Define delayed event ratelimit category (#18019)

Apply ratelimiting on delayed event management separately from messages.

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---------

Co-authored-by: Andrew Morgan <1342360+anoadragon453@users.noreply.github.com>

changelog.d/18019.feature

@@ -0,0 +1 @@
+Define ratelimit configuration for delayed event management.

demo/start.sh

@@ -142,6 +142,9 @@ for port in 8080 8081 8082; do
 			  per_user:
 			    per_second: 1000
 			    burst_count: 1000
+			rc_delayed_event_mgmt:
+			  per_second: 1000
+			  burst_count: 1000
 			RC
 			)
             echo "${ratelimiting}" >> "$port.config"

docker/complement/conf/workers-shared-extra.yaml.j2

@@ -94,6 +94,10 @@ rc_presence:
     per_second: 9999
     burst_count: 9999
 
+rc_delayed_event_mgmt:
+  per_second: 9999
+  burst_count: 9999
+
 federation_rr_transactions_per_room_per_second: 9999
 
 allow_device_name_lookup_over_federation: true

docs/usage/configuration/config_documentation.md

@@ -1947,6 +1947,29 @@ rc_presence:
     burst_count: 1
 ```
 ---
+### `rc_delayed_event_mgmt`
+
+Ratelimiting settings for delayed event management.
+
+This is a ratelimiting option that ratelimits
+attempts to restart, cancel, or view delayed events
+based on the sending client's account and device ID.
+It defaults to: `per_second: 1`, `burst_count: 5`.
+
+Attempts to create or send delayed events are ratelimited not by this setting, but by `rc_message`.
+
+Setting this to a high value allows clients to make delayed event management requests often
+(such as repeatedly restarting a delayed event with a short timeout,
+or restarting several different delayed events all at once)
+without the risk of being ratelimited.
+
+Example configuration:
+```yaml
+rc_delayed_event_mgmt:
+  per_second: 2
+  burst_count: 20
+```
+---
 ### `federation_rr_transactions_per_room_per_second`
 
 Sets outgoing federation transaction frequency for sending read-receipts,

synapse/config/ratelimiting.py

@@ -234,3 +234,9 @@ class RatelimitConfig(Config):
             "rc_presence.per_user",
             defaults={"per_second": 0.1, "burst_count": 1},
         )
+
+        self.rc_delayed_event_mgmt = RatelimitSettings.parse(
+            config,
+            "rc_delayed_event_mgmt",
+            defaults={"per_second": 1, "burst_count": 5},
+        )

synapse/handlers/delayed_events.py

@@ -19,6 +19,7 @@ from twisted.internet.interfaces import IDelayedCall
 
 from synapse.api.constants import EventTypes
 from synapse.api.errors import ShadowBanError
+from synapse.api.ratelimiting import Ratelimiter
 from synapse.config.workers import MAIN_PROCESS_INSTANCE_NAME
 from synapse.logging.opentracing import set_tag
 from synapse.metrics import event_processing_positions
@@ -57,10 +58,19 @@ class DelayedEventsHandler:
         self._storage_controllers = hs.get_storage_controllers()
         self._config = hs.config
         self._clock = hs.get_clock()
-        self._request_ratelimiter = hs.get_request_ratelimiter()
         self._event_creation_handler = hs.get_event_creation_handler()
         self._room_member_handler = hs.get_room_member_handler()
 
+        self._request_ratelimiter = hs.get_request_ratelimiter()
+
+        # Ratelimiter for management of existing delayed events,
+        # keyed by the sending user ID & device ID.
+        self._delayed_event_mgmt_ratelimiter = Ratelimiter(
+            store=self._store,
+            clock=self._clock,
+            cfg=self._config.ratelimiting.rc_delayed_event_mgmt,
+        )
+
         self._next_delayed_event_call: Optional[IDelayedCall] = None
 
         # The current position in the current_state_delta stream
@@ -227,6 +237,9 @@ class DelayedEventsHandler:
         Raises:
             SynapseError: if the delayed event fails validation checks.
         """
+        # Use standard request limiter for scheduling new delayed events.
+        # TODO: Instead apply ratelimiting based on the scheduled send time.
+        # See https://github.com/element-hq/synapse/issues/18021
         await self._request_ratelimiter.ratelimit(requester)
 
         self._event_creation_handler.validator.validate_builder(
@@ -285,7 +298,10 @@ class DelayedEventsHandler:
             NotFoundError: if no matching delayed event could be found.
         """
         assert self._is_master
-        await self._request_ratelimiter.ratelimit(requester)
+        await self._delayed_event_mgmt_ratelimiter.ratelimit(
+            requester,
+            (requester.user.to_string(), requester.device_id),
+        )
         await self._initialized_from_db
 
         next_send_ts = await self._store.cancel_delayed_event(
@@ -308,7 +324,10 @@ class DelayedEventsHandler:
             NotFoundError: if no matching delayed event could be found.
         """
         assert self._is_master
-        await self._request_ratelimiter.ratelimit(requester)
