cpython/Lib/test/test_concurrent_futures.py at f5b7372f458d0c085b99b494cbd92eae29d6646e · graingert/cpython

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from test import support

from test.support import import_helper

from test.support import threading_helper

# Skip tests if _multiprocessing wasn't built.

import_helper.import_module('_multiprocessing')

from test.support import hashlib_helper

from test.support.script_helper import assert_python_ok

import contextlib

import itertools

import logging

from logging.handlers import QueueHandler

import os

import queue

import sys

import threading

import time

import unittest

import weakref

from pickle import PicklingError

from concurrent import futures

from concurrent.futures._base import (

PENDING, RUNNING, CANCELLED, CANCELLED_AND_NOTIFIED, FINISHED, Future,

BrokenExecutor)

from concurrent.futures.process import BrokenProcessPool, _check_system_limits

import multiprocessing.process

import multiprocessing.util

import multiprocessing as mp

if support.check_sanitizer(address=True, memory=True):

# bpo-46633: Skip the test because it is too slow when Python is built

# with ASAN/MSAN: between 5 and 20 minutes on GitHub Actions.

raise unittest.SkipTest("test too slow on ASAN/MSAN build")

def create_future(state=PENDING, exception=None, result=None):

f = Future()

f._state = state

f._exception = exception

f._result = result

return f

PENDING_FUTURE = create_future(state=PENDING)

RUNNING_FUTURE = create_future(state=RUNNING)

CANCELLED_FUTURE = create_future(state=CANCELLED)

CANCELLED_AND_NOTIFIED_FUTURE = create_future(state=CANCELLED_AND_NOTIFIED)

EXCEPTION_FUTURE = create_future(state=FINISHED, exception=OSError())

SUCCESSFUL_FUTURE = create_future(state=FINISHED, result=42)

INITIALIZER_STATUS = 'uninitialized'

def mul(x, y):

return x * y

def capture(*args, **kwargs):

return args, kwargs

def sleep_and_raise(t):

time.sleep(t)

raise Exception('this is an exception')

def sleep_and_print(t, msg):

time.sleep(t)

print(msg)

sys.stdout.flush()

def init(x):

global INITIALIZER_STATUS

INITIALIZER_STATUS = x

def get_init_status():

return INITIALIZER_STATUS

def init_fail(log_queue=None):

if log_queue is not None:

logger = logging.getLogger('concurrent.futures')

logger.addHandler(QueueHandler(log_queue))

logger.setLevel('CRITICAL')

logger.propagate = False

time.sleep(0.1) # let some futures be scheduled

raise ValueError('error in initializer')

class MyObject(object):

def my_method(self):

pass

class EventfulGCObj():

def __init__(self, mgr):

self.event = mgr.Event()

def __del__(self):

self.event.set()

def make_dummy_object(_):

return MyObject()

class BaseTestCase(unittest.TestCase):

def setUp(self):

self._thread_key = threading_helper.threading_setup()

def tearDown(self):

support.reap_children()

threading_helper.threading_cleanup(*self._thread_key)

class ExecutorMixin:

worker_count = 5

executor_kwargs = {}

def setUp(self):

super().setUp()

self.t1 = time.monotonic()

if hasattr(self, "ctx"):

self.executor = self.executor_type(

max_workers=self.worker_count,

mp_context=self.get_context(),

**self.executor_kwargs)

else:

self.executor = self.executor_type(

max_workers=self.worker_count,

**self.executor_kwargs)

def tearDown(self):

self.executor.shutdown(wait=True)

self.executor = None

dt = time.monotonic() - self.t1

if support.verbose:

print("%.2fs" % dt, end=' ')

self.assertLess(dt, 300, "synchronization issue: test lasted too long")

super().tearDown()

def get_context(self):

return mp.get_context(self.ctx)

class ThreadPoolMixin(ExecutorMixin):

executor_type = futures.ThreadPoolExecutor

class ProcessPoolForkMixin(ExecutorMixin):

executor_type = futures.ProcessPoolExecutor

ctx = "fork"

def get_context(self):

try:

