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Merge pull request #457 from matrix-org/markjh/cached_sync
Add a cache for initialSync responses that expires after 5 minutes
This commit is contained in:
commit
8d6dde7825
3 changed files with 177 additions and 1 deletions
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@ -22,6 +22,7 @@ from synapse.events.utils import serialize_event
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from synapse.events.validator import EventValidator
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from synapse.util import unwrapFirstError
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from synapse.util.logcontext import PreserveLoggingContext
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from synapse.util.caches.snapshot_cache import SnapshotCache
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from synapse.types import UserID, RoomStreamToken, StreamToken
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from ._base import BaseHandler
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@ -45,6 +46,7 @@ class MessageHandler(BaseHandler):
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self.state = hs.get_state_handler()
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self.clock = hs.get_clock()
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self.validator = EventValidator()
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self.snapshot_cache = SnapshotCache()
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@defer.inlineCallbacks
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def get_message(self, msg_id=None, room_id=None, sender_id=None,
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@ -326,7 +328,6 @@ class MessageHandler(BaseHandler):
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[serialize_event(c, now) for c in room_state.values()]
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)
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@defer.inlineCallbacks
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def snapshot_all_rooms(self, user_id=None, pagin_config=None,
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as_client_event=True, include_archived=False):
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"""Retrieve a snapshot of all rooms the user is invited or has joined.
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@ -346,6 +347,28 @@ class MessageHandler(BaseHandler):
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is joined on, may return a "messages" key with messages, depending
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on the specified PaginationConfig.
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"""
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key = (
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user_id,
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pagin_config.from_token,
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pagin_config.to_token,
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pagin_config.direction,
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pagin_config.limit,
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as_client_event,
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include_archived,
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)
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now_ms = self.clock.time_msec()
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result = self.snapshot_cache.get(now_ms, key)
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if result is not None:
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return result
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return self.snapshot_cache.set(now_ms, key, self._snapshot_all_rooms(
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user_id, pagin_config, as_client_event, include_archived
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))
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@defer.inlineCallbacks
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def _snapshot_all_rooms(self, user_id=None, pagin_config=None,
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as_client_event=True, include_archived=False):
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memberships = [Membership.INVITE, Membership.JOIN]
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if include_archived:
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memberships.append(Membership.LEAVE)
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93
synapse/util/caches/snapshot_cache.py
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93
synapse/util/caches/snapshot_cache.py
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@ -0,0 +1,93 @@
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# -*- coding: utf-8 -*-
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# Copyright 2015 OpenMarket Ltd
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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from synapse.util.async import ObservableDeferred
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class SnapshotCache(object):
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"""Cache for snapshots like the response of /initialSync.
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The response of initialSync only has to be a recent snapshot of the
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server state. It shouldn't matter to clients if it is a few minutes out
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of date.
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This caches a deferred response. Until the deferred completes it will be
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returned from the cache. This means that if the client retries the request
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while the response is still being computed, that original response will be
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used rather than trying to compute a new response.
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Once the deferred completes it will removed from the cache after 5 minutes.
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We delay removing it from the cache because a client retrying its request
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could race with us finishing computing the response.
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Rather than tracking precisely how long something has been in the cache we
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keep two generations of completed responses. Every 5 minutes discard the
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old generation, move the new generation to the old generation, and set the
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new generation to be empty. This means that a result will be in the cache
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somewhere between 5 and 10 minutes.
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"""
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DURATION_MS = 5 * 60 * 1000 # Cache results for 5 minutes.
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def __init__(self):
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self.pending_result_cache = {} # Request that haven't finished yet.
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self.prev_result_cache = {} # The older requests that have finished.
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self.next_result_cache = {} # The newer requests that have finished.
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self.time_last_rotated_ms = 0
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def rotate(self, time_now_ms):
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# Rotate once if the cache duration has passed since the last rotation.
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if time_now_ms - self.time_last_rotated_ms >= self.DURATION_MS:
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self.prev_result_cache = self.next_result_cache
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self.next_result_cache = {}
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self.time_last_rotated_ms += self.DURATION_MS
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# Rotate again if the cache duration has passed twice since the last
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# rotation.
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if time_now_ms - self.time_last_rotated_ms >= self.DURATION_MS:
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self.prev_result_cache = self.next_result_cache
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self.next_result_cache = {}
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self.time_last_rotated_ms = time_now_ms
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def get(self, time_now_ms, key):
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self.rotate(time_now_ms)
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# This cache is intended to deduplicate requests, so we expect it to be
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# missed most of the time. So we just lookup the key in all of the
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# dictionaries rather than trying to short circuit the lookup if the
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# key is found.
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result = self.prev_result_cache.get(key)
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result = self.next_result_cache.get(key, result)
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result = self.pending_result_cache.get(key, result)
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if result is not None:
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return result.observe()
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else:
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return None
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def set(self, time_now_ms, key, deferred):
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self.rotate(time_now_ms)
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result = ObservableDeferred(deferred)
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self.pending_result_cache[key] = result
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def shuffle_along(r):
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# When the deferred completes we shuffle it along to the first
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# generation of the result cache. So that it will eventually
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# expire from the rotation of that cache.
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self.next_result_cache[key] = result
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self.pending_result_cache.pop(key, None)
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result.observe().addBoth(shuffle_along)
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return result.observe()
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60
tests/util/test_snapshot_cache.py
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60
tests/util/test_snapshot_cache.py
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# -*- coding: utf-8 -*-
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# Copyright 2015 OpenMarket Ltd
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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from .. import unittest
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from synapse.util.caches.snapshot_cache import SnapshotCache
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from twisted.internet.defer import Deferred
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class SnapshotCacheTestCase(unittest.TestCase):
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def setUp(self):
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self.cache = SnapshotCache()
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self.cache.DURATION_MS = 1
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def test_get_set(self):
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# Check that getting a missing key returns None
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self.assertEquals(self.cache.get(0, "key"), None)
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# Check that setting a key with a deferred returns
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# a deferred that resolves when the initial deferred does
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d = Deferred()
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set_result = self.cache.set(0, "key", d)
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self.assertIsNotNone(set_result)
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self.assertFalse(set_result.called)
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# Check that getting the key before the deferred has resolved
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# returns a deferred that resolves when the initial deferred does.
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get_result_at_10 = self.cache.get(10, "key")
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self.assertIsNotNone(get_result_at_10)
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self.assertFalse(get_result_at_10.called)
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# Check that the returned deferreds resolve when the initial deferred
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# does.
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d.callback("v")
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self.assertTrue(set_result.called)
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self.assertTrue(get_result_at_10.called)
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# Check that getting the key after the deferred has resolved
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# before the cache expires returns a resolved deferred.
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get_result_at_11 = self.cache.get(11, "key")
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self.assertIsNotNone(get_result_at_11)
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self.assertTrue(get_result_at_11.called)
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# Check that getting the key after the deferred has resolved
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# after the cache expires returns None
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get_result_at_12 = self.cache.get(12, "key")
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self.assertIsNone(get_result_at_12)
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