test_event_federation.py

# Copyright 2018 New Vector Ltd
#
# 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 datetime
from typing import Dict, List, Tuple, Union

import attr
from parameterized import parameterized

from twisted.test.proto_helpers import MemoryReactor

from synapse.api.constants import EventTypes
from synapse.api.room_versions import (
    KNOWN_ROOM_VERSIONS,
    EventFormatVersions,
    RoomVersion,
)
from synapse.events import _EventInternalMetadata
from synapse.server import HomeServer
from synapse.storage.database import LoggingTransaction
from synapse.types import JsonDict
from synapse.util import Clock, json_encoder

import tests.unittest
import tests.utils


@attr.s(auto_attribs=True, frozen=True, slots=True)
class _BackfillSetupInfo:
    room_id: str
    depth_map: Dict[str, int]


class EventFederationWorkerStoreTestCase(tests.unittest.HomeserverTestCase):
    def prepare(self, reactor: MemoryReactor, clock: Clock, hs: HomeServer) -> None:
        self.store = hs.get_datastores().main

    def test_get_prev_events_for_room(self):
        room_id = "@ROOM:local"

        # add a bunch of events and hashes to act as forward extremities
        def insert_event(txn, i):
            event_id = "$event_%i:local" % i

            txn.execute(
                (
                    "INSERT INTO events ("
                    "   room_id, event_id, type, depth, topological_ordering,"
                    "   content, processed, outlier, stream_ordering) "
                    "VALUES (?, ?, 'm.test', ?, ?, 'test', ?, ?, ?)"
                ),
                (room_id, event_id, i, i, True, False, i),
            )

            txn.execute(
                (
                    "INSERT INTO event_forward_extremities (room_id, event_id) "
                    "VALUES (?, ?)"
                ),
                (room_id, event_id),
            )

        for i in range(0, 20):
            self.get_success(
                self.store.db_pool.runInteraction("insert", insert_event, i)
            )

        # this should get the last ten
        r = self.get_success(self.store.get_prev_events_for_room(room_id))
        self.assertEqual(10, len(r))
        for i in range(0, 10):
            self.assertEqual("$event_%i:local" % (19 - i), r[i])

    def test_get_rooms_with_many_extremities(self):
        room1 = "#room1"
        room2 = "#room2"
        room3 = "#room3"

        def insert_event(txn, i, room_id):
            event_id = "$event_%i:local" % i
            txn.execute(
                (
                    "INSERT INTO event_forward_extremities (room_id, event_id) "
                    "VALUES (?, ?)"
                ),
                (room_id, event_id),
            )

        for i in range(0, 20):
            self.get_success(
                self.store.db_pool.runInteraction("insert", insert_event, i, room1)
            )
            self.get_success(
                self.store.db_pool.runInteraction("insert", insert_event, i, room2)
            )
            self.get_success(
                self.store.db_pool.runInteraction("insert", insert_event, i, room3)
            )

        # Test simple case
        r = self.get_success(self.store.get_rooms_with_many_extremities(5, 5, []))
        self.assertEqual(len(r), 3)

        # Does filter work?

        r = self.get_success(self.store.get_rooms_with_many_extremities(5, 5, [room1]))
        self.assertTrue(room2 in r)
        self.assertTrue(room3 in r)
        self.assertEqual(len(r), 2)

        r = self.get_success(
            self.store.get_rooms_with_many_extremities(5, 5, [room1, room2])
        )
        self.assertEqual(r, [room3])

        # Does filter and limit work?

        r = self.get_success(self.store.get_rooms_with_many_extremities(5, 1, [room1]))
        self.assertTrue(r == [room2] or r == [room3])

    def _setup_auth_chain(self, use_chain_cover_index: bool) -> str:
        room_id = "@ROOM:local"

