Faster room joins: fix race in recalculation of current room state

changelog.d/13151.misc

@@ -0,0 +1 @@
+Faster room joins: fix race in recalculation of current room state.

synapse/handlers/federation.py

@@ -1543,14 +1543,9 @@ async def _sync_partial_state_room(
                 # all the events are updated, so we can update current state and
                 # clear the lazy-loading flag.
                 logger.info("Updating current state for %s", room_id)
-                # TODO(faster_joins): support workers
+                # TODO(faster_joins): notify workers in notify_room_un_partial_stated
                 #   https://github.com/matrix-org/synapse/issues/12994
-                assert (
-                    self._storage_controllers.persistence is not None
-                ), "worker-mode deployments not currently supported here"
-                await self._storage_controllers.persistence.update_current_state(
-                    room_id
-                )
+                await self.state_handler.update_current_state(room_id)
 
                 logger.info("Clearing partial-state flag for %s", room_id)
                 success = await self.store.clear_partial_state_room(room_id)

synapse/replication/http/__init__.py

@@ -25,6 +25,7 @@
     push,
     register,
     send_event,
+    state,
     streams,
 )
 
@@ -48,6 +49,7 @@ def register_servlets(self, hs: "HomeServer") -> None:
         streams.register_servlets(hs, self)
         account_data.register_servlets(hs, self)
         push.register_servlets(hs, self)
+        state.register_servlets(hs, self)
 
         # The following can't currently be instantiated on workers.
         if hs.config.worker.worker_app is None:

synapse/replication/http/state.py

@@ -0,0 +1,75 @@
+# Copyright 2022 The Matrix.org Foundation C.I.C.
+#
+# 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.
+
+import logging
+from typing import TYPE_CHECKING, Tuple
+
+from twisted.web.server import Request
+
+from synapse.api.errors import SynapseError
+from synapse.http.server import HttpServer
+from synapse.replication.http._base import ReplicationEndpoint
+from synapse.types import JsonDict
+
+if TYPE_CHECKING:
+    from synapse.server import HomeServer
+
+logger = logging.getLogger(__name__)
+
+
+class ReplicationUpdateCurrentStateRestServlet(ReplicationEndpoint):
+    """Recalculates the current state for a room, and persists it.
+
+    The API looks like:
+
+        POST /_synapse/replication/update_current_state/:room_id
+
+        {}
+
+        200 OK
+
+        {}
+    """
+
+    NAME = "update_current_state"
+    PATH_ARGS = ("room_id",)
+
+    def __init__(self, hs: "HomeServer"):
+        super().__init__(hs)
+
+        self._state_handler = hs.get_state_handler()
+        self._events_shard_config = hs.config.worker.events_shard_config
+        self._instance_name = hs.get_instance_name()
+
+    @staticmethod
+    async def _serialize_payload(room_id: str) -> JsonDict:  # type: ignore[override]
+        return {}
+
+    async def _handle_request(  # type: ignore[override]
+        self, request: Request, room_id: str
+    ) -> Tuple[int, JsonDict]:
+        writer_instance = self._events_shard_config.get_instance(room_id)
+        if writer_instance != self._instance_name:
+            raise SynapseError(
+                400, "/update_current_state request was routed to the wrong worker"
+            )
+
+        await self._state_handler.update_current_state(room_id)
+
+        return 200, {}
+
+
+def register_servlets(hs: "HomeServer", http_server: HttpServer) -> None:
+    if hs.get_instance_name() in hs.config.worker.writers.events:
+        ReplicationUpdateCurrentStateRestServlet(hs).register(http_server)

synapse/state/__init__.py

@@ -43,6 +43,7 @@
 from synapse.events import EventBase
 from synapse.events.snapshot import EventContext
 from synapse.logging.context import ContextResourceUsage
+from synapse.replication.http.state import ReplicationUpdateCurrentStateRestServlet
 from synapse.state import v1, v2
 from synapse.storage.databases.main.events_worker import EventRedactBehaviour
 from synapse.storage.roommember import ProfileInfo
@@ -129,6 +130,12 @@ def __init__(self, hs: "HomeServer"):
         self.hs = hs
         self._state_resolution_handler = hs.get_state_resolution_handler()
         self._storage_controllers = hs.get_storage_controllers()
+        self._events_shard_config = hs.config.worker.events_shard_config
+        self._instance_name = hs.get_instance_name()
+
+        self._update_current_state = (
+            ReplicationUpdateCurrentStateRestServlet.make_client(hs)
+        )
 
     async def get_current_state_ids(
         self,
@@ -417,6 +424,24 @@ async def resolve_events(
 
         return {key: state_map[ev_id] for key, ev_id in new_state.items()}
 
+    async def update_current_state(self, room_id: str) -> None:
+        """Recalculates the current state for a room, and persists it.
+
+        Raises:
+            SynapseError(502): if all attempts to connect to the event persister worker
+                fail
+        """
+        writer_instance = self._events_shard_config.get_instance(room_id)
+        if writer_instance != self._instance_name:
+            await self._update_current_state(
+                instance_name=writer_instance,
+                room_id=room_id,
+            )
+            return
+
+        assert self._storage_controllers.persistence is not None
+        await self._storage_controllers.persistence.update_current_state(room_id)
+
 
 @attr.s(slots=True, auto_attribs=True)
 class _StateResMetrics: