diff --git a/synapse/handlers/message.py b/synapse/handlers/message.py
index ccdd3d8473..bef477b31e 100644
--- a/synapse/handlers/message.py
+++ b/synapse/handlers/message.py
@@ -22,6 +22,7 @@ from synapse.events.utils import serialize_event
from synapse.events.validator import EventValidator
from synapse.util import unwrapFirstError
from synapse.util.logcontext import PreserveLoggingContext
+from synapse.util.caches.snapshot_cache import SnapshotCache
from synapse.types import UserID, RoomStreamToken, StreamToken
from ._base import BaseHandler
@@ -45,6 +46,7 @@ class MessageHandler(BaseHandler):
self.state = hs.get_state_handler()
self.clock = hs.get_clock()
self.validator = EventValidator()
+ self.snapshot_cache = SnapshotCache()
@defer.inlineCallbacks
def get_message(self, msg_id=None, room_id=None, sender_id=None,
@@ -326,9 +328,29 @@ class MessageHandler(BaseHandler):
[serialize_event(c, now) for c in room_state.values()]
)
- @defer.inlineCallbacks
def snapshot_all_rooms(self, user_id=None, pagin_config=None,
as_client_event=True, include_archived=False):
+ key = (
+ user_id,
+ pagin_config.from_token,
+ pagin_config.to_token,
+ pagin_config.direction,
+ pagin_config.limit,
+ as_client_event,
+ include_archived,
+ )
+ now_ms = self.clock.time_msec()
+ result = self.snapshot_cache.get(now_ms, key)
+ if result is not None:
+ return result
+
+ return self.snapshot_cache.set(now_ms, key, self._snapshot_all_rooms(
+ user_id, pagin_config, as_client_event, include_archived
+ ))
+
+ @defer.inlineCallbacks
+ def _snapshot_all_rooms(self, user_id=None, pagin_config=None,
+ as_client_event=True, include_archived=False):
"""Retrieve a snapshot of all rooms the user is invited or has joined.
This snapshot may include messages for all rooms where the user is
diff --git a/synapse/util/caches/snapshot_cache.py b/synapse/util/caches/snapshot_cache.py
new file mode 100644
index 0000000000..b19aca05ab
--- /dev/null
+++ b/synapse/util/caches/snapshot_cache.py
@@ -0,0 +1,71 @@
+# -*- coding: utf-8 -*-
+# Copyright 2015 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.async import ObservableDeferred
+
+
+class SnapshotCache(object):
+
+ DURATION_MS = 5 * 60 * 1000 # Cache results for 2 minutes.
+
+ def __init__(self):
+ self.pending_result_cache = {} # Request that haven't finished yet.
+ self.prev_result_cache = {} # The older requests that have finished.
+ self.next_result_cache = {} # The newer requests that have finished.
+ self.time_last_rotated_ms = 0
+
+ def rotate(self, time_now_ms):
+ # Rotate once if the cache duration has passed since the last rotation.
+ if time_now_ms - self.time_last_rotated_ms > self.DURATION_MS:
+ self.prev_result_cache = self.next_result_cache
+ self.next_result_cache = {}
+ self.time_last_rotated_ms += self.DURATION_MS
+
+ # Rotate again if the cache duration has passed twice since the last
+ # rotation.
+ if time_now_ms - self.time_last_rotated_ms > self.DURATION_MS:
+ self.prev_result_cache = self.next_result_cache
+ self.next_result_cache = {}
+ self.time_last_rotated_ms = time_now_ms
+
+ def get(self, time_now_ms, key):
+ self.rotate(time_now_ms)
+ # This cache is intended to deduplicate requests, so we expect it to be
+ # missed most of the time. So we just lookup the key in all of the
+ # dictionaries rather than trying to short circuit the lookup if the
+ # key is found.
+ result = self.prev_result_cache.get(key)
+ result = self.next_result_cache.get(key, result)
+ result = self.pending_result_cache.get(key, result)
+ if result is not None:
+ return result.observe()
+
+ def set(self, time_now_ms, key, deferred):
+ self.rotate(time_now_ms)
+
+ result = ObservableDeferred(deferred)
+
+ self.pending_result_cache[key] = result
+
+ def shuffle_along(r):
+ # When the deferred completes we shuffle it along to the first
+ # generation of the result cache. So that it will eventually
+ # expire from the rotation of that cache.
+ self.next_result_cache[key] = result
+ self.pending_result_cache.pop(key, None)
+
+ result.observe().addBoth(shuffle_along)
+
+ return result.observe()
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