_check_system_limits()

except NotImplementedError:

self.skipTest("ProcessPoolExecutor unavailable on this system")

if sys.platform == "win32":

self.skipTest("require unix system")

return super().get_context()

class ProcessPoolSpawnMixin(ExecutorMixin):

executor_type = futures.ProcessPoolExecutor

ctx = "spawn"

def get_context(self):

try:

_check_system_limits()

except NotImplementedError:

self.skipTest("ProcessPoolExecutor unavailable on this system")

return super().get_context()

class ProcessPoolForkserverMixin(ExecutorMixin):

executor_type = futures.ProcessPoolExecutor

ctx = "forkserver"

def get_context(self):

try:

_check_system_limits()

except NotImplementedError:

self.skipTest("ProcessPoolExecutor unavailable on this system")

if sys.platform == "win32":

self.skipTest("require unix system")

return super().get_context()

def create_executor_tests(mixin, bases=(BaseTestCase,),

executor_mixins=(ThreadPoolMixin,

ProcessPoolForkMixin,

ProcessPoolForkserverMixin,

ProcessPoolSpawnMixin)):

def strip_mixin(name):

if name.endswith(('Mixin', 'Tests')):

return name[:-5]

elif name.endswith('Test'):

return name[:-4]

else:

return name

for exe in executor_mixins:

name = ("%s%sTest"

% (strip_mixin(exe.__name__), strip_mixin(mixin.__name__)))

cls = type(name, (mixin,) + (exe,) + bases, {})

globals()[name] = cls

class InitializerMixin(ExecutorMixin):

worker_count = 2

def setUp(self):

global INITIALIZER_STATUS

INITIALIZER_STATUS = 'uninitialized'

self.executor_kwargs = dict(initializer=init,

initargs=('initialized',))

super().setUp()

def test_initializer(self):

futures = [self.executor.submit(get_init_status)

for _ in range(self.worker_count)]

for f in futures:

self.assertEqual(f.result(), 'initialized')

class FailingInitializerMixin(ExecutorMixin):

worker_count = 2

def setUp(self):

if hasattr(self, "ctx"):

# Pass a queue to redirect the child's logging output

self.mp_context = self.get_context()

self.log_queue = self.mp_context.Queue()

self.executor_kwargs = dict(initializer=init_fail,

initargs=(self.log_queue,))

else:

# In a thread pool, the child shares our logging setup

# (see _assert_logged())

self.mp_context = None

self.log_queue = None

self.executor_kwargs = dict(initializer=init_fail)

super().setUp()

def test_initializer(self):

with self._assert_logged('ValueError: error in initializer'):

try:

future = self.executor.submit(get_init_status)

except BrokenExecutor:

# Perhaps the executor is already broken

pass

else:

with self.assertRaises(BrokenExecutor):

future.result()

# At some point, the executor should break

for _ in support.sleeping_retry(support.SHORT_TIMEOUT,

"executor not broken"):

if self.executor._broken:

break

# ... and from this point submit() is guaranteed to fail

with self.assertRaises(BrokenExecutor):

self.executor.submit(get_init_status)

@contextlib.contextmanager

def _assert_logged(self, msg):

if self.log_queue is not None:

yield

output = []

try:

while True:

output.append(self.log_queue.get_nowait().getMessage())

except queue.Empty:

pass

else:

with self.assertLogs('concurrent.futures', 'CRITICAL') as cm:

yield

output = cm.output

self.assertTrue(any(msg in line for line in output),

output)

create_executor_tests(InitializerMixin)

create_executor_tests(FailingInitializerMixin)

class ExecutorShutdownTest:

def test_run_after_shutdown(self):

self.executor.shutdown()

self.assertRaises(RuntimeError,

self.executor.submit,

pow, 2, 5)

def test_interpreter_shutdown(self):

