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[3.13] gh-128364: Fix flaky test_concurrent_futures.test_wait tests (gh-130742)
Use events instead of relying on `time.sleep()`. The tests are also now about four times faster. (cherry picked from commit c4d37ee) Co-authored-by: Sam Gross <[email protected]>
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‎Lib/test/test_concurrent_futures/test_wait.py‎

Lines changed: 101 additions & 61 deletions
Original file line numberDiff line numberDiff line change
@@ -1,9 +1,9 @@
11
import sys
22
import threading
3-
import time
43
import unittest
54
from concurrent import futures
65
from test import support
6+
from test.support import threading_helper
77

88
from .util import (
99
CANCELLED_FUTURE, CANCELLED_AND_NOTIFIED_FUTURE, EXCEPTION_FUTURE,
@@ -16,82 +16,118 @@
1616
def mul(x, y):
1717
return x * y
1818

19-
def sleep_and_raise(t):
20-
time.sleep(t)
19+
def wait_and_raise(e):
20+
e.wait()
2121
raise Exception('this is an exception')
2222

2323

2424
class WaitTests:
2525
def test_20369(self):
2626
# See https://bugs.python.org/issue20369
27-
future = self.executor.submit(time.sleep, 1.5)
27+
future = self.executor.submit(mul, 1, 2)
2828
done, not_done = futures.wait([future, future],
2929
return_when=futures.ALL_COMPLETED)
3030
self.assertEqual({future}, done)
3131
self.assertEqual(set(), not_done)
3232

3333

3434
def test_first_completed(self):
35+
event = self.create_event()
3536
future1 = self.executor.submit(mul, 21, 2)
36-
future2 = self.executor.submit(time.sleep, 1.5)
37+
future2 = self.executor.submit(event.wait)
3738

38-
done, not_done = futures.wait(
39-
[CANCELLED_FUTURE, future1, future2],
40-
return_when=futures.FIRST_COMPLETED)
39+
try:
40+
done, not_done = futures.wait(
41+
[CANCELLED_FUTURE, future1, future2],
42+
return_when=futures.FIRST_COMPLETED)
4143

42-
self.assertEqual(set([future1]), done)
43-
self.assertEqual(set([CANCELLED_FUTURE, future2]), not_done)
44+
self.assertEqual(set([future1]), done)
45+
self.assertEqual(set([CANCELLED_FUTURE, future2]), not_done)
46+
finally:
47+
event.set()
48+
future2.result() # wait for job to finish
4449

4550
def test_first_completed_some_already_completed(self):
46-
future1 = self.executor.submit(time.sleep, 1.5)
47-
48-
finished, pending = futures.wait(
49-
[CANCELLED_AND_NOTIFIED_FUTURE, SUCCESSFUL_FUTURE, future1],
50-
return_when=futures.FIRST_COMPLETED)
51+
event = self.create_event()
52+
future1 = self.executor.submit(event.wait)
5153

52-
self.assertEqual(
53-
set([CANCELLED_AND_NOTIFIED_FUTURE, SUCCESSFUL_FUTURE]),
54-
finished)
55-
self.assertEqual(set([future1]), pending)
54+
try:
55+
finished, pending = futures.wait(
56+
[CANCELLED_AND_NOTIFIED_FUTURE, SUCCESSFUL_FUTURE, future1],
57+
return_when=futures.FIRST_COMPLETED)
58+
59+
self.assertEqual(
60+
set([CANCELLED_AND_NOTIFIED_FUTURE, SUCCESSFUL_FUTURE]),
61+
finished)
62+
self.assertEqual(set([future1]), pending)
63+
finally:
64+
event.set()
65+
future1.result() # wait for job to finish
5666

