anonymousland-synapse/synapse/handlers/space_summary.py
Patrick Cloke 27c375f812
Sort child events according to MSC1772 for the spaces summary API. (#9954)
This should help ensure that equivalent results are achieved between
homeservers querying for the summary of a space.

This implements modified MSC1772 rules, according to MSC2946.
The different is that the origin_server_ts of the m.room.create event
is not used as a tie-breaker since this might not be known if the
homeserver is not part of the room.
2021-05-11 12:57:39 -04:00

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# Copyright 2021 The Matrix.org Foundation C.I.C.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
import itertools
import logging
import re
from collections import deque
from typing import TYPE_CHECKING, Iterable, List, Optional, Sequence, Set, Tuple, cast
import attr
from synapse.api.constants import EventContentFields, EventTypes, HistoryVisibility
from synapse.api.errors import AuthError
from synapse.events import EventBase
from synapse.events.utils import format_event_for_client_v2
from synapse.types import JsonDict
if TYPE_CHECKING:
from synapse.server import HomeServer
logger = logging.getLogger(__name__)
# number of rooms to return. We'll stop once we hit this limit.
# TODO: allow clients to reduce this with a request param.
MAX_ROOMS = 50
# max number of events to return per room.
MAX_ROOMS_PER_SPACE = 50
# max number of federation servers to hit per room
MAX_SERVERS_PER_SPACE = 3
class SpaceSummaryHandler:
def __init__(self, hs: "HomeServer"):
self._clock = hs.get_clock()
self._auth = hs.get_auth()
self._room_list_handler = hs.get_room_list_handler()
self._state_handler = hs.get_state_handler()
self._store = hs.get_datastore()
self._event_serializer = hs.get_event_client_serializer()
self._server_name = hs.hostname
self._federation_client = hs.get_federation_client()
async def get_space_summary(
self,
requester: str,
room_id: str,
suggested_only: bool = False,
max_rooms_per_space: Optional[int] = None,
) -> JsonDict:
"""
Implementation of the space summary C-S API
Args:
requester: user id of the user making this request
room_id: room id to start the summary at
suggested_only: whether we should only return children with the "suggested"
flag set.
max_rooms_per_space: an optional limit on the number of child rooms we will
return. This does not apply to the root room (ie, room_id), and
is overridden by MAX_ROOMS_PER_SPACE.
Returns:
summary dict to return
"""
# first of all, check that the user is in the room in question (or it's
# world-readable)
await self._auth.check_user_in_room_or_world_readable(room_id, requester)
# the queue of rooms to process
room_queue = deque((_RoomQueueEntry(room_id, ()),))
# rooms we have already processed
processed_rooms = set() # type: Set[str]
# events we have already processed. We don't necessarily have their event ids,
# so instead we key on (room id, state key)
processed_events = set() # type: Set[Tuple[str, str]]
rooms_result = [] # type: List[JsonDict]
events_result = [] # type: List[JsonDict]
while room_queue and len(rooms_result) < MAX_ROOMS:
queue_entry = room_queue.popleft()
room_id = queue_entry.room_id
if room_id in processed_rooms:
# already done this room
continue
logger.debug("Processing room %s", room_id)
is_in_room = await self._store.is_host_joined(room_id, self._server_name)
# The client-specified max_rooms_per_space limit doesn't apply to the
# room_id specified in the request, so we ignore it if this is the
# first room we are processing.
max_children = max_rooms_per_space if processed_rooms else None
if is_in_room:
rooms, events = await self._summarize_local_room(
requester, room_id, suggested_only, max_children
)
else:
rooms, events = await self._summarize_remote_room(
queue_entry,
suggested_only,
max_children,
exclude_rooms=processed_rooms,
)
logger.debug(
"Query of %s returned rooms %s, events %s",
queue_entry.room_id,
[room.get("room_id") for room in rooms],
["%s->%s" % (ev["room_id"], ev["state_key"]) for ev in events],
)
rooms_result.extend(rooms)
# any rooms returned don't need visiting again
processed_rooms.update(cast(str, room.get("room_id")) for room in rooms)
# the room we queried may or may not have been returned, but don't process
# it again, anyway.
processed_rooms.add(room_id)
# XXX: is it ok that we blindly iterate through any events returned by
# a remote server, whether or not they actually link to any rooms in our
# tree?
for ev in events:
