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/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)