Fix incorrect logcontexts after a Deferred was cancelled (#4407)

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Richard van der Hoff 2019-01-17 14:00:23 +00:00 committed by GitHub
parent 9feb5d0b71
commit 676cf2ee26
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4 changed files with 117 additions and 3 deletions

1
changelog.d/4407.bugfix Normal file
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@ -0,0 +1 @@
Fix incorrect logcontexts after a Deferred was cancelled

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@ -40,7 +40,11 @@ REQUIREMENTS = [
"signedjson>=1.0.0",
"pynacl>=1.2.1",
"service_identity>=16.0.0",
"Twisted>=17.1.0",
# our logcontext handling relies on the ability to cancel inlineCallbacks
# (https://twistedmatrix.com/trac/ticket/4632) which landed in Twisted 18.7.
"Twisted>=18.7.0",
"treq>=15.1",
# Twisted has required pyopenssl 16.0 since about Twisted 16.6.
"pyopenssl>=16.0.0",
@ -59,8 +63,11 @@ REQUIREMENTS = [
# prometheus_client 0.4.0 changed the format of counter metrics
# (cf https://github.com/matrix-org/synapse/issues/4001)
"prometheus_client>=0.0.18,<0.4.0",
# we use attr.s(slots), which arrived in 16.0.0
"attrs>=16.0.0",
# Twisted 18.7.0 requires attrs>=17.4.0
"attrs>=17.4.0",
"netaddr>=0.7.18",
]

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@ -387,12 +387,14 @@ def timeout_deferred(deferred, timeout, reactor, on_timeout_cancel=None):
deferred that wraps and times out the given deferred, correctly handling
the case where the given deferred's canceller throws.
(See https://twistedmatrix.com/trac/ticket/9534)
NOTE: Unlike `Deferred.addTimeout`, this function returns a new deferred
Args:
deferred (Deferred)
timeout (float): Timeout in seconds
reactor (twisted.internet.reactor): The twisted reactor to use
reactor (twisted.interfaces.IReactorTime): The twisted reactor to use
on_timeout_cancel (callable): A callable which is called immediately
after the deferred times out, and not if this deferred is
otherwise cancelled before the timeout.

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@ -0,0 +1,104 @@
# -*- coding: utf-8 -*-
# Copyright 2019 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.
from twisted.internet import defer
from twisted.internet.defer import CancelledError, Deferred
from twisted.internet.task import Clock
from synapse.util import logcontext
from synapse.util.async_helpers import timeout_deferred
from synapse.util.logcontext import LoggingContext
from tests.unittest import TestCase
class TimeoutDeferredTest(TestCase):
def setUp(self):
self.clock = Clock()
def test_times_out(self):
"""Basic test case that checks that the original deferred is cancelled and that
the timing-out deferred is errbacked
"""
cancelled = [False]
def canceller(_d):
cancelled[0] = True
non_completing_d = Deferred(canceller)
timing_out_d = timeout_deferred(non_completing_d, 1.0, self.clock)
self.assertNoResult(timing_out_d)
self.assertFalse(cancelled[0], "deferred was cancelled prematurely")
self.clock.pump((1.0, ))
self.assertTrue(cancelled[0], "deferred was not cancelled by timeout")
self.failureResultOf(timing_out_d, defer.TimeoutError, )
def test_times_out_when_canceller_throws(self):
"""Test that we have successfully worked around
https://twistedmatrix.com/trac/ticket/9534"""
def canceller(_d):
raise Exception("can't cancel this deferred")
non_completing_d = Deferred(canceller)
timing_out_d = timeout_deferred(non_completing_d, 1.0, self.clock)
self.assertNoResult(timing_out_d)
self.clock.pump((1.0, ))
self.failureResultOf(timing_out_d, defer.TimeoutError, )
def test_logcontext_is_preserved_on_cancellation(self):
blocking_was_cancelled = [False]
@defer.inlineCallbacks
def blocking():
non_completing_d = Deferred()
with logcontext.PreserveLoggingContext():
try:
yield non_completing_d
except CancelledError:
blocking_was_cancelled[0] = True
raise
with logcontext.LoggingContext("one") as context_one:
# the errbacks should be run in the test logcontext
def errback(res, deferred_name):
self.assertIs(
LoggingContext.current_context(), context_one,
"errback %s run in unexpected logcontext %s" % (
deferred_name, LoggingContext.current_context(),
)
)
return res
original_deferred = blocking()
original_deferred.addErrback(errback, "orig")
timing_out_d = timeout_deferred(original_deferred, 1.0, self.clock)
self.assertNoResult(timing_out_d)
self.assertIs(LoggingContext.current_context(), LoggingContext.sentinel)
timing_out_d.addErrback(errback, "timingout")
self.clock.pump((1.0, ))
self.assertTrue(
blocking_was_cancelled[0],
"non-completing deferred was not cancelled",
)
self.failureResultOf(timing_out_d, defer.TimeoutError, )
self.assertIs(LoggingContext.current_context(), context_one)