        # The silly auth graph we use to test the auth difference algorithm,
        # where the top are the most recent events.
        #
        #   A   B
        #    \ /
        #  D  E
        #  \  |
        #   ` F   C
        #     |  /|
        #     G ´ |
        #     | \ |
        #     H   I
        #     |   |
        #     K   J

        auth_graph = {
            "a": ["e"],
            "b": ["e"],
            "c": ["g", "i"],
            "d": ["f"],
            "e": ["f"],
            "f": ["g"],
            "g": ["h", "i"],
            "h": ["k"],
            "i": ["j"],
            "k": [],
            "j": [],
        }

        depth_map = {
            "a": 7,
            "b": 7,
            "c": 4,
            "d": 6,
            "e": 6,
            "f": 5,
            "g": 3,
            "h": 2,
            "i": 2,
            "k": 1,
            "j": 1,
        }

        # Mark the room as maybe having a cover index.

        def store_room(txn):
            self.store.db_pool.simple_insert_txn(
                txn,
                "rooms",
                {
                    "room_id": room_id,
                    "creator": "room_creator_user_id",
                    "is_public": True,
                    "room_version": "6",
                    "has_auth_chain_index": use_chain_cover_index,
                },
            )

        self.get_success(self.store.db_pool.runInteraction("store_room", store_room))

        # We rudely fiddle with the appropriate tables directly, as that's much
        # easier than constructing events properly.

        def insert_event(txn):
            stream_ordering = 0

            for event_id in auth_graph:
                stream_ordering += 1
                depth = depth_map[event_id]

                self.store.db_pool.simple_insert_txn(
                    txn,
                    table="events",
                    values={
                        "event_id": event_id,
                        "room_id": room_id,
                        "depth": depth,
                        "topological_ordering": depth,
                        "type": "m.test",
                        "processed": True,
                        "outlier": False,
                        "stream_ordering": stream_ordering,
                    },
                )

            self.hs.datastores.persist_events._persist_event_auth_chain_txn(
                txn,
                [
                    FakeEvent(event_id, room_id, auth_graph[event_id])
                    for event_id in auth_graph
                ],
            )

        self.get_success(
            self.store.db_pool.runInteraction(
                "insert",
                insert_event,
            )
        )

        return room_id

    @parameterized.expand([(True,), (False,)])
    def test_auth_chain_ids(self, use_chain_cover_index: bool):
        room_id = self._setup_auth_chain(use_chain_cover_index)

        # a and b have the same auth chain.
        auth_chain_ids = self.get_success(self.store.get_auth_chain_ids(room_id, ["a"]))
        self.assertCountEqual(auth_chain_ids, ["e", "f", "g", "h", "i", "j", "k"])
        auth_chain_ids = self.get_success(self.store.get_auth_chain_ids(room_id, ["b"]))
        self.assertCountEqual(auth_chain_ids, ["e", "f", "g", "h", "i", "j", "k"])
        auth_chain_ids = self.get_success(
            self.store.get_auth_chain_ids(room_id, ["a", "b"])
        )
        self.assertCountEqual(auth_chain_ids, ["e", "f", "g", "h", "i", "j", "k"])

        auth_chain_ids = self.get_success(self.store.get_auth_chain_ids(room_id, ["c"]))
        self.assertCountEqual(auth_chain_ids, ["g", "h", "i", "j", "k"])

        # d and e have the same auth chain.
        auth_chain_ids = self.get_success(self.store.get_auth_chain_ids(room_id, ["d"]))
        self.assertCountEqual(auth_chain_ids, ["f", "g", "h", "i", "j", "k"])
        auth_chain_ids = self.get_success(self.store.get_auth_chain_ids(room_id, ["e"]))
        self.assertCountEqual(auth_chain_ids, ["f", "g", "h", "i", "j", "k"])

        auth_chain_ids = self.get_success(self.store.get_auth_chain_ids(room_id, ["f"]))
        self.assertCountEqual(auth_chain_ids, ["g", "h", "i", "j", "k"])

        auth_chain_ids = self.get_success(self.store.get_auth_chain_ids(room_id, ["g"]))
        self.assertCountEqual(auth_chain_ids, ["h", "i", "j", "k"])

        auth_chain_ids = self.get_success(self.store.get_auth_chain_ids(room_id, ["h"]))
        self.assertEqual(auth_chain_ids, {"k"})

        auth_chain_ids = self.get_success(self.store.get_auth_chain_ids(room_id, ["i"]))
        self.assertEqual(auth_chain_ids, {"j"})