# remote servers might return events we have already processed
# (eg, Dendrite returns inward pointers as well as outward ones), so
# we need to filter them out, to avoid returning duplicate links to the
# client.
ev_key = (ev["room_id"], ev["state_key"])
if ev_key in processed_events:
continue
events_result.append(ev)
# add the child to the queue. we have already validated
# that the vias are a list of server names.
room_queue.append(
_RoomQueueEntry(ev["state_key"], ev["content"]["via"])
)
processed_events.add(ev_key)
return {"rooms": rooms_result, "events": events_result}
async def federation_space_summary(
self,
room_id: str,
suggested_only: bool,
max_rooms_per_space: Optional[int],
exclude_rooms: Iterable[str],
) -> JsonDict:
"""
Implementation of the space summary Federation API
Args:
room_id: room id to start the summary at
suggested_only: whether we should only return children with the "suggested"
flag set.
max_rooms_per_space: an optional limit on the number of child rooms we will
return. Unlike the C-S API, this applies to the root room (room_id).
It is clipped to MAX_ROOMS_PER_SPACE.
exclude_rooms: a list of rooms to skip over (presumably because the
calling server has already seen them).
Returns:
summary dict to return
"""
# the queue of rooms to process
room_queue = deque((room_id,))
# the set of rooms that we should not walk further. Initialise it with the
# excluded-rooms list; we will add other rooms as we process them so that
# we do not loop.
processed_rooms = set(exclude_rooms) # type: Set[str]
rooms_result = [] # type: List[JsonDict]
events_result = [] # type: List[JsonDict]
while room_queue and len(rooms_result) < MAX_ROOMS:
room_id = room_queue.popleft()
if room_id in processed_rooms:
# already done this room
continue
logger.debug("Processing room %s", room_id)
rooms, events = await self._summarize_local_room(
None, room_id, suggested_only, max_rooms_per_space
)
processed_rooms.add(room_id)
rooms_result.extend(rooms)
events_result.extend(events)
# add any children to the queue
room_queue.extend(edge_event["state_key"] for edge_event in events)
return {"rooms": rooms_result, "events": events_result}
async def _summarize_local_room(
self,
requester: Optional[str],
room_id: str,
suggested_only: bool,
max_children: Optional[int],
) -> Tuple[Sequence[JsonDict], Sequence[JsonDict]]:
"""
Generate a room entry and a list of event entries for a given room.
Args:
requester: The requesting user, or None if this is over federation.
room_id: The room ID to summarize.
suggested_only: True if only suggested children should be returned.
Otherwise, all children are returned.
max_children: The maximum number of children to return for this node.
Returns:
A tuple of:
An iterable of a single value of the room.
An iterable of the sorted children events. This may be limited
to a maximum size or may include all children.
"""
if not await self._is_room_accessible(room_id, requester):
return (), ()
room_entry = await self._build_room_entry(room_id)
# look for child rooms/spaces.
child_events = await self._get_child_events(room_id)
if suggested_only:
# we only care about suggested children
child_events = filter(_is_suggested_child_event, child_events)
if max_children is None or max_children > MAX_ROOMS_PER_SPACE:
max_children = MAX_ROOMS_PER_SPACE
now = self._clock.time_msec()
events_result = [] # type: List[JsonDict]
for edge_event in itertools.islice(child_events, max_children):
events_result.append(
await self._event_serializer.serialize_event(
edge_event,
time_now=now,
event_format=format_event_for_client_v2,
)
)
return (room_entry,), events_result
async def _summarize_remote_room(
self,
room: "_RoomQueueEntry",
suggested_only: bool,
max_children: Optional[int],
exclude_rooms: Iterable[str],
) -> Tuple[Sequence[JsonDict], Sequence[JsonDict]]:
room_id = room.room_id
logger.info("Requesting summary for %s via %s", room_id, room.via)
# we need to make the exclusion list json-serialisable
exclude_rooms = list(exclude_rooms)
via = itertools.islice(room.via, MAX_SERVERS_PER_SPACE)
try:
res = await self._federation_client.get_space_summary(
via,
room_id,
suggested_only=suggested_only,
max_rooms_per_space=max_children,
exclude_rooms=exclude_rooms,
)
except Exception as e:
logger.warning(
"Unable to get summary of %s via federation: %s",
room_id,
e,
exc_info=logger.isEnabledFor(logging.DEBUG),
)
return (), ()
return res.rooms, tuple(
ev.data
for ev in res.events
if ev.event_type == EventTypes.MSC1772_SPACE_CHILD
