docker-compose with multiple files and automatic path extension

[kaninaba94]

Description

This is my folder structure:

├── project_root
│   ├── docker-compose.yml
│   ├── volume
│   │       ├── source
│   ├── folder1
│   │   ├── docker-compose.yml
│   │   ├── volume1
│   │       ├── source

docker-compose.yml:

version: "3.4"

services:
    service:
        .
        .
        volumes: ./volume/source:/volume/destination
        .

folder1/docker-compose.yml:

version: "3.4"

services:
    service1:
        .
        volumes: ./volume1/source:/volume1/destination
        .
        .

At the moment, executing docker-compose -f docker-compose.yml -f folder1/docker-compose.yml config from the project-root gives me:

version: "3.4"

services:
    service1:
        .
        .
        volumes: /home/.../project-root/volume/source:/volume1/destination
        .
    service2:
        .
        volumes: /home/.../project-root/volume1/source:/volume1/destination
        .
        .

It would be nice to have an option to combine the two docker files that automically adapts the volume source location according to the host's folder structure, like this:

version: "3.4"

services:
    service1:
        .
        .
        volumes: /home/.../project-root/volume/source:/volume1/destination
        .
    service2:
        .
        volumes: /home/.../project-root/folder1/volume1/source:/volume1/destination
        .
        .

Note the changed volume source location in service2.

[kaninaba94]

There would have to be a way to insert the file location into the docker-compose config.

Doesn't anybody else think that this would be a useful feature? It would mean you could more flexibly plug in software modules.

[ndeloof]

The way ./ is expanded to actual path in a compose file is a mix of legacy decision, which results sometimes in weird behaviors. I agree we should add support for a "relative to compose file" path notation, but to avoid ambiguities and compatibility break, this would need to rely on a new notation, aside ./path and ~/path we already support.
I'm open to suggestions :)

[kaninaba94]

My suggestion is to introduce a flag, e.g. --relative-to-compose-file, which would lead to the behavior. That way, we would avoid legacy issues. And perhaps it would be used in more and more systems.

[ndeloof]

The risk with a flag is that some users would rely on it on a daily basis but might forget to set the flag, still we can't make this the default behavior. An explicit syntax in the compose file would avoid this issue.

[kaninaba94]

If it is possible to have an environment variable named, e.g., CONFIG_PATH that is passed to each config file individually, that would be convenient and would eliminate the need for additional syntax. E.g., if you do docker-compose -f docker-compose.yml -f folder1/docker-compose.yml -f folder2/folder21/docker-compose.yml config, and the individual files look like this:

version: "3.4"

services:
    service:
.
.
        volumes:
            - ./${CONFIG_PATH}/volume_path:volume_path
.
.

version: "3.4"

services:
    service1:
.
.
        volumes:
            - ./${CONFIG_PATH}/volume1_path:volume1_path
.
.

version: "3.4"

services:
    service21:
.
.
        volumes:
            - ./${CONFIG_PATH}/volume21_path:volume21_path
.
.

then CONFIG_PATH would resolve to , folder1 and folder2/folder21 in the resulting config.

Alternatively, the CONFIG_PATH could be resolved to the absolute paths.

[ndeloof]

closing this issue, please see compose-spec/compose-go#335