Faster joins: omit partial rooms from eager syncs until the resync completes (#14870)

* Allow `AbstractSet` in `StrCollection`

Or else frozensets are excluded. This will be useful in an upcoming
commit where I plan to change a function that accepts `List[str]` to
accept `StrCollection` instead.

* `rooms_to_exclude` -> `rooms_to_exclude_globally`

I am about to make use of this exclusion mechanism to exclude rooms for
a specific user and a specific sync. This rename helps to clarify the
distinction between the global config and the rooms to exclude for a
specific sync.

* Better function names for internal sync methods

* Track a list of excluded rooms on SyncResultBuilder

I plan to feed a list of partially stated rooms for this sync to ignore

* Exclude partial state rooms during eager sync

using the mechanism established in the previous commit

* Track un-partial-state stream in sync tokens

So that we can work out which rooms have become fully-stated during a
given sync period.

* Fix mutation of `@cached` return value

This was fouling up a complement test added alongside this PR.
Excluding a room would mean the set of forgotten rooms in the cache
would be extended. This means that room could be erroneously considered
forgotten in the future.

Introduced in #12310, Synapse 1.57.0. I don't think this had any
user-visible side effects (until now).

* SyncResultBuilder: track rooms to force as newly joined

Similar plan as before. We've omitted rooms from certain sync responses;
now we establish the mechanism to reintroduce them into future syncs.

* Read new field, to present rooms as newly joined

* Force un-partial-stated rooms to be newly-joined

for eager incremental syncs only, provided they're still fully stated

* Notify user stream listeners to wake up long polling syncs

* Changelog

* Typo fix

Co-authored-by: Sean Quah <8349537+squahtx@users.noreply.github.com>

* Unnecessary list cast

Co-authored-by: Sean Quah <8349537+squahtx@users.noreply.github.com>

* Rephrase comment

Co-authored-by: Sean Quah <8349537+squahtx@users.noreply.github.com>

* Another comment

Co-authored-by: Sean Quah <8349537+squahtx@users.noreply.github.com>

* Fixup merge(?)

* Poke notifier when receiving un-partial-stated msg over replication

* Fixup merge whoops

Thanks MV :)

Co-authored-by: Mathieu Velen <mathieuv@matrix.org>

Co-authored-by: Mathieu Velten <mathieuv@matrix.org>
Co-authored-by: Sean Quah <8349537+squahtx@users.noreply.github.com>

9 files changed, 159 insertions, 36 deletions

diff --git a/synapse/handlers/federation.py b/synapse/handlers/federation.py
index 3217127865..233f8c113d 100644
--- a/synapse/handlers/federation.py
+++ b/synapse/handlers/federation.py
@@ -1868,22 +1868,17 @@ class FederationHandler:
 
                 async with self._is_partial_state_room_linearizer.queue(room_id):
                     logger.info("Clearing partial-state flag for %s", room_id)
-                    success = await self.store.clear_partial_state_room(room_id)
+                    new_stream_id = await self.store.clear_partial_state_room(room_id)
 
-                    # Poke the notifier so that other workers see the write to
-                    # the un-partial-stated rooms stream.
-                    self._notifier.notify_replication()
-
-                if success:
+                if new_stream_id is not None:
                     logger.info("State resync complete for %s", room_id)
                     self._storage_controllers.state.notify_room_un_partial_stated(
                         room_id
                     )
 
-                    # Poke the notifier so that other workers see the write to
-                    # the un-partial-stated rooms stream.
-                    self._notifier.notify_replication()
-
+                    await self._notifier.on_un_partial_stated_room(
+                        room_id, new_stream_id
+                    )
                     return
 
                 # we raced against more events arriving with partial state. Go round
diff --git a/synapse/handlers/sync.py b/synapse/handlers/sync.py
index 78d488f2b1..ee11764567 100644
--- a/synapse/handlers/sync.py
+++ b/synapse/handlers/sync.py
@@ -290,7 +290,7 @@ class SyncHandler:
             expiry_ms=LAZY_LOADED_MEMBERS_CACHE_MAX_AGE,
         )
 
