forked-synapse/tests/util/test_async_helpers.py

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# 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.
import traceback
from parameterized import parameterized_class
from twisted.internet import defer
from twisted.internet.defer import CancelledError, Deferred, ensureDeferred
from twisted.internet.task import Clock
from twisted.python.failure import Failure
from synapse.logging.context import (
SENTINEL_CONTEXT,
LoggingContext,
PreserveLoggingContext,
current_context,
make_deferred_yieldable,
)
from synapse.util.async_helpers import (
ObservableDeferred,
concurrently_execute,
delay_cancellation,
stop_cancellation,
timeout_deferred,
)
from tests.unittest import TestCase
class ObservableDeferredTest(TestCase):
def test_succeed(self):
origin_d = Deferred()
observable = ObservableDeferred(origin_d)
observer1 = observable.observe()
observer2 = observable.observe()
self.assertFalse(observer1.called)
self.assertFalse(observer2.called)
# check the first observer is called first
def check_called_first(res):
self.assertFalse(observer2.called)
return res
observer1.addBoth(check_called_first)
# store the results
results = [None, None]
def check_val(res, idx):
results[idx] = res
return res
observer1.addCallback(check_val, 0)
observer2.addCallback(check_val, 1)
origin_d.callback(123)
self.assertEqual(results[0], 123, "observer 1 callback result")
self.assertEqual(results[1], 123, "observer 2 callback result")
def test_failure(self):
origin_d = Deferred()
observable = ObservableDeferred(origin_d, consumeErrors=True)
observer1 = observable.observe()
observer2 = observable.observe()
self.assertFalse(observer1.called)
self.assertFalse(observer2.called)
# check the first observer is called first
def check_called_first(res):
self.assertFalse(observer2.called)
return res
observer1.addBoth(check_called_first)
# store the results
results = [None, None]
def check_val(res, idx):
results[idx] = res
return None
observer1.addErrback(check_val, 0)
observer2.addErrback(check_val, 1)
try:
raise Exception("gah!")
except Exception as e:
origin_d.errback(e)
self.assertEqual(str(results[0].value), "gah!", "observer 1 errback result")
self.assertEqual(str(results[1].value), "gah!", "observer 2 errback result")
def test_cancellation(self):
"""Test that cancelling an observer does not affect other observers."""
origin_d: "Deferred[int]" = Deferred()
observable = ObservableDeferred(origin_d, consumeErrors=True)
observer1 = observable.observe()
observer2 = observable.observe()
observer3 = observable.observe()
self.assertFalse(observer1.called)
self.assertFalse(observer2.called)
self.assertFalse(observer3.called)
# cancel the second observer
observer2.cancel()
self.assertFalse(observer1.called)
self.failureResultOf(observer2, CancelledError)
self.assertFalse(observer3.called)
# other observers resolve as normal
origin_d.callback(123)
self.assertEqual(observer1.result, 123, "observer 1 callback result")
self.assertEqual(observer3.result, 123, "observer 3 callback result")
# additional observers resolve as normal
observer4 = observable.observe()
self.assertEqual(observer4.result, 123, "observer 4 callback result")
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")
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self.clock.pump((1.0,))
self.assertTrue(cancelled[0], "deferred was not cancelled by timeout")
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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)
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self.clock.pump((1.0,))
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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 PreserveLoggingContext():
try:
yield non_completing_d
except CancelledError:
blocking_was_cancelled[0] = True
raise
with LoggingContext("one") as context_one:
# the errbacks should be run in the test logcontext
def errback(res, deferred_name):
self.assertIs(
current_context(),
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context_one,
"errback %s run in unexpected logcontext %s"
% (deferred_name, 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(current_context(), SENTINEL_CONTEXT)
timing_out_d.addErrback(errback, "timingout")
