尝试启动服务器时检测到死锁

Question

我有一个简单的应用程序，我同时使用 django 和 django-rest-framework。

很多时候，当我尝试启动本地服务器 (python manage.py runserver) 时，我会收到以下异常：

Watching for file changes with StatReloader
Exception in thread Thread-1:
Traceback (most recent call last):
  File "/project/venv/lib/python3.7/site-packages/django/template/utils.py", line 66, in __getitem__
    return self._engines[alias]
KeyError: 'django'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/usr/local/Cellar/python/3.7.2_2/Frameworks/Python.framework/Versions/3.7/lib/python3.7/threading.py", line 917, in _bootstrap_inner
    self.run()
  File "/usr/local/Cellar/python/3.7.2_2/Frameworks/Python.framework/Versions/3.7/lib/python3.7/threading.py", line 865, in run
    self._target(*self._args, **self._kwargs)
  File "/project/venv/lib/python3.7/site-packages/django/utils/autoreload.py", line 54, in wrapper
    fn(*args, **kwargs)
  File "/project/venv/lib/python3.7/site-packages/django/core/management/commands/runserver.py", line 117, in inner_run
    self.check(display_num_errors=True)
  File "/project/venv/lib/python3.7/site-packages/django/core/management/base.py", line 390, in check
    include_deployment_checks=include_deployment_checks,
  File "/project/venv/lib/python3.7/site-packages/django/core/management/base.py", line 377, in _run_checks
    return checks.run_checks(**kwargs)
  File "/project/venv/lib/python3.7/site-packages/django/core/checks/registry.py", line 72, in run_checks
    new_errors = check(app_configs=app_configs)
  File "/project/venv/lib/python3.7/site-packages/django/contrib/admin/checks.py", line 80, in check_dependencies
    for engine in engines.all():
  File "/project/venv/lib/python3.7/site-packages/django/template/utils.py", line 90, in all
    return [self[alias] for alias in self]
  File "/project/venv/lib/python3.7/site-packages/django/template/utils.py", line 90, in <listcomp>
    return [self[alias] for alias in self]
  File "/project/venv/lib/python3.7/site-packages/django/template/utils.py", line 81, in __getitem__
    engine = engine_cls(params)
  File "/project/venv/lib/python3.7/site-packages/django/template/backends/django.py", line 25, in __init__
    options['libraries'] = self.get_templatetag_libraries(libraries)
  File "/project/venv/lib/python3.7/site-packages/django/template/backends/django.py", line 43, in get_templatetag_libraries
    libraries = get_installed_libraries()
  File "/project/venv/lib/python3.7/site-packages/django/template/backends/django.py", line 108, in get_installed_libraries
    for name in get_package_libraries(pkg):
  File "/project/venv/lib/python3.7/site-packages/django/template/backends/django.py", line 121, in get_package_libraries
    module = import_module(entry[1])
  File "/project/venv/lib/python3.7/importlib/__init__.py", line 127, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
  File "<frozen importlib._bootstrap>", line 1006, in _gcd_import
  File "<frozen importlib._bootstrap>", line 983, in _find_and_load
  File "<frozen importlib._bootstrap>", line 967, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 677, in _load_unlocked
  File "<frozen importlib._bootstrap_external>", line 728, in exec_module
  File "<frozen importlib._bootstrap>", line 219, in _call_with_frames_removed
  File "/project/venv/lib/python3.7/site-packages/rest_framework/templatetags/rest_framework.py", line 15, in <module>
    from rest_framework.renderers import HTMLFormRenderer
  File "/project/venv/lib/python3.7/site-packages/rest_framework/renderers.py", line 20, in <module>
    from django.test.client import encode_multipart
  File "/project/venv/lib/python3.7/site-packages/django/test/client.py", line 23, in <module>
    from django.test import signals
  File "<frozen importlib._bootstrap>", line 980, in _find_and_load
  File "<frozen importlib._bootstrap>", line 149, in __enter__
  File "<frozen importlib._bootstrap>", line 94, in acquire
_frozen_importlib._DeadlockError: deadlock detected by _ModuleLock('django.test.signals') at 4420467792

Performing system checks...

重试几次后，服务器成功启动。因此，它不是一个炫耀的东西，但它很烦人。

由于我对 Django 很陌生，我想知道是否有办法防止此类错误。

Answer 1

我遇到了同样的问题，我还不知道如何重现它以及它为什么会发生。 不过貌似和新版Django有关系。

来自this comment 的问题似乎与虚拟环境中的 .pyc 文件有关。

我就是这样做的：

• 使用此命令删除了项目中的所有 .pyc 文件：find . -regex '*.pyc' -delete

• 停用虚拟环境并重新激活它。

问题消失了

Answer 2

我遇到了同样的问题，无法可靠地重现它。我尝试删除我的 .pyc 文件，但仍然遇到同样的问题。我将“rest_framework”移到了我的 INSTALLED_APPS 列表的末尾，这似乎对我有用。

Answer 3

错误是由于 Django Rest Framework 造成的，您可以通过删除它并看到错误消失来检查它。 更具体地说，在我的情况下，只需删除

from rest_framework.urlpatterns import format_suffix_patterns

来自 urls.py 解决了这个问题，仍然安装了 Django Rest Framework。