        # j and k have no parents.
        auth_chain_ids = self.get_success(self.store.get_auth_chain_ids(room_id, ["j"]))
        self.assertEqual(auth_chain_ids, set())
        auth_chain_ids = self.get_success(self.store.get_auth_chain_ids(room_id, ["k"]))
        self.assertEqual(auth_chain_ids, set())

        # More complex input sequences.
        auth_chain_ids = self.get_success(
            self.store.get_auth_chain_ids(room_id, ["b", "c", "d"])
        )
        self.assertCountEqual(auth_chain_ids, ["e", "f", "g", "h", "i", "j", "k"])

        auth_chain_ids = self.get_success(
            self.store.get_auth_chain_ids(room_id, ["h", "i"])
        )
        self.assertCountEqual(auth_chain_ids, ["k", "j"])

        # e gets returned even though include_given is false, but it is in the
        # auth chain of b.
        auth_chain_ids = self.get_success(
            self.store.get_auth_chain_ids(room_id, ["b", "e"])
        )
        self.assertCountEqual(auth_chain_ids, ["e", "f", "g", "h", "i", "j", "k"])

        # Test include_given.
        auth_chain_ids = self.get_success(
            self.store.get_auth_chain_ids(room_id, ["i"], include_given=True)
        )
        self.assertCountEqual(auth_chain_ids, ["i", "j"])

    @parameterized.expand([(True,), (False,)])
    def test_auth_difference(self, use_chain_cover_index: bool):
        room_id = self._setup_auth_chain(use_chain_cover_index)

        # Now actually test that various combinations give the right result:

        difference = self.get_success(
            self.store.get_auth_chain_difference(room_id, [{"a"}, {"b"}])
        )
        self.assertSetEqual(difference, {"a", "b"})

        difference = self.get_success(
            self.store.get_auth_chain_difference(room_id, [{"a"}, {"b"}, {"c"}])
        )
        self.assertSetEqual(difference, {"a", "b", "c", "e", "f"})

        difference = self.get_success(
            self.store.get_auth_chain_difference(room_id, [{"a", "c"}, {"b"}])
        )
        self.assertSetEqual(difference, {"a", "b", "c"})

        difference = self.get_success(
            self.store.get_auth_chain_difference(room_id, [{"a", "c"}, {"b", "c"}])
        )
        self.assertSetEqual(difference, {"a", "b"})

        difference = self.get_success(
            self.store.get_auth_chain_difference(room_id, [{"a"}, {"b"}, {"d"}])
        )
        self.assertSetEqual(difference, {"a", "b", "d", "e"})

        difference = self.get_success(
            self.store.get_auth_chain_difference(room_id, [{"a"}, {"b"}, {"c"}, {"d"}])
        )
        self.assertSetEqual(difference, {"a", "b", "c", "d", "e", "f"})

        difference = self.get_success(
            self.store.get_auth_chain_difference(room_id, [{"a"}, {"b"}, {"e"}])
        )
        self.assertSetEqual(difference, {"a", "b"})

        difference = self.get_success(
            self.store.get_auth_chain_difference(room_id, [{"a"}])
        )
        self.assertSetEqual(difference, set())

    def test_auth_difference_partial_cover(self):
        """Test that we correctly handle rooms where not all events have a chain
        cover calculated. This can happen in some obscure edge cases, including
        during the background update that calculates the chain cover for old
        rooms.
        """

        room_id = "@ROOM:local"

