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Django测试并行化：AppRegistryNotReady问题。

pythondjangotestingparallel-processing
6

我希望了解如何在内存中使用sqlite3并行运行Django测试的方法。

我的Django应用程序结构如下：

gbook
    order
        ...
        tests
            __init__.py
            test_a1.py
            test_b1.py
            utils.py

test_a1.py和test_b1.py包含相同的代码:

import time
from order import models
from .utils import BackendTestCase


class ATestCase(BackendTestCase):
    def test_a(self):
        time.sleep(1)
        a = models.City.objects.count()
        self.assertEqual(a, a)

class BTestCase(BackendTestCase):
    def test_b(self):
        time.sleep(1)
        a = models.City.objects.count()
        self.assertEqual(a, a)

utils.py是：

from django.test import TestCase, Client
from order import models
from django.conf import settings

from order.utils import to_hash


class BackendTestCase(TestCase):
    fixtures = ['City.json', 'Agency.json']

    def setUp(self):
        self.client = Client()
        self.lang_codes = (i[0] for i in settings.LANGUAGES)
        ...

settings_test.py:

from .settings import *

DEBUG = False

TEMPLATE_DEBUG = False

STATICFILES_STORAGE = 'django.contrib.staticfiles.storage.StaticFilesStorage'

PASSWORD_HASHERS = ['django.contrib.auth.hashers.MD5PasswordHasher',]  # faster

DATABASES['default'] = {
    'ENGINE': 'django.db.backends.sqlite3',
}

当我在单进程中运行测试时，一切顺利（约4秒）：
python.exe manage.py test order --settings=gbook.settings_test

接下来我尝试同时运行测试：

python.exe manage.py test order --settings=gbook.settings_test --parallel=2

我收到了这个跟踪信息（控制台）：
Creating test database for alias 'default'...

Cloning test database for alias 'default'...
Cloning test database for alias 'default'...
System check identified no issues (0 silenced).
Process SpawnPoolWorker-2:
Process SpawnPoolWorker-1:
Traceback (most recent call last):
Traceback (most recent call last):
  File "C:\python\Python36-32\lib\multiprocessing\process.py", line 258, in _bootstrap
    self.run()
  File "C:\python\Python36-32\lib\multiprocessing\process.py", line 258, in _bootstrap
    self.run()
  File "C:\python\Python36-32\lib\multiprocessing\process.py", line 93, in run
    self._target(*self._args, **self._kwargs)
  File "C:\python\Python36-32\lib\multiprocessing\process.py", line 93, in run
    self._target(*self._args, **self._kwargs)
  File "C:\python\Python36-32\lib\multiprocessing\pool.py", line 108, in worker
    task = get()
  File "C:\python\Python36-32\lib\multiprocessing\pool.py", line 108, in worker
    task = get()
  File "C:\python\Python36-32\lib\multiprocessing\queues.py", line 337, in get
    return _ForkingPickler.loads(res)
  File "C:\python\Python36-32\lib\multiprocessing\queues.py", line 337, in get
    return _ForkingPickler.loads(res)
  File "C:\kvk\develop\Python\gbook\order\tests\test_a1.py", line 2, in <module>
    from order import models
  File "C:\kvk\develop\Python\gbook\order\tests\test_a1.py", line 2, in <module>
    from order import models
  File "C:\kvk\develop\Python\gbook\order\models.py", line 79, in <module>
    class Agency(models.Model):
  File "C:\kvk\develop\Python\gbook\order\models.py", line 79, in <module>
    class Agency(models.Model):
  File "C:\python\venv\gbook\lib\site-packages\django\db\models\base.py", line 110, in __new__
    app_config = apps.get_containing_app_config(module)
  File "C:\python\venv\gbook\lib\site-packages\django\db\models\base.py", line 110, in __new__
    app_config = apps.get_containing_app_config(module)
  File "C:\python\venv\gbook\lib\site-packages\django\apps\registry.py", line 247, in get_containing_app_config
    self.check_apps_ready()
  File "C:\python\venv\gbook\lib\site-packages\django\apps\registry.py", line 247, in get_containing_app_config
    self.check_apps_ready()
  File "C:\python\venv\gbook\lib\site-packages\django\apps\registry.py", line 125, in check_apps_ready
    raise AppRegistryNotReady("Apps aren't loaded yet.")
  File "C:\python\venv\gbook\lib\site-packages\django\apps\registry.py", line 125, in check_apps_ready
    raise AppRegistryNotReady("Apps aren't loaded yet.")
django.core.exceptions.AppRegistryNotReady: Apps aren't loaded yet.
django.core.exceptions.AppRegistryNotReady: Apps aren't loaded yet.

从Pycharm中跟踪的结果与其他工具不同：

...