-        self.rooms_to_exclude = hs.config.server.rooms_to_exclude_from_sync
+        self.rooms_to_exclude_globally = hs.config.server.rooms_to_exclude_from_sync
 
     async def wait_for_sync_for_user(
         self,
@@ -1340,7 +1340,10 @@ class SyncHandler:
         membership_change_events = []
         if since_token:
             membership_change_events = await self.store.get_membership_changes_for_user(
-                user_id, since_token.room_key, now_token.room_key, self.rooms_to_exclude
+                user_id,
+                since_token.room_key,
+                now_token.room_key,
+                self.rooms_to_exclude_globally,
             )
 
             mem_last_change_by_room_id: Dict[str, EventBase] = {}
@@ -1375,12 +1378,39 @@ class SyncHandler:
                 else:
                     mutable_joined_room_ids.discard(room_id)
 
+        # Tweak the set of rooms to return to the client for eager (non-lazy) syncs.
+        mutable_rooms_to_exclude = set(self.rooms_to_exclude_globally)
+        if not sync_config.filter_collection.lazy_load_members():
+            # Non-lazy syncs should never include partially stated rooms.
+            # Exclude all partially stated rooms from this sync.
+            for room_id in mutable_joined_room_ids:
+                if await self.store.is_partial_state_room(room_id):
+                    mutable_rooms_to_exclude.add(room_id)
+
+        # Incremental eager syncs should additionally include rooms that
+        # - we are joined to
+        # - are full-stated
+        # - became fully-stated at some point during the sync period
+        #   (These rooms will have been omitted during a previous eager sync.)
+        forced_newly_joined_room_ids = set()
+        if since_token and not sync_config.filter_collection.lazy_load_members():
+            un_partial_stated_rooms = (
+                await self.store.get_un_partial_stated_rooms_between(
+                    since_token.un_partial_stated_rooms_key,
+                    now_token.un_partial_stated_rooms_key,
+                    mutable_joined_room_ids,
+                )
+            )
+            for room_id in un_partial_stated_rooms:
+                if not await self.store.is_partial_state_room(room_id):
+                    forced_newly_joined_room_ids.add(room_id)
+
         # Now we have our list of joined room IDs, exclude as configured and freeze
         joined_room_ids = frozenset(
             (
                 room_id
                 for room_id in mutable_joined_room_ids
-                if room_id not in self.rooms_to_exclude
+                if room_id not in mutable_rooms_to_exclude
             )
         )
 
@@ -1397,6 +1427,8 @@ class SyncHandler:
             since_token=since_token,
             now_token=now_token,
             joined_room_ids=joined_room_ids,
+            excluded_room_ids=frozenset(mutable_rooms_to_exclude),
+            forced_newly_joined_room_ids=frozenset(forced_newly_joined_room_ids),
             membership_change_events=membership_change_events,
         )
 
@@ -1834,14 +1866,16 @@ class SyncHandler:
         # 3. Work out which rooms need reporting in the sync response.
         ignored_users = await self.store.ignored_users(user_id)
         if since_token:
-            room_changes = await self._get_rooms_changed(
+            room_changes = await self._get_room_changes_for_incremental_sync(
                 sync_result_builder, ignored_users
             )
             tags_by_room = await self.store.get_updated_tags(
                 user_id, since_token.account_data_key
             )
         else:
-            room_changes = await self._get_all_rooms(sync_result_builder, ignored_users)
+            room_changes = await self._get_room_changes_for_initial_sync(
+                sync_result_builder, ignored_users
+            )
             tags_by_room = await self.store.get_tags_for_user(user_id)
 
         log_kv({"rooms_changed": len(room_changes.room_entries)})
@@ -1900,7 +1934,7 @@ class SyncHandler:
 
         assert since_token
 
-        if membership_change_events:
+        if membership_change_events or sync_result_builder.forced_newly_joined_room_ids:
             return True
 
         stream_id = since_token.room_key.stream
@@ -1909,7 +1943,7 @@ class SyncHandler:
                 return True
         return False
 