        # The silly auth graph we use to test the auth difference algorithm,
        # where the top are the most recent events.
        #
        #   A   B
        #    \ /
        #  D  E
        #  \  |
        #   ` F   C
        #     |  /|
        #     G ´ |
        #     | \ |
        #     H   I
        #     |   |
        #     K   J

        auth_graph = {
            "a": ["e"],
            "b": ["e"],
            "c": ["g", "i"],
            "d": ["f"],
            "e": ["f"],
            "f": ["g"],
            "g": ["h", "i"],
            "h": ["k"],
            "i": ["j"],
            "k": [],
            "j": [],
        }

        depth_map = {
            "a": 7,
            "b": 7,
            "c": 4,
            "d": 6,
            "e": 6,
            "f": 5,
            "g": 3,
            "h": 2,
            "i": 2,
            "k": 1,
            "j": 1,
        }

        # We rudely fiddle with the appropriate tables directly, as that's much
        # easier than constructing events properly.

        def insert_event(txn):
            # First insert the room and mark it as having a chain cover.
            self.store.db_pool.simple_insert_txn(
                txn,
                "rooms",
                {
                    "room_id": room_id,
                    "creator": "room_creator_user_id",
                    "is_public": True,
                    "room_version": "6",
                    "has_auth_chain_index": True,
                },
            )

            stream_ordering = 0

            for event_id in auth_graph:
                stream_ordering += 1
                depth = depth_map[event_id]

                self.store.db_pool.simple_insert_txn(
                    txn,
                    table="events",
                    values={
                        "event_id": event_id,
                        "room_id": room_id,
                        "depth": depth,
                        "topological_ordering": depth,
                        "type": "m.test",
                        "processed": True,
                        "outlier": False,
                        "stream_ordering": stream_ordering,
                    },
                )

            # Insert all events apart from 'B'
            self.hs.datastores.persist_events._persist_event_auth_chain_txn(
                txn,
                [
                    FakeEvent(event_id, room_id, auth_graph[event_id])
                    for event_id in auth_graph
                    if event_id != "b"
                ],
            )

            # Now we insert the event 'B' without a chain cover, by temporarily
            # pretending the room doesn't have a chain cover.

            self.store.db_pool.simple_update_txn(
                txn,
                table="rooms",
                keyvalues={"room_id": room_id},
                updatevalues={"has_auth_chain_index": False},
            )

            self.hs.datastores.persist_events._persist_event_auth_chain_txn(
                txn,
                [FakeEvent("b", room_id, auth_graph["b"])],
            )

            self.store.db_pool.simple_update_txn(
                txn,
                table="rooms",
                keyvalues={"room_id": room_id},
                updatevalues={"has_auth_chain_index": True},
            )

        self.get_success(
            self.store.db_pool.runInteraction(
                "insert",
                insert_event,
            )
        )

        # Now actually test that various combinations give the right result:

        difference = self.get_success(
            self.store.get_auth_chain_difference(room_id, [{"a"}, {"b"}])
        )
        self.assertSetEqual(difference, {"a", "b"})

        difference = self.get_success(
            self.store.get_auth_chain_difference(room_id, [{"a"}, {"b"}, {"c"}])
        )
        self.assertSetEqual(difference, {"a", "b", "c", "e", "f"})

        difference = self.get_success(
            self.store.get_auth_chain_difference(room_id, [{"a", "c"}, {"b"}])
        )
        self.assertSetEqual(difference, {"a", "b", "c"})

        difference = self.get_success(
            self.store.get_auth_chain_difference(room_id, [{"a", "c"}, {"b", "c"}])
        )
        self.assertSetEqual(difference, {"a", "b"})

        difference = self.get_success(
            self.store.get_auth_chain_difference(room_id, [{"a"}, {"b"}, {"d"}])
        )
        self.assertSetEqual(difference, {"a", "b", "d", "e"})

        difference = self.get_success(
            self.store.get_auth_chain_difference(room_id, [{"a"}, {"b"}, {"c"}, {"d"}])
        )
        self.assertSetEqual(difference, {"a", "b", "c", "d", "e", "f"})

        difference = self.get_success(
            self.store.get_auth_chain_difference(room_id, [{"a"}, {"b"}, {"e"}])
        )
        self.assertSetEqual(difference, {"a", "b"})

        difference = self.get_success(
            self.store.get_auth_chain_difference(room_id, [{"a"}])
        )
        self.assertSetEqual(difference, set())

