在Django Rest Framework中运行docker-compose up时出现异常

在Django Rest Framework中配置安全WebSocket时，我在docker-compose.yml中添加了如下Daphne服务配置：

daphne:
  platform: linux/amd64
  build:
    context: .
    dockerfile: Dockerfile.dev
  command: 'sh -c "daphne -b 0.0.0.0 -p 8000  apps.asgi:application"'
  restart: always

执行docker-compose up时出现如下错误，移除Daphne条目后错误消失，且此前该compose项目能正常构建运行：

daphne_1   | Traceback (most recent call last):
daphne_1   |   File "/usr/local/lib/python3.8/site-packages/urllib3/connectionpool.py", line 703, in urlopen
daphne_1   |     httplib_response = self._make_request(
daphne_1   |   File "/usr/local/lib/python3.8/site-packages/urllib3/connectionpool.py", line 398, in _make_request
daphne_1   |     conn.request(method, url, **httplib_request_kw)
daphne_1   |   File "/usr/local/lib/python3.8/http/client.py", line 1256, in request
daphne_1   |     self._send_request(method, url, body, headers, encode_chunked)
daphne_1   |   File "/usr/local/lib/python3.8/http/client.py", line 1302, in _send_request
daphne_1   |     self.endheaders(body, encode_chunked=encode_chunked)
daphne_1   |   File "/usr/local/lib/python3.8/http/client.py", line 1251, in endheaders
daphne_1   |     self._send_output(message_body, encode_chunked=encode_chunked)
daphne_1   |   File "/usr/local/lib/python3.8/http/client.py", line 1011, in _send_output
daphne_1   |     self.send(msg)
daphne_1   |   File "/usr/local/lib/python3.8/http/client.py", line 951, in send
daphne_1   |     self.connect()
daphne_1   |   File "/usr/local/lib/python3.8/site-packages/docker/transport/unixconn.py", line 30, in connect
daphne_1   |     sock.connect(self.unix_socket)
daphne_1   | FileNotFoundError: [Errno 2] No such file or directory
daphne_1   |
daphne_1   | During handling of the above exception, another exception occurred:
daphne_1   |
daphne_1   | Traceback (most recent call last):
daphne_1   |   File "/usr/local/lib/python3.8/site-packages/requests/adapters.py", line 440, in send
daphne_1   |     resp = conn.urlopen(
daphne_1   |   File "/usr/local/lib/python3.8/site-packages/urllib3/connectionpool.py", line 785, in urlopen
daphne_1   |     retries = retries.increment(
daphne_1   |   File "/usr/local/lib/python3.8/site-packages/urllib3/util/retry.py", line 550, in increment
daphne_1   |     raise six.reraise(type(error), error, _stacktrace)
daphne_1   |   File "/usr/local/lib/python3.8/site-packages/urllib3/packages/six.py", line 769, in reraise
daphne_1   |     raise value.with_traceback(tb)
daphne_1   |   File "/usr/local/lib/python3.8/site-packages/urllib3/connectionpool.py", line 703, in urlopen
daphne_1   |     httplib_response = self._make_request(
daphne_1   |   File "/usr/local/lib/python3.8/site-packages/urllib3/connectionpool.py", line 398, in _make_request
daphne_1   |     conn.request(method, url, **httplib_request_kw)
daphne_1   |   File "/usr/local/lib/python3.8/http/client.py", line 1256, in request
daphne_1   |     self._send_request(method, url, body, headers, encode_chunked)
daphne_1   |   File "/usr/local/lib/python3.8/http/client.py", line 1302, in _send_request
daphne_1   |     self.endheaders(body, encode_chunked=encode_chunked)
daphne_1   |   File "/usr/local/lib/python3.8/http/client.py", line 1251, in endheaders
daphne_1   |     self._send_output(message_body, encode_chunked=encode_chunked)
daphne_1   |   File "/usr/local/lib/python3.8/http/client.py", line 1011, in _send_output
daphne_1   |     self.send(msg)
daphne_1   |   File "/usr/local/lib/python3.8/http/client.py", line 951, in send
daphne_1   |     self.connect()
daphne_1   |   File "/usr/local/lib/python3.8/site-packages/docker/transport/unixconn.py", line 30, in connect
daphne_1   |     sock.connect(self.unix_socket)
daphne_1   | urllib3.exceptions.ProtocolError: ('Connection aborted.', FileNotFoundError(2, 'No such file or directory'))
daphne_1   |
daphne_1   | During handling of the above exception, another exception occurred:
daphne_1   |
daphne_1   | Traceback (most recent call last):
daphne_1   |   File "/usr/local/lib/python3.8/site-packages/docker/api/client.py", line 214, in _retrieve_server_version
daphne_1   |     return self.version(api_version=False)["ApiVersion"]
daphne_1   |   File "/usr/local/lib/python3.8/site-packages/docker/api/daemon.py", line 181, in version
daphne_1   |     return self._result(self._get(url), json=True)
daphne_1   |   File "/usr/local/lib/python3.8/site-packages/docker/utils/decorators.py", line 46, in inner
daphne_1   |     return f(self, *args, **kwargs)
daphne_1   |   File "/usr/local/lib/python3.8/site-packages/docker/api/client.py", line 237, in _get
daphne_1   |     return self.get(url, **self._set_request_timeout(kwargs))
daphne_1   |   File "/usr/local/lib/python3.8/site-packages/requests/sessions.py", line 542, in get
daphne_1   |     return self.request('GET', url, **kwargs)
daphne_1   |   File "/usr/local/lib/python3.8/site-packages/requests/sessions.py", line 529, in request
daphne_1   |     resp = self.send(prep, **send_kwargs)
daphne_1   |   File "/usr/local/lib/python3.8/site-packages/requests/sessions.py", line 645, in send
daphne_1   |     r = adapter.send(request, **kwargs)
daphne_1   |   File "/usr/local/lib/python3.8/site-packages/requests/adapters.py", line 501, in send
daphne_1   |     raise ConnectionError(err, request=request)
daphne_1   | requests.exceptions.ConnectionError: ('Connection aborted.', FileNotFoundError(2, 'No such file or directory'))
daphne_1   |
daphne_1   | During handling of the above exception, another exception occurred:
daphne_1   |
daphne_1   | Traceback (most recent call last):
daphne_1   |   File "/usr/local/bin/daphne", line 8, in <module>
daphne_1   |     sys.exit(CommandLineInterface.entrypoint())
daphne_1   |   File "/usr/local/lib/python3.8/site-packages/daphne/cli.py", line 170, in entrypoint
daphne_1   |     cls().run(sys.argv[1:])
daphne_1   |   File "/usr/local/lib/python3.8/site-packages/daphne/cli.py", line 232, in run
daphne_1   |     application = import_by_path(args.application)
daphne_1   |   File "/usr/local/lib/python3.8/site-packages/daphne/utils.py", line 12, in import_by_path
daphne_1   |     target = importlib.import_module(module_path)
daphne_1   |   File "/usr/local/lib/python3.8/importlib/__init__.py", line 127, in import_module
daphne_1   |     return _bootstrap._gcd_import(name[level:], package, level)
daphne_1   |   File "<frozen importlib._bootstrap>", line 1014, in _gcd_import
daphne_1   |   File "<frozen importlib._bootstrap>", line 991, in _find_and_load
daphne_1   |   File "<frozen importlib._bootstrap>", line 975, in _find_and_load_unlocked
daphne_1   |   File "<frozen importlib._bootstrap>", line 671, in _load_unlocked
daphne_1   |   File "<frozen importlib._bootstrap_external>", line 843, in exec_module
daphne_1   |   File "<frozen importlib._bootstrap>", line 219, in _call_with_frames_removed
daphne_1   |   File "/app/./apps/asgi.py", line 14, in <module>
daphne_1   |     django_asgi_app = get_asgi_application()
daphne_1   |   File "/usr/local/lib/python3.8/site-packages/django/core/asgi.py", line 12, in get_asgi_application
daphne_1   |     django.setup(set_prefix=False)
daphne_1   |   File "/usr/local/lib/python3.8/site-packages/django/__init__.py", line 24, in setup
daphne_1   |     apps.populate(settings.INSTALLED_APPS)
daphne_1   |   File "/usr/local/lib/python3.8/site-packages/django/apps/registry.py", line 122, in populate
daphne_1   |     app_config.ready()
daphne_1   |   File "/app/./apps/environments/apps.py", line 8, in ready
daphne_1   |     from . import signals
daphne_1   |   File "/app/./apps/environments/signals.py", line 6, in <module>
daphne_1   |     from apps.cloud.tasks import remove_periodic_tasks
daphne_1   |   File "/app/./apps/cloud/tasks.py", line 21, in <module>
daphne_1   |     from apps.cloud.utils import (
daphne_1   |   File "/app/./apps/cloud/utils.py", line 10, in <module>
daphne_1   |     client: DockerClient = docker.from_env()
daphne_1   |   File "/usr/local/lib/python3.8/site-packages/docker/client.py", line 96, in from_env
daphne_1   |     return cls(
daphne_1   |   File "/usr/local/lib/python3.8/site-packages/docker/client.py", line 45, in __init__
daphne_1   |     self.api = APIClient(*args, **kwargs)
daphne_1   |   File "/usr/local/lib/python3.8/site-packages/docker/api/client.py", line 197, in __init__
daphne_1   |     self._version = self._retrieve_server_version()
daphne_1   |   File "/usr/local/lib/python3.8/site-packages/docker/api/client.py", line 221, in _retrieve_server_version
daphne_1   |     raise DockerException(
daphne_1   | docker.errors.DockerException: Error while fetching server API version: ('Connection aborted.', FileNotFoundError(2, 'No such file or directory'))