-    async def _get_rooms_changed(
+    async def _get_room_changes_for_incremental_sync(
         self,
         sync_result_builder: "SyncResultBuilder",
         ignored_users: FrozenSet[str],
@@ -1947,7 +1981,9 @@ class SyncHandler:
         for event in membership_change_events:
             mem_change_events_by_room_id.setdefault(event.room_id, []).append(event)
 
-        newly_joined_rooms: List[str] = []
+        newly_joined_rooms: List[str] = list(
+            sync_result_builder.forced_newly_joined_room_ids
+        )
         newly_left_rooms: List[str] = []
         room_entries: List[RoomSyncResultBuilder] = []
         invited: List[InvitedSyncResult] = []
@@ -2153,7 +2189,7 @@ class SyncHandler:
             newly_left_rooms,
         )
 
-    async def _get_all_rooms(
+    async def _get_room_changes_for_initial_sync(
         self,
         sync_result_builder: "SyncResultBuilder",
         ignored_users: FrozenSet[str],
@@ -2178,7 +2214,7 @@ class SyncHandler:
         room_list = await self.store.get_rooms_for_local_user_where_membership_is(
             user_id=user_id,
             membership_list=Membership.LIST,
-            excluded_rooms=self.rooms_to_exclude,
+            excluded_rooms=sync_result_builder.excluded_room_ids,
         )
 
         room_entries = []
@@ -2549,6 +2585,13 @@ class SyncResultBuilder:
         since_token: The token supplied by user, or None.
         now_token: The token to sync up to.
         joined_room_ids: List of rooms the user is joined to
+        excluded_room_ids: Set of room ids we should omit from the /sync response.
+        forced_newly_joined_room_ids:
+            Rooms that should be presented in the /sync response as if they were
+            newly joined during the sync period, even if that's not the case.
+            (This is useful if the room was previously excluded from a /sync response,
+            and now the client should be made aware of it.)
+            Only used by incremental syncs.
 
         # The following mirror the fields in a sync response
         presence
@@ -2565,6 +2608,8 @@ class SyncResultBuilder:
     since_token: Optional[StreamToken]
     now_token: StreamToken
     joined_room_ids: FrozenSet[str]
+    excluded_room_ids: FrozenSet[str]
+    forced_newly_joined_room_ids: FrozenSet[str]
     membership_change_events: List[EventBase]
 
     presence: List[UserPresenceState] = attr.Factory(list)
diff --git a/synapse/notifier.py b/synapse/notifier.py
index 28f0d4a25a..2b0e52f23c 100644
--- a/synapse/notifier.py
+++ b/synapse/notifier.py
@@ -314,6 +314,32 @@ class Notifier:
             event_entries.append((entry, event.event_id))
         await self.notify_new_room_events(event_entries, max_room_stream_token)
 
+    async def on_un_partial_stated_room(
+        self,
+        room_id: str,
+        new_token: int,
+    ) -> None:
+        """Used by the resync background processes to wake up all listeners
+        of this room when it is un-partial-stated.
+
+        It will also notify replication listeners of the change in stream.
+        """
+
+        # Wake up all related user stream notifiers
+        user_streams = self.room_to_user_streams.get(room_id, set())
+        time_now_ms = self.clock.time_msec()
+        for user_stream in user_streams:
+            try:
+                user_stream.notify(
+                    StreamKeyType.UN_PARTIAL_STATED_ROOMS, new_token, time_now_ms
+                )
+            except Exception:
+                logger.exception("Failed to notify listener")
+
+        # Poke the replication so that other workers also see the write to
+        # the un-partial-stated rooms stream.
+        self.notify_replication()
+
     async def notify_new_room_events(
         self,
         event_entries: List[Tuple[_PendingRoomEventEntry, str]],
diff --git a/synapse/replication/tcp/client.py b/synapse/replication/tcp/client.py
index 2a9cb499a4..cc0528bd8e 100644
--- a/synapse/replication/tcp/client.py
+++ b/synapse/replication/tcp/client.py
@@ -260,6 +260,7 @@ class ReplicationDataHandler:
                 self._state_storage_controller.notify_room_un_partial_stated(
                     row.room_id
                 )
+                await self.notifier.on_un_partial_stated_room(row.room_id, token)
         elif stream_name == UnPartialStatedEventStream.NAME:
             for row in rows:
                 assert isinstance(row, UnPartialStatedEventStreamRow)
diff --git a/synapse/storage/databases/main/relations.py b/synapse/storage/databases/main/relations.py
index aea96e9d24..84f844b79e 100644
--- a/synapse/storage/databases/main/relations.py
+++ b/synapse/storage/databases/main/relations.py
@@ -292,6 +292,7 @@ class RelationsWorkerStore(SQLBaseStore):
                         to_device_key=0,
                         device_list_key=0,
                         groups_key=0,
+                        un_partial_stated_rooms_key=0,
                     )
 