    @parameterized.expand(
        [(room_version,) for room_version in KNOWN_ROOM_VERSIONS.values()]
    )
    def test_prune_inbound_federation_queue(self, room_version: RoomVersion):
        """Test that pruning of inbound federation queues work"""

        room_id = "some_room_id"

        def prev_event_format(prev_event_id: str) -> Union[Tuple[str, dict], str]:
            """Account for differences in prev_events format across room versions"""
            if room_version.event_format == EventFormatVersions.ROOM_V1_V2:
                return prev_event_id, {}

            return prev_event_id

        # Insert a bunch of events that all reference the previous one.
        self.get_success(
            self.store.db_pool.simple_insert_many(
                table="federation_inbound_events_staging",
                keys=(
                    "origin",
                    "room_id",
                    "received_ts",
                    "event_id",
                    "event_json",
                    "internal_metadata",
                ),
                values=[
                    (
                        "some_origin",
                        room_id,
                        0,
                        f"$fake_event_id_{i + 1}",
                        json_encoder.encode(
                            {"prev_events": [prev_event_format(f"$fake_event_id_{i}")]}
                        ),
                        "{}",
                    )
                    for i in range(500)
                ],
                desc="test_prune_inbound_federation_queue",
            )
        )

        # Calling prune once should return True, i.e. a prune happen. The second
        # time it shouldn't.
        pruned = self.get_success(
            self.store.prune_staged_events_in_room(room_id, room_version)
        )
        self.assertTrue(pruned)

        pruned = self.get_success(
            self.store.prune_staged_events_in_room(room_id, room_version)
        )
        self.assertFalse(pruned)

        # Assert that we only have a single event left in the queue, and that it
        # is the last one.
        count = self.get_success(
            self.store.db_pool.simple_select_one_onecol(
                table="federation_inbound_events_staging",
                keyvalues={"room_id": room_id},
                retcol="COUNT(*)",
                desc="test_prune_inbound_federation_queue",
            )
        )
        self.assertEqual(count, 1)

        next_staged_event_info = self.get_success(
            self.store.get_next_staged_event_id_for_room(room_id)
        )
        assert next_staged_event_info
        _, event_id = next_staged_event_info
        self.assertEqual(event_id, "$fake_event_id_500")

    def _setup_room_for_backfill_tests(self) -> _BackfillSetupInfo:
        """
        Sets up a room with various events and backward extremities to test
        backfill functions against.

        Returns:
            _BackfillSetupInfo including the `room_id` to test against and
            `depth_map` of events in the room
        """
        room_id = "!backfill-room-test:some-host"

        # The silly graph we use to test grabbing backward extremities,
        # where the top is the oldest events.
        #    1 (oldest)
        #    |
        #    2 ⹁
        #    |  \
        #    |   [b1, b2, b3]
        #    |   |
        #    |   A
        #    |  /
        #    3 {
        #    |  \
        #    |   [b4, b5, b6]
        #    |   |
        #    |   B
        #    |  /
        #    4 ´
        #    |
        #    5 (newest)

        event_graph: Dict[str, List[str]] = {
            "1": [],
            "2": ["1"],
            "3": ["2", "A"],
            "4": ["3", "B"],
            "5": ["4"],
            "A": ["b1", "b2", "b3"],
            "b1": ["2"],
            "b2": ["2"],
            "b3": ["2"],
            "B": ["b4", "b5", "b6"],
            "b4": ["3"],
            "b5": ["3"],
            "b6": ["3"],
        }

        depth_map: Dict[str, int] = {
            "1": 1,
            "2": 2,
            "b1": 3,
            "b2": 3,
            "b3": 3,
            "A": 4,
            "3": 5,
            "b4": 6,
            "b5": 6,
            "b6": 6,
            "B": 7,
            "4": 8,
            "5": 9,
        }

