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Back out in-flight state caching changes. (#12126)

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1
changelog.d/10870.misc
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Deduplicate in-flight requests in `_get_state_for_groups`.

1
changelog.d/11608.misc
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@ -1 +0,0 @@
Deduplicate in-flight requests in `_get_state_for_groups`.

1
changelog.d/11610.misc
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Deduplicate in-flight requests in `_get_state_for_groups`.

1
changelog.d/12033.misc
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@ -1 +0,0 @@
Deduplicate in-flight requests in `_get_state_for_groups`.

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changelog.d/12126.removal Normal file
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Back out in-flight state caching changes.

243
synapse/storage/databases/state/store.py
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@ -13,24 +13,11 @@
# limitations under the License.
import logging
from typing import (
TYPE_CHECKING,
Collection,
Dict,
Iterable,
Optional,
Sequence,
Set,
Tuple,
)
from typing import TYPE_CHECKING, Collection, Dict, Iterable, List, Optional, Set, Tuple
import attr
from sortedcontainers import SortedDict
from twisted.internet import defer
from synapse.api.constants import EventTypes
from synapse.logging.context import make_deferred_yieldable, run_in_background
from synapse.storage._base import SQLBaseStore
from synapse.storage.database import (
DatabasePool,
@ -42,12 +29,6 @@ from synapse.storage.state import StateFilter
from synapse.storage.types import Cursor
from synapse.storage.util.sequence import build_sequence_generator
from synapse.types import MutableStateMap, StateKey, StateMap
from synapse.util import unwrapFirstError
from synapse.util.async_helpers import (
AbstractObservableDeferred,
ObservableDeferred,
yieldable_gather_results,
)
from synapse.util.caches.descriptors import cached
from synapse.util.caches.dictionary_cache import DictionaryCache
@ -56,8 +37,8 @@ if TYPE_CHECKING:
logger = logging.getLogger(__name__)
MAX_STATE_DELTA_HOPS = 100
MAX_INFLIGHT_REQUESTS_PER_GROUP = 5
@attr.s(slots=True, frozen=True, auto_attribs=True)
@ -73,24 +54,6 @@ class _GetStateGroupDelta:
return len(self.delta_ids) if self.delta_ids else 0
def state_filter_rough_priority_comparator(
state_filter: StateFilter,
) -> Tuple[int, int]:
"""
Returns a comparable value that roughly indicates the relative size of this
state filter compared to others.
'Larger' state filters should sort first when using ascending order, so
this is essentially the opposite of 'size'.
It should be treated as a rough guide only and should not be interpreted to
have any particular meaning. The representation may also change
The current implementation returns a tuple of the form:
* -1 for include_others, 0 otherwise
* -(number of entries in state_filter.types)
"""
return -int(state_filter.include_others), -len(state_filter.types)
class StateGroupDataStore(StateBackgroundUpdateStore, SQLBaseStore):
"""A data store for fetching/storing state groups."""
@ -143,12 +106,6 @@ class StateGroupDataStore(StateBackgroundUpdateStore, SQLBaseStore):
500000,
)
# Current ongoing get_state_for_groups in-flight requests
# {group ID -> {StateFilter -> ObservableDeferred}}
self._state_group_inflight_requests: Dict[
int, SortedDict[StateFilter, AbstractObservableDeferred[StateMap[str]]]
] = {}
def get_max_state_group_txn(txn: Cursor) -> int:
txn.execute("SELECT COALESCE(max(id), 0) FROM state_groups")
return txn.fetchone()[0] # type: ignore
@ -200,7 +157,7 @@ class StateGroupDataStore(StateBackgroundUpdateStore, SQLBaseStore):
)
async def _get_state_groups_from_groups(
self, groups: Sequence[int], state_filter: StateFilter
self, groups: List[int], state_filter: StateFilter
) -> Dict[int, StateMap[str]]:
"""Returns the state groups for a given set of groups from the
database, filtering on types of state events.
