diff --git a/synapse/handlers/message.py b/synapse/handlers/message.py
index ccdd3d8473..a1bed9b0dc 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,
@@ -326,7 +328,6 @@ 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):
"""Retrieve a snapshot of all rooms the user is invited or has joined.
@@ -346,6 +347,28 @@ class MessageHandler(BaseHandler):
is joined on, may return a "messages" key with messages, depending
on the specified PaginationConfig.
"""
+ 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):
+
memberships = [Membership.INVITE, Membership.JOIN]
if include_archived:
memberships.append(Membership.LEAVE)
diff --git a/synapse/util/caches/snapshot_cache.py b/synapse/util/caches/snapshot_cache.py
new file mode 100644
index 0000000000..09f00afbc5
--- /dev/null
+++ b/synapse/util/caches/snapshot_cache.py
@@ -0,0 +1,93 @@
+# -*- 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):
+ """Cache for snapshots like the response of /initialSync.
+ The response of initialSync only has to be a recent snapshot of the
+ server state. It shouldn't matter to clients if it is a few minutes out
+ of date.
+
+ This caches a deferred response. Until the deferred completes it will be
+ returned from the cache. This means that if the client retries the request
+ while the response is still being computed, that original response will be
+ used rather than trying to compute a new response.
+
+ Once the deferred completes it will removed from the cache after 5 minutes.
+ We delay removing it from the cache because a client retrying its request
+ could race with us finishing computing the response.
+
+ Rather than tracking precisely how long something has been in the cache we
+ keep two generations of completed responses. Every 5 minutes discard the
+ old generation, move the new generation to the old generation, and set the
+ new generation to be empty. This means that a result will be in the cache
+ somewhere between 5 and 10 minutes.
+ """
+
+ DURATION_MS = 5 * 60 * 1000 # Cache results for 5 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()
+ else:
+ return None
+
+ 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()
diff --git a/tests/util/test_snapshot_cache.py b/tests/util/test_snapshot_cache.py
new file mode 100644
index 0000000000..f58576c941
--- /dev/null
+++ b/tests/util/test_snapshot_cache.py
@@ -0,0 +1,60 @@
+# -*- 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 .. import unittest
+
+from synapse.util.caches.snapshot_cache import SnapshotCache
+from twisted.internet.defer import Deferred
+
+class SnapshotCacheTestCase(unittest.TestCase):
+
+ def setUp(self):
+ self.cache = SnapshotCache()
+ self.cache.DURATION_MS = 1
+
+ def test_get_set(self):
+ # Check that getting a missing key returns None
+ self.assertEquals(self.cache.get(0, "key"), None)
+
+ # Check that setting a key with a deferred returns
+ # a deferred that resolves when the initial deferred does
+ d = Deferred()
+ set_result = self.cache.set(0, "key", d)
+ self.assertIsNotNone(set_result)
+ self.assertFalse(set_result.called)
+
+ # Check that getting the key before the deferred has resolved
+ # returns a deferred that resolves when the initial deferred does.
+ get_result_at_10 = self.cache.get(10, "key")
+ self.assertIsNotNone(get_result_at_10)
+ self.assertFalse(get_result_at_10.called)
+
+ # Check that the returned deferreds resolve when the initial deferred
+ # does.
+ d.callback("v")
+ self.assertTrue(set_result.called)
+ self.assertTrue(get_result_at_10.called)
+
+ # Check that getting the key after the deferred has resolved
+ # before the cache expires returns a resolved deferred.
+ get_result_at_11 = self.cache.get(11, "key")
+ self.assertIsNotNone(get_result_at_11)
+ self.assertTrue(get_result_at_11.called)
+
+ # Check that getting the key after the deferred has resolved
+ # after the cache expires returns None
+ get_result_at_12 = self.cache.get(12, "key")
+ self.assertIsNone(get_result_at_12)
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