             return events[:limit], next_token
diff --git a/synapse/storage/databases/main/room.py b/synapse/storage/databases/main/room.py
index 6a65b2a89b..3aa7b94560 100644
--- a/synapse/storage/databases/main/room.py
+++ b/synapse/storage/databases/main/room.py
@@ -26,6 +26,7 @@ from typing import (
     Mapping,
     Optional,
     Sequence,
+    Set,
     Tuple,
     Union,
     cast,
@@ -1294,10 +1295,44 @@ class RoomWorkerStore(CacheInvalidationWorkerStore):
             instance_name
         )
 
+    async def get_un_partial_stated_rooms_between(
+        self, last_id: int, current_id: int, room_ids: Collection[str]
+    ) -> Set[str]:
+        """Get all rooms that got un partial stated between `last_id` exclusive and
+        `current_id` inclusive.
+
+        Returns:
+            The list of room ids.
+        """
+
+        if last_id == current_id:
+            return set()
+
+        def _get_un_partial_stated_rooms_between_txn(
+            txn: LoggingTransaction,
+        ) -> Set[str]:
+            sql = """
+                SELECT DISTINCT room_id FROM un_partial_stated_room_stream
+                WHERE ? < stream_id AND stream_id <= ? AND
+            """
+
+            clause, args = make_in_list_sql_clause(
+                self.database_engine, "room_id", room_ids
+            )
+
+            txn.execute(sql + clause, [last_id, current_id] + args)
+
+            return {r[0] for r in txn}
+
+        return await self.db_pool.runInteraction(
+            "get_un_partial_stated_rooms_between",
+            _get_un_partial_stated_rooms_between_txn,
+        )
+
     async def get_un_partial_stated_rooms_from_stream(
         self, instance_name: str, last_id: int, current_id: int, limit: int
     ) -> Tuple[List[Tuple[int, Tuple[str]]], int, bool]:
-        """Get updates for caches replication stream.
+        """Get updates for un partial stated rooms replication stream.
 
         Args:
             instance_name: The writer we want to fetch updates from. Unused
@@ -2304,16 +2339,16 @@ class RoomStore(RoomBackgroundUpdateStore, RoomWorkerStore):
             (room_id,),
         )
 
-    async def clear_partial_state_room(self, room_id: str) -> bool:
+    async def clear_partial_state_room(self, room_id: str) -> Optional[int]:
         """Clears the partial state flag for a room.
 
         Args:
             room_id: The room whose partial state flag is to be cleared.
 
         Returns:
-            `True` if the partial state flag has been cleared successfully.
+            The corresponding stream id for the un-partial-stated rooms stream.
 