@ -271,170 +228,6 @@ class StateGroupDataStore(StateBackgroundUpdateStore, SQLBaseStore):
return state_filter.filter_state(state_dict_ids), not missing_types
def _get_state_for_group_gather_inflight_requests(
self, group: int, state_filter_left_over: StateFilter
) -> Tuple[Sequence[AbstractObservableDeferred[StateMap[str]]], StateFilter]:
"""
Attempts to gather in-flight requests and re-use them to retrieve state
for the given state group, filtered with the given state filter.
If there are more than MAX_INFLIGHT_REQUESTS_PER_GROUP in-flight requests,
and there *still* isn't enough information to complete the request by solely
reusing others, a full state filter will be requested to ensure that subsequent
requests can reuse this request.
Used as part of _get_state_for_group_using_inflight_cache.
Returns:
Tuple of two values:
A sequence of ObservableDeferreds to observe
A StateFilter representing what else needs to be requested to fulfill the request
"""
inflight_requests = self._state_group_inflight_requests.get(group)
if inflight_requests is None:
# no requests for this group, need to retrieve it all ourselves
return (), state_filter_left_over
# The list of ongoing requests which will help narrow the current request.
reusable_requests = []
# Iterate over existing requests in roughly biggest-first order.
for request_state_filter in inflight_requests:
request_deferred = inflight_requests[request_state_filter]
new_state_filter_left_over = state_filter_left_over.approx_difference(
request_state_filter
)
if new_state_filter_left_over == state_filter_left_over:
# Reusing this request would not gain us anything, so don't bother.
continue
reusable_requests.append(request_deferred)
state_filter_left_over = new_state_filter_left_over
if state_filter_left_over == StateFilter.none():
# we have managed to collect enough of the in-flight requests
# to cover our StateFilter and give us the state we need.
break
if (
state_filter_left_over != StateFilter.none()
and len(inflight_requests) >= MAX_INFLIGHT_REQUESTS_PER_GROUP
):
# There are too many requests for this group.
# To prevent even more from building up, we request the whole
# state filter to guarantee that we can be reused by any subsequent
# requests for this state group.
return (), StateFilter.all()
return reusable_requests, state_filter_left_over
async def _get_state_for_group_fire_request(
self, group: int, state_filter: StateFilter
) -> StateMap[str]:
"""
Fires off a request to get the state at a state group,
potentially filtering by type and/or state key.
This request will be tracked in the in-flight request cache and automatically
removed when it is finished.
Used as part of _get_state_for_group_using_inflight_cache.
Args:
group: ID of the state group for which we want to get state
state_filter: the state filter used to fetch state from the database
"""
cache_sequence_nm = self._state_group_cache.sequence
cache_sequence_m = self._state_group_members_cache.sequence
# Help the cache hit ratio by expanding the filter a bit
db_state_filter = state_filter.return_expanded()
async def _the_request() -> StateMap[str]:
group_to_state_dict = await self._get_state_groups_from_groups(
(group,), state_filter=db_state_filter
)
# Now let's update the caches
self._insert_into_cache(
group_to_state_dict,
db_state_filter,
cache_seq_num_members=cache_sequence_m,
cache_seq_num_non_members=cache_sequence_nm,
)
# Remove ourselves from the in-flight cache
group_request_dict = self._state_group_inflight_requests[group]
del group_request_dict[db_state_filter]
if not group_request_dict:
# If there are no more requests in-flight for this group,
# clean up the cache by removing the empty dictionary
del self._state_group_inflight_requests[group]
return group_to_state_dict[group]
# We don't immediately await the result, so must use run_in_background
# But we DO await the result before the current log context (request)
# finishes, so don't need to run it as a background process.
request_deferred = run_in_background(_the_request)
observable_deferred = ObservableDeferred(request_deferred, consumeErrors=True)
# Insert the ObservableDeferred into the cache
group_request_dict = self._state_group_inflight_requests.setdefault(
group, SortedDict(state_filter_rough_priority_comparator)
)
group_request_dict[db_state_filter] = observable_deferred
return await make_deferred_yieldable(observable_deferred.observe())
async def _get_state_for_group_using_inflight_cache(
self, group: int, state_filter: StateFilter
) -> MutableStateMap[str]:
"""
Gets the state at a state group, potentially filtering by type and/or
state key.
