diff options
Diffstat (limited to 'synapse/handlers/federation.py')
| -rw-r--r-- | synapse/handlers/federation.py | 234 |
1 files changed, 145 insertions, 89 deletions
diff --git a/synapse/handlers/federation.py b/synapse/handlers/federation.py index 1434e99056..d2ba70a814 100644 --- a/synapse/handlers/federation.py +++ b/synapse/handlers/federation.py @@ -1,4 +1,4 @@ -# Copyright 2014-2021 The Matrix.org Foundation C.I.C. +# Copyright 2014-2022 The Matrix.org Foundation C.I.C. # Copyright 2020 Sorunome # # Licensed under the Apache License, Version 2.0 (the "License"); @@ -15,10 +15,14 @@ """Contains handlers for federation events.""" +import enum +import itertools import logging +from enum import Enum from http import HTTPStatus from typing import TYPE_CHECKING, Dict, Iterable, List, Optional, Tuple, Union +import attr from signedjson.key import decode_verify_key_bytes from signedjson.sign import verify_signed_json from unpaddedbase64 import decode_base64 @@ -92,6 +96,24 @@ def get_domains_from_state(state: StateMap[EventBase]) -> List[Tuple[str, int]]: return sorted(joined_domains.items(), key=lambda d: d[1]) +class _BackfillPointType(Enum): + # a regular backwards extremity (ie, an event which we don't yet have, but which + # is referred to by other events in the DAG) + BACKWARDS_EXTREMITY = enum.auto() + + # an MSC2716 "insertion event" + INSERTION_PONT = enum.auto() + + +@attr.s(slots=True, auto_attribs=True, frozen=True) +class _BackfillPoint: + """A potential point we might backfill from""" + + event_id: str + depth: int + type: _BackfillPointType + + class FederationHandler: """Handles general incoming federation requests @@ -157,89 +179,51 @@ class FederationHandler: async def _maybe_backfill_inner( self, room_id: str, current_depth: int, limit: int ) -> bool: - oldest_events_with_depth = ( - await self.store.get_oldest_event_ids_with_depth_in_room(room_id) - ) + backwards_extremities = [ + _BackfillPoint(event_id, depth, _BackfillPointType.BACKWARDS_EXTREMITY) + for event_id, depth in await self.store.get_oldest_event_ids_with_depth_in_room( + room_id + ) + ] - insertion_events_to_be_backfilled: Dict[str, int] = {} + insertion_events_to_be_backfilled: List[_BackfillPoint] = [] if self.hs.config.experimental.msc2716_enabled: - insertion_events_to_be_backfilled = ( - await self.store.get_insertion_event_backward_extremities_in_room( + insertion_events_to_be_backfilled = [ + _BackfillPoint(event_id, depth, _BackfillPointType.INSERTION_PONT) + for event_id, depth in await self.store.get_insertion_event_backward_extremities_in_room( room_id ) - ) + ] logger.debug( - "_maybe_backfill_inner: extremities oldest_events_with_depth=%s insertion_events_to_be_backfilled=%s", - oldest_events_with_depth, + "_maybe_backfill_inner: backwards_extremities=%s insertion_events_to_be_backfilled=%s", + backwards_extremities, insertion_events_to_be_backfilled, ) - if not oldest_events_with_depth and not insertion_events_to_be_backfilled: + if not backwards_extremities and not insertion_events_to_be_backfilled: logger.debug("Not backfilling as no extremeties found.") return False - # We only want to paginate if we can actually see the events we'll get, - # as otherwise we'll just spend a lot of resources to get redacted - # events. - # - # We do this by filtering all the backwards extremities and seeing if - # any remain. Given we don't have the extremity events themselves, we - # need to actually check the events that reference them. - # - # *Note*: the spec wants us to keep backfilling until we reach the start - # of the room in case we are allowed to see some of the history. However - # in practice that causes more issues than its worth, as a) its - # relatively rare for there to be any visible history and b) even when - # there is its often sufficiently long ago that clients would stop - # attempting to paginate before backfill reached the visible history. - # - # TODO: If we do do a backfill then we should filter the backwards - # extremities to only include those that point to visible portions of - # history. - # - # TODO: Correctly handle the case where we are allowed to see the - # forward event but not the backward extremity, e.g. in the case of - # initial join of the server where we are allowed to see the join - # event but not anything before it. This would require looking at the - # state *before* the event, ignoring the special casing certain event - # types have. - - forward_event_ids = await self.store.get_successor_events( - list(oldest_events_with_depth) - ) - - extremities_events = await self.store.get_events( - forward_event_ids, - redact_behaviour=EventRedactBehaviour.AS_IS, - get_prev_content=False, + # we now have a list of potential places to backpaginate from. We prefer to + # start with the most recent (ie, max depth), so let's sort the list. + sorted_backfill_points: List[_BackfillPoint] = sorted( + itertools.chain( + backwards_extremities, + insertion_events_to_be_backfilled, + ), + key=lambda e: -int(e.depth), ) - # We set `check_history_visibility_only` as we might otherwise get false - # positives from users having been erased. - filtered_extremities = await filter_events_for_server( - self.storage, - self.server_name, - list(extremities_events.values()), - redact=False, - check_history_visibility_only=True, - ) logger.debug( - "_maybe_backfill_inner: filtered_extremities %s", filtered_extremities + "_maybe_backfill_inner: room_id: %s: current_depth: %s, limit: %s, " + "backfill points (%d): %s", + room_id, + current_depth, + limit, + len(sorted_backfill_points), + sorted_backfill_points, ) - if not filtered_extremities and not insertion_events_to_be_backfilled: - return False - - extremities = { - **oldest_events_with_depth, - # TODO: