Question

How to target a particular stage in a Docker image using App Platform?

Posted on November 12, 2023
Docker DigitalOcean App Platform
Asked by Aplato

I’m trying to create a new project using DigitalOcean’s App Platform with a monorepo. I’m loosely following this guide on how to structure the project, but I’m not sure how to target a particular build step within DigitalOcean.

This is the Docker command:

docker build . --target app1 --tag app1:latest

This is how I would target it in docker compose:

version: '3.8'
services:
    web:
        container_name: sample-app1
        image: sample-app1
        build:
            context: .
            target: app1
        ports:
            - '3000:3000'

Is there a way I can configure this using the App Platform?

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Bobby Iliev

Site Moderator

• November 27, 2023

Accepted Answer

Hey @aplato,

I believe that this is not available as an app spec argument yet:

https://docs.digitalocean.com/products/app-platform/reference/app-spec/

The best thing to do to get your voice heard regarding this would be to head over to our Product Ideas board and post a new idea, including as much information as possible for what you’d like to see implemented.

https://ideas.digitalocean.com/

For the time being, since the docker_build_target attribute is not supported yet, you would need to structure your Dockerfile to have the desired target stage as the last stage in the Dockerfile when using the App Platform. That way, the App Platform builds the final image based on the last stage of your Dockerfile by default.

Alternatively, you can build your Docker images externally (using GitHub Actions, GitLab CI/CD, or another CI/CD tool), push the images to a container registry (like Docker Hub or DigitalOcean Container Registry), and then deploy the pre-built images to the App Platform.

Hope that helps!

- Bobby.