1. Calls _get_state_for_group_gather_inflight_requests to gather any
ongoing requests which might overlap with the current request.
2. Fires a new request, using _get_state_for_group_fire_request,
for any state which cannot be gathered from ongoing requests.
Args:
group: ID of the state group for which we want to get state
state_filter: the state filter used to fetch state from the database
Returns:
state map
"""
# first, figure out whether we can re-use any in-flight requests
# (and if so, what would be left over)
(
reusable_requests,
state_filter_left_over,
) = self._get_state_for_group_gather_inflight_requests(group, state_filter)
if state_filter_left_over != StateFilter.none():
# Fetch remaining state
remaining = await self._get_state_for_group_fire_request(
group, state_filter_left_over
)
assembled_state: MutableStateMap[str] = dict(remaining)
else:
assembled_state = {}
gathered = await make_deferred_yieldable(
defer.gatherResults(
(r.observe() for r in reusable_requests), consumeErrors=True
)
).addErrback(unwrapFirstError)
# assemble our result.
for result_piece in gathered:
assembled_state.update(result_piece)
# Filter out any state that may be more than what we asked for.
return state_filter.filter_state(assembled_state)
async def _get_state_for_groups(
self, groups: Iterable[int], state_filter: Optional[StateFilter] = None
) -> Dict[int, MutableStateMap[str]]:
@ -476,17 +269,31 @@ class StateGroupDataStore(StateBackgroundUpdateStore, SQLBaseStore):
if not incomplete_groups:
return state
async def get_from_cache(group: int, state_filter: StateFilter) -> None:
state[group] = await self._get_state_for_group_using_inflight_cache(
group, state_filter
)
cache_sequence_nm = self._state_group_cache.sequence
cache_sequence_m = self._state_group_members_cache.sequence
await yieldable_gather_results(
get_from_cache,
incomplete_groups,
state_filter,
# Help the cache hit ratio by expanding the filter a bit
db_state_filter = state_filter.return_expanded()
group_to_state_dict = await self._get_state_groups_from_groups(
list(incomplete_groups), state_filter=db_state_filter
)
# Now lets update the caches
self._insert_into_cache(
group_to_state_dict,
db_state_filter,
cache_seq_num_members=cache_sequence_m,
cache_seq_num_non_members=cache_sequence_nm,
)
# And finally update the result dict, by filtering out any extra
# stuff we pulled out of the database.
for group, group_state_dict in group_to_state_dict.items():
# We just replace any existing entries, as we will have loaded
# everything we need from the database anyway.
state[group] = state_filter.filter_state(group_state_dict)
return state
def _get_state_for_groups_using_cache(

454
tests/storage/databases/test_state_store.py
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@ -1,454 +0,0 @@
# Copyright 2022 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 typing
from typing import Dict, List, Sequence, Tuple
from unittest.mock import patch
from parameterized import parameterized
from twisted.internet.defer import Deferred, ensureDeferred
from twisted.test.proto_helpers import MemoryReactor
from synapse.api.constants import EventTypes
from synapse.storage.databases.state.store import (
MAX_INFLIGHT_REQUESTS_PER_GROUP,
state_filter_rough_priority_comparator,
)
from synapse.storage.state import StateFilter
from synapse.types import StateMap
from synapse.util import Clock
from tests.unittest import HomeserverTestCase
if typing.TYPE_CHECKING:
from synapse.server import HomeServer
# StateFilter for ALL non-m.room.member state events
ALL_NON_MEMBERS_STATE_FILTER = StateFilter.freeze(
types={EventTypes.Member: set()},
include_others=True,
)
FAKE_STATE = {
(EventTypes.Member, "@alice:test"): "join",
(EventTypes.Member, "@bob:test"): "leave",
(EventTypes.Member, "@charlie:test"): "invite",
("test.type", "a"): "AAA",
("test.type", "b"): "BBB",
("other.event.type", "state.key"): "123",
}
class StateGroupInflightCachingTestCase(HomeserverTestCase):
def prepare(
self, reactor: MemoryReactor, clock: Clock, homeserver: "HomeServer"
) -> None:
