diff --git a/synapse/util/caches/stream_change_cache.py b/synapse/util/caches/stream_change_cache.py
index e54f80d76e..2a161bf244 100644
--- a/synapse/util/caches/stream_change_cache.py
+++ b/synapse/util/caches/stream_change_cache.py
@@ -14,6 +14,7 @@
# limitations under the License.
import logging
+import math
from typing import Dict, FrozenSet, List, Mapping, Optional, Set, Union
from six import integer_types
@@ -46,7 +47,8 @@ class StreamChangeCache:
max_size=10000,
prefilled_cache: Optional[Mapping[EntityType, int]] = None,
):
- self._max_size = int(max_size * caches.CACHE_SIZE_FACTOR)
+ 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.
@@ -58,12 +60,31 @@ class StreamChangeCache:
#
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 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
"""
@@ -171,6 +192,7 @@ class StreamChangeCache:
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:
@@ -179,6 +201,13 @@ class StreamChangeCache:
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
|
