diff options
| -rw-r--r-- | synapse/handlers/message.py | 25 | ||||
| -rw-r--r-- | synapse/util/caches/snapshot_cache.py | 93 | ||||
| -rw-r--r-- | tests/util/test_snapshot_cache.py | 60 |
3 files changed, 177 insertions, 1 deletions
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) |