diff --git a/synapse/handlers/sliding_sync.py b/synapse/handlers/sliding_sync.py
new file mode 100644
index 0000000000..34ae21ba50
--- /dev/null
+++ b/synapse/handlers/sliding_sync.py
@@ -0,0 +1,610 @@
+#
+# This file is licensed under the Affero General Public License (AGPL) version 3.
+#
+# Copyright (C) 2024 New Vector, Ltd
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as
+# published by the Free Software Foundation, either version 3 of the
+# License, or (at your option) any later version.
+#
+# See the GNU Affero General Public License for more details:
+# <https://www.gnu.org/licenses/agpl-3.0.html>.
+#
+# Originally licensed under the Apache License, Version 2.0:
+# <http://www.apache.org/licenses/LICENSE-2.0>.
+#
+# [This file includes modifications made by New Vector Limited]
+#
+#
+import logging
+from enum import Enum
+from typing import TYPE_CHECKING, AbstractSet, Dict, Final, List, Optional, Tuple
+
+import attr
+from immutabledict import immutabledict
+
+from synapse._pydantic_compat import HAS_PYDANTIC_V2
+
+if TYPE_CHECKING or HAS_PYDANTIC_V2:
+ from pydantic.v1 import Extra
+else:
+ from pydantic import Extra
+
+from synapse.api.constants import Membership
+from synapse.events import EventBase
+from synapse.rest.client.models import SlidingSyncBody
+from synapse.types import JsonMapping, Requester, RoomStreamToken, StreamToken, UserID
+
+if TYPE_CHECKING:
+ from synapse.server import HomeServer
+
+logger = logging.getLogger(__name__)
+
+
+def filter_membership_for_sync(*, membership: str, user_id: str, sender: str) -> bool:
+ """
+ Returns True if the membership event should be included in the sync response,
+ otherwise False.
+
+ Attributes:
+ membership: The membership state of the user in the room.
+ user_id: The user ID that the membership applies to
+ sender: The person who sent the membership event
+ """
+
+ # Everything except `Membership.LEAVE` because we want everything that's *still*
+ # relevant to the user. There are few more things to include in the sync response
+ # (newly_left) but those are handled separately.
+ #
+ # This logic includes kicks (leave events where the sender is not the same user) and
+ # can be read as "anything that isn't a leave or a leave with a different sender".
+ return membership != Membership.LEAVE or sender != user_id
+
+
+class SlidingSyncConfig(SlidingSyncBody):
+ """
+ Inherit from `SlidingSyncBody` since we need all of the same fields and add a few
+ extra fields that we need in the handler
+ """
+
+ user: UserID
+ device_id: Optional[str]
+
+ # Pydantic config
+ class Config:
+ # By default, ignore fields that we don't recognise.
+ extra = Extra.ignore
+ # By default, don't allow fields to be reassigned after parsing.
+ allow_mutation = False
+ # Allow custom types like `UserID` to be used in the model
+ arbitrary_types_allowed = True
+
+
+class OperationType(Enum):
+ """
+ Represents the operation types in a Sliding Sync window.
+
+ Attributes:
+ SYNC: Sets a range of entries. Clients SHOULD discard what they previous knew about
+ entries in this range.
+ INSERT: Sets a single entry. If the position is not empty then clients MUST move
+ entries to the left or the right depending on where the closest empty space is.
+ DELETE: Remove a single entry. Often comes before an INSERT to allow entries to move
+ places.
+ INVALIDATE: Remove a range of entries. Clients MAY persist the invalidated range for
+ offline support, but they should be treated as empty when additional operations
+ which concern indexes in the range arrive from the server.
+ """
+
+ SYNC: Final = "SYNC"
+ INSERT: Final = "INSERT"
+ DELETE: Final = "DELETE"
+ INVALIDATE: Final = "INVALIDATE"
+
+
+@attr.s(slots=True, frozen=True, auto_attribs=True)
+class SlidingSyncResult:
+ """
+ The Sliding Sync result to be serialized to JSON for a response.
