diff --git a/synapse/storage/data_stores/main/cache.py b/synapse/storage/data_stores/main/cache.py
new file mode 100644
index 0000000000..6efcc5f3b0
--- /dev/null
+++ b/synapse/storage/data_stores/main/cache.py
@@ -0,0 +1,131 @@
+# -*- coding: utf-8 -*-
+# Copyright 2019 The Matrix.org Foundation C.I.C.
+#
+# 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.
+
+
+import itertools
+import logging
+
+from twisted.internet import defer
+
+from synapse.storage._base import SQLBaseStore
+from synapse.storage.engines import PostgresEngine
+from synapse.util import batch_iter
+
+logger = logging.getLogger(__name__)
+
+
+# This is a special cache name we use to batch multiple invalidations of caches
+# based on the current state when notifying workers over replication.
+_CURRENT_STATE_CACHE_NAME = "cs_cache_fake"
+
+
+class CacheInvalidationStore(SQLBaseStore):
+ def _invalidate_cache_and_stream(self, txn, cache_func, keys):
+ """Invalidates the cache and adds it to the cache stream so slaves
+ will know to invalidate their caches.
+
+ This should only be used to invalidate caches where slaves won't
+ otherwise know from other replication streams that the cache should
+ be invalidated.
+ """
+ txn.call_after(cache_func.invalidate, keys)
+ self._send_invalidation_to_replication(txn, cache_func.__name__, keys)
+
+ def _invalidate_state_caches_and_stream(self, txn, room_id, members_changed):
+ """Special case invalidation of caches based on current state.
+
+ We special case this so that we can batch the cache invalidations into a
+ single replication poke.
+
+ Args:
+ txn
+ room_id (str): Room where state changed
+ members_changed (iterable[str]): The user_ids of members that have changed
+ """
+ txn.call_after(self._invalidate_state_caches, room_id, members_changed)
+
+ if members_changed:
+ # We need to be careful that the size of the `members_changed` list
+ # isn't so large that it causes problems sending over replication, so we
+ # send them in chunks.
+ # Max line length is 16K, and max user ID length is 255, so 50 should
+ # be safe.
+ for chunk in batch_iter(members_changed, 50):
+ keys = itertools.chain([room_id], chunk)
+ self._send_invalidation_to_replication(
+ txn, _CURRENT_STATE_CACHE_NAME, keys
+ )
+ else:
+ # if no members changed, we still need to invalidate the other caches.
+ self._send_invalidation_to_replication(
+ txn, _CURRENT_STATE_CACHE_NAME, [room_id]
+ )
+
+ def _send_invalidation_to_replication(self, txn, cache_name, keys):
+ """Notifies replication that given cache has been invalidated.
+
+ Note that this does *not* invalidate the cache locally.
+
+ Args:
+ txn
+ cache_name (str)
+ keys (iterable[str])
+ """
+
+ if isinstance(self.database_engine, PostgresEngine):
+ # get_next() returns a context manager which is designed to wrap
+ # the transaction. However, we want to only get an ID when we want
+ # to use it, here, so we need to call __enter__ manually, and have
+ # __exit__ called after the transaction finishes.
+ ctx = self._cache_id_gen.get_next()
+ stream_id = ctx.__enter__()
+ txn.call_on_exception(ctx.__exit__, None, None, None)
+ txn.call_after(ctx.__exit__, None, None, None)
+ txn.call_after(self.hs.get_notifier().on_new_replication_data)
+
+ self._simple_insert_txn(
+ txn,
+ table="cache_invalidation_stream",
+ values={
+ "stream_id": stream_id,
+ "cache_func": cache_name,
+ "keys": list(keys),
+ "invalidation_ts": self.clock.time_msec(),
+ },
+ )
+
+ def get_all_updated_caches(self, last_id, current_id, limit):
+ if last_id == current_id:
+ return defer.succeed([])
+
+ def get_all_updated_caches_txn(txn):
+ # We purposefully don't bound by the current token, as we want to
+ # send across cache invalidations as quickly as possible. Cache
+ # invalidations are idempotent, so duplicates are fine.
+ sql = (
+ "SELECT stream_id, cache_func, keys, invalidation_ts"
+ " FROM cache_invalidation_stream"
+ " WHERE stream_id > ? ORDER BY stream_id ASC LIMIT ?"
+ )
+ txn.execute(sql, (last_id, limit))
+ return txn.fetchall()
+
+ return self.runInteraction("get_all_updated_caches", get_all_updated_caches_txn)
+
+ def get_cache_stream_token(self):
+ if self._cache_id_gen:
+ return self._cache_id_gen.get_current_token()
+ else:
+ return 0
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