        # The events we have persisted on our server.
        # The rest are events in the room but not backfilled tet.
        our_server_events = {"5", "4", "B", "3", "A"}

        complete_event_dict_map: Dict[str, JsonDict] = {}
        stream_ordering = 0
        for (event_id, prev_event_ids) in event_graph.items():
            depth = depth_map[event_id]

            complete_event_dict_map[event_id] = {
                "event_id": event_id,
                "type": "test_regular_type",
                "room_id": room_id,
                "sender": "@sender",
                "prev_event_ids": prev_event_ids,
                "auth_event_ids": [],
                "origin_server_ts": stream_ordering,
                "depth": depth,
                "stream_ordering": stream_ordering,
                "content": {"body": "event" + event_id},
            }

            stream_ordering += 1

        def populate_db(txn: LoggingTransaction):
            # Insert the room to satisfy the foreign key constraint of
            # `event_failed_pull_attempts`
            self.store.db_pool.simple_insert_txn(
                txn,
                "rooms",
                {
                    "room_id": room_id,
                    "creator": "room_creator_user_id",
                    "is_public": True,
                    "room_version": "6",
                },
            )

            # Insert our server events
            for event_id in our_server_events:
                event_dict = complete_event_dict_map[event_id]

                self.store.db_pool.simple_insert_txn(
                    txn,
                    table="events",
                    values={
                        "event_id": event_dict.get("event_id"),
                        "type": event_dict.get("type"),
                        "room_id": event_dict.get("room_id"),
                        "depth": event_dict.get("depth"),
                        "topological_ordering": event_dict.get("depth"),
                        "stream_ordering": event_dict.get("stream_ordering"),
                        "processed": True,
                        "outlier": False,
                    },
                )

            # Insert the event edges
            for event_id in our_server_events:
                for prev_event_id in event_graph[event_id]:
                    self.store.db_pool.simple_insert_txn(
                        txn,
                        table="event_edges",
                        values={
                            "event_id": event_id,
                            "prev_event_id": prev_event_id,
                            "room_id": room_id,
                        },
                    )

            # Insert the backward extremities
            prev_events_of_our_events = {
                prev_event_id
                for our_server_event in our_server_events
                for prev_event_id in complete_event_dict_map[our_server_event][
                    "prev_event_ids"
                ]
            }
            backward_extremities = prev_events_of_our_events - our_server_events
            for backward_extremity in backward_extremities:
                self.store.db_pool.simple_insert_txn(
                    txn,
                    table="event_backward_extremities",
                    values={
                        "event_id": backward_extremity,
                        "room_id": room_id,
                    },
                )

        self.get_success(
            self.store.db_pool.runInteraction(
                "_setup_room_for_backfill_tests_populate_db",
                populate_db,
            )
        )

        return _BackfillSetupInfo(room_id=room_id, depth_map=depth_map)

    def test_get_backfill_points_in_room(self):
        """
        Test to make sure we get some backfill points
        """
        setup_info = self._setup_room_for_backfill_tests()
        room_id = setup_info.room_id

        backfill_points = self.get_success(
            self.store.get_backfill_points_in_room(room_id)
        )
        backfill_event_ids = [backfill_point[0] for backfill_point in backfill_points]
        self.assertListEqual(
            backfill_event_ids, ["b6", "b5", "b4", "2", "b3", "b2", "b1"]
        )

    def test_get_backfill_points_in_room_excludes_events_we_have_attempted(
        self,
    ):
        """
        Test to make sure that events we have attempted to backfill (and within
        backoff timeout duration) do not show up as an event to backfill again.
        """
        setup_info = self._setup_room_for_backfill_tests()
        room_id = setup_info.room_id