self.state_storage = homeserver.get_storage().state
self.state_datastore = homeserver.get_datastores().state
# Patch out the `_get_state_groups_from_groups`.
# This is useful because it lets us pretend we have a slow database.
get_state_groups_patch = patch.object(
self.state_datastore,
"_get_state_groups_from_groups",
self._fake_get_state_groups_from_groups,
)
get_state_groups_patch.start()
self.addCleanup(get_state_groups_patch.stop)
self.get_state_group_calls: List[
Tuple[Tuple[int, ...], StateFilter, Deferred[Dict[int, StateMap[str]]]]
] = []
def _fake_get_state_groups_from_groups(
self, groups: Sequence[int], state_filter: StateFilter
) -> "Deferred[Dict[int, StateMap[str]]]":
d: Deferred[Dict[int, StateMap[str]]] = Deferred()
self.get_state_group_calls.append((tuple(groups), state_filter, d))
return d
def _complete_request_fake(
self,
groups: Tuple[int, ...],
state_filter: StateFilter,
d: "Deferred[Dict[int, StateMap[str]]]",
) -> None:
"""
Assemble a fake database response and complete the database request.
"""
# Return a filtered copy of the fake state
d.callback({group: state_filter.filter_state(FAKE_STATE) for group in groups})
def test_duplicate_requests_deduplicated(self) -> None:
"""
Tests that duplicate requests for state are deduplicated.
This test:
- requests some state (state group 42, 'all' state filter)
- requests it again, before the first request finishes
- checks to see that only one database query was made
- completes the database query
- checks that both requests see the same retrieved state
"""
req1 = ensureDeferred(
self.state_datastore._get_state_for_group_using_inflight_cache(
42, StateFilter.all()
)
)
self.pump(by=0.1)
# This should have gone to the database
self.assertEqual(len(self.get_state_group_calls), 1)
self.assertFalse(req1.called)
req2 = ensureDeferred(
self.state_datastore._get_state_for_group_using_inflight_cache(
42, StateFilter.all()
)
)
self.pump(by=0.1)
# No more calls should have gone to the database
self.assertEqual(len(self.get_state_group_calls), 1)
self.assertFalse(req1.called)
self.assertFalse(req2.called)
groups, sf, d = self.get_state_group_calls[0]
self.assertEqual(groups, (42,))
self.assertEqual(sf, StateFilter.all())
# Now we can complete the request
self._complete_request_fake(groups, sf, d)
self.assertEqual(self.get_success(req1), FAKE_STATE)
self.assertEqual(self.get_success(req2), FAKE_STATE)
def test_smaller_request_deduplicated(self) -> None:
"""
Tests that duplicate requests for state are deduplicated.
This test:
- requests some state (state group 42, 'all' state filter)
- requests a subset of that state, before the first request finishes
- checks to see that only one database query was made
- completes the database query
- checks that both requests see the correct retrieved state
"""
req1 = ensureDeferred(
self.state_datastore._get_state_for_group_using_inflight_cache(
42, StateFilter.from_types((("test.type", None),))
)
)
self.pump(by=0.1)
# This should have gone to the database
self.assertEqual(len(self.get_state_group_calls), 1)
self.assertFalse(req1.called)
req2 = ensureDeferred(
self.state_datastore._get_state_for_group_using_inflight_cache(
42, StateFilter.from_types((("test.type", "b"),))
)
)
self.pump(by=0.1)
# No more calls should have gone to the database, because the second
# request was already in the in-flight cache!
self.assertEqual(len(self.get_state_group_calls), 1)
self.assertFalse(req1.called)
self.assertFalse(req2.called)
groups, sf, d = self.get_state_group_calls[0]
self.assertEqual(groups, (42,))
# The state filter is expanded internally for increased cache hit rate,
# so we the database sees a wider state filter than requested.
self.assertEqual(sf, ALL_NON_MEMBERS_STATE_FILTER)
# Now we can complete the request
self._complete_request_fake(groups, sf, d)
self.assertEqual(
self.get_success(req1),
{("test.type", "a"): "AAA", ("test.type", "b"): "BBB"},
)
self.assertEqual(self.get_success(req2), {("test.type", "b"): "BBB"})
def test_partially_overlapping_request_deduplicated(self) -> None:
"""
Tests that partially-overlapping requests are partially deduplicated.