从错误栈可以定位到：Daphne启动时，Django初始化过程中加载了apps/cloud/utils.py里的docker.from_env()调用——这个调用试图连接宿主机的Docker守护进程，但默认容器内没有挂载Docker套接字，导致找不到套接文件报错。

提供两种解决思路：

思路一：挂载Docker套接字到容器 #

修改docker-compose.yml的Daphne服务配置，添加Docker套接字挂载：

daphne:
  platform: linux/amd64
  build:
    context: .
    dockerfile: Dockerfile.dev
  command: 'sh -c "daphne -b 0.0.0.0 -p 8000  apps.asgi:application"'
  restart: always
  volumes:
    - /var/run/docker.sock:/var/run/docker.sock  # 挂载宿主机Docker套接字

注意：如果容器内运行Daphne的用户没有读写Docker套接字的权限，需要确保该用户属于docker组，或者调整套接字权限（生产环境优先用组权限方式）。

思路二：延迟Docker客户端初始化 #

如果应用不需要在Django启动阶段就初始化Docker客户端，可以把docker.from_env()的调用延迟到实际使用时（比如任务函数内部），避免启动阶段触发连接。

修改apps/cloud/utils.py：

# 原代码
client: DockerClient = docker.from_env()

# 修改后
def get_docker_client():
    return docker.from_env()

# 在需要使用的地方调用
# client = get_docker_client()

内容的提问来源于stack exchange，提问作者Neo