+        await self._delayed_event_mgmt_ratelimiter.ratelimit(
+            requester,
+            (requester.user.to_string(), requester.device_id),
+        )
         await self._initialized_from_db
 
         next_send_ts = await self._store.restart_delayed_event(
@@ -332,6 +351,8 @@ class DelayedEventsHandler:
             NotFoundError: if no matching delayed event could be found.
         """
         assert self._is_master
+        # Use standard request limiter for sending delayed events on-demand,
+        # as an on-demand send is similar to sending a regular event.
         await self._request_ratelimiter.ratelimit(requester)
         await self._initialized_from_db
 
@@ -415,7 +436,10 @@ class DelayedEventsHandler:
 
     async def get_all_for_user(self, requester: Requester) -> List[JsonDict]:
         """Return all pending delayed events requested by the given user."""
-        await self._request_ratelimiter.ratelimit(requester)
+        await self._delayed_event_mgmt_ratelimiter.ratelimit(
+            requester,
+            (requester.user.to_string(), requester.device_id),
+        )
         return await self._store.get_all_delayed_events_for_user(
             requester.user.localpart
         )

tests/rest/client/test_delayed_events.py

@@ -109,6 +109,27 @@ class DelayedEventsTestCase(HomeserverTestCase):
         )
         self.assertEqual(setter_expected, content.get(setter_key), content)
 
+    @unittest.override_config(
+        {"rc_delayed_event_mgmt": {"per_second": 0.5, "burst_count": 1}}
+    )
+    def test_get_delayed_events_ratelimit(self) -> None:
+        args = ("GET", PATH_PREFIX)
+
+        channel = self.make_request(*args)
+        self.assertEqual(HTTPStatus.OK, channel.code, channel.result)
+
+        channel = self.make_request(*args)
+        self.assertEqual(HTTPStatus.TOO_MANY_REQUESTS, channel.code, channel.result)
+
+        # Add the current user to the ratelimit overrides, allowing them no ratelimiting.
+        self.get_success(
+            self.hs.get_datastores().main.set_ratelimit_for_user(self.user_id, 0, 0)
+        )
+
+        # Test that the request isn't ratelimited anymore.
+        channel = self.make_request(*args)
+        self.assertEqual(HTTPStatus.OK, channel.code, channel.result)
+
     def test_update_delayed_event_without_id(self) -> None:
         channel = self.make_request(
             "POST",
@@ -206,6 +227,46 @@ class DelayedEventsTestCase(HomeserverTestCase):
             expect_code=HTTPStatus.NOT_FOUND,
         )
 
+    @unittest.override_config(
+        {"rc_delayed_event_mgmt": {"per_second": 0.5, "burst_count": 1}}
+    )
+    def test_cancel_delayed_event_ratelimit(self) -> None:
+        delay_ids = []
+        for _ in range(2):
+            channel = self.make_request(
+                "POST",
+                _get_path_for_delayed_send(self.room_id, _EVENT_TYPE, 100000),
+                {},
+            )
+            self.assertEqual(HTTPStatus.OK, channel.code, channel.result)
+            delay_id = channel.json_body.get("delay_id")
+            self.assertIsNotNone(delay_id)
+            delay_ids.append(delay_id)
+
+        channel = self.make_request(
+            "POST",
+            f"{PATH_PREFIX}/{delay_ids.pop(0)}",
+            {"action": "cancel"},
+        )
+        self.assertEqual(HTTPStatus.OK, channel.code, channel.result)
+
+        args = (
+            "POST",
+            f"{PATH_PREFIX}/{delay_ids.pop(0)}",
+            {"action": "cancel"},
+        )
+        channel = self.make_request(*args)
+        self.assertEqual(HTTPStatus.TOO_MANY_REQUESTS, channel.code, channel.result)
+
+        # Add the current user to the ratelimit overrides, allowing them no ratelimiting.
+        self.get_success(
+            self.hs.get_datastores().main.set_ratelimit_for_user(self.user_id, 0, 0)
+        )
+
+        # Test that the request isn't ratelimited anymore.
+        channel = self.make_request(*args)
+        self.assertEqual(HTTPStatus.OK, channel.code, channel.result)
+
     def test_send_delayed_state_event(self) -> None:
         state_key = "to_send_on_request"
 
@@ -250,6 +311,44 @@ class DelayedEventsTestCase(HomeserverTestCase):
         )
         self.assertEqual(setter_expected, content.get(setter_key), content)
 
+    @unittest.override_config({"rc_message": {"per_second": 3.5, "burst_count": 4}})
+    def test_send_delayed_event_ratelimit(self) -> None:
+        delay_ids = []
+        for _ in range(2):
+            channel = self.make_request(
+                "POST",
+                _get_path_for_delayed_send(self.room_id, _EVENT_TYPE, 100000),
+                {},
+            )
+            self.assertEqual(HTTPStatus.OK, channel.code, channel.result)
+            delay_id = channel.json_body.get("delay_id")
+            self.assertIsNotNone(delay_id)
+            delay_ids.append(delay_id)
+
+        channel = self.make_request(
+            "POST",
+            f"{PATH_PREFIX}/{delay_ids.pop(0)}",
+            {"action": "send"},
+        )
+        self.assertEqual(HTTPStatus.OK, channel.code, channel.result)
+
+        args = (
+            "POST",
+            f"{PATH_PREFIX}/{delay_ids.pop(0)}",
+            {"action": "send"},
+        )
+        channel = self.make_request(*args)
+        self.assertEqual(HTTPStatus.TOO_MANY_REQUESTS, channel.code, channel.result)
+
+        # Add the current user to the ratelimit overrides, allowing them no ratelimiting.
+        self.get_success(
+            self.hs.get_datastores().main.set_ratelimit_for_user(self.user_id, 0, 0)
+        )
+
+        # Test that the request isn't ratelimited anymore.
+        channel = self.make_request(*args)
+        self.assertEqual(HTTPStatus.OK, channel.code, channel.result)
+
     def test_restart_delayed_state_event(self) -> None:
         state_key = "to_send_on_restarted_timeout"
 
@@ -309,6 +408,46 @@ class DelayedEventsTestCase(HomeserverTestCase):
         )
         self.assertEqual(setter_expected, content.get(setter_key), content)
 
+    @unittest.override_config(
+        {"rc_delayed_event_mgmt": {"per_second": 0.5, "burst_count": 1}}
+    )
+    def test_restart_delayed_event_ratelimit(self) -> None:
+        delay_ids = []
+        for _ in range(2):
+            channel = self.make_request(
+                "POST",
+                _get_path_for_delayed_send(self.room_id, _EVENT_TYPE, 100000),
+                {},
+            )
+            self.assertEqual(HTTPStatus.OK, channel.code, channel.result)
+            delay_id = channel.json_body.get("delay_id")
+            self.assertIsNotNone(delay_id)
+            delay_ids.append(delay_id)
+
+        channel = self.make_request(
+            "POST",
+            f"{PATH_PREFIX}/{delay_ids.pop(0)}",
+            {"action": "restart"},
+        )
+        self.assertEqual(HTTPStatus.OK, channel.code, channel.result)
+
+        args = (
+            "POST",
+            f"{PATH_PREFIX}/{delay_ids.pop(0)}",
+            {"action": "restart"},
+        )
+        channel = self.make_request(*args)
+        self.assertEqual(HTTPStatus.TOO_MANY_REQUESTS, channel.code, channel.result)
+
+        # Add the current user to the ratelimit overrides, allowing them no ratelimiting.
+        self.get_success(
+            self.hs.get_datastores().main.set_ratelimit_for_user(self.user_id, 0, 0)
+        )
+
+        # Test that the request isn't ratelimited anymore.
+        channel = self.make_request(*args)
+        self.assertEqual(HTTPStatus.OK, channel.code, channel.result)
+
     def test_delayed_state_events_are_cancelled_by_more_recent_state(self) -> None:
         state_key = "to_be_cancelled"
 
@@ -374,3 +513,7 @@ def _get_path_for_delayed_state(
     room_id: str, event_type: str, state_key: str, delay_ms: int
 ) -> str:
     return f"rooms/{room_id}/state/{event_type}/{state_key}?org.matrix.msc4140.delay={delay_ms}"
+
+
+def _get_path_for_delayed_send(room_id: str, event_type: str, delay_ms: int) -> str:
+    return f"rooms/{room_id}/send/{event_type}?org.matrix.msc4140.delay={delay_ms}"

tests/rest/client/test_rooms.py

@@ -2399,6 +2399,41 @@ class RoomDelayedEventTestCase(RoomBase):
         )
         self.assertEqual(HTTPStatus.OK, channel.code, channel.result)
 
+    @unittest.override_config(
+        {
+            "max_event_delay_duration": "24h",
+            "rc_message": {"per_second": 1, "burst_count": 2},
+        }
+    )
+    def test_add_delayed_event_ratelimit(self) -> None:
+        """Test that requests to schedule new delayed events are ratelimited by a RateLimiter,
+        which ratelimits them correctly, including by not limiting when the requester is
+        exempt from ratelimiting.
+        """
+
+        # Test that new delayed events are correctly ratelimited.
+        args = (
+            "POST",
+            (
+                "rooms/%s/send/m.room.message?org.matrix.msc4140.delay=2000"
+                % self.room_id
+            ).encode("ascii"),
+            {"body": "test", "msgtype": "m.text"},
+        )
+        channel = self.make_request(*args)
+        self.assertEqual(HTTPStatus.OK, channel.code, channel.result)
+        channel = self.make_request(*args)
+        self.assertEqual(HTTPStatus.TOO_MANY_REQUESTS, channel.code, channel.result)
+
+        # Add the current user to the ratelimit overrides, allowing them no ratelimiting.
+        self.get_success(
+            self.hs.get_datastores().main.set_ratelimit_for_user(self.user_id, 0, 0)
+        )
+
+        # Test that the new delayed events aren't ratelimited anymore.
+        channel = self.make_request(*args)
+        self.assertEqual(HTTPStatus.OK, channel.code, channel.result)
+
 
 class RoomSearchTestCase(unittest.HomeserverTestCase):
     servlets = [