diff options
Diffstat (limited to 'synapse/util/caches/stream_change_cache.py')
| -rw-r--r-- | synapse/util/caches/stream_change_cache.py | 158 |
1 files changed, 113 insertions, 45 deletions
diff --git a/synapse/util/caches/stream_change_cache.py b/synapse/util/caches/stream_change_cache.py index 235f64049c..2a161bf244 100644 --- a/synapse/util/caches/stream_change_cache.py +++ b/synapse/util/caches/stream_change_cache.py @@ -14,17 +14,23 @@ # limitations under the License. import logging +import math +from typing import Dict, FrozenSet, List, Mapping, Optional, Set, Union from six import integer_types from sortedcontainers import SortedDict +from synapse.types import Collection from synapse.util import caches logger = logging.getLogger(__name__) +# for now, assume all entities in the cache are strings +EntityType = str -class StreamChangeCache(object): + +class StreamChangeCache: """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. @@ -34,19 +40,52 @@ class StreamChangeCache(object): old then the cache will simply return all given entities. """ - def __init__(self, name, current_stream_pos, max_size=10000, prefilled_cache=None): - self._max_size = int(max_size * caches.CACHE_SIZE_FACTOR) - self._entity_to_key = {} - self._cache = SortedDict() + def __init__( + self, + name: str, + current_stream_pos: int, + max_size=10000, + prefilled_cache: Optional[Mapping[EntityType, int]] = None, + ): + self._original_max_size = max_size + self._max_size = math.floor(max_size) + self._entity_to_key = {} # type: Dict[EntityType, int] + + # map from stream id to the a set of entities which changed at that stream id. + self._cache = SortedDict() # type: SortedDict[int, Set[EntityType]] + + # the earliest stream_pos for which we can reliably answer + # get_all_entities_changed. In other words, one less than the earliest + # stream_pos for which we know _cache is valid. + # self._earliest_known_stream_pos = current_stream_pos self.name = name - self.metrics = caches.register_cache("cache", self.name, self._cache) + self.metrics = caches.register_cache( + "cache", self.name, self._cache, resize_callback=self.set_cache_factor + ) if prefilled_cache: for entity, stream_pos in prefilled_cache.items(): self.entity_has_changed(entity, stream_pos) - def has_entity_changed(self, entity, stream_pos): + def set_cache_factor(self, factor: float) -> bool: + """ + Set the cache factor for this individual cache. + + This will trigger a resize if it changes, which may require evicting + items from the cache. + + Returns: + bool: Whether the cache changed size or not. + """ + new_size = math.floor(self._original_max_size * factor) + if new_size != self._max_size: + self.max_size = new_size + self._evict() + return True + return False + + def has_entity_changed(self, entity: EntityType, stream_pos: int) -> bool: """Returns True if the entity may have been updated since stream_pos """ assert type(stream_pos) in integer_types @@ -67,22 +106,27 @@ class StreamChangeCache(object): self.metrics.inc_hits() return False - def get_entities_changed(self, entities, stream_pos): + def get_entities_changed( + self, entities: Collection[EntityType], stream_pos: int + ) -> Union[Set[EntityType], FrozenSet[EntityType]]: """ Returns subset of entities that have had new things since the given position. Entities unknown to the cache will be returned. 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: - changed_entities = { - self._cache[k] - for k in self._cache.islice(start=self._cache.bisect_right(stream_pos)) - } - - result = changed_entities.intersection(entities) - + changed_entities = self.get_all_entities_changed(stream_pos) + if changed_entities is not None: + # We now do an intersection, trying to do so in the most efficient + # way possible (some of these sets are *large*). First check in the + # given iterable is already set that we can reuse, otherwise we + # create a set of the *smallest* of the two iterables and call + # `intersection(..)` on it (this can be twice as fast as the reverse). + if isinstance(entities, (set, frozenset)): + result = entities.intersection(changed_entities) + elif len(changed_entities) < len(entities): + result = set(changed_entities).intersection(entities) + else: + result = set(entities).intersection(changed_entities) self.metrics.inc_hits() else: result = set(entities) @@ -90,13 +134,13 @@ class StreamChangeCache(object): return result - def has_any_entity_changed(self, stream_pos): + def has_any_entity_changed(self, stream_pos: int) -> bool: """Returns if any entity has changed """ assert type(stream_pos) is int if not self._cache: - # If we have no cache, nothing can have changed. + # If the cache is empty, nothing can have changed. return False if stream_pos >= self._earliest_known_stream_pos: @@ -106,42 +150,66 @@ class StreamChangeCache(object): 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 + def get_all_entities_changed(self, stream_pos: int) -> Optional[List[EntityType]]: + """Returns all entities that have had new things since the given position. If the position is too old it will return None. + + Returns the entities in the order that they were changed. """ assert type(stream_pos) is int - if stream_pos >= self._earliest_known_stream_pos: - return [ - self._cache[k] - for k in self._cache.islice(start=self._cache.bisect_right(stream_pos)) - ] - else: + if stream_pos < self._earliest_known_stream_pos: return None - def entity_has_changed(self, entity, stream_pos): + changed_entities = [] # type: List[EntityType] + + for k in self._cache.islice(start=self._cache.bisect_right(stream_pos)): + changed_entities.extend(self._cache[k]) + return changed_entities + + def entity_has_changed(self, entity: EntityType, stream_pos: int) -> None: """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(0) - 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): + if stream_pos <= self._earliest_known_stream_pos: + return + + old_pos = self._entity_to_key.get(entity, None) + if old_pos is not None: + if old_pos >= stream_pos: + # nothing to do + return + e = self._cache[old_pos] + e.remove(entity) + if not e: + # cache at this point is now empty + del self._cache[old_pos] + + e1 = self._cache.get(stream_pos) + if e1 is None: + e1 = self._cache[stream_pos] = set() + e1.add(entity) + self._entity_to_key[entity] = stream_pos + self._evict() + + # if the cache is too big, remove entries + while len(self._cache) > self._max_size: + k, r = self._cache.popitem(0) + self._earliest_known_stream_pos = max(k, self._earliest_known_stream_pos) + for entity in r: + del self._entity_to_key[entity] + + def _evict(self): + while len(self._cache) > self._max_size: + k, r = self._cache.popitem(0) + self._earliest_known_stream_pos = max(k, self._earliest_known_stream_pos) + for entity in r: + self._entity_to_key.pop(entity, None) + + def get_max_pos_of_last_change(self, entity: EntityType) -> int: + """Returns an upper bound of the stream id of the last change to an entity. """ |