        # Record some attempts to backfill these events which will make
        # `get_backfill_points_in_room` exclude them because we
        # haven't passed the backoff interval.
        self.get_success(
            self.store.record_event_failed_pull_attempt(room_id, "b5", "fake cause")
        )
        self.get_success(
            self.store.record_event_failed_pull_attempt(room_id, "b4", "fake cause")
        )
        self.get_success(
            self.store.record_event_failed_pull_attempt(room_id, "b3", "fake cause")
        )
        self.get_success(
            self.store.record_event_failed_pull_attempt(room_id, "b2", "fake cause")
        )

        # No time has passed since we attempted to backfill ^

        backfill_points = self.get_success(
            self.store.get_backfill_points_in_room(room_id)
        )
        backfill_event_ids = [backfill_point[0] for backfill_point in backfill_points]
        # Only the backfill points that we didn't record earlier exist here.
        self.assertListEqual(backfill_event_ids, ["b6", "2", "b1"])

    def test_get_backfill_points_in_room_attempted_event_retry_after_backoff_duration(
        self,
    ):
        """
        Test to make sure after we fake attempt to backfill event "b3" many times,
        we can see retry and see the "b3" again after the backoff timeout duration
        has exceeded.
        """
        setup_info = self._setup_room_for_backfill_tests()
        room_id = setup_info.room_id

        # Record some attempts to backfill these events which will make
        # `get_backfill_points_in_room` exclude them because we
        # haven't passed the backoff interval.
        self.get_success(
            self.store.record_event_failed_pull_attempt(room_id, "b3", "fake cause")
        )
        self.get_success(
            self.store.record_event_failed_pull_attempt(room_id, "b1", "fake cause")
        )
        self.get_success(
            self.store.record_event_failed_pull_attempt(room_id, "b1", "fake cause")
        )
        self.get_success(
            self.store.record_event_failed_pull_attempt(room_id, "b1", "fake cause")
        )
        self.get_success(
            self.store.record_event_failed_pull_attempt(room_id, "b1", "fake cause")
        )

        # Now advance time by 2 hours and we should only be able to see "b3"
        # because we have waited long enough for the single attempt (2^1 hours)
        # but we still shouldn't see "b1" because we haven't waited long enough
        # for this many attempts. We didn't do anything to "b2" so it should be
        # visible regardless.
        self.reactor.advance(datetime.timedelta(hours=2).total_seconds())

        # Make sure that "b1" is not in the list because we've
        # already attempted many times
        backfill_points = self.get_success(
            self.store.get_backfill_points_in_room(room_id)
        )
        backfill_event_ids = [backfill_point[0] for backfill_point in backfill_points]
        self.assertListEqual(backfill_event_ids, ["b6", "b5", "b4", "2", "b3", "b2"])

        # Now advance time by 20 hours (above 2^4 because we made 4 attemps) and
        # see if we can now backfill it
        self.reactor.advance(datetime.timedelta(hours=20).total_seconds())

        # Try again after we advanced enough time and we should see "b3" again
        backfill_points = self.get_success(
            self.store.get_backfill_points_in_room(room_id)
        )
        backfill_event_ids = [backfill_point[0] for backfill_point in backfill_points]
        self.assertListEqual(
            backfill_event_ids, ["b6", "b5", "b4", "2", "b3", "b2", "b1"]
        )

    def _setup_room_for_insertion_backfill_tests(self) -> _BackfillSetupInfo:
        """
        Sets up a room with various insertion event backward extremities to test
        backfill functions against.