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self.clock.pump((1.0,))
self.assertTrue(
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blocking_was_cancelled[0], "non-completing deferred was not cancelled"
)
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self.failureResultOf(timing_out_d, defer.TimeoutError)
self.assertIs(current_context(), context_one)
class _TestException(Exception):
pass
class ConcurrentlyExecuteTest(TestCase):
def test_limits_runners(self):
"""If we have more tasks than runners, we should get the limit of runners"""
started = 0
waiters = []
processed = []
async def callback(v):
# when we first enter, bump the start count
nonlocal started
started += 1
# record the fact we got an item
processed.append(v)
# wait for the goahead before returning
d2 = Deferred()
waiters.append(d2)
await d2
# set it going
d2 = ensureDeferred(concurrently_execute(callback, [1, 2, 3, 4, 5], 3))
# check we got exactly 3 processes
self.assertEqual(started, 3)
self.assertEqual(len(waiters), 3)
# let one finish
waiters.pop().callback(0)
# ... which should start another
self.assertEqual(started, 4)
self.assertEqual(len(waiters), 3)
# we still shouldn't be done
self.assertNoResult(d2)
# finish the job
while waiters:
waiters.pop().callback(0)
# check everything got done
self.assertEqual(started, 5)
self.assertCountEqual(processed, [1, 2, 3, 4, 5])
self.successResultOf(d2)
def test_preserves_stacktraces(self):
"""Test that the stacktrace from an exception thrown in the callback is preserved"""
d1 = Deferred()
async def callback(v):
# alas, this doesn't work at all without an await here
await d1
raise _TestException("bah")
async def caller():
try:
await concurrently_execute(callback, [1], 2)
except _TestException as e:
tb = traceback.extract_tb(e.__traceback__)
# we expect to see "caller", "concurrently_execute" and "callback".
self.assertEqual(tb[0].name, "caller")
self.assertEqual(tb[1].name, "concurrently_execute")
self.assertEqual(tb[-1].name, "callback")
else:
self.fail("No exception thrown")
d2 = ensureDeferred(caller())
d1.callback(0)
self.successResultOf(d2)
def test_preserves_stacktraces_on_preformed_failure(self):
"""Test that the stacktrace on a Failure returned by the callback is preserved"""
d1 = Deferred()
f = Failure(_TestException("bah"))
async def callback(v):
# alas, this doesn't work at all without an await here
await d1
await defer.fail(f)
async def caller():
try:
await concurrently_execute(callback, [1], 2)
except _TestException as e:
tb = traceback.extract_tb(e.__traceback__)
# we expect to see "caller", "concurrently_execute", "callback",
# and some magic from inside ensureDeferred that happens when .fail
# is called.
self.assertEqual(tb[0].name, "caller")
self.assertEqual(tb[1].name, "concurrently_execute")
self.assertEqual(tb[-2].name, "callback")
else:
self.fail("No exception thrown")
d2 = ensureDeferred(caller())
d1.callback(0)
self.successResultOf(d2)
@parameterized_class(
("wrapper",),
[("stop_cancellation",), ("delay_cancellation",)],
)
class CancellationWrapperTests(TestCase):
"""Common tests for the `stop_cancellation` and `delay_cancellation` functions."""
wrapper: str
def wrap_deferred(self, deferred: "Deferred[str]") -> "Deferred[str]":
if self.wrapper == "stop_cancellation":
return stop_cancellation(deferred)
elif self.wrapper == "delay_cancellation":
return delay_cancellation(deferred)
else:
raise ValueError(f"Unsupported wrapper type: {self.wrapper}")
def test_succeed(self):
"""Test that the new `Deferred` receives the result."""
deferred: "Deferred[str]" = Deferred()
wrapper_deferred = self.wrap_deferred(deferred)
# Success should propagate through.
deferred.callback("success")
self.assertTrue(wrapper_deferred.called)
self.assertEqual("success", self.successResultOf(wrapper_deferred))
def test_failure(self):
"""Test that the new `Deferred` receives the `Failure`."""
deferred: "Deferred[str]" = Deferred()
wrapper_deferred = self.wrap_deferred(deferred)
# Failure should propagate through.
deferred.errback(ValueError("abc"))
self.assertTrue(wrapper_deferred.called)
self.failureResultOf(wrapper_deferred, ValueError)
self.assertIsNone(deferred.result, "`Failure` was not consumed")
class StopCancellationTests(TestCase):
"""Tests for the `stop_cancellation` function."""
