How to create a common base docker image for flask and celery applications

Question

My project using flask and celery libraries. I have deployed my application in AWS ECS Fargate. Here are the two docker files for flask and celery.

# Flask Docker File
FROM python:3.6

RUN apt-get update -y

RUN pip3 install pipenv

ENV USER dockeruser
RUN useradd -ms /bin/bash $USER

ENV APP_PATH /home/$USER/my_project
RUN mkdir -p $APP_PATH
COPY . $APP_PATH
WORKDIR $APP_PATH

RUN chown -R $USER:$USER $APP_PATH

RUN pipenv install --system --deploy

USER $USER

EXPOSE 5000

CMD gunicorn run:my_app -b 0.0.0.0:5000 -w 4

# Celery Docker File
FROM python:3.6

RUN apt-get update -y

RUN pip3 install pipenv

ENV USER dockeruser
RUN useradd -ms /bin/bash $USER

ENV APP_PATH /home/$USER/my_project
RUN mkdir -p $APP_PATH
COPY . $APP_PATH
WORKDIR $APP_PATH

RUN chown -R $USER:$USER $APP_PATH

RUN pipenv install --system --deploy

USER $USER

CMD celery -A celery_tasks.celery worker -l INFO -E --autoscale=2,1 -Q apple,ball,cat

Both docker files are the same for celery and flask application. Is there is a way to create a common base image file both docker files? I am using AWS ECR to store docker images.

Answer 1

You can start a Dockerfile FROM any image you want, including one you built yourself. If you built the Flask image as

docker build -t me/flaskapp .

then you can build a derived image that just overrides its CMD as

FROM me/flaskapp
CMD celery -A celery_tasks.celery worker -l INFO -E --autoscale=2,1 -Q apple,ball,cat

If you prefer you can have an image that includes the source code but no default CMD . Since you can't un- EXPOSE a port, this has the minor advantage that it doesn't look like your Celery worker has a network listener. ("Expose" as a verb means almost nothing in modern Docker, though.)

FROM me/code-base
EXPOSE 5000
CMD gunicorn run:my_app -b 0.0.0.0:5000 -w 4

@Frank's answer suggests a Docker Compose path. If you're routinely using Compose you might prefer that path, since there's not an easy way to make it build multiple images in correct dependency order. All of the ways to run a container have a way to specify an alternate command (from extra docker run options through a Kubernetes pod command: setting) so this isn't an especially limiting approach. Conversely, in a CI environment, you generally can specify multiple things to build in sequence, but you'll probably want to use an ARG to specify the image tag .

Answer 2

I think you can use docker-compose( https://docs.docker.com/compose/ ). You can specify more than 1 docker instance inside docker-compose YAML config file and run them base on the same docker image.

One Example:

test.yaml:

version: '2.0'
services:
  web:
    image: sameimage
    ports:
    - "5000:5000"
    volumes:
    - .:/code
    - logvolume01:/var/log
    links:
    - redis
    command: ["gunicorn", "run:my_app", "-b", "0.0.0.0:5000", "-w", "4"]
  celery:
    image: sameimage
    command: ["celery", "-A", "celery_tasks.celery"]
volumes:
  logvolume01: {}

You can run it by:

docker-compose -f test.yaml -p sameiamge up --no-deps