+
+ Attributes:
+ next_pos: The next position token in the sliding window to request (next_batch).
+ lists: Sliding window API. A map of list key to list results.
+ rooms: Room subscription API. A map of room ID to room subscription to room results.
+ extensions: Extensions API. A map of extension key to extension results.
+ """
+
+ @attr.s(slots=True, frozen=True, auto_attribs=True)
+ class RoomResult:
+ """
+ Attributes:
+ name: Room name or calculated room name.
+ avatar: Room avatar
+ heroes: List of stripped membership events (containing `user_id` and optionally
+ `avatar_url` and `displayname`) for the users used to calculate the room name.
+ initial: Flag which is set when this is the first time the server is sending this
+ data on this connection. Clients can use this flag to replace or update
+ their local state. When there is an update, servers MUST omit this flag
+ entirely and NOT send "initial":false as this is wasteful on bandwidth. The
+ absence of this flag means 'false'.
+ required_state: The current state of the room
+ timeline: Latest events in the room. The last event is the most recent
+ is_dm: Flag to specify whether the room is a direct-message room (most likely
+ between two people).
+ invite_state: Stripped state events. Same as `rooms.invite.$room_id.invite_state`
+ in sync v2, absent on joined/left rooms
+ prev_batch: A token that can be passed as a start parameter to the
+ `/rooms/<room_id>/messages` API to retrieve earlier messages.
+ limited: True if their are more events than fit between the given position and now.
+ Sync again to get more.
+ joined_count: The number of users with membership of join, including the client's
+ own user ID. (same as sync `v2 m.joined_member_count`)
+ invited_count: The number of users with membership of invite. (same as sync v2
+ `m.invited_member_count`)
+ notification_count: The total number of unread notifications for this room. (same
+ as sync v2)
+ highlight_count: The number of unread notifications for this room with the highlight
+ flag set. (same as sync v2)
+ num_live: The number of timeline events which have just occurred and are not historical.
+ The last N events are 'live' and should be treated as such. This is mostly
+ useful to determine whether a given @mention event should make a noise or not.
+ Clients cannot rely solely on the absence of `initial: true` to determine live
+ events because if a room not in the sliding window bumps into the window because
+ of an @mention it will have `initial: true` yet contain a single live event
+ (with potentially other old events in the timeline).
+ """
+
+ name: str
+ avatar: Optional[str]
+ heroes: Optional[List[EventBase]]
+ initial: bool
+ required_state: List[EventBase]
+ timeline: List[EventBase]
+ is_dm: bool
+ invite_state: List[EventBase]
+ prev_batch: StreamToken
+ limited: bool
+ joined_count: int
+ invited_count: int
+ notification_count: int
+ highlight_count: int
+ num_live: int
+
+ @attr.s(slots=True, frozen=True, auto_attribs=True)
+ class SlidingWindowList:
+ """
+ Attributes:
+ count: The total number of entries in the list. Always present if this list
+ is.
+ ops: The sliding list operations to perform.
+ """
+
+ @attr.s(slots=True, frozen=True, auto_attribs=True)
+ class Operation:
+ """
+ Attributes:
+ op: The operation type to perform.
+ range: Which index positions are affected by this operation. These are
+ both inclusive.
+ room_ids: Which room IDs are affected by this operation. These IDs match
+ up to the positions in the `range`, so the last room ID in this list
+ matches the 9th index. The room data is held in a separate object.
+ """
+
+ op: OperationType
+ range: Tuple[int, int]
+ room_ids: List[str]
+
+ count: int
+ ops: List[Operation]
+
+ next_pos: StreamToken
+ lists: Dict[str, SlidingWindowList]
+ rooms: Dict[str, RoomResult]
+ extensions: JsonMapping
+
+ def __bool__(self) -> bool:
+ """Make the result appear empty if there are no updates. This is used
+ to tell if the notifier needs to wait for more events when polling for
+ events.