This test:
- requests a single type of wildcard state
(This is internally expanded to be all non-member state)
- requests the entire state in parallel
- checks to see that two database queries were made, but that the second
one is only for member state.
- completes the database queries
- checks that both requests have the correct result.
"""
req1 = ensureDeferred(
self.state_datastore._get_state_for_group_using_inflight_cache(
42, StateFilter.from_types((("test.type", None),))
)
)
self.pump(by=0.1)
# This should have gone to the database
self.assertEqual(len(self.get_state_group_calls), 1)
self.assertFalse(req1.called)
req2 = ensureDeferred(
self.state_datastore._get_state_for_group_using_inflight_cache(
42, StateFilter.all()
)
)
self.pump(by=0.1)
# Because it only partially overlaps, this also went to the database
self.assertEqual(len(self.get_state_group_calls), 2)
self.assertFalse(req1.called)
self.assertFalse(req2.called)
# First request:
groups, sf, d = self.get_state_group_calls[0]
self.assertEqual(groups, (42,))
# The state filter is expanded internally for increased cache hit rate,
# so we the database sees a wider state filter than requested.
self.assertEqual(sf, ALL_NON_MEMBERS_STATE_FILTER)
self._complete_request_fake(groups, sf, d)
# Second request:
groups, sf, d = self.get_state_group_calls[1]
self.assertEqual(groups, (42,))
# The state filter is narrowed to only request membership state, because
# the remainder of the state is already being queried in the first request!
self.assertEqual(
sf, StateFilter.freeze({EventTypes.Member: None}, include_others=False)
)
self._complete_request_fake(groups, sf, d)
# Check the results are correct
self.assertEqual(
self.get_success(req1),
{("test.type", "a"): "AAA", ("test.type", "b"): "BBB"},
)
self.assertEqual(self.get_success(req2), FAKE_STATE)
def test_in_flight_requests_stop_being_in_flight(self) -> None:
"""
Tests that in-flight request deduplication doesn't somehow 'hold on'
to completed requests: once they're done, they're taken out of the
in-flight cache.
"""
req1 = ensureDeferred(
self.state_datastore._get_state_for_group_using_inflight_cache(
42, StateFilter.all()
)
)
self.pump(by=0.1)
# This should have gone to the database
self.assertEqual(len(self.get_state_group_calls), 1)
self.assertFalse(req1.called)
# Complete the request right away.
self._complete_request_fake(*self.get_state_group_calls[0])
self.assertTrue(req1.called)
# Send off another request
req2 = ensureDeferred(
self.state_datastore._get_state_for_group_using_inflight_cache(
42, StateFilter.all()
)
)
self.pump(by=0.1)
# It should have gone to the database again, because the previous request
# isn't in-flight and therefore isn't available for deduplication.
self.assertEqual(len(self.get_state_group_calls), 2)
self.assertFalse(req2.called)
# Complete the request right away.
self._complete_request_fake(*self.get_state_group_calls[1])
self.assertTrue(req2.called)
groups, sf, d = self.get_state_group_calls[0]
self.assertEqual(self.get_success(req1), FAKE_STATE)
self.assertEqual(self.get_success(req2), FAKE_STATE)
def test_inflight_requests_capped(self) -> None:
"""
Tests that the number of in-flight requests is capped to 5.