57-
@support.requires_resource('walltime')
5867
def test_first_exception(self):
59-
future1 = self.executor.submit(mul, 2, 21)
60-
future2 = self.executor.submit(sleep_and_raise, 1.5)
61-
future3 = self.executor.submit(time.sleep, 3)
68+
event1 = self.create_event()
69+
event2 = self.create_event()
70+
try:
71+
future1 = self.executor.submit(mul, 2, 21)
72+
future2 = self.executor.submit(wait_and_raise, event1)
73+
future3 = self.executor.submit(event2.wait)
6274

63-
finished, pending = futures.wait(
64-
[future1, future2, future3],
65-
return_when=futures.FIRST_EXCEPTION)
75+
# Ensure that future1 is completed before future2 finishes
76+
def wait_for_future1():
77+
future1.result()
78+
event1.set()
79+
80+
t = threading.Thread(target=wait_for_future1)
81+
t.start()
82+
83+
finished, pending = futures.wait(
84+
[future1, future2, future3],
85+
return_when=futures.FIRST_EXCEPTION)
6686

67-
self.assertEqual(set([future1, future2]), finished)
68-
self.assertEqual(set([future3]), pending)
87+
self.assertEqual(set([future1, future2]), finished)
88+
self.assertEqual(set([future3]), pending)
89+
90+
threading_helper.join_thread(t)
91+
finally:
92+
event1.set()
93+
event2.set()
94+
future3.result() # wait for job to finish
6995

7096
def test_first_exception_some_already_complete(self):
97+
event = self.create_event()
7198
future1 = self.executor.submit(divmod, 21, 0)
72-
future2 = self.executor.submit(time.sleep, 1.5)
73-
74-
finished, pending = futures.wait(
75-
[SUCCESSFUL_FUTURE,
76-
CANCELLED_FUTURE,
77-
CANCELLED_AND_NOTIFIED_FUTURE,
78-
future1, future2],
79-
return_when=futures.FIRST_EXCEPTION)
99+
future2 = self.executor.submit(event.wait)
80100

81-
self.assertEqual(set([SUCCESSFUL_FUTURE,
82-
CANCELLED_AND_NOTIFIED_FUTURE,
83-
future1]), finished)
84-
self.assertEqual(set([CANCELLED_FUTURE, future2]), pending)
101+
try:
102+
finished, pending = futures.wait(
103+
[SUCCESSFUL_FUTURE,
104+
CANCELLED_FUTURE,
105+
CANCELLED_AND_NOTIFIED_FUTURE,
106+
future1, future2],
107+
return_when=futures.FIRST_EXCEPTION)
108+
109+
self.assertEqual(set([SUCCESSFUL_FUTURE,
110+
CANCELLED_AND_NOTIFIED_FUTURE,
111+
future1]), finished)
112+
self.assertEqual(set([CANCELLED_FUTURE, future2]), pending)
113+
finally:
114+
event.set()
115+
future2.result() # wait for job to finish
85116

86117
def test_first_exception_one_already_failed(self):
87-
future1 = self.executor.submit(time.sleep, 2)
118+
event = self.create_event()
119+
future1 = self.executor.submit(event.wait)
88120

89-
finished, pending = futures.wait(
90-
[EXCEPTION_FUTURE, future1],
91-
return_when=futures.FIRST_EXCEPTION)
121+
try:
122+
finished, pending = futures.wait(
123+
[EXCEPTION_FUTURE, future1],
124+
return_when=futures.FIRST_EXCEPTION)
92125

93-
self.assertEqual(set([EXCEPTION_FUTURE]), finished)
94-
self.assertEqual(set([future1]), pending)
126+
self.assertEqual(set([EXCEPTION_FUTURE]), finished)
127+
self.assertEqual(set([future1]), pending)
128+
finally:
129+
event.set()
130+
future1.result() # wait for job to finish
95131

96132
def test_all_completed(self):
97133
future1 = self.executor.submit(divmod, 2, 0)
@@ -114,23 +150,27 @@ def test_all_completed(self):
114150

115151
def test_timeout(self):
116152
short_timeout = 0.050
117-
long_timeout = short_timeout * 10
118153