Traceback (most recent call last):
  File "C:\python\Python36-32\lib\unittest\suite.py", line 163, in _handleClassSetUp
    setUpClass()
  File "C:\python\venv\gbook\lib\site-packages\django\test\testcases.py", line 1036, in setUpClass
    'database': db_name,
  File "C:\python\venv\gbook\lib\site-packages\django\core\management\__init__.py", line 131, in call_command
    return command.execute(*args, **defaults)
  File "C:\python\venv\gbook\lib\site-packages\django\core\management\base.py", line 330, in execute
    output = self.handle(*args, **options)
  File "C:\python\venv\gbook\lib\site-packages\modeltranslation\management\commands\loaddata.py", line 61, in handle
    return super(Command, self).handle(*fixture_labels, **options)
  File "C:\python\venv\gbook\lib\site-packages\django\core\management\commands\loaddata.py", line 69, in handle
    self.loaddata(fixture_labels)
  File "C:\python\venv\gbook\lib\site-packages\django\core\management\commands\loaddata.py", line 109, in loaddata
    self.load_label(fixture_label)
  File "C:\python\venv\gbook\lib\site-packages\django\core\management\commands\loaddata.py", line 175, in load_label
    obj.save(using=self.using)
  File "C:\python\venv\gbook\lib\site-packages\django\core\serializers\base.py", line 205, in save
    models.Model.save_base(self.object, using=using, raw=True, **kwargs)
  File "C:\python\venv\gbook\lib\site-packages\django\db\models\base.py", line 838, in save_base
    updated = self._save_table(raw, cls, force_insert, force_update, using, update_fields)
  File "C:\python\venv\gbook\lib\site-packages\django\db\models\base.py", line 905, in _save_table
    forced_update)
  File "C:\python\venv\gbook\lib\site-packages\django\db\models\base.py", line 955, in _do_update
    return filtered._update(values) > 0
  File "C:\python\venv\gbook\lib\site-packages\django\db\models\query.py", line 664, in _update
    return query.get_compiler(self.db).execute_sql(CURSOR)
  File "C:\python\venv\gbook\lib\site-packages\django\db\models\sql\compiler.py", line 1204, in execute_sql
    cursor = super(SQLUpdateCompiler, self).execute_sql(result_type)
  File "C:\python\venv\gbook\lib\site-packages\django\db\models\sql\compiler.py", line 899, in execute_sql
    raise original_exception
  File "C:\python\venv\gbook\lib\site-packages\django\db\models\sql\compiler.py", line 889, in execute_sql
    cursor.execute(sql, params)
  File "C:\python\venv\gbook\lib\site-packages\django\db\backends\utils.py", line 64, in execute
    return self.cursor.execute(sql, params)
  File "C:\python\venv\gbook\lib\site-packages\django\db\utils.py", line 94, in __exit__
    six.reraise(dj_exc_type, dj_exc_value, traceback)
  File "C:\python\venv\gbook\lib\site-packages\django\utils\six.py", line 685, in reraise
    raise value.with_traceback(tb)
  File "C:\python\venv\gbook\lib\site-packages\django\db\backends\utils.py", line 64, in execute
    return self.cursor.execute(sql, params)
  File "C:\python\venv\gbook\lib\site-packages\django\db\backends\sqlite3\base.py", line 328, in execute
    return Database.Cursor.execute(self, query, params)
django.db.utils.OperationalError: Problem installing fixture 'C:\kvk\develop\Python\gbook\order\fixtures\AirportInfo.json': Could not load order.AirportInfo(pk=2411): no such table: GB_AIRPORT_INFO

似乎迁移不支持并行操作，但是为什么？
文档中说：“--parallel”会在独立的进程中运行测试。每个进程都有自己的数据库。使用它时，我无需更改代码。
请帮我理解，我做错了什么。
multiprocessing.cpu_count() = 4
Django版本1.11.10
Python 3.6.5
4个回答
12

与上面相同的问题出现在MacOS和Python 3.8+中。您必须在settings.py文件的顶部明确设置import multiprocessing; multiprocessing.set_start_method('fork')。但是在执行此操作之前，请务必了解其副作用！

3
谢谢！这确实解决了我的问题（在MacOs上）。如果您能包括使用此方法的后果，您的回答会更好。此外，只为测试启用它非常容易 :) - Menth
谢谢，已经在MacOS上解决了这个问题。我刚刚把它添加到settings_test.py中。 - Ivan Rostovsky
4
我在Windows上尝试使用--parallel功能时遇到了类似的问题。
Django的文档指出：

此功能在Windows上不可用。它也不适用于Oracle数据库后端。

在Linux上运行相同的命令没有任何问题。
1
我猜这是因为在Windows上没有可用的fork，所以multiprocessing使用spawn代替，但它不太擅长复制全局状态。 - Gordon Wrigley
4
至今在Windows平台上仍然禁用了并行运行。你可以在这里跟踪保持此功能进展的票证：https://code.djangoproject.com/ticket/31169。
下面是在Windows上禁用此选项的代码块：
def default_test_processes():
    """Default number of test processes when using the --parallel option."""
    # The current implementation of the parallel test runner requires
    # multiprocessing to start subprocesses with fork().
    if multiprocessing.get_start_method() != 'fork':
        return 1
    try:
        return int(os.environ['DJANGO_TEST_PROCESSES'])
    except KeyError:
        return multiprocessing.cpu_count()

来源：https://github.com/django/django/blob/59b4e99dd00b9c36d56055b889f96885995e4240/django/test/runner.py#L286-L295

这个链接指向django测试运行器的Python源代码。
2
作为对@Menth的回复，这是我如何启用仅供测试的方法：
# near the top of settings.py
if "test" in sys.argv[1:]:
    import multiprocessing

    logging.info("Using multiproc for testing.")
    multiprocessing.set_start_method("fork")
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