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>

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: