Handle remote device list updates during partial join (#13913)

c.f. #12993 (comment), point 3

This stores all device list updates that we receive while partial joins are ongoing, and processes them once we have the full state.

Note: We don't actually process the device lists in the same ways as if we weren't partially joined. Instead of updating the device list remote cache, we simply notify local users that a change in the remote user's devices has happened. I think this is safe as if the local user requests the keys for the remote user and we don't have them we'll simply fetch them as normal.

2 files changed, 66 insertions, 0 deletions

diff --git a/synapse/handlers/device.py b/synapse/handlers/device.py
index bad262731c..f2ef591103 100644
--- a/synapse/handlers/device.py
+++ b/synapse/handlers/device.py
@@ -309,6 +309,17 @@ class DeviceWorkerHandler:
             "self_signing_key": self_signing_key,
         }
 
+    async def handle_room_un_partial_stated(self, room_id: str) -> None:
+        """Handles sending appropriate device list updates in a room that has
+        gone from partial to full state.
+        """
+
+        # TODO(faster_joins): worker mode support
+        #   https://github.com/matrix-org/synapse/issues/12994
+        logger.error(
+            "Trying handling device list state for partial join: not supported on workers."
+        )
+
 
 class DeviceHandler(DeviceWorkerHandler):
     def __init__(self, hs: "HomeServer"):
@@ -746,6 +757,15 @@ class DeviceHandler(DeviceWorkerHandler):
         finally:
             self._handle_new_device_update_is_processing = False
 
+    async def handle_room_un_partial_stated(self, room_id: str) -> None:
+        """Handles sending appropriate device list updates in a room that has
+        gone from partial to full state.
+        """
+
+        # We defer to the device list updater implementation as we're on the
+        # right worker.
+        await self.device_list_updater.handle_room_un_partial_stated(room_id)
+
 
 def _update_device_from_client_ips(
     device: JsonDict, client_ips: Mapping[Tuple[str, str], Mapping[str, Any]]
@@ -836,6 +856,16 @@ class DeviceListUpdater:
             )
             return
 
+        # Check if we are partially joining any rooms. If so we need to store
+        # all device list updates so that we can handle them correctly once we
+        # know who is in the room.
+        partial_rooms = await self.store.get_partial_state_rooms_and_servers()
+        if partial_rooms:
+            await self.store.add_remote_device_list_to_pending(
+                user_id,
+                device_id,
+            )
+
         room_ids = await self.store.get_rooms_for_user(user_id)
         if not room_ids:
             # We don't share any rooms with this user. Ignore update, as we
@@ -1175,3 +1205,35 @@ class DeviceListUpdater:
             device_ids.append(verify_key.version)
 
         return device_ids
+
+    async def handle_room_un_partial_stated(self, room_id: str) -> None:
+        """Handles sending appropriate device list updates in a room that has
+        gone from partial to full state.
+        """
+
+        pending_updates = (
+            await self.store.get_pending_remote_device_list_updates_for_room(room_id)
+        )
+
+        for user_id, device_id in pending_updates:
+            logger.info(
+                "Got pending device list update in room %s: %s / %s",
+                room_id,
+                user_id,
+                device_id,
+            )
+            position = await self.store.add_device_change_to_streams(
+                user_id,
+                [device_id],
+                room_ids=[room_id],
+            )
+
+            if not position:
+                # This should only happen if there are no updates, which
+                # shouldn't happen when we've passed in a non-empty set of
+                # device IDs.
+                continue
+
+            self.device_handler.notifier.on_new_event(
+                StreamKeyType.DEVICE_LIST, position, rooms=[room_id]
+            )
diff --git a/synapse/handlers/federation.py b/synapse/handlers/federation.py
index 8f847ff845..360ab6fee2 100644
--- a/synapse/handlers/federation.py
+++ b/synapse/handlers/federation.py
@@ -149,6 +149,7 @@ class FederationHandler:
         self.http_client = hs.get_proxied_blacklisted_http_client()
         self._replication = hs.get_replication_data_handler()
         self._federation_event_handler = hs.get_federation_event_handler()
+        self._device_handler = hs.get_device_handler()
         self._bulk_push_rule_evaluator = hs.get_bulk_push_rule_evaluator()
 
         self._clean_room_for_join_client = ReplicationCleanRoomRestServlet.make_client(
@@ -1631,6 +1632,9 @@ class FederationHandler:
                 #   https://github.com/matrix-org/synapse/issues/12994
                 await self.state_handler.update_current_state(room_id)
 
+                logger.info("Handling any pending device list updates")
+                await self._device_handler.handle_room_un_partial_stated(room_id)
+
                 logger.info("Clearing partial-state flag for %s", room_id)
                 success = await self.store.clear_partial_state_room(room_id)
                 if success: