Add ratelimit callbacks to module API to allow dynamic ratelimiting (#18458)

synapse/module_api/__init__.py

@@ -94,6 +94,9 @@ from synapse.module_api.callbacks.media_repository_callbacks import (
     GET_MEDIA_CONFIG_FOR_USER_CALLBACK,
     IS_USER_ALLOWED_TO_UPLOAD_MEDIA_OF_SIZE_CALLBACK,
 )
+from synapse.module_api.callbacks.ratelimit_callbacks import (
+    GET_RATELIMIT_OVERRIDE_FOR_USER_CALLBACK,
+)
 from synapse.module_api.callbacks.spamchecker_callbacks import (
     CHECK_EVENT_FOR_SPAM_CALLBACK,
     CHECK_LOGIN_FOR_SPAM_CALLBACK,
@@ -367,6 +370,20 @@ class ModuleApi:
             on_legacy_admin_request=on_legacy_admin_request,
         )
 
+    def register_ratelimit_callbacks(
+        self,
+        *,
+        get_ratelimit_override_for_user: Optional[
+            GET_RATELIMIT_OVERRIDE_FOR_USER_CALLBACK
+        ] = None,
+    ) -> None:
+        """Registers callbacks for ratelimit capabilities.
+        Added in Synapse v1.132.0.
+        """
+        return self._callbacks.ratelimit.register_callbacks(
+            get_ratelimit_override_for_user=get_ratelimit_override_for_user,
+        )
+
     def register_media_repository_callbacks(
         self,
         *,
@@ -376,7 +393,7 @@ class ModuleApi:
         ] = None,
     ) -> None:
         """Registers callbacks for media repository capabilities.
-        Added in Synapse v1.x.x.
+        Added in Synapse v1.132.0.
         """
         return self._callbacks.media_repository.register_callbacks(
             get_media_config_for_user=get_media_config_for_user,

synapse/module_api/callbacks/__init__.py

@@ -30,6 +30,9 @@ from synapse.module_api.callbacks.account_validity_callbacks import (
 from synapse.module_api.callbacks.media_repository_callbacks import (
     MediaRepositoryModuleApiCallbacks,
 )
+from synapse.module_api.callbacks.ratelimit_callbacks import (
+    RatelimitModuleApiCallbacks,
+)
 from synapse.module_api.callbacks.spamchecker_callbacks import (
     SpamCheckerModuleApiCallbacks,
 )
@@ -42,5 +45,6 @@ class ModuleApiCallbacks:
     def __init__(self, hs: "HomeServer") -> None:
         self.account_validity = AccountValidityModuleApiCallbacks()
         self.media_repository = MediaRepositoryModuleApiCallbacks(hs)
+        self.ratelimit = RatelimitModuleApiCallbacks(hs)
         self.spam_checker = SpamCheckerModuleApiCallbacks(hs)
         self.third_party_event_rules = ThirdPartyEventRulesModuleApiCallbacks(hs)

synapse/module_api/callbacks/ratelimit_callbacks.py

@@ -0,0 +1,62 @@
+#
+# This file is licensed under the Affero General Public License (AGPL) version 3.
+#
+# Copyright (C) 2025 New Vector, Ltd
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as
+# published by the Free Software Foundation, either version 3 of the
+# License, or (at your option) any later version.
+#
+# See the GNU Affero General Public License for more details:
+# <https://www.gnu.org/licenses/agpl-3.0.html>.
+#
+
+import logging
+from typing import TYPE_CHECKING, Awaitable, Callable, List, Optional
+
+from synapse.storage.databases.main.room import RatelimitOverride
+from synapse.util.async_helpers import delay_cancellation
+from synapse.util.metrics import Measure
+
+if TYPE_CHECKING:
+    from synapse.server import HomeServer
+
+logger = logging.getLogger(__name__)
+
+GET_RATELIMIT_OVERRIDE_FOR_USER_CALLBACK = Callable[
+    [str, str], Awaitable[Optional[RatelimitOverride]]
+]
+
+
+class RatelimitModuleApiCallbacks:
+    def __init__(self, hs: "HomeServer") -> None:
+        self.clock = hs.get_clock()
+        self._get_ratelimit_override_for_user_callbacks: List[
+            GET_RATELIMIT_OVERRIDE_FOR_USER_CALLBACK
+        ] = []
+
+    def register_callbacks(
+        self,
+        get_ratelimit_override_for_user: Optional[
+            GET_RATELIMIT_OVERRIDE_FOR_USER_CALLBACK
+        ] = None,
+    ) -> None:
+        """Register callbacks from module for each hook."""
+        if get_ratelimit_override_for_user is not None:
+            self._get_ratelimit_override_for_user_callbacks.append(
+                get_ratelimit_override_for_user
+            )
+
+    async def get_ratelimit_override_for_user(
+        self, user_id: str, limiter_name: str
+    ) -> Optional[RatelimitOverride]:
+        for callback in self._get_ratelimit_override_for_user_callbacks:
+            with Measure(self.clock, f"{callback.__module__}.{callback.__qualname__}"):
+                res: Optional[RatelimitOverride] = await delay_cancellation(
+                    callback(user_id, limiter_name)
+                )
+            if res:
+                return res
+
+        return None