insertion_events_to_be_backfilled is currently skipping the filtered_extremities checks - **insertion_events_to_be_backfilled, - } - - # Check if we reached a point where we should start backfilling. - sorted_extremeties_tuple = sorted(extremities.items(), key=lambda e: -int(e[1])) - max_depth = sorted_extremeties_tuple[0][1] - # If we're approaching an extremity we trigger a backfill, otherwise we # no-op. # @@ -249,6 +233,11 @@ class FederationHandler: # chose more than one times the limit in case of failure, but choosing a # much larger factor will result in triggering a backfill request much # earlier than necessary. + # + # XXX: shouldn't we do this *after* the filter by depth below? Again, we don't + # care about events that have happened after our current position. + # + max_depth = sorted_backfill_points[0].depth if current_depth - 2 * limit > max_depth: logger.debug( "Not backfilling as we don't need to. %d < %d - 2 * %d", @@ -265,31 +254,98 @@ class FederationHandler: # 2. we have likely previously tried and failed to backfill from that # extremity, so to avoid getting "stuck" requesting the same # backfill repeatedly we drop those extremities. - filtered_sorted_extremeties_tuple = [ - t for t in sorted_extremeties_tuple if int(t[1]) <= current_depth - ] - - logger.debug( - "room_id: %s, backfill: current_depth: %s, limit: %s, max_depth: %s, extrems (%d): %s filtered_sorted_extremeties_tuple: %s", - room_id, - current_depth, - limit, - max_depth, - len(sorted_extremeties_tuple), - sorted_extremeties_tuple, - filtered_sorted_extremeties_tuple, - ) - + # # However, we need to check that the filtered extremities are non-empty. # If they are empty then either we can a) bail or b) still attempt to # backfill. We opt to try backfilling anyway just in case we do get # relevant events. - if filtered_sorted_extremeties_tuple: - sorted_extremeties_tuple = filtered_sorted_extremeties_tuple + # + filtered_sorted_backfill_points = [ + t for t in sorted_backfill_points if t.depth <= current_depth + ] + if filtered_sorted_backfill_points: + logger.debug( + "_maybe_backfill_inner: backfill points before current depth: %s", + filtered_sorted_backfill_points, + ) + sorted_backfill_points = filtered_sorted_backfill_points + else: + logger.debug( + "_maybe_backfill_inner: all backfill points are *after* current depth. Backfilling anyway." + ) + + # For performance's sake, we only want to paginate from a particular extremity + # if we can actually see the events we'll get. Otherwise, we'd just spend a lot + # of resources to get redacted events. We check each extremity in turn and + # ignore those which users on our server wouldn't be able to see. + # + # Additionally, we limit ourselves to backfilling from at most 5 extremities, + # for two reasons: + # + # - The check which determines if we can see an extremity's events can be + # expensive (we load the full state for the room at each of the backfill + # points, or (worse) their successors) + # - We want to avoid the server-server API request URI becoming too long. + # + # *Note*: the spec wants us to keep backfilling until we reach the start + # of the room in case we are allowed to see some of the history. However, + # in practice that causes more issues than its worth, as (a) it's + # relatively rare for there to be any visible history and (b) even when + # there is it's often sufficiently long ago that clients would stop + # attempting to paginate before backfill reached the visible history. - # We don't want to specify too many extremities as it causes the backfill - # request URI to be too long. - extremities = dict(sorted_extremeties_tuple[:5]) + extremities_to_request: List[str] = [] + for bp in sorted_backfill_points: + if len(extremities_to_request) >= 5: + break + + # For regular backwards extremities, we don't have the extremity events + # themselves, so we need to actually check the events that reference them - + # their "successor" events. + # + # TODO: Correctly handle the case where we are allowed to see the + # successor event but not the backward extremity, e.g. in the case of + # initial join of the server where we are allowed to see the join + # event but not anything before it. This would require looking at the + # state *before* the event, ignoring the special casing certain event + # types have. + if bp.type == _BackfillPointType.INSERTION_PONT: + event_ids_to_check = [bp.event_id] + else: + event_ids_to_check = await self.store.get_successor_events(bp.event_id) + + events_to_check = await self.store.get_events_as_list( + event_ids_to_check, + redact_behaviour=EventRedactBehaviour.AS_IS, + get_prev_content=False, + ) + + # We set `check_history_visibility_only` as we might otherwise get false + # positives from users having been erased. + filtered_extremities = await filter_events_for_server( + self.storage, + self.server_name, + events_to_check, + redact=False, + check_history_visibility_only=True, + ) + if filtered_extremities: + extremities_to_request.append(bp.event_id) + else: + logger.debug( + "_maybe_backfill_inner: skipping extremity %s as it would not be visible", + bp, + ) + + if not extremities_to_request: + logger.debug( + "_maybe_backfill_inner: found no extremities which would be visible" + ) + return False + + logger.debug( + "_maybe_backfill_inner: extremities_to_request %s", extremities_to_request + ) # Now we need to decide which hosts to hit first. @@ -309,7 +365,7 @@ class FederationHandler: for dom in domains: try: await self._federation_event_handler.backfill( - dom, room_id, limit=100, extremities=extremities + dom, room_id, limit=100, extremities=extremities_to_request ) # If this succeeded then we probably already have the # appropriate stuff. |