The RoomFinder accesses s.allRooms and is used when sorting the
room list, where we would expect many accesses. Previously, we
returned copies of room metadata, which caused significant amounts
of GC churn, enough to show up on traces.
Swap to using pointers and rename the function to `ReadOnlyRoom(roomID)`
to indicate that it isn't safe to write to this return value.
Features:
- Add `typing` extension.
- Add `receipts` extension.
- Add comprehensive prometheus `/metrics` activated via `SYNCV3_PROM`.
- Add `SYNCV3_PPROF` support.
- Add `by_notification_level` sort order.
- Add `include_old_rooms` support.
- Add support for `$ME` and `$LAZY`.
- Add correct filtering when `*,*` is used as `required_state`.
- Add `num_live` to each room response to indicate how many timeline entries are live.
Bug fixes:
- Use a stricter comparison function on ranges: fixes an issue whereby UTs fail on go1.19 due to change in sorting algorithm.
- Send back an `errcode` on HTTP errors (e.g expired sessions).
- Remove `unsigned.txn_id` on insertion into the DB. Otherwise other users would see other users txn IDs :(
- Improve range delta algorithm: previously it didn't handle cases like `[0,20] -> [20,30]` and would panic.
- Send HTTP 400 for invalid range requests.
- Don't publish no-op unread counts which just adds extra noise.
- Fix leaking DB connections which could eventually consume all available connections.
- Ensure we always unblock WaitUntilInitialSync even on invalid access tokens. Other code relies on WaitUntilInitialSync() actually returning at _some_ point e.g on startup we have N workers which bound the number of concurrent pollers made at any one time, we need to not just hog a worker forever.
Improvements:
- Greatly improve startup times of sync3 handlers by improving `JoinedRoomsTracker`: a modest amount of data would take ~28s to create the handler, now it takes 4s.
- Massively improve initial initial v3 sync times, by refactoring `JoinedRoomsTracker`, from ~47s to <1s.
- Add `SlidingSyncUntil...` in tests to reduce races.
- Tweak the API shape of JoinedUsersForRoom to reduce state block processing time for large rooms from 63s to 39s.
- Add trace task for initial syncs.
- Include the proxy version in UA strings.
- HTTP errors now wait 1s before returning to stop clients tight-looping on error.
- Pending event buffer is now 2000.
- Index the room ID first to cull the most events when returning timeline entries. Speeds up `SelectLatestEventsBetween` by a factor of 8.
- Remove cancelled `m.room_key_requests` from the to-device inbox. Cuts down the amount of events in the inbox by ~94% for very large (20k+) inboxes, ~50% for moderate sized (200 events) inboxes. Adds book-keeping to remember the unacked to-device position for each client.
This is part of a series of refactors aimed to improve the performance
and complexity of calculating list deltas, which up until now exists in
its current form due to organic growth of the codebase.
This specific refactor introduces a new interface `RoomFinder` which
can map room IDs to `*RoomConnMetadata` which is used by `ConnState`.
All the sliding sync lists now use the `RoomFinder` instead of keeping
their own copies of `RoomConnMetadata`, meaning per-connection, rooms
just have 1 copy in-memory. This cuts down on memory usage as well as
cuts down on GC churn as we would constantly be replacing N rooms for
each update, where N is the total number of lists on that connection.
For Element-Web, N=7 currently to handle Favourites, Low Priority, DMs,
Rooms, Spaces, Invites, Search. This also has the benefit of creating
a single source of truth in `InternalRequestLists.allRooms` which can
be updated once and then a list of list deltas can be calculated off
the back of that. Previously, `allRooms` was _only_ used to seed new
lists, which created a weird imbalance as we would need to update both
`allRooms` _and_ each `FilteredSortableRooms` to keep things in-sync.
This refactor is incomplete in its present form, as we need to make
use of the new `RoomDelta` struct to efficiently package list updates.
Caused by us not updating the `CanonicalisedName` which is what we use to sort on.
This field is a bit of an oddity because it lived outside the user/global cache
fields because it is a calculated value from the global cache data in the scope
of a user, whereas other user cache values are derived directly from specific
data (notif counts, DM-ness). This is a silly distinction however, since spaces
are derived from global room data as well, so move `CanonicalisedName` to the
UserCache and keep it updated when the room name changes.
Longer term: we need to clean this up so only the user cache is responsible
for updating user cache fields, and connstate treats user room data and global
room data as immutable. This is _mostly_ true today, but isn't always, and it
causes headaches. In addition, it looks like we maintain O(n) caches based on
the number of lists the user has made: we needn't do this and should lean
much more heavily on `s.allRooms`, just keeping pointers to this slice from
whatever lists the user requests.
We weren't doing this previously, but things didn't blow up because
we would almost always call resort() shortly afterwards which _would_
update the map with the new sort positions. In some cases this could
cause the lists to be sorting with incorrect index positions, notably:
- when an invite is retired.
- when a room no longer meets filter criteria and is removed.
This could be a major source of duplicate rooms.
caches pkg is required to avoid import loops as sync3 depends on extensions
as the extension type is embedded in the `sync3.Request`, but extensions will
need to know about the caches for account data to function correctly.