# Test the atexit hook for shutdown of worker threads and processes

rc, out, err = assert_python_ok('-c', """if 1:

from concurrent.futures import {executor_type}

from time import sleep

from test.test_concurrent_futures import sleep_and_print

if __name__ == "__main__":

context = '{context}'

if context == "":

t = {executor_type}(5)

else:

from multiprocessing import get_context

context = get_context(context)

t = {executor_type}(5, mp_context=context)

t.submit(sleep_and_print, 1.0, "apple")

""".format(executor_type=self.executor_type.__name__,

context=getattr(self, "ctx", "")))

# Errors in atexit hooks don't change the process exit code, check

# stderr manually.

self.assertFalse(err)

self.assertEqual(out.strip(), b"apple")

def test_submit_after_interpreter_shutdown(self):

# Test the atexit hook for shutdown of worker threads and processes

rc, out, err = assert_python_ok('-c', """if 1:

import atexit

@atexit.register

def run_last():

try:

t.submit(id, None)

except RuntimeError:

print("runtime-error")

raise

from concurrent.futures import {executor_type}

if __name__ == "__main__":

context = '{context}'

if not context:

t = {executor_type}(5)

else:

from multiprocessing import get_context

context = get_context(context)

t = {executor_type}(5, mp_context=context)

t.submit(id, 42).result()

""".format(executor_type=self.executor_type.__name__,

context=getattr(self, "ctx", "")))

# Errors in atexit hooks don't change the process exit code, check

# stderr manually.

self.assertIn("RuntimeError: cannot schedule new futures", err.decode())

self.assertEqual(out.strip(), b"runtime-error")

def test_hang_issue12364(self):

fs = [self.executor.submit(time.sleep, 0.1) for _ in range(50)]

self.executor.shutdown()

for f in fs:

f.result()

def test_cancel_futures(self):

assert self.worker_count <= 5, "test needs few workers"

fs = [self.executor.submit(time.sleep, .1) for _ in range(50)]

self.executor.shutdown(cancel_futures=True)

# We can't guarantee the exact number of cancellations, but we can

# guarantee that *some* were cancelled. With few workers, many of

# the submitted futures should have been cancelled.

cancelled = [fut for fut in fs if fut.cancelled()]

self.assertGreater(len(cancelled), 20)

# Ensure the other futures were able to finish.

# Use "not fut.cancelled()" instead of "fut.done()" to include futures

# that may have been left in a pending state.

others = [fut for fut in fs if not fut.cancelled()]

for fut in others:

self.assertTrue(fut.done(), msg=f"{fut._state=}")

self.assertIsNone(fut.exception())

# Similar to the number of cancelled futures, we can't guarantee the

# exact number that completed. But, we can guarantee that at least

# one finished.

self.assertGreater(len(others), 0)

def test_hang_gh83386(self):

"""shutdown(wait=False) doesn't hang at exit with running futures.

See https://github.com/python/cpython/issues/83386.

"""

if self.executor_type == futures.ProcessPoolExecutor:

raise unittest.SkipTest(

"Hangs, see https://github.com/python/cpython/issues/83386")

rc, out, err = assert_python_ok('-c', """if True:

from concurrent.futures import {executor_type}

from test.test_concurrent_futures import sleep_and_print

if __name__ == "__main__":

if {context!r}: multiprocessing.set_start_method({context!r})

t = {executor_type}(max_workers=3)

t.submit(sleep_and_print, 1.0, "apple")

t.shutdown(wait=False)