+ """
+ return bool(self.lists or self.rooms or self.extensions)
+
+ @staticmethod
+ def empty(next_pos: StreamToken) -> "SlidingSyncResult":
+ "Return a new empty result"
+ return SlidingSyncResult(
+ next_pos=next_pos,
+ lists={},
+ rooms={},
+ extensions={},
+ )
+
+
+class SlidingSyncHandler:
+ def __init__(self, hs: "HomeServer"):
+ self.clock = hs.get_clock()
+ self.store = hs.get_datastores().main
+ self.auth_blocking = hs.get_auth_blocking()
+ self.notifier = hs.get_notifier()
+ self.event_sources = hs.get_event_sources()
+ self.rooms_to_exclude_globally = hs.config.server.rooms_to_exclude_from_sync
+
+ async def wait_for_sync_for_user(
+ self,
+ requester: Requester,
+ sync_config: SlidingSyncConfig,
+ from_token: Optional[StreamToken] = None,
+ timeout_ms: int = 0,
+ ) -> SlidingSyncResult:
+ """Get the sync for a client if we have new data for it now. Otherwise
+ wait for new data to arrive on the server. If the timeout expires, then
+ return an empty sync result.
+ """
+ # If the user is not part of the mau group, then check that limits have
+ # not been exceeded (if not part of the group by this point, almost certain
+ # auth_blocking will occur)
+ await self.auth_blocking.check_auth_blocking(requester=requester)
+
+ # TODO: If the To-Device extension is enabled and we have a `from_token`, delete
+ # any to-device messages before that token (since we now know that the device
+ # has received them). (see sync v2 for how to do this)
+
+ # If we're working with a user-provided token, we need to make sure to wait for
+ # this worker to catch up with the token so we don't skip past any incoming
+ # events or future events if the user is nefariously, manually modifying the
+ # token.
+ if from_token is not None:
+ # We need to make sure this worker has caught up with the token. If
+ # this returns false, it means we timed out waiting, and we should
+ # just return an empty response.
+ before_wait_ts = self.clock.time_msec()
+ if not await self.notifier.wait_for_stream_token(from_token):
+ logger.warning(
+ "Timed out waiting for worker to catch up. Returning empty response"
+ )
+ return SlidingSyncResult.empty(from_token)
+
+ # If we've spent significant time waiting to catch up, take it off
+ # the timeout.
+ after_wait_ts = self.clock.time_msec()
+ if after_wait_ts - before_wait_ts > 1_000:
+ timeout_ms -= after_wait_ts - before_wait_ts
+ timeout_ms = max(timeout_ms, 0)
+
+ # We're going to respond immediately if the timeout is 0 or if this is an
+ # initial sync (without a `from_token`) so we can avoid calling
+ # `notifier.wait_for_events()`.
+ if timeout_ms == 0 or from_token is None:
+ now_token = self.event_sources.get_current_token()
+ result = await self.current_sync_for_user(
+ sync_config,
+ from_token=from_token,
+ to_token=now_token,
+ )
+ else:
+ # Otherwise, we wait for something to happen and report it to the user.
+ async def current_sync_callback(
+ before_token: StreamToken, after_token: StreamToken
+ ) -> SlidingSyncResult:
+ return await self.current_sync_for_user(
+ sync_config,
+ from_token=from_token,
+ to_token=after_token,
+ )
+
+ result = await self.notifier.wait_for_events(
+ sync_config.user.to_string(),
+ timeout_ms,
+ current_sync_callback,
+ from_token=from_token,
+ )
+
+ return result
+
+ async def current_sync_for_user(
+ self,
+ sync_config: SlidingSyncConfig,
+ to_token: StreamToken,
+ from_token: Optional[StreamToken] = None,
+ ) -> SlidingSyncResult:
+ """
+ Generates the response body of a Sliding Sync result, represented as a
+ `SlidingSyncResult`.
+ """
+ user_id = sync_config.user.to_string()
+ app_service = self.store.get_app_service_by_user_id(user_id)
+ if app_service:
+ # We no longer support AS users using /sync directly.