or ev.event_type == EventTypes.SpaceChild
)
async def _is_room_accessible(self, room_id: str, requester: Optional[str]) -> bool:
# if we have an authenticated requesting user, first check if they are in the
# room
if requester:
try:
await self._auth.check_user_in_room(room_id, requester)
return True
except AuthError:
pass
# otherwise, check if the room is peekable
hist_vis_ev = await self._state_handler.get_current_state(
room_id, EventTypes.RoomHistoryVisibility, ""
)
if hist_vis_ev:
hist_vis = hist_vis_ev.content.get("history_visibility")
if hist_vis == HistoryVisibility.WORLD_READABLE:
return True
logger.info(
"room %s is unpeekable and user %s is not a member, omitting from summary",
room_id,
requester,
)
return False
async def _build_room_entry(self, room_id: str) -> JsonDict:
"""Generate en entry suitable for the 'rooms' list in the summary response"""
stats = await self._store.get_room_with_stats(room_id)
# currently this should be impossible because we call
# check_user_in_room_or_world_readable on the room before we get here, so
# there should always be an entry
assert stats is not None, "unable to retrieve stats for %s" % (room_id,)
current_state_ids = await self._store.get_current_state_ids(room_id)
create_event = await self._store.get_event(
current_state_ids[(EventTypes.Create, "")]
)
# TODO: update once MSC1772 lands
room_type = create_event.content.get(EventContentFields.ROOM_TYPE)
if not room_type:
room_type = create_event.content.get(EventContentFields.MSC1772_ROOM_TYPE)
entry = {
"room_id": stats["room_id"],
"name": stats["name"],
"topic": stats["topic"],
"canonical_alias": stats["canonical_alias"],
"num_joined_members": stats["joined_members"],
"avatar_url": stats["avatar"],
"world_readable": (
stats["history_visibility"] == HistoryVisibility.WORLD_READABLE
),
"guest_can_join": stats["guest_access"] == "can_join",
"creation_ts": create_event.origin_server_ts,
"room_type": room_type,
}
# Filter out Nones rather omit the field altogether
room_entry = {k: v for k, v in entry.items() if v is not None}
return room_entry
async def _get_child_events(self, room_id: str) -> Iterable[EventBase]:
"""
Get the child events for a given room.
The returned results are sorted for stability.
Args:
room_id: The room id to get the children of.
Returns:
An iterable of sorted child events.
"""
# look for child rooms/spaces.
current_state_ids = await self._store.get_current_state_ids(room_id)
events = await self._store.get_events_as_list(
[
event_id
for key, event_id in current_state_ids.items()
# TODO: update once MSC1772 has been FCP for a period of time.
if key[0] == EventTypes.MSC1772_SPACE_CHILD
or key[0] == EventTypes.SpaceChild
]
)
# filter out any events without a "via" (which implies it has been redacted),
# and order to ensure we return stable results.
return sorted(filter(_has_valid_via, events), key=_child_events_comparison_key)
@attr.s(frozen=True, slots=True)
class _RoomQueueEntry:
room_id = attr.ib(type=str)
via = attr.ib(type=Sequence[str])
def _has_valid_via(e: EventBase) -> bool:
via = e.content.get("via")
if not via or not isinstance(via, Sequence):
return False
for v in via:
if not isinstance(v, str):
logger.debug("Ignoring edge event %s with invalid via entry", e.event_id)
return False
return True
def _is_suggested_child_event(edge_event: EventBase) -> bool:
suggested = edge_event.content.get("suggested")
if isinstance(suggested, bool) and suggested:
return True
logger.debug("Ignorning not-suggested child %s", edge_event.state_key)
return False
# Order may only contain characters in the range of \x20 (space) to \x7F (~).
_INVALID_ORDER_CHARS_RE = re.compile(r"[^\x20-\x7F]")
def _child_events_comparison_key(child: EventBase) -> Tuple[bool, Optional[str], str]:
"""
Generate a value for comparing two child events for ordering.
The rules for ordering are supposed to be:
1. The 'order' key, if it is valid.
2. The 'origin_server_ts' of the 'm.room.create' event.
3. The 'room_id'.
But we skip step 2 since we may not have any state from the room.
Args:
child: The event for generating a comparison key.
Returns:
The comparison key as a tuple of:
False if the ordering is valid.
The ordering field.
The room ID.
"""
order = child.content.get("order")
# If order is not a string or doesn't meet the requirements, ignore it.
if not isinstance(order, str):
order = None
elif len(order) > 50 or _INVALID_ORDER_CHARS_RE.search(order):
order = None
# Items without an order come last.
return (order is None, order, child.room_id)