""".format(executor_type=self.executor_type.__name__,

context=getattr(self, 'ctx', None)))

self.assertFalse(err)

self.assertEqual(out.strip(), b"apple")

class ThreadPoolShutdownTest(ThreadPoolMixin, ExecutorShutdownTest, BaseTestCase):

def test_threads_terminate(self):

def acquire_lock(lock):

lock.acquire()

sem = threading.Semaphore(0)

for i in range(3):

self.executor.submit(acquire_lock, sem)

self.assertEqual(len(self.executor._threads), 3)

for i in range(3):

sem.release()

self.executor.shutdown()

for t in self.executor._threads:

t.join()

def test_context_manager_shutdown(self):

with futures.ThreadPoolExecutor(max_workers=5) as e:

executor = e

self.assertEqual(list(e.map(abs, range(-5, 5))),

[5, 4, 3, 2, 1, 0, 1, 2, 3, 4])

for t in executor._threads:

t.join()

def test_del_shutdown(self):

executor = futures.ThreadPoolExecutor(max_workers=5)

res = executor.map(abs, range(-5, 5))

threads = executor._threads

del executor

for t in threads:

t.join()

# Make sure the results were all computed before the

# executor got shutdown.

assert all([r == abs(v) for r, v in zip(res, range(-5, 5))])

def test_shutdown_no_wait(self):

# Ensure that the executor cleans up the threads when calling

# shutdown with wait=False

executor = futures.ThreadPoolExecutor(max_workers=5)

res = executor.map(abs, range(-5, 5))

threads = executor._threads

executor.shutdown(wait=False)

for t in threads:

t.join()

# Make sure the results were all computed before the

# executor got shutdown.

assert all([r == abs(v) for r, v in zip(res, range(-5, 5))])

def test_thread_names_assigned(self):

executor = futures.ThreadPoolExecutor(

max_workers=5, thread_name_prefix='SpecialPool')

executor.map(abs, range(-5, 5))

threads = executor._threads

del executor

support.gc_collect() # For PyPy or other GCs.

for t in threads:

self.assertRegex(t.name, r'^SpecialPool_[0-4]$')

t.join()

def test_thread_names_default(self):

executor = futures.ThreadPoolExecutor(max_workers=5)

executor.map(abs, range(-5, 5))

threads = executor._threads

del executor

support.gc_collect() # For PyPy or other GCs.

for t in threads:

# Ensure that our default name is reasonably sane and unique when

# no thread_name_prefix was supplied.

self.assertRegex(t.name, r'ThreadPoolExecutor-\d+_[0-4]$')

t.join()

def test_cancel_futures_wait_false(self):

# Can only be reliably tested for TPE, since PPE often hangs with

# `wait=False` (even without *cancel_futures*).

rc, out, err = assert_python_ok('-c', """if True:

from concurrent.futures import ThreadPoolExecutor

from test.test_concurrent_futures import sleep_and_print

if __name__ == "__main__":

t = ThreadPoolExecutor()

t.submit(sleep_and_print, .1, "apple")

t.shutdown(wait=False, cancel_futures=True)

""")

# Errors in atexit hooks don't change the process exit code, check

# stderr manually.

self.assertFalse(err)

self.assertEqual(out.strip(), b"apple")

class ProcessPoolShutdownTest(ExecutorShutdownTest):

def test_processes_terminate(self):

def acquire_lock(lock):

lock.acquire()

mp_context = self.get_context()

if mp_context.get_start_method(allow_none=False) == "fork":

# fork pre-spawns, not on demand.

expected_num_processes = self.worker_count

else:

expected_num_processes = 3

sem = mp_context.Semaphore(0)

for _ in range(3):

self.executor.submit(acquire_lock, sem)

self.assertEqual(len(self.executor._processes), expected_num_processes)

for _ in range(3):

sem.release()

processes = self.executor._processes

self.executor.shutdown()

for p in processes.values():

p.join()

def test_context_manager_shutdown(self):

with futures.ProcessPoolExecutor(

max_workers=5, mp_context=self.get_context()) as e:

processes = e._processes

self.assertEqual(list(e.map(abs, range(-5, 5))),

[5, 4, 3, 2, 1, 0, 1, 2, 3, 4])

for p in processes.values():

p.join()

def test_del_shutdown(self):

executor = futures.ProcessPoolExecutor(

max_workers=5, mp_context=self.get_context())

res = executor.map(abs, range(-5, 5))

executor_manager_thread = executor._executor_manager_thread

processes = executor._processes

call_queue = executor._call_queue

executor_manager_thread = executor._executor_manager_thread

del executor

support.gc_collect() # For PyPy or other GCs.