+ # See https://github.com/matrix-org/matrix-doc/issues/1144
+ raise NotImplementedError()
+
+ # Get all of the room IDs that the user should be able to see in the sync
+ # response
+ room_id_set = await self.get_sync_room_ids_for_user(
+ sync_config.user,
+ from_token=from_token,
+ to_token=to_token,
+ )
+
+ # Assemble sliding window lists
+ lists: Dict[str, SlidingSyncResult.SlidingWindowList] = {}
+ if sync_config.lists:
+ for list_key, list_config in sync_config.lists.items():
+ # TODO: Apply filters
+ #
+ # TODO: Exclude partially stated rooms unless the `required_state` has
+ # `["m.room.member", "$LAZY"]`
+ filtered_room_ids = room_id_set
+ # TODO: Apply sorts
+ sorted_room_ids = sorted(filtered_room_ids)
+
+ ops: List[SlidingSyncResult.SlidingWindowList.Operation] = []
+ if list_config.ranges:
+ for range in list_config.ranges:
+ ops.append(
+ SlidingSyncResult.SlidingWindowList.Operation(
+ op=OperationType.SYNC,
+ range=range,
+ room_ids=sorted_room_ids[range[0] : range[1]],
+ )
+ )
+
+ lists[list_key] = SlidingSyncResult.SlidingWindowList(
+ count=len(sorted_room_ids),
+ ops=ops,
+ )
+
+ return SlidingSyncResult(
+ next_pos=to_token,
+ lists=lists,
+ # TODO: Gather room data for rooms in lists and `sync_config.room_subscriptions`
+ rooms={},
+ extensions={},
+ )
+
+ async def get_sync_room_ids_for_user(
+ self,
+ user: UserID,
+ to_token: StreamToken,
+ from_token: Optional[StreamToken] = None,
+ ) -> AbstractSet[str]:
+ """
+ Fetch room IDs that should be listed for this user in the sync response (the
+ full room list that will be filtered, sorted, and sliced).
+
+ We're looking for rooms where the user has the following state in the token
+ range (> `from_token` and <= `to_token`):
+
+ - `invite`, `join`, `knock`, `ban` membership events
+ - Kicks (`leave` membership events where `sender` is different from the
+ `user_id`/`state_key`)
+ - `newly_left` (rooms that were left during the given token range)
+ - In order for bans/kicks to not show up in sync, you need to `/forget` those
+ rooms. This doesn't modify the event itself though and only adds the
+ `forgotten` flag to the `room_memberships` table in Synapse. There isn't a way
+ to tell when a room was forgotten at the moment so we can't factor it into the
+ from/to range.
+ """
+ user_id = user.to_string()
+
+ # First grab a current snapshot rooms for the user
+ # (also handles forgotten rooms)
+ room_for_user_list = await self.store.get_rooms_for_local_user_where_membership_is(
+ user_id=user_id,
+ # We want to fetch any kind of membership (joined and left rooms) in order
+ # to get the `event_pos` of the latest room membership event for the
+ # user.
+ #
+ # We will filter out the rooms that don't belong below (see
+ # `filter_membership_for_sync`)
+ membership_list=Membership.LIST,
+ excluded_rooms=self.rooms_to_exclude_globally,
+ )
+
+ # If the user has never joined any rooms before, we can just return an empty list
+ if not room_for_user_list:
+ return set()
+
+ # Our working list of rooms that can show up in the sync response
+ sync_room_id_set = {
+ room_for_user.room_id
+ for room_for_user in room_for_user_list
+ if filter_membership_for_sync(
+ membership=room_for_user.membership,
+ user_id=user_id,
+ sender=room_for_user.sender,
+ )
+ }
+
+ # Get the `RoomStreamToken` that represents the spot we queried up to when we got
+ # our membership snapshot from `get_rooms_for_local_user_where_membership_is()`.
+ #
+ # First, we need to get the max stream_ordering of each event persister instance
+ # that we queried events from.
