Optimise calculating device_list changes in `/sync`. (#11974)
For users with large accounts it is inefficient to calculate the set of
users they share a room with (and takes a lot of space in the cache).
Instead we can look at users whose devices have changed since the last
sync and check if they share a room with the syncing user.
1 files changed, 53 insertions, 15 deletions
diff --git a/synapse/handlers/sync.py b/synapse/handlers/sync.py
index aa9a76f8a9..e6050cbce6 100644
--- a/synapse/handlers/sync.py
+++ b/synapse/handlers/sync.py
@@ -1289,23 +1289,54 @@ class SyncHandler:
# room with by looking at all users that have left a room plus users
# that were in a room we've left.
- users_who_share_room = await self.store.get_users_who_share_room_with_user(
- user_id
- )
-
- # Always tell the user about their own devices. We check as the user
- # ID is almost certainly already included (unless they're not in any
- # rooms) and taking a copy of the set is relatively expensive.
- if user_id not in users_who_share_room:
- users_who_share_room = set(users_who_share_room)
- users_who_share_room.add(user_id)
+ users_that_have_changed = set()
- tracked_users = users_who_share_room
+ joined_rooms = sync_result_builder.joined_room_ids
- # Step 1a, check for changes in devices of users we share a room with
- users_that_have_changed = await self.store.get_users_whose_devices_changed(
- since_token.device_list_key, tracked_users
+ # Step 1a, check for changes in devices of users we share a room
+ # with
+ #
+ # We do this in two different ways depending on what we have cached.
+ # If we already have a list of all the user that have changed since
+ # the last sync then it's likely more efficient to compare the rooms
+ # they're in with the rooms the syncing user is in.
+ #
+ # If we don't have that info cached then we get all the users that
+ # share a room with our user and check if those users have changed.
+ changed_users = self.store.get_cached_device_list_changes(
+ since_token.device_list_key
)
+ if changed_users is not None:
+ result = await self.store.get_rooms_for_users_with_stream_ordering(
+ changed_users
+ )
+
+ for changed_user_id, entries in result.items():
+ # Check if the changed user shares any rooms with the user,
+ # or if the changed user is the syncing user (as we always
+ # want to include device list updates of their own devices).
+ if user_id == changed_user_id or any(
+ e.room_id in joined_rooms for e in entries
+ ):
+ users_that_have_changed.add(changed_user_id)
+ else:
+ users_who_share_room = (
+ await self.store.get_users_who_share_room_with_user(user_id)
+ )
+
+ # Always tell the user about their own devices. We check as the user
+ # ID is almost certainly already included (unless they're not in any
+ # rooms) and taking a copy of the set is relatively expensive.
+ if user_id not in users_who_share_room:
+ users_who_share_room = set(users_who_share_room)
+ users_who_share_room.add(user_id)
+
+ tracked_users = users_who_share_room
+ users_that_have_changed = (
+ await self.store.get_users_whose_devices_changed(
+ since_token.device_list_key, tracked_users
+ )
+ )
# Step 1b, check for newly joined rooms
for room_id in newly_joined_rooms:
@@ -1329,7 +1360,14 @@ class SyncHandler:
newly_left_users.update(left_users)
# Remove any users that we still share a room with.
- newly_left_users -= users_who_share_room
+ left_users_rooms = (
+ await self.store.get_rooms_for_users_with_stream_ordering(
+ newly_left_users
+ )
+ )
+ for user_id, entries in left_users_rooms.items():
+ if any(e.room_id in joined_rooms for e in entries):
+ newly_left_users.discard(user_id)
return DeviceLists(changed=users_that_have_changed, left=newly_left_users)
else:
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