docker-compose dynamic volume names for replicas

moved over from https://github.com/moby/moby/issues/43079

Tried some of the "solutions" from this thread and stackoverflow. No swarm, node or other hosts at all. Just trying to get it to work locally first without starting containers around docker-compose. Main idea is to get rid of these copies and just use replicas:

  configsvr0:
    image: mongo
    command: mongod --configsvr --replSet configsvr --port 27017 --dbpath /data/db --keyFile /data/keyfile
    volumes:
      - configsvr0:/data/db
      - ./keyfile:/data/keyfile:ro
  configsvr1:
    image: mongo
    command: mongod --configsvr --replSet configsvr --port 27017 --dbpath /data/db --keyFile /data/keyfile
    volumes:
      - configsvr1:/data/db
      - ./keyfile:/data/keyfile:ro
  configsvr2:
    image: mongo
    command: mongod --configsvr --replSet configsvr --port 27017 --dbpath /data/db --keyFile /data/keyfile
    volumes:
      - configsvr2:/data/db
      - ./keyfile:/data/keyfile:ro

volumes:
  configsvr0:
  configsvr1:
  configsvr2:

See the difference? It's just counting up on the volume name...

It would be great to just have something like this:

  configsvr0:
    image: mongo
    command: mongod --configsvr --replSet configsvr --port 27017 --dbpath /data/db --keyFile /data/keyfile
    volumes:
      - configsvr:/data/db
      - ./keyfile:/data/keyfile:ro

volumes:
  configsvr:
    name: 'configsvr-{{.Task.Slot}}'

Tried this (see below) but it didn't work.

Note: Below I only copied small junks from my yml that I thought are important for this.

test 1 - volume name

would require to add entries under volumes so that's not really dynamic - but I gave it a try:

    volumes:
      - "configsvr{{.Task.Slot}}:/data/db"

➜  msc git:(develop) ✗ docker-compose up configsvr0
service "configsvr0" refers to undefined volume configsvr{{.Task.Slot}}: invalid compose project

test2 - dynamic name with task slot

that would be dynamic but still doesn't work though it was accepted in stackoverflow. That's actually my sample from top.

    volumes:
      - configsvr:/data/db

volumes:
  configsvr:
    name: 'configsvr-{{.Task.Slot}}'

➜  msc git:(develop) ✗ docker-compose up configsvr0
[+] Running 0/0
 ⠿ Volume "configsvr-{{.Task.Slot}}"  Error                                                                                                                                                          0.0s
Error response from daemon: create configsvr-{{.Task.Slot}}: "configsvr-{{.Task.Slot}}" includes invalid characters for a local volume name, only "[a-zA-Z0-9][a-zA-Z0-9_.-]" are allowed. If you intended to pass a host directory, use absolute path

my env

mac monteray with docker desktop.

➜  msc git:(develop) ✗ docker -v
Docker version 20.10.11, build dea9396
➜  msc git:(develop) ✗ docker-compose -v
Docker Compose version v2.2.1

docker-compose.yml version: 3.9

Start by reproducing the two documented examples with Docker Compose v2.2.1, using the provided docker-compose.yml snippets and the reported docker-compose up configsvr0 commands. Read the Compose handling for service replicas and volume names; done means a single declared volume can produce valid per-replica names without requiring copied service or volume entries.