# Make sure that all the executor resources were properly cleaned by

# the shutdown process

executor_manager_thread.join()

for p in processes.values():

p.join()

call_queue.join_thread()

# Make sure the results were all computed before the

# executor got shutdown.

assert all([r == abs(v) for r, v in zip(res, range(-5, 5))])

def test_shutdown_no_wait(self):

# Ensure that the executor cleans up the processes when calling

# shutdown with wait=False

executor = futures.ProcessPoolExecutor(

max_workers=5, mp_context=self.get_context())

res = executor.map(abs, range(-5, 5))

processes = executor._processes

call_queue = executor._call_queue

executor_manager_thread = executor._executor_manager_thread

executor.shutdown(wait=False)

# Make sure that all the executor resources were properly cleaned by

# the shutdown process

executor_manager_thread.join()

for p in processes.values():

p.join()

call_queue.join_thread()

# Make sure the results were all computed before the executor got

# shutdown.

assert all([r == abs(v) for r, v in zip(res, range(-5, 5))])

create_executor_tests(ProcessPoolShutdownTest,

executor_mixins=(ProcessPoolForkMixin,

ProcessPoolForkserverMixin,

ProcessPoolSpawnMixin))

class WaitTests:

def test_20369(self):

# See https://bugs.python.org/issue20369

future = self.executor.submit(time.sleep, 1.5)

done, not_done = futures.wait([future, future],

return_when=futures.ALL_COMPLETED)

self.assertEqual({future}, done)

self.assertEqual(set(), not_done)

def test_first_completed(self):

future1 = self.executor.submit(mul, 21, 2)

future2 = self.executor.submit(time.sleep, 1.5)

done, not_done = futures.wait(

[CANCELLED_FUTURE, future1, future2],

return_when=futures.FIRST_COMPLETED)

self.assertEqual(set([future1]), done)

self.assertEqual(set([CANCELLED_FUTURE, future2]), not_done)

def test_first_completed_some_already_completed(self):

future1 = self.executor.submit(time.sleep, 1.5)

finished, pending = futures.wait(

[CANCELLED_AND_NOTIFIED_FUTURE, SUCCESSFUL_FUTURE, future1],

return_when=futures.FIRST_COMPLETED)

self.assertEqual(

set([CANCELLED_AND_NOTIFIED_FUTURE, SUCCESSFUL_FUTURE]),

finished)

self.assertEqual(set([future1]), pending)

def test_first_exception(self):

future1 = self.executor.submit(mul, 2, 21)

future2 = self.executor.submit(sleep_and_raise, 1.5)

future3 = self.executor.submit(time.sleep, 3)

finished, pending = futures.wait(

[future1, future2, future3],

return_when=futures.FIRST_EXCEPTION)

self.assertEqual(set([future1, future2]), finished)

self.assertEqual(set([future3]), pending)

def test_first_exception_some_already_complete(self):

future1 = self.executor.submit(divmod, 21, 0)

future2 = self.executor.submit(time.sleep, 1.5)

finished, pending = futures.wait(

[SUCCESSFUL_FUTURE,

CANCELLED_FUTURE,

CANCELLED_AND_NOTIFIED_FUTURE,

future1, future2],

return_when=futures.FIRST_EXCEPTION)

self.assertEqual(set([SUCCESSFUL_FUTURE,

CANCELLED_AND_NOTIFIED_FUTURE,

future1]), finished)

self.assertEqual(set([CANCELLED_FUTURE, future2]), pending)

def test_first_exception_one_already_failed(self):

future1 = self.executor.submit(time.sleep, 2)

