diff --git a/synapse/config/server.py b/synapse/config/server.py
index 7d56e2d141..6e5b46e6c3 100644
--- a/synapse/config/server.py
+++ b/synapse/config/server.py
@@ -317,6 +317,12 @@ class ServerConfig(Config):
_check_resource_config(self.listeners)
+ # An experimental option to try and periodically clean up extremities
+ # by sending dummy events.
+ self.cleanup_extremities_with_dummy_events = config.get(
+ "cleanup_extremities_with_dummy_events", False,
+ )
+
def has_tls_listener(self):
return any(l["tls"] for l in self.listeners)
diff --git a/synapse/events/__init__.py b/synapse/events/__init__.py
index 1edd19cc13..f1fbb3d14a 100644
--- a/synapse/events/__init__.py
+++ b/synapse/events/__init__.py
@@ -92,6 +92,18 @@ class _EventInternalMetadata(object):
"""
return getattr(self, "soft_failed", False)
+ def should_proactively_send(self):
+ """Whether the eventm, if ours, should be sent to other clients and
+ servers.
+
+ This is used for sending dummy events internally. Servers and clients
+ can still explicitly fetch the event.
+
+ Returns:
+ bool
+ """
+ return getattr(self, "proactively_send", True)
+
def _event_dict_property(key):
# We want to be able to use hasattr with the event dict properties.
diff --git a/synapse/federation/sender/__init__.py b/synapse/federation/sender/__init__.py
index 4f0f939102..4224b29ecf 100644
--- a/synapse/federation/sender/__init__.py
+++ b/synapse/federation/sender/__init__.py
@@ -168,6 +168,9 @@ class FederationSender(object):
if not is_mine and send_on_behalf_of is None:
return
+ if not event.internal_metadata.should_proactively_send():
+ return
+
try:
# Get the state from before the event.
# We need to make sure that this is the state from before
diff --git a/synapse/handlers/message.py b/synapse/handlers/message.py
index 11650dc80c..3b5942b7ae 100644
--- a/synapse/handlers/message.py
+++ b/synapse/handlers/message.py
@@ -36,7 +36,7 @@ from synapse.api.urls import ConsentURIBuilder
from synapse.events.validator import EventValidator
from synapse.replication.http.send_event import ReplicationSendEventRestServlet
from synapse.storage.state import StateFilter
-from synapse.types import RoomAlias, UserID
+from synapse.types import RoomAlias, UserID, create_requester
from synapse.util.async_helpers import Linearizer
from synapse.util.frozenutils import frozendict_json_encoder
from synapse.util.logcontext import run_in_background
@@ -261,6 +261,16 @@ class EventCreationHandler(object):
if self._block_events_without_consent_error:
self._consent_uri_builder = ConsentURIBuilder(self.config)
+ if (
+ not self.config.worker_app
+ and self.config.cleanup_extremities_with_dummy_events
+ ):
+ # XXX: Send dummy events.
+ self.clock.looping_call(
+ self._send_dummy_events_to_fill_extremities,
+ 5 * 60 * 1000,
+ )
+
@defer.inlineCallbacks
def create_event(self, requester, event_dict, token_id=None, txn_id=None,
prev_events_and_hashes=None, require_consent=True):
@@ -874,3 +884,63 @@ class EventCreationHandler(object):
yield presence.bump_presence_active_time(user)
except Exception:
logger.exception("Error bumping presence active time")
+
+ @defer.inlineCallbacks
+ def _send_dummy_events_to_fill_extremities(self):
+ """Background task to send dummy events into rooms that have a large
+ number of extremities
+ """
+
+ room_ids = yield self.store.get_rooms_with_many_extremities(
+ min_count=10, limit=5,
+ )
+
+ for room_id in room_ids:
+ # For each room we need to find a joined member we can use to send
+ # the dummy event with.
+
+ prev_events_and_hashes = yield self.store.get_prev_events_for_room(
+ room_id,
+ )
+
+ latest_event_ids = (
+ event_id for (event_id, _, _) in prev_events_and_hashes
+ )
+
+ members = yield self.state.get_current_users_in_room(
+ room_id, latest_event_ids=latest_event_ids,
+ )
+
+ user_id = None
+ for member in members:
+ if self.hs.is_mine_id(member):
+ user_id = member
+ break
+
+ if not user_id:
+ # We don't have a joined user.
