docker-compose dynamic volume names for replicas

[mbogner]

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

[thaJeztah]

(let me leave this comment here as well)

In general, I think that having some templating options added to the compose-spec would be a nice addition in addition to substituting environment-variables (I recall I started writing up some ideas, but never got round to completing those 😓).

That said, it will likely require some discussion, as the idea behind the compose-spec is to also make it portable enough to be useful in different scenarios (e.g. also to include deploy to ACI and ECR; https://docs.docker.com/cloud/ecs-integration/), so it may need to be looked into of all of those are "portable" enough to be used for such cases.

[Murazaki]

Hi, I see this issue is closed, is there an available solution to do this today ?

[traverseda]

@mbogner is there a PR to go along with marking this as completed? I can't find any documentation on this feature, or when it will be available.

[mbogner]

I haven't heard about any update. Can't remember why I closed the issue.

[tobiasbhn]

+1 for this feature. any updates on this?

[JavierCane]

just in case this helps anyone, at least in my case (Docker Swarm) it worked fine with something like @mbogner showed in the "test2 - dynamic name with task slot" approach from the original post. Here you have the example:

Considerations regarding template variables:

• '{{.Service.Name}}_{{.Task.Slot}}' produce volume names like:
  • n8n_n8n-main_1
  • n8n_n8n-worker_1
  • n8n_n8n-worker_2
• If you use {{.Task.Name}} it will include the unique identifier of the task, so you will be generating a new volume each time you restart a container while updating the n8n version for instance
• You have to reference them from the services with the volumes key, that is, n8n_data in my case

Full example:

version: '3.7'

volumes:
  n8n_data:
    name: '{{.Service.Name}}_{{.Task.Slot}}'
  redis_data:

x-common-env: &common-env
  NODE_ENV: production
  N8N_LOG_LEVEL: warn
  EXECUTIONS_MODE: queue
  QUEUE_BULL_REDIS_HOST: redis
  DB_TYPE: postgresdb
  # … (redacted for brevity)

services:
  n8n-main:
    image: n8nio/n8n:1.40.0
    ports:
      - "80:5678"
    environment:
      <<: *common-env
    volumes:
      - n8n_data:/home/node/.n8n
      - /home/${user}/n8n-workflow_executions_shared_files:/home/node/n8n-workflow_executions_shared_files
    deploy:
      replicas: 1
      # … (redacted for brevity)

  n8n-worker:
    image: n8nio/n8n:1.40.0
    command: worker
    environment:
      <<: *common-env
      # Specific configuration for workers
      QUEUE_HEALTH_CHECK_ACTIVE: "true"
      QUEUE_HEALTH_CHECK_PORT: 5678
    volumes:
      - n8n_data:/home/node/.n8n
      - /home/${user}/n8n_workflow_executions-shared_files:/home/node/n8n_workflow_executions-shared_files
    deploy:
      replicas: 3
      # … (redacted for brevity)

  redis:
    image: "redis:7.2.4"
    volumes:
      - redis_data:/data
    deploy:
      replicas: 1
      # … (redacted for brevity)