finished, pending = futures.wait(

[EXCEPTION_FUTURE, future1],

return_when=futures.FIRST_EXCEPTION)

self.assertEqual(set([EXCEPTION_FUTURE]), finished)

self.assertEqual(set([future1]), pending)

def test_all_completed(self):

future1 = self.executor.submit(divmod, 2, 0)

future2 = self.executor.submit(mul, 2, 21)

finished, pending = futures.wait(

[SUCCESSFUL_FUTURE,

CANCELLED_AND_NOTIFIED_FUTURE,

EXCEPTION_FUTURE,

future1,

future2],

return_when=futures.ALL_COMPLETED)

self.assertEqual(set([SUCCESSFUL_FUTURE,

CANCELLED_AND_NOTIFIED_FUTURE,

EXCEPTION_FUTURE,

future1,

future2]), finished)

self.assertEqual(set(), pending)

def test_timeout(self):

future1 = self.executor.submit(mul, 6, 7)

future2 = self.executor.submit(time.sleep, 6)

finished, pending = futures.wait(

[CANCELLED_AND_NOTIFIED_FUTURE,

EXCEPTION_FUTURE,

SUCCESSFUL_FUTURE,

future1, future2],

timeout=5,

return_when=futures.ALL_COMPLETED)

self.assertEqual(set([CANCELLED_AND_NOTIFIED_FUTURE,

EXCEPTION_FUTURE,

SUCCESSFUL_FUTURE,

future1]), finished)

self.assertEqual(set([future2]), pending)

class ThreadPoolWaitTests(ThreadPoolMixin, WaitTests, BaseTestCase):

def test_pending_calls_race(self):

# Issue #14406: multi-threaded race condition when waiting on all

# futures.

event = threading.Event()

def future_func():

event.wait()

oldswitchinterval = sys.getswitchinterval()

sys.setswitchinterval(1e-6)

try:

fs = {self.executor.submit(future_func) for i in range(100)}

event.set()

futures.wait(fs, return_when=futures.ALL_COMPLETED)

finally:

sys.setswitchinterval(oldswitchinterval)

create_executor_tests(WaitTests,

executor_mixins=(ProcessPoolForkMixin,

ProcessPoolForkserverMixin,

ProcessPoolSpawnMixin))

class AsCompletedTests:

# TODO(brian@sweetapp.com): Should have a test with a non-zero timeout.

def test_no_timeout(self):

future1 = self.executor.submit(mul, 2, 21)

future2 = self.executor.submit(mul, 7, 6)

completed = set(futures.as_completed(

[CANCELLED_AND_NOTIFIED_FUTURE,

EXCEPTION_FUTURE,

SUCCESSFUL_FUTURE,

future1, future2]))

self.assertEqual(set(

[CANCELLED_AND_NOTIFIED_FUTURE,

EXCEPTION_FUTURE,

SUCCESSFUL_FUTURE,

future1, future2]),

completed)

def test_zero_timeout(self):

future1 = self.executor.submit(time.sleep, 2)

completed_futures = set()

try:

for future in futures.as_completed(

[CANCELLED_AND_NOTIFIED_FUTURE,

EXCEPTION_FUTURE,

SUCCESSFUL_FUTURE,

future1],

timeout=0):

completed_futures.add(future)

except futures.TimeoutError:

pass

self.assertEqual(set([CANCELLED_AND_NOTIFIED_FUTURE,

EXCEPTION_FUTURE,

SUCCESSFUL_FUTURE]),

completed_futures)

def test_duplicate_futures(self):

# Issue 20367. Duplicate futures should not raise exceptions or give

# duplicate responses.

# Issue #31641: accept arbitrary iterables.

future1 = self.executor.submit(time.sleep, 2)

completed = [

f for f in futures.as_completed(itertools.repeat(future1, 3))

]

self.assertEqual(len(completed), 1)

def test_free_reference_yielded_future(self):

