Dockerfile build from parent directory

Question

I have a python application which uses celery workers which I would like to dockerise. Unfortunately, both python and Celery are using the same code base. Although they have to be separate containers for easier scaling. If I build them separately and run the containers it works fine. The problem starts when I introduce docker-compose, therefore I can't swap the dockerfiles out in the code folder and the containers need to be built from outside of the folder. The folder structure is the following:

/application
    /application-build
       Dockerfile
    /celery-build
       Dockerfile
    /code
       application.py
       otherfiles.py

I have been digging around for a bit now and unfortunately, as far as I know files from the parent directory can't be copied in the dockerfile. Although I would like to copy the same code into both of the containers. (Mind that the following dockerfiles are not the exact ones I use.)

Dockerfile1:

FROM python:3.6
ADD /code .
COPY requirements.txt requirements.txt
RUN python3.6 -m pip install -r requirements.txt
CMD ["python3.6", "application.py"]

Dockerfile2:

FROM python:3.6
ADD /code .
COPY /code/requirements.txt .
RUN python3.6 -m pip install -r requirements.txt
CMD ["celery","-A application.celery", "worker","work1@host"]

One solution I see is to reorganise the folders so the code directory is always the child of the dockerfile's directory like so:

/application
   /application-build
      Dockerfile
      /celery-build
         Dockerfile
         /code
            application.py
            otherfiles.py

Although it doesn't look clever at all.

Answer 1

There is no problem. In Dockerfile you cant get out (access parent folder) of build context, not Dockerfile's folder.

Leave you structure as it was, and explicitly specify path to Dockerfile:

docker build -t app -f application-build/Dockerfile . 
docker build -t celery -f celery-build/Dockerfile . 

And inside your Dockerfiles remember that path is /application. So you can easily copy:

Dockerfile

...
COPY code /code
...

Answer 2

Supplementing grapes's answer with a Docker Compose equivalent to the docker build commands:

# docker-compose.yml
version: '3.7'

services:
  application:
    build:
      context: .
      dockerfile: application-build/Dockerfile

  celery:
    build:
      context: .
      dockerfile: celery-build/Dockerfile

# Run this command in the directory of your `docker-compose.yml` file
# (Which is this question's case would be /application/docker-compose.yml)
docker-compose build

When each Dockerfile builds, it will use /application as its build context.