-            `False` if the partial state flag could not be cleared because the room
+            `None` if the partial state flag could not be cleared because the room
             still contains events with partial state.
         """
         try:
@@ -2324,7 +2359,7 @@ class RoomStore(RoomBackgroundUpdateStore, RoomWorkerStore):
                     room_id,
                     un_partial_state_room_stream_id,
                 )
-                return True
+                return un_partial_state_room_stream_id
         except self.db_pool.engine.module.IntegrityError as e:
             # Assume that any `IntegrityError`s are due to partial state events.
             logger.info(
@@ -2332,7 +2367,7 @@ class RoomStore(RoomBackgroundUpdateStore, RoomWorkerStore):
                 room_id,
                 e,
             )
-            return False
+            return None
 
     def _clear_partial_state_room_txn(
         self,
diff --git a/synapse/storage/databases/main/roommember.py b/synapse/storage/databases/main/roommember.py
index f02c1d7ea7..8e2ba7b7b4 100644
--- a/synapse/storage/databases/main/roommember.py
+++ b/synapse/storage/databases/main/roommember.py
@@ -15,6 +15,7 @@
 import logging
 from typing import (
     TYPE_CHECKING,
+    AbstractSet,
     Collection,
     Dict,
     FrozenSet,
@@ -47,7 +48,13 @@ from synapse.storage.roommember import (
     ProfileInfo,
     RoomsForUser,
 )
-from synapse.types import JsonDict, PersistedEventPosition, StateMap, get_domain_from_id
+from synapse.types import (
+    JsonDict,
+    PersistedEventPosition,
+    StateMap,
+    StrCollection,
+    get_domain_from_id,
+)
 from synapse.util.async_helpers import Linearizer
 from synapse.util.caches import intern_string
 from synapse.util.caches.descriptors import _CacheContext, cached, cachedList
@@ -385,7 +392,7 @@ class RoomMemberWorkerStore(EventsWorkerStore):
         self,
         user_id: str,
         membership_list: Collection[str],
-        excluded_rooms: Optional[List[str]] = None,
+        excluded_rooms: StrCollection = (),
     ) -> List[RoomsForUser]:
         """Get all the rooms for this *local* user where the membership for this user
         matches one in the membership list.
@@ -412,10 +419,12 @@ class RoomMemberWorkerStore(EventsWorkerStore):
         )
 
         # Now we filter out forgotten and excluded rooms
-        rooms_to_exclude: Set[str] = await self.get_forgotten_rooms_for_user(user_id)
+        rooms_to_exclude = await self.get_forgotten_rooms_for_user(user_id)
 
         if excluded_rooms is not None:
-            rooms_to_exclude.update(set(excluded_rooms))
+            # Take a copy to avoid mutating the in-cache set
+            rooms_to_exclude = set(rooms_to_exclude)
+            rooms_to_exclude.update(excluded_rooms)
 
         return [room for room in rooms if room.room_id not in rooms_to_exclude]
 
@@ -1169,7 +1178,7 @@ class RoomMemberWorkerStore(EventsWorkerStore):
         return count == 0
 
     @cached()
-    async def get_forgotten_rooms_for_user(self, user_id: str) -> Set[str]:
+    async def get_forgotten_rooms_for_user(self, user_id: str) -> AbstractSet[str]:
         """Gets all rooms the user has forgotten.
 
         Args:
diff --git a/synapse/streams/events.py b/synapse/streams/events.py
index 619eb7f601..d7084d2358 100644
--- a/synapse/streams/events.py
+++ b/synapse/streams/events.py
@@ -53,11 +53,15 @@ class EventSources:
             *(attribute.type(hs) for attribute in attr.fields(_EventSourcesInner))
         )
         self.store = hs.get_datastores().main
+        self._instance_name = hs.get_instance_name()
 
     def get_current_token(self) -> StreamToken:
         push_rules_key = self.store.get_max_push_rules_stream_id()
         to_device_key = self.store.get_to_device_stream_token()
         device_list_key = self.store.get_device_stream_token()
+        un_partial_stated_rooms_key = self.store.get_un_partial_stated_rooms_token(
+            self._instance_name
+        )
 
         token = StreamToken(
             room_key=self.sources.room.get_current_key(),
@@ -70,6 +74,7 @@ class EventSources:
             device_list_key=device_list_key,
             # Groups key is unused.
             groups_key=0,
+            un_partial_stated_rooms_key=un_partial_stated_rooms_key,
         )
         return token
 
