Dockerfile can't find app.py

Question

I have the following folder structure in a flask app that I am embedding in a docker image.

├── Dockerfile
├── README.md
├── app
│   ├── __init__.py
│   ├── app.py
│   ├── db
│   ├── imgcomp
│   │   └── __init__.py
│   ├── static
│   └── templates
│       ├── comparison_result.html
│       ├── display_images.html
│       ├── index.html
│       └── upload.html
├── docker-compose.yml
├── requirements.txt
└── tests

These are the contents of the docker-compose.yml:

version: '2'
services:
    web:
    build: .
    ports:
       - "5000:5000"
    volumes:
       - .:/code

These are the contents of Dockerfile:

FROM python:3.4-alpine
ADD . /code
WORKDIR /code
RUN pip install -r requirements.txt
CMD ["python", "app.py"]

When I run docker-compose up, I get the error:

web_1  | python: can't open file 'app.py': [Errno 2] No such file or directory

Simply because its in the subfolder. Changing the argument to app/app.py doesn't help. Also, when I run docker-compose down, then edit the file, it doesn't seem to be registering any changes to the file when I run docker-compose up again. What am I missing?

Answer 1

You have the same problem in issue 1616

the issue appears to primarily be a consequence of the ADD/WORKDIR in the Dockerfile:

ADD . /code
WORKDIR /code

Conflicting with the volume mapping in the docker-compose.yml

volumes:
 - .:/code

I may have misread the instructions but had both.

The reason:

When running an app on a remote host, you'll need to remove any volumes entries that mount anything in from a local directory.

The reason we promote both adding your code to the image and mounting it as a volume is so that doing a docker-compose build gets you an image that's ready to deploy to a remote server, but whose code can still be mounted when developing locally so it can be live-reloaded.

If you want to use Compose to both develop an app locally and deploy it to the cloud, the best practice is to have a file for each - docker-compose.yml for local development and something else (eg remote.yml ) for remote deployment - and use the -f flag to pass the alternate file in when deploying.

You can use the extends option to reduce duplication between both files.

---

On Windows, be careful about your path and its shared state: see issue 3157 .

Answer 2

For windows:

One solution is removing the "volume" in your "docker-compose.yml" .

The problem is, it will not update/sync your files in your host. (That is my case) I tried playing around with volumes and found out that the "." in volume ( ".:/code" ) is not working. It makes my code directory in docker empty.

What I would suggest to do is transfer your project in C:/Users/YourUsername/ (Can be a deeper directory, as long it's under the path), then in volume parameter in docker-compose, change the ".:/code" to "C:/Users/YourUsername/project_folder:/code"