119-
future = self.executor.submit(time.sleep, long_timeout)
154+
event = self.create_event()
155+
future = self.executor.submit(event.wait)
120156

121-
finished, pending = futures.wait(
122-
[CANCELLED_AND_NOTIFIED_FUTURE,
123-
EXCEPTION_FUTURE,
124-
SUCCESSFUL_FUTURE,
125-
future],
126-
timeout=short_timeout,
127-
return_when=futures.ALL_COMPLETED)
128-
129-
self.assertEqual(set([CANCELLED_AND_NOTIFIED_FUTURE,
130-
EXCEPTION_FUTURE,
131-
SUCCESSFUL_FUTURE]),
132-
finished)
133-
self.assertEqual(set([future]), pending)
157+
try:
158+
finished, pending = futures.wait(
159+
[CANCELLED_AND_NOTIFIED_FUTURE,
160+
EXCEPTION_FUTURE,
161+
SUCCESSFUL_FUTURE,
162+
future],
163+
timeout=short_timeout,
164+
return_when=futures.ALL_COMPLETED)
165+
166+
self.assertEqual(set([CANCELLED_AND_NOTIFIED_FUTURE,
167+
EXCEPTION_FUTURE,
168+
SUCCESSFUL_FUTURE]),
169+
finished)
170+
self.assertEqual(set([future]), pending)
171+
finally:
172+
event.set()
173+
future.result() # wait for job to finish
134174

135175

136176
class ThreadPoolWaitTests(ThreadPoolMixin, WaitTests, BaseTestCase):

‎Lib/test/test_concurrent_futures/util.py‎

Lines changed: 18 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -1,5 +1,6 @@
11
import multiprocessing
22
import sys
3+
import threading
34
import time
45
import unittest
56
from concurrent import futures
@@ -50,14 +51,19 @@ def setUp(self):
5051
max_workers=self.worker_count,
5152
mp_context=self.get_context(),
5253
**self.executor_kwargs)
54+
self.manager = self.get_context().Manager()
5355
else:
5456
self.executor = self.executor_type(
5557
max_workers=self.worker_count,
5658
**self.executor_kwargs)
59+
self.manager = None
5760

5861
def tearDown(self):
5962
self.executor.shutdown(wait=True)
6063
self.executor = None
64+
if self.manager is not None:
65+
self.manager.shutdown()
66+
self.manager = None
6167

6268
dt = time.monotonic() - self.t1
6369
if support.verbose:
@@ -73,6 +79,9 @@ def get_context(self):
7379
class ThreadPoolMixin(ExecutorMixin):
7480
executor_type = futures.ThreadPoolExecutor
7581

82+
def create_event(self):
83+
return threading.Event()
84+
7685

7786
class ProcessPoolForkMixin(ExecutorMixin):
7887
executor_type = futures.ProcessPoolExecutor
@@ -89,6 +98,9 @@ def get_context(self):
8998
self.skipTest("TSAN doesn't support threads after fork")
9099
return super().get_context()
91100

101+
def create_event(self):
102+
return self.manager.Event()
103+
92104

93105
class ProcessPoolSpawnMixin(ExecutorMixin):
94106
executor_type = futures.ProcessPoolExecutor
@@ -101,6 +113,9 @@ def get_context(self):
101113
self.skipTest("ProcessPoolExecutor unavailable on this system")
102114
return super().get_context()
103115

116+
def create_event(self):
117+
return self.manager.Event()
118+
104119

105120
class ProcessPoolForkserverMixin(ExecutorMixin):
106121
executor_type = futures.ProcessPoolExecutor
@@ -117,6 +132,9 @@ def get_context(self):
117132
self.skipTest("TSAN doesn't support threads after fork")
118133
return super().get_context()
119134

135+
def create_event(self):
136+
return self.manager.Event()
137+
120138

121139
def create_executor_tests(remote_globals, mixin, bases=(BaseTestCase,),
122140
executor_mixins=(ThreadPoolMixin,

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