@@ -107,5 +112,6 @@ class EventSources:
             to_device_key=0,
             device_list_key=0,
             groups_key=0,
+            un_partial_stated_rooms_key=0,
         )
         return token
diff --git a/synapse/types/__init__.py b/synapse/types/__init__.py
index c59eca2430..f82d1cfc29 100644
--- a/synapse/types/__init__.py
+++ b/synapse/types/__init__.py
@@ -17,6 +17,7 @@ import re
 import string
 from typing import (
     TYPE_CHECKING,
+    AbstractSet,
     Any,
     ClassVar,
     Dict,
@@ -79,7 +80,7 @@ JsonSerializable = object
 
 # Collection[str] that does not include str itself; str being a Sequence[str]
 # is very misleading and results in bugs.
-StrCollection = Union[Tuple[str, ...], List[str], Set[str]]
+StrCollection = Union[Tuple[str, ...], List[str], AbstractSet[str]]
 
 
 # Note that this seems to require inheriting *directly* from Interface in order
@@ -633,6 +634,7 @@ class StreamKeyType:
     PUSH_RULES: Final = "push_rules_key"
     TO_DEVICE: Final = "to_device_key"
     DEVICE_LIST: Final = "device_list_key"
+    UN_PARTIAL_STATED_ROOMS = "un_partial_stated_rooms_key"
 
 
 @attr.s(slots=True, frozen=True, auto_attribs=True)
@@ -640,7 +642,7 @@ class StreamToken:
     """A collection of keys joined together by underscores in the following
     order and which represent the position in their respective streams.
 
-    ex. `s2633508_17_338_6732159_1082514_541479_274711_265584_1`
+    ex. `s2633508_17_338_6732159_1082514_541479_274711_265584_1_379`
         1. `room_key`: `s2633508` which is a `RoomStreamToken`
            - `RoomStreamToken`'s can also look like `t426-2633508` or `m56~2.58~3.59`
            - See the docstring for `RoomStreamToken` for more details.
@@ -652,12 +654,13 @@ class StreamToken:
         7. `to_device_key`: `274711`
         8. `device_list_key`: `265584`
         9. `groups_key`: `1` (note that this key is now unused)
+        10. `un_partial_stated_rooms_key`: `379`
 
     You can see how many of these keys correspond to the various
     fields in a "/sync" response:
     ```json
     {
-        "next_batch": "s12_4_0_1_1_1_1_4_1",
+        "next_batch": "s12_4_0_1_1_1_1_4_1_1",
         "presence": {
             "events": []
         },
@@ -669,7 +672,7 @@ class StreamToken:
                 "!QrZlfIDQLNLdZHqTnt:hs1": {
                     "timeline": {
                         "events": [],
-                        "prev_batch": "s10_4_0_1_1_1_1_4_1",
+                        "prev_batch": "s10_4_0_1_1_1_1_4_1_1",
                         "limited": false
                     },
                     "state": {
@@ -705,6 +708,7 @@ class StreamToken:
     device_list_key: int
     # Note that the groups key is no longer used and may have bogus values.
     groups_key: int
+    un_partial_stated_rooms_key: int
 
     _SEPARATOR = "_"
     START: ClassVar["StreamToken"]
@@ -743,6 +747,7 @@ class StreamToken:
                 # serialized so that there will not be confusion in the future
                 # if additional tokens are added.
                 str(self.groups_key),
+                str(self.un_partial_stated_rooms_key),
             ]
         )
 
@@ -775,7 +780,7 @@ class StreamToken:
         return attr.evolve(self, **{key: new_value})
 
 
-StreamToken.START = StreamToken(RoomStreamToken(None, 0), 0, 0, 0, 0, 0, 0, 0, 0)
+StreamToken.START = StreamToken(RoomStreamToken(None, 0), 0, 0, 0, 0, 0, 0, 0, 0, 0)
 
 
 @attr.s(slots=True, frozen=True, auto_attribs=True)