        Returns:
            _BackfillSetupInfo including the `room_id` to test against and
            `depth_map` of events in the room
        """
        room_id = "!backfill-room-test:some-host"

        depth_map: Dict[str, int] = {
            "1": 1,
            "2": 2,
            "insertion_eventA": 3,
            "3": 4,
            "insertion_eventB": 5,
            "4": 6,
            "5": 7,
        }

        def populate_db(txn: LoggingTransaction):
            # Insert the room to satisfy the foreign key constraint of
            # `event_failed_pull_attempts`
            self.store.db_pool.simple_insert_txn(
                txn,
                "rooms",
                {
                    "room_id": room_id,
                    "creator": "room_creator_user_id",
                    "is_public": True,
                    "room_version": "6",
                },
            )

            # Insert our server events
            stream_ordering = 0
            for event_id, depth in depth_map.items():
                self.store.db_pool.simple_insert_txn(
                    txn,
                    table="events",
                    values={
                        "event_id": event_id,
                        "type": EventTypes.MSC2716_INSERTION
                        if event_id.startswith("insertion_event")
                        else "test_regular_type",
                        "room_id": room_id,
                        "depth": depth,
                        "topological_ordering": depth,
                        "stream_ordering": stream_ordering,
                        "processed": True,
                        "outlier": False,
                    },
                )

                if event_id.startswith("insertion_event"):
                    self.store.db_pool.simple_insert_txn(
                        txn,
                        table="insertion_event_extremities",
                        values={
                            "event_id": event_id,
                            "room_id": room_id,
                        },
                    )

                stream_ordering += 1

        self.get_success(
            self.store.db_pool.runInteraction(
                "_setup_room_for_insertion_backfill_tests_populate_db",
                populate_db,
            )
        )

        return _BackfillSetupInfo(room_id=room_id, depth_map=depth_map)

    def test_get_insertion_event_backward_extremities_in_room(self):
        """
        Test to make sure insertion event backward extremities are returned.
        """
        setup_info = self._setup_room_for_insertion_backfill_tests()
        room_id = setup_info.room_id

        backfill_points = self.get_success(
            self.store.get_insertion_event_backward_extremities_in_room(room_id)
        )
        backfill_event_ids = [backfill_point[0] for backfill_point in backfill_points]
        self.assertListEqual(
            backfill_event_ids, ["insertion_eventB", "insertion_eventA"]
        )

    def test_get_insertion_event_backward_extremities_in_room_excludes_events_we_have_attempted(
        self,
    ):
        """
        Test to make sure that insertion events we have attempted to backfill
        (and within backoff timeout duration) do not show up as an event to
        backfill again.
        """
        setup_info = self._setup_room_for_insertion_backfill_tests()
        room_id = setup_info.room_id

        # Record some attempts to backfill these events which will make
        # `get_insertion_event_backward_extremities_in_room` exclude them
        # because we haven't passed the backoff interval.
        self.get_success(
            self.store.record_event_failed_pull_attempt(
                room_id, "insertion_eventA", "fake cause"
            )
        )

        # No time has passed since we attempted to backfill ^

        backfill_points = self.get_success(
            self.store.get_insertion_event_backward_extremities_in_room(room_id)
        )
        backfill_event_ids = [backfill_point[0] for backfill_point in backfill_points]
        # Only the backfill points that we didn't record earlier exist here.
        self.assertListEqual(backfill_event_ids, ["insertion_eventB"])

    def test_get_insertion_event_backward_extremities_in_room_attempted_event_retry_after_backoff_duration(
        self,
    ):
        """
        Test to make sure after we fake attempt to backfill event
        "insertion_eventA" many times, we can see retry and see the
        "insertion_eventA" again after the backoff timeout duration has
        exceeded.
        """
        setup_info = self._setup_room_for_insertion_backfill_tests()
        room_id = setup_info.room_id

        # Record some attempts to backfill these events which will make
        # `get_backfill_points_in_room` exclude them because we
        # haven't passed the backoff interval.
        self.get_success(
            self.store.record_event_failed_pull_attempt(
                room_id, "insertion_eventB", "fake cause"