+ instance_to_max_stream_ordering_map: Dict[str, int] = {}
+ for room_for_user in room_for_user_list:
+ instance_name = room_for_user.event_pos.instance_name
+ stream_ordering = room_for_user.event_pos.stream
+
+ current_instance_max_stream_ordering = (
+ instance_to_max_stream_ordering_map.get(instance_name)
+ )
+ if (
+ current_instance_max_stream_ordering is None
+ or stream_ordering > current_instance_max_stream_ordering
+ ):
+ instance_to_max_stream_ordering_map[instance_name] = stream_ordering
+
+ # Then assemble the `RoomStreamToken`
+ membership_snapshot_token = RoomStreamToken(
+ # Minimum position in the `instance_map`
+ stream=min(instance_to_max_stream_ordering_map.values()),
+ instance_map=immutabledict(instance_to_max_stream_ordering_map),
+ )
+
+ # If our `to_token` is already the same or ahead of the latest room membership
+ # for the user, we can just straight-up return the room list (nothing has
+ # changed)
+ if membership_snapshot_token.is_before_or_eq(to_token.room_key):
+ return sync_room_id_set
+
+ # Since we fetched the users room list at some point in time after the from/to
+ # tokens, we need to revert/rewind some membership changes to match the point in
+ # time of the `to_token`. In particular, we need to make these fixups:
+ #
+ # - 1a) Remove rooms that the user joined after the `to_token`
+ # - 1b) Add back rooms that the user left after the `to_token`
+ # - 2) Add back newly_left rooms (> `from_token` and <= `to_token`)
+ #
+ # Below, we're doing two separate lookups for membership changes. We could
+ # request everything for both fixups in one range, [`from_token.room_key`,
+ # `membership_snapshot_token`), but we want to avoid raw `stream_ordering`
+ # comparison without `instance_name` (which is flawed). We could refactor
+ # `event.internal_metadata` to include `instance_name` but it might turn out a
+ # little difficult and a bigger, broader Synapse change than we want to make.
+
+ # 1) -----------------------------------------------------
+
+ # 1) Fetch membership changes that fall in the range from `to_token` up to
+ # `membership_snapshot_token`
+ membership_change_events_after_to_token = (
+ await self.store.get_membership_changes_for_user(
+ user_id,
+ from_key=to_token.room_key,
+ to_key=membership_snapshot_token,
+ excluded_rooms=self.rooms_to_exclude_globally,
+ )
+ )
+
+ # 1) Assemble a list of the last membership events in some given ranges. Someone
+ # could have left and joined multiple times during the given range but we only
+ # care about end-result so we grab the last one.
+ last_membership_change_by_room_id_after_to_token: Dict[str, EventBase] = {}
+ # We also need the first membership event after the `to_token` so we can step
+ # backward to the previous membership that would apply to the from/to range.
+ first_membership_change_by_room_id_after_to_token: Dict[str, EventBase] = {}
+ for event in membership_change_events_after_to_token:
+ last_membership_change_by_room_id_after_to_token[event.room_id] = event
+ # Only set if we haven't already set it
+ first_membership_change_by_room_id_after_to_token.setdefault(
+ event.room_id, event
+ )
+
+ # 1) Fixup
+ for (
+ last_membership_change_after_to_token
+ ) in last_membership_change_by_room_id_after_to_token.values():
+ room_id = last_membership_change_after_to_token.room_id
+
+ # We want to find the first membership change after the `to_token` then step
+ # backward to know the membership in the from/to range.
+ first_membership_change_after_to_token = (
+ first_membership_change_by_room_id_after_to_token.get(room_id)
+ )
+ assert first_membership_change_after_to_token is not None, (
+ "If there was a `last_membership_change_after_to_token` that we're iterating over, "
+ + "then there should be corresponding a first change. For example, even if there "
+ + "is only one event after the `to_token`, the first and last event will be same event. "
+ + "This is probably a mistake in assembling the `last_membership_change_by_room_id_after_to_token`"
+ + "/`first_membership_change_by_room_id_after_to_token` dicts above."
