python - 使用 docker 部署时 Flask CLI 抛出 "[Errno 2] No such file"

Question

我正在学习 testdriven.io 上的微服务类(class)。在本类(class)中，我需要使用 Docker 部署 Flask 应用程序。为了运行我使用 Flask-cli 的应用程序，它在启动时给我一个错误:

No such file or directory: '/usr/src/app/manage.py': '/usr/src/app/manage.py'

为了部署容器，我使用 Docker-compose。我在我的 Windows 10 机器上运行命令并使用标准 Python 图像 (python:3.7.2-alpine)。我已经尝试更改文件的权限，但没有帮助。

这是我的撰写文件的样子:

version: '3.7'

services:

  users:
    build:
      context: ./services/users
      dockerfile: Dockerfile-dev
    volumes:
      - './services/users:/usr/src/app'
    ports:
      - 6001:6000
    environment:
      - FLASK_APP=project/__init__.py
      - FLASK_ENV=development
      - COMPOSE_CONVERT_WINDOWS_PATHS=1

我的 docker 文件:

# base image
FROM python:3.7.2-alpine

# set working directory
WORKDIR /usr/src/app

# add and install requirements
COPY ./requirements.txt /usr/src/app/requirements.txt
RUN pip install -r requirements.txt

# add app
COPY . /usr/src/app

# i tried to give it the right rights.. but it didn't help
RUN chmod +x /usr/src/app/manage.py

# run server
CMD python manage.py run -h 0.0.0.0

我的 manage.py 文件将启动应用程序:

#!/usr/bin/python3
# services/users/manage.py

from flask.cli import FlaskGroup

from project import app

cli = FlaskGroup(app)

if __name__ == '__main__':
    cli()

所以我希望这会启动应用程序并使其在端口 6001 上可用，但它会给我以下错误:

Successfully tagged testdriven-app_users:latest
Recreating testdriven-app_users_1 ... done
Attaching to testdriven-app_users_1
users_1  |  * Serving Flask app "project/__init__.py" (lazy loading)
users_1  |  * Environment: development
users_1  |  * Debug mode: on
users_1  |  * Running on http://0.0.0.0:5000/ (Press CTRL+C to quit)
users_1  |  * Restarting with stat
users_1  | Traceback (most recent call last):
users_1  |   File "manage.py", line 11, in <module>
users_1  |     cli()
users_1  |   File "/usr/local/lib/python3.7/site-packages/click/core.py", line 764, in __call__
users_1  |     return self.main(*args, **kwargs)
users_1  |   File "/usr/local/lib/python3.7/site-packages/flask/cli.py", line 557, in main
users_1  |     return super(FlaskGroup, self).main(*args, **kwargs)
users_1  |   File "/usr/local/lib/python3.7/site-packages/click/core.py", line 717, in main
users_1  |     rv = self.invoke(ctx)
users_1  |   File "/usr/local/lib/python3.7/site-packages/click/core.py", line 1137, in invoke
users_1  |     return _process_result(sub_ctx.command.invoke(sub_ctx))
users_1  |   File "/usr/local/lib/python3.7/site-packages/click/core.py", line 956, in invoke
users_1  |     return ctx.invoke(self.callback, **ctx.params)
users_1  |   File "/usr/local/lib/python3.7/site-packages/click/core.py", line 555, in invoke
users_1  |     return callback(*args, **kwargs)
users_1  |   File "/usr/local/lib/python3.7/site-packages/click/decorators.py", line 64, in new_func
users_1  |     return ctx.invoke(f, obj, *args, **kwargs)
users_1  |   File "/usr/local/lib/python3.7/site-packages/click/core.py", line 555, in invoke
users_1  |     return callback(*args, **kwargs)
users_1  |   File "/usr/local/lib/python3.7/site-packages/flask/cli.py", line 771, in run_command
users_1  |     threaded=with_threads, ssl_context=cert)
users_1  |   File "/usr/local/lib/python3.7/site-packages/werkzeug/serving.py", line 988, in run_simple
users_1  |     run_with_reloader(inner, extra_files, reloader_interval, reloader_type)
users_1  |   File "/usr/local/lib/python3.7/site-packages/werkzeug/_reloader.py", line 332, in run_with_reloader
users_1  |     sys.exit(reloader.restart_with_reloader())
users_1  |   File "/usr/local/lib/python3.7/site-packages/werkzeug/_reloader.py", line 176, in restart_with_reloader
users_1  |     exit_code = subprocess.call(args, env=new_environ, close_fds=False)
users_1  |   File "/usr/local/lib/python3.7/subprocess.py", line 323, in call
users_1  |     with Popen(*popenargs, **kwargs) as p:
users_1  |   File "/usr/local/lib/python3.7/subprocess.py", line 775, in __init__
users_1  |     restore_signals, start_new_session)
users_1  |   File "/usr/local/lib/python3.7/subprocess.py", line 1522, in _execute_child
users_1  |     raise child_exception_type(errno_num, err_msg, err_filename)
users_1  | FileNotFoundError: [Errno 2] No such file or directory: '/usr/src/app/manage.py': '/usr/src/app/manage.py'
testdriven-app_users_1 exited with code 1

Answer 1

当您执行脚本时，内核会查找在 shebang (#!) 中指定的解释器。提取解释器的位置，然后启动解释器(例如 python3)，执行脚本本身。如果未找到解释器二进制文件，执行将失败并出现 No such file or directory (ENOENT) 错误(根据 man 2 execve):

ERRORS
<...>
    ENOENT The file filename or a script or ELF interpreter does not exist,
           or a shared library needed for the file or interpreter cannot be found.

您已在您的 shebang 中指定了 #!/usr/bin/python3，但在您使用 (python:3.7.2-alpine) 的基础镜像中 python3 二进制文件在不同的位置:

$ docker run -it python:3.7.2-alpine sh
/ # which python3
/usr/local/bin/python3

因此，即使您的应用程序在您的主机本地运行(如果是 Windows，它甚至可能不关心 shebang)，当您将它移入 Docker 容器时它会停止运行。

为了避免这种情况，脚本中的 shebang 通常不是指解释器本身 (#!/usr/bin/python3)，而是指 /usr/bin/env 二进制，查找并执行解释器:

#!/usr/bin/env python3

当您通过 env 运行 python3 时，后者通过 PATH 执行搜索，因此它允许您的 shebang 不依赖于特定位置python3 二进制文件。

最后，您的脚本的正确版本如下:

#!/usr/bin/env python3
# services/users/manage.py

from flask.cli import FlaskGroup

from project import app

cli = FlaskGroup(app)

if __name__ == '__main__':
    cli()