- requests several pieces of state separately
(5 to hit the limit, 1 to 'shunt out', another that comes after the
group has been 'shunted out')
- checks to see that the torrent of requests is shunted out by
rewriting one of the filters as the 'all' state filter
- requests after that one do not cause any additional queries
"""
# 5 at the time of writing.
CAP_COUNT = MAX_INFLIGHT_REQUESTS_PER_GROUP
reqs = []
# Request 7 different keys (1 to 7) of the `some.state` type.
for req_id in range(CAP_COUNT + 2):
reqs.append(
ensureDeferred(
self.state_datastore._get_state_for_group_using_inflight_cache(
42,
StateFilter.freeze(
{"some.state": {str(req_id + 1)}}, include_others=False
),
)
)
)
self.pump(by=0.1)
# There should only be 6 calls to the database, not 7.
self.assertEqual(len(self.get_state_group_calls), CAP_COUNT + 1)
# Assert that the first 5 are exact requests for the individual pieces
# wanted
for req_id in range(CAP_COUNT):
groups, sf, d = self.get_state_group_calls[req_id]
self.assertEqual(
sf,
StateFilter.freeze(
{"some.state": {str(req_id + 1)}}, include_others=False
),
)
# The 6th request should be the 'all' state filter
groups, sf, d = self.get_state_group_calls[CAP_COUNT]
self.assertEqual(sf, StateFilter.all())
# Complete the queries and check which requests complete as a result
for req_id in range(CAP_COUNT):
# This request should not have been completed yet
self.assertFalse(reqs[req_id].called)
groups, sf, d = self.get_state_group_calls[req_id]
self._complete_request_fake(groups, sf, d)
# This should have only completed this one request
self.assertTrue(reqs[req_id].called)
# Now complete the final query; the last 2 requests should complete
# as a result
self.assertFalse(reqs[CAP_COUNT].called)
self.assertFalse(reqs[CAP_COUNT + 1].called)
groups, sf, d = self.get_state_group_calls[CAP_COUNT]
self._complete_request_fake(groups, sf, d)
self.assertTrue(reqs[CAP_COUNT].called)
self.assertTrue(reqs[CAP_COUNT + 1].called)
@parameterized.expand([(False,), (True,)])
def test_ordering_of_request_reuse(self, reverse: bool) -> None:
"""
Tests that 'larger' in-flight requests are ordered first.
This is mostly a design decision in order to prevent a request from
hanging on to multiple queries when it would have been sufficient to
hang on to only one bigger query.
The 'size' of a state filter is a rough heuristic.
- requests two pieces of state, one 'larger' than the other, but each
spawning a query
- requests a third piece of state
- completes the larger of the first two queries
- checks that the third request gets completed (and doesn't needlessly
wait for the other query)
Parameters:
reverse: whether to reverse the order of the initial requests, to ensure
that the effect doesn't depend on the order of request submission.
"""
# We add in an extra state type to make sure that both requests spawn
# queries which are not optimised out.
state_filters = [
StateFilter.freeze(
{"state.type": {"A"}, "other.state.type": {"a"}}, include_others=False
),
StateFilter.freeze(
{
"state.type": None,
"other.state.type": {"b"},
# The current rough size comparator uses the number of state types
# as an indicator of size.
# To influence it to make this state filter bigger than the previous one,
# we add another dummy state type.
"extra.state.type": {"c"},
},
include_others=False,
),
]
if reverse:
# For fairness, we perform one test run with the list reversed.
state_filters.reverse()
smallest_state_filter_idx = 1
biggest_state_filter_idx = 0
else:
smallest_state_filter_idx = 0
biggest_state_filter_idx = 1
# This assertion is for our own sanity more than anything else.
self.assertLess(
state_filter_rough_priority_comparator(
state_filters[biggest_state_filter_idx]
),
state_filter_rough_priority_comparator(
state_filters[smallest_state_filter_idx]
),
"Test invalid: bigger state filter is not actually bigger.",
)
# Spawn the initial two requests
for state_filter in state_filters:
ensureDeferred(
self.state_datastore._get_state_for_group_using_inflight_cache(
42,
state_filter,
)
)
# Spawn a third request
req = ensureDeferred(
self.state_datastore._get_state_for_group_using_inflight_cache(
42,
StateFilter.freeze(
{
"state.type": {"A"},
},
include_others=False,
),
)
)
self.pump(by=0.1)
self.assertFalse(req.called)
# Complete the largest request's query to make sure that the final request
# only waits for that one (and doesn't needlessly wait for both queries)
self._complete_request_fake(
*self.get_state_group_calls[biggest_state_filter_idx]
)
# That should have been sufficient to complete the third request
self.assertTrue(req.called)