Passing arguments for Dockerfiles using Docker compose

Question

I'm trying to use parametrize my dockerfiles on build phase and use arguments in Docker-compose. For example in Docker compose I have defined one service called bpp as following:

bpp:
  build:
    context: .
    dockerfile: Dockerfile.bpp
    args:
      gp : 8080
  image: serv/bpp
  restart: always
  depends_on:
    - data
  links:
    - data

I'm trying to pass argument named gp to Dockerfile.bpp, where I'm using argument when starting a Python application, exposing a port etc. For example in dockerfile.bpp in trying to expose port gp as following:

EXPOSE gp

However, when building docker file by command docker-compose build I get following error: ERROR: Service 'bpp' failed to build: Invalid containerPort: gp

It seems that argument gp is not visible in dockerfile. Any suggestions?

Answer 1

You need to add ARG gp to your Dockerfile.

...
ARG gp

EXPOSE $gp
...

https://docs.docker.com/engine/reference/builder/#arg

Worth mentioning that this isn't going to expose the port when you're running it via compose though, you would need to add a ports instruction to your docker-compose.yml for that.

Answer 2

First, the syntax is:

build:
  args:
    buildno: 1
    user: someuser

build:
  args:
    - buildno=1
    - user=someuser

So try with gp: 8080, not gp : 8080.

Second, make sure you are using version 2 of the docker-compose.yml format.

Third, try

EXPOSE $gp