docker-compose: (Re)Build Dockerfile from inside docker-compose file?

Question

Had a hard time googling this question as most suggestions is how to do it through command line which I sadly do not have access to in this environment. Is it possible to do the equivalent of

docker-compose up --build --force-recreate

From inside a docker-compose file?

Answer 1

The environment you describe sounds similar to Kubernetes in a couple of ways, except that it's driven by a Docker Compose YAML file. The strategies that work for Kubernetes will work here too. In Compose there's no way to put "actions" in a YAML file, or flag that a service always needs to be rebuilt or recreated. It sounds like the only thing it's possible to do in your environment is run docker-compose up -d.

The trick that I'd use here is to change the image: for a container whenever you have a change you need to deploy. That means the image tag needs to be something unique; it could be a date stamp or source control ID.

version: '3.8'
services:
  myapp:
    image: registry.example.com/myapp:20220209

Now when you have a change to your application, you (or your CI system) need to build a new copy of it, offline, and docker push it to a registry. Then change this image: value, and push the updated file to the deployment system. Compose will see that it's only running version 20220208 from yesterday and recreate that specific container.

If you have the ability to specify environment variables, you can use that in the Compose setup

    image: registry.example.com/myapp:${MYAPP_TAG:-latest}

to avoid having to physically modify the file.