# Issue #14406: Generator should not keep references

# to finished futures.

futures_list = [Future() for _ in range(8)]

futures_list.append(create_future(state=CANCELLED_AND_NOTIFIED))

futures_list.append(create_future(state=FINISHED, result=42))

with self.assertRaises(futures.TimeoutError):

for future in futures.as_completed(futures_list, timeout=0):

futures_list.remove(future)

wr = weakref.ref(future)

del future

support.gc_collect() # For PyPy or other GCs.

self.assertIsNone(wr())

futures_list[0].set_result("test")

for future in futures.as_completed(futures_list):

futures_list.remove(future)

wr = weakref.ref(future)

del future

support.gc_collect() # For PyPy or other GCs.

self.assertIsNone(wr())

if futures_list:

futures_list[0].set_result("test")

def test_correct_timeout_exception_msg(self):

futures_list = [CANCELLED_AND_NOTIFIED_FUTURE, PENDING_FUTURE,

RUNNING_FUTURE, SUCCESSFUL_FUTURE]

with self.assertRaises(futures.TimeoutError) as cm:

list(futures.as_completed(futures_list, timeout=0))

self.assertEqual(str(cm.exception), '2 (of 4) futures unfinished')

create_executor_tests(AsCompletedTests)

class ExecutorTest:

# Executor.shutdown() and context manager usage is tested by

# ExecutorShutdownTest.

def test_submit(self):

future = self.executor.submit(pow, 2, 8)

self.assertEqual(256, future.result())

def test_submit_keyword(self):

future = self.executor.submit(mul, 2, y=8)

self.assertEqual(16, future.result())

future = self.executor.submit(capture, 1, self=2, fn=3)

self.assertEqual(future.result(), ((1,), {'self': 2, 'fn': 3}))

with self.assertRaises(TypeError):

self.executor.submit(fn=capture, arg=1)

with self.assertRaises(TypeError):

self.executor.submit(arg=1)

def test_map(self):

self.assertEqual(

list(self.executor.map(pow, range(10), range(10))),

list(map(pow, range(10), range(10))))

self.assertEqual(

list(self.executor.map(pow, range(10), range(10), chunksize=3)),

list(map(pow, range(10), range(10))))

def test_map_exception(self):

i = self.executor.map(divmod, [1, 1, 1, 1], [2, 3, 0, 5])

self.assertEqual(i.__next__(), (0, 1))

self.assertRaises(ZeroDivisionError, i.__next__)

def test_map_timeout(self):

results = []

try:

for i in self.executor.map(time.sleep,

[0, 0, 6],

timeout=5):

results.append(i)

except futures.TimeoutError:

pass

else:

self.fail('expected TimeoutError')

self.assertEqual([None, None], results)

def test_shutdown_race_issue12456(self):

# Issue #12456: race condition at shutdown where trying to post a

# sentinel in the call queue blocks (the queue is full while processes

# have exited).

self.executor.map(str, [2] * (self.worker_count + 1))

self.executor.shutdown()

@support.cpython_only

def test_no_stale_references(self):

# Issue #16284: check that the executors don't unnecessarily hang onto

# references.

my_object = MyObject()

my_object_collected = threading.Event()

my_object_callback = weakref.ref(

my_object, lambda obj: my_object_collected.set())

# Deliberately discarding the future.

self.executor.submit(my_object.my_method)

del my_object

collected = my_object_collected.wait(timeout=support.SHORT_TIMEOUT)

self.assertTrue(collected,

"Stale reference not collected within timeout.")

def test_max_workers_negative(self):

for number in (0, -1):

with self.assertRaisesRegex(ValueError,

"max_workers must be greater "

"than 0"):

self.executor_type(max_workers=number)

def test_free_reference(self):

# Issue #14406: Result iterator should not keep an internal

# reference to result objects.

for obj in self.executor.map(make_dummy_object, range(10)):

wr = weakref.ref(obj)

del obj

support.gc_collect() # For PyPy or other GCs.