+ # TODO: We should do something here to stop the room from
+ # appearing next time.
+ continue
+
+ requester = create_requester(user_id)
+
+ event, context = yield self.create_event(
+ requester,
+ {
+ "type": "org.matrix.dummy_event",
+ "content": {},
+ "room_id": room_id,
+ "sender": user_id,
+ },
+ prev_events_and_hashes=prev_events_and_hashes,
+ )
+
+ event.internal_metadata.proactively_send = False
+
+ yield self.send_nonmember_event(
+ requester,
+ event,
+ context,
+ ratelimit=False,
+ )
diff --git a/synapse/storage/event_federation.py b/synapse/storage/event_federation.py
index 09e39c2c28..e8d16edbc8 100644
--- a/synapse/storage/event_federation.py
+++ b/synapse/storage/event_federation.py
@@ -190,6 +190,35 @@ class EventFederationWorkerStore(EventsWorkerStore, SignatureWorkerStore, SQLBas
room_id,
)
+ def get_rooms_with_many_extremities(self, min_count, limit):
+ """Get the top rooms with at least N extremities.
+
+ Args:
+ min_count (int): The minimum number of extremities
+ limit (int): The maximum number of rooms to return.
+
+ Returns:
+ Deferred[list]: At most `limit` room IDs that have at least
+ `min_count` extremities, sorted by extremity count.
+ """
+
+ def _get_rooms_with_many_extremities_txn(txn):
+ sql = """
+ SELECT room_id FROM event_forward_extremities
+ GROUP BY room_id
+ HAVING count(*) > ?
+ ORDER BY count(*) DESC
+ LIMIT ?
+ """
+
+ txn.execute(sql, (min_count, limit))
+ return [room_id for room_id, in txn]
+
+ return self.runInteraction(
+ "get_rooms_with_many_extremities",
+ _get_rooms_with_many_extremities_txn,
+ )
+
@cached(max_entries=5000, iterable=True)
def get_latest_event_ids_in_room(self, room_id):
return self._simple_select_onecol(
diff --git a/tests/storage/test_cleanup_extrems.py b/tests/storage/test_cleanup_extrems.py
index f4c81ef77d..ed5d58f58c 100644
--- a/tests/storage/test_cleanup_extrems.py
+++ b/tests/storage/test_cleanup_extrems.py
@@ -222,3 +222,44 @@ class CleanupExtremBackgroundUpdateStoreTestCase(HomeserverTestCase):
self.store.get_latest_event_ids_in_room(self.room_id)
)
self.assertEqual(set(latest_event_ids), set([event_id_b, event_id_c]))
+
+
+class CleanupExtremDummyEventsTestCase(HomeserverTestCase):
+ def make_homeserver(self, reactor, clock):
+ config = self.default_config()
+ config["cleanup_extremities_with_dummy_events"] = True
+ return self.setup_test_homeserver(config=config)
+
+ def prepare(self, reactor, clock, homeserver):
+ self.store = homeserver.get_datastore()
+ self.room_creator = homeserver.get_room_creation_handler()
+
+ # Create a test user and room
+ self.user = UserID("alice", "test")
+ self.requester = Requester(self.user, None, False, None, None)
+ info = self.get_success(self.room_creator.create_room(self.requester, {}))
+ self.room_id = info["room_id"]
+
+ def test_send_dummy_event(self):
+ # Create a bushy graph with 50 extremities.
+
+ event_id_start = self.create_and_send_event(self.room_id, self.user)
+
+ for _ in range(50):
+ self.create_and_send_event(
+ self.room_id, self.user, prev_event_ids=[event_id_start]
+ )
+
+ latest_event_ids = self.get_success(
+ self.store.get_latest_event_ids_in_room(self.room_id)
+ )
+ self.assertEqual(len(latest_event_ids), 50)
+
+ # Bump the reacto repeatedly so that the background updates have a
+ # chance to run.
+ self.pump(10 * 60)
+
+ latest_event_ids = self.get_success(
+ self.store.get_latest_event_ids_in_room(self.room_id)
+ )
+ self.assertTrue(len(latest_event_ids) < 10, len(latest_event_ids))
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