def test_cancellation(self):
"""Test that cancellation of the new `Deferred` leaves the original running."""
deferred: "Deferred[str]" = Deferred()
wrapper_deferred = stop_cancellation(deferred)
# Cancel the new `Deferred`.
wrapper_deferred.cancel()
self.assertTrue(wrapper_deferred.called)
self.failureResultOf(wrapper_deferred, CancelledError)
self.assertFalse(
deferred.called, "Original `Deferred` was unexpectedly cancelled"
)
# Now make the original `Deferred` fail.
# The `Failure` must be consumed, otherwise unwanted tracebacks will be printed
# in logs.
deferred.errback(ValueError("abc"))
self.assertIsNone(deferred.result, "`Failure` was not consumed")
class DelayCancellationTests(TestCase):
"""Tests for the `delay_cancellation` function."""
def test_cancellation(self):
"""Test that cancellation of the new `Deferred` waits for the original."""
deferred: "Deferred[str]" = Deferred()
wrapper_deferred = delay_cancellation(deferred)
# Cancel the new `Deferred`.
wrapper_deferred.cancel()
self.assertNoResult(wrapper_deferred)
self.assertFalse(
deferred.called, "Original `Deferred` was unexpectedly cancelled"
)
# Now make the original `Deferred` fail.
# The `Failure` must be consumed, otherwise unwanted tracebacks will be printed
# in logs.
deferred.errback(ValueError("abc"))
self.assertIsNone(deferred.result, "`Failure` was not consumed")
# Now that the original `Deferred` has failed, we should get a `CancelledError`.
self.failureResultOf(wrapper_deferred, CancelledError)
def test_suppresses_second_cancellation(self):
"""Test that a second cancellation is suppressed.
Identical to `test_cancellation` except the new `Deferred` is cancelled twice.
"""
deferred: "Deferred[str]" = Deferred()
wrapper_deferred = delay_cancellation(deferred)
# Cancel the new `Deferred`, twice.
wrapper_deferred.cancel()
wrapper_deferred.cancel()
self.assertNoResult(wrapper_deferred)
self.assertFalse(
deferred.called, "Original `Deferred` was unexpectedly cancelled"
)
# Now make the original `Deferred` fail.
# The `Failure` must be consumed, otherwise unwanted tracebacks will be printed
# in logs.
deferred.errback(ValueError("abc"))
self.assertIsNone(deferred.result, "`Failure` was not consumed")
# Now that the original `Deferred` has failed, we should get a `CancelledError`.
self.failureResultOf(wrapper_deferred, CancelledError)
def test_propagates_cancelled_error(self):
"""Test that a `CancelledError` from the original `Deferred` gets propagated."""
deferred: "Deferred[str]" = Deferred()
wrapper_deferred = delay_cancellation(deferred)
# Fail the original `Deferred` with a `CancelledError`.
cancelled_error = CancelledError()
deferred.errback(cancelled_error)
# The new `Deferred` should fail with exactly the same `CancelledError`.
self.assertTrue(wrapper_deferred.called)
self.assertIs(cancelled_error, self.failureResultOf(wrapper_deferred).value)
def test_preserves_logcontext(self):
"""Test that logging contexts are preserved."""
blocking_d: "Deferred[None]" = Deferred()
async def inner():
await make_deferred_yieldable(blocking_d)
async def outer():
with LoggingContext("c") as c:
try:
await delay_cancellation(defer.ensureDeferred(inner()))
self.fail("`CancelledError` was not raised")
except CancelledError:
self.assertEqual(c, current_context())
# Succeed with no error, unless the logging context is wrong.
# Run and block inside `inner()`.
d = defer.ensureDeferred(outer())
self.assertEqual(SENTINEL_CONTEXT, current_context())
d.cancel()
# Now unblock. `outer()` will consume the `CancelledError` and check the
# logging context.
blocking_d.callback(None)
self.successResultOf(d)