Make the stack name available in Docker Swarm configuration as an environment variable

[antran22]

Is your feature request related to a problem? Please describe.
This request is not related to a problem, but is a minor enhancement for the application templating workflow.
For Docker Swarm cluster using a label based load balancer/reverse proxy (such as Traefik) for exposing applications, I need to specify several labels in the Docker Swarm configuration, which looks something like this:

labels:
  - traefik.enable=true
  - traefik.docker.network=traefik-public
  - traefik.constraint-label=traefik-public
  - traefik.http.routers.${STACK_NAME}-http.rule=Host(`${DOMAIN}`)
  - traefik.http.routers.${STACK_NAME}-http.entrypoints=http
  - traefik.http.routers.${STACK_NAME}-http.middlewares=https-redirect
  - traefik.http.routers.${STACK_NAME}-https.rule=Host(`${DOMAIN}`)
  - traefik.http.routers.${STACK_NAME}-https.entrypoints=https
  - traefik.http.routers.${STACK_NAME}-https.tls=true
  - traefik.http.routers.${STACK_NAME}-https.tls.certresolver=le
  - traefik.http.services.${STACK_NAME}.loadbalancer.server.port=80

The $STACK_NAME variable is used because labels for each stack must be different in order for Traefik to differentiate between stacks.

Describe the solution you'd like
We can provide the STACK_NAME variable somewhere around here.
The code would look something like this:

env := make([]string, 0)
for _, envvar := range stack.Env {
    env = append(env, envvar.Name+"="+envvar.Value)
}
env = append(env, "STACK_NAME="+stack.Name)

The variable name can be discussed so that it may not clash with existing users. PORTAINER_STACK_NAME is also a viable alternative.

Describe alternatives you've considered
For now, I have to specify STACK_NAME in the env of the App Template file in order for the configuration to interpolate correctly.

[jamescarppe]

Thanks for the feedback - I've written this up as an internal ticket for the team to assess for the future.

[robjuz]

Any update on this? I'm deploying the same stack multiple times and this is the one remaining part to make it full automated.

[sergioisidoro]

It might make sense to focus efforts on Docker itself exposing COMPOSE_PROJECT_NAME which I assume is the same in a deployed swarm stack.

docker/compose#2294