
- """
- def __init__(self, name, current_stream_pos, max_size=10000, prefilled_cache={}):
- self._max_size = int(max_size * CACHE_SIZE_FACTOR)
- self._entity_to_key = {}
- self._cache = sorteddict()
- self._earliest_known_stream_pos = current_stream_pos
- self.name = name
- self.metrics = register_cache("cache", self.name, self._cache)
- for entity, stream_pos in prefilled_cache.items():
- self.entity_has_changed(entity, stream_pos)
- def has_entity_changed(self, entity, stream_pos):
- """Returns True if the entity may have been updated since stream_pos
- """
- assert type(stream_pos) is int or type(stream_pos) is long
- if stream_pos < self._earliest_known_stream_pos:
- self.metrics.inc_misses()
- return True
- latest_entity_change_pos = self._entity_to_key.get(entity, None)
- if latest_entity_change_pos is None:
- self.metrics.inc_hits()
- return False
- if stream_pos < latest_entity_change_pos:
- self.metrics.inc_misses()
- return True
- self.metrics.inc_hits()
- return False
- def get_entities_changed(self, entities, stream_pos):
- """Returns subset of entities that have had new things since the
- given position. If the position is too old it will just return the given list.
- """
- assert type(stream_pos) is int
- if stream_pos >= self._earliest_known_stream_pos:
- keys = self._cache.keys()
- i = keys.bisect_right(stream_pos)
- result = set(
- self._cache[k] for k in keys[i:]
- ).intersection(entities)
- self.metrics.inc_hits()
- else:
- result = entities
- self.metrics.inc_misses()
- return result
- def has_any_entity_changed(self, stream_pos):
- """Returns if any entity has changed
- """
- assert type(stream_pos) is int
- if stream_pos >= self._earliest_known_stream_pos:
- self.metrics.inc_hits()
- keys = self._cache.keys()
- i = keys.bisect_right(stream_pos)
- return i < len(keys)
- else:
- self.metrics.inc_misses()
- return True
- def get_all_entities_changed(self, stream_pos):
- """Returns all entites that have had new things since the given
- position. If the position is too old it will return None.
- """
- assert type(stream_pos) is int
- if stream_pos >= self._earliest_known_stream_pos:
- keys = self._cache.keys()
- i = keys.bisect_right(stream_pos)
- return [self._cache[k] for k in keys[i:]]
- else:
- return None
- def entity_has_changed(self, entity, stream_pos):
- """Informs the cache that the entity has been changed at the given
- position.
- """
- assert type(stream_pos) is int
- if stream_pos > self._earliest_known_stream_pos:
- old_pos = self._entity_to_key.get(entity, None)
- if old_pos is not None:
- stream_pos = max(stream_pos, old_pos)
- self._cache.pop(old_pos, None)
- self._cache[stream_pos] = entity
- self._entity_to_key[entity] = stream_pos
- while len(self._cache) > self._max_size:
- k, r = self._cache.popitem()
- self._earliest_known_stream_pos = max(k, self._earliest_known_stream_pos)
- self._entity_to_key.pop(r, None)
- def get_max_pos_of_last_change(self, entity):
- """Returns an upper bound of the stream id of the last change to an
- entity.
- """
- return self._entity_to_key.get(entity, self._earliest_known_stream_pos)
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