Share volumes between separate docker compose files

Question

I am trying to allow nginx to proxy between multiple containers while also accessing the static files from those containers.

To share volumes between containers created

Answer 1

By separating the 2 docker-compose.yml files as you did in your question, 2 different volumes are actually created; that's the reason you don't see data from web service inside volume of nginx service, because there are just 2 different volumes.

Example : let's say you have the following structure :

example/
    |- web/
        |- docker-compose.yml # your first docker compose file
    |- nginx/
        |- docker-compose.yml # your second docker compose file

Running docker-compose up from web folder (or docker-compose -f web/docker-compose.yml up from example directory) will actually create a volume named web_static-files (name of the volume defined in docker-compose.yml file, prefixed by the folder where this file is located).

So, running docker-compose up from nginx folder will actually create nginx_static-files instead of re-using web_static-files as you want.

You can use the volume created by web/docker-compose.yml by specifying in the 2nd docker compose file (nginx/docker-compose.yml) that this is an external volume, and its name :

volumes:
  static-files:
    external:
      name: web_static-files

Note that if you don't want the volume (and all resources) to be prefixed by the folder name (default), but by something else, you can add -p option to docker-compose command :

docker-compose \
    -f web/docker-compose.yml \
    -p abcd \
    up

This command will now create a volume named abcd_static-files (that you can use in the 2nd docker compose file).

You can also define the volumes creation on its own docker-compose file (like volumes/docker-compose.yml) :

version: '3.6'

volumes:
  static-files:

And reference this volume as external, with name volumes_static-files, in web and nginx docker-compose.yml files :

volumes:
  volumes_static-files:
    external: true

Unfortunately, you cannot set the volume name in docker compose, it will be automatically prefixed. If this is really a problem, you can also create the volume manually (docker volume create static-files) before running any docker-compose up command (I do not recommand this solution though because it adds a manual step that can be forgotten if you reproduce your deployment on another environment).