+ )
+ # TODO: Instead of reading from `unsigned`, refactor this to use the
+ # `current_state_delta_stream` table in the future. Probably a new
+ # `get_membership_changes_for_user()` function that uses
+ # `current_state_delta_stream` with a join to `room_memberships`. This would
+ # help in state reset scenarios since `prev_content` is looking at the
+ # current branch vs the current room state. This is all just data given to
+ # the client so no real harm to data integrity, but we'd like to be nice to
+ # the client. Since the `current_state_delta_stream` table is new, it
+ # doesn't have all events in it. Since this is Sliding Sync, if we ever need
+ # to, we can signal the client to throw all of their state away by sending
+ # "operation: RESET".
+ prev_content = first_membership_change_after_to_token.unsigned.get(
+ "prev_content", {}
+ )
+ prev_membership = prev_content.get("membership", None)
+ prev_sender = first_membership_change_after_to_token.unsigned.get(
+ "prev_sender", None
+ )
+
+ # Check if the previous membership (membership that applies to the from/to
+ # range) should be included in our `sync_room_id_set`
+ should_prev_membership_be_included = (
+ prev_membership is not None
+ and prev_sender is not None
+ and filter_membership_for_sync(
+ membership=prev_membership,
+ user_id=user_id,
+ sender=prev_sender,
+ )
+ )
+
+ # Check if the last membership (membership that applies to our snapshot) was
+ # already included in our `sync_room_id_set`
+ was_last_membership_already_included = filter_membership_for_sync(
+ membership=last_membership_change_after_to_token.membership,
+ user_id=user_id,
+ sender=last_membership_change_after_to_token.sender,
+ )
+
+ # 1a) Add back rooms that the user left after the `to_token`
+ #
+ # For example, if the last membership event after the `to_token` is a leave
+ # event, then the room was excluded from `sync_room_id_set` when we first
+ # crafted it above. We should add these rooms back as long as the user also
+ # was part of the room before the `to_token`.
+ if (
+ not was_last_membership_already_included
+ and should_prev_membership_be_included
+ ):
+ sync_room_id_set.add(room_id)
+ # 1b) Remove rooms that the user joined (hasn't left) after the `to_token`
+ #
+ # For example, if the last membership event after the `to_token` is a "join"
+ # event, then the room was included `sync_room_id_set` when we first crafted
+ # it above. We should remove these rooms as long as the user also wasn't
+ # part of the room before the `to_token`.
+ elif (
+ was_last_membership_already_included
+ and not should_prev_membership_be_included
+ ):
+ sync_room_id_set.discard(room_id)
+
+ # 2) -----------------------------------------------------
+ # We fix-up newly_left rooms after the first fixup because it may have removed
+ # some left rooms that we can figure out our newly_left in the following code
+
+ # 2) Fetch membership changes that fall in the range from `from_token` up to `to_token`
+ membership_change_events_in_from_to_range = []
+ if from_token:
+ membership_change_events_in_from_to_range = (
+ await self.store.get_membership_changes_for_user(
+ user_id,
+ from_key=from_token.room_key,
+ to_key=to_token.room_key,
+ excluded_rooms=self.rooms_to_exclude_globally,
+ )
+ )
+
+ # 2) Assemble a list of the last membership events in some given ranges. Someone
+ # could have left and joined multiple times during the given range but we only
+ # care about end-result so we grab the last one.
+ last_membership_change_by_room_id_in_from_to_range: Dict[str, EventBase] = {}
+ for event in membership_change_events_in_from_to_range:
+ last_membership_change_by_room_id_in_from_to_range[event.room_id] = event
+
+ # 2) Fixup
+ for (
+ last_membership_change_in_from_to_range
+ ) in last_membership_change_by_room_id_in_from_to_range.values():
+ room_id = last_membership_change_in_from_to_range.room_id
+
+ # 2) Add back newly_left rooms (> `from_token` and <= `to_token`). We
+ # include newly_left rooms because the last event that the user should see
+ # is their own leave event
+ if last_membership_change_in_from_to_range.membership == Membership.LEAVE:
+ sync_room_id_set.add(room_id)
+
+ return sync_room_id_set
|