self.assertIsNone(wr())

class ThreadPoolExecutorTest(ThreadPoolMixin, ExecutorTest, BaseTestCase):

def test_map_submits_without_iteration(self):

"""Tests verifying issue 11777."""

finished = []

def record_finished(n):

finished.append(n)

self.executor.map(record_finished, range(10))

self.executor.shutdown(wait=True)

self.assertCountEqual(finished, range(10))

def test_default_workers(self):

executor = self.executor_type()

expected = min(32, (os.cpu_count() or 1) + 4)

self.assertEqual(executor._max_workers, expected)

def test_saturation(self):

executor = self.executor_type(4)

def acquire_lock(lock):

lock.acquire()

sem = threading.Semaphore(0)

for i in range(15 * executor._max_workers):

executor.submit(acquire_lock, sem)

self.assertEqual(len(executor._threads), executor._max_workers)

for i in range(15 * executor._max_workers):

sem.release()

executor.shutdown(wait=True)

def test_idle_thread_reuse(self):

executor = self.executor_type()

executor.submit(mul, 21, 2).result()

executor.submit(mul, 6, 7).result()

executor.submit(mul, 3, 14).result()

self.assertEqual(len(executor._threads), 1)

executor.shutdown(wait=True)

@unittest.skipUnless(hasattr(os, 'register_at_fork'), 'need os.register_at_fork')

def test_hang_global_shutdown_lock(self):

# bpo-45021: _global_shutdown_lock should be reinitialized in the child

# process, otherwise it will never exit

def submit(pool):

pool.submit(submit, pool)

with futures.ThreadPoolExecutor(1) as pool:

pool.submit(submit, pool)

for _ in range(50):

with futures.ProcessPoolExecutor(1, mp_context=mp.get_context('fork')) as workers:

workers.submit(tuple)

def test_executor_map_current_future_cancel(self):

stop_event = threading.Event()

log = []

def log_n_wait(ident):

log.append(f"{ident=} started")

try:

stop_event.wait()

finally:

log.append(f"{ident=} stopped")

with self.executor_type(max_workers=1) as pool:

# submit work to saturate the pool

fut = pool.submit(log_n_wait, ident="first")

try:

with contextlib.closing(

pool.map(log_n_wait, ["second", "third"], timeout=0)

) as gen:

with self.assertRaises(TimeoutError):

next(gen)

finally:

stop_event.set()

fut.result()

# ident='second' is cancelled as a result of raising a TimeoutError

# ident='third' is cancelled because it remained in the collection of futures

self.assertListEqual(log, ["ident='first' started", "ident='first' stopped"])

class ProcessPoolExecutorTest(ExecutorTest):

@unittest.skipUnless(sys.platform=='win32', 'Windows-only process limit')

def test_max_workers_too_large(self):

with self.assertRaisesRegex(ValueError,

"max_workers must be <= 61"):

futures.ProcessPoolExecutor(max_workers=62)

def test_killed_child(self):

# When a child process is abruptly terminated, the whole pool gets

# "broken".

futures = [self.executor.submit(time.sleep, 3)]

# Get one of the processes, and terminate (kill) it

p = next(iter(self.executor._processes.values()))

p.terminate()

for fut in futures:

self.assertRaises(BrokenProcessPool, fut.result)

# Submitting other jobs fails as well.

self.assertRaises(BrokenProcessPool, self.executor.submit, pow, 2, 8)

def test_map_chunksize(self):

def bad_map():

list(self.executor.map(pow, range(40), range(40), chunksize=-1))

ref = list(map(pow, range(40), range(40)))

self.assertEqual(

list(self.executor.map(pow, range(40), range(40), chunksize=6)),

ref)

self.assertEqual(

list(self.executor.map(pow, range(40), range(40), chunksize=50)),

ref)

self.assertEqual(

list(self.executor.map(pow, range(40), range(40), chunksize=40)),

ref)

self.assertRaises(ValueError, bad_map)

@classmethod

def _test_traceback(cls):

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