Example Docker Stack Deploy with Node/Service/Task values

docker-stackfile.yml

## docker stack deploy -c docker-stackfile.yml gist_demo
version: "3.8"

services:
  playground:
    image: node:alpine
    hostname: '{{.Task.Name}}'
    environment:
      SWARM_TASK: '{{.Task.Name}}'
      SWARM_PEERS: "tasks.{{.Service.Name}}"
      SWARM_TASK_FQN: '{{.Task.Name}}.{{index .Service.Labels "com.docker.stack.namespace"}}_default'
      SWARM_PEERS_FQN: 'tasks.{{.Service.Name}}.{{index .Service.Labels "com.docker.stack.namespace"}}_default'
      SWARM_INFO: |
        { "service": "{{.Service.Name}}", "labels": "{{.Service.Labels}}"
        , "id": "{{.Service.ID}} {{.Task.ID}} {{.Node.ID}}"
        , "node": "{{.Node}}", "task": "{{.Task.Name}}"
        , "stack": "{{index .Service.Labels "com.docker.stack.namespace"}}"
        , "image": "{{index .Service.Labels "com.docker.stack.image"}}" }

    command: 
      - 'node'
      - '-e'
      - |
        let {resolve4} = require("dns/promises"), as_err = err => ({err})
        let {HOSTNAME, SWARM_INFO, SWARM_TASK, SWARM_PEERS} = process.env
        require("http").createServer()
        .on('request', async (req,res) => {
          res.end(JSON.stringify({
            "req": [req.method, req.httpVersion, req.url],
            "info": JSON.parse(SWARM_INFO),
            "env": {HOSTNAME, SWARM_TASK, SWARM_PEERS},
            "dns": {
              HOSTNAME: await resolve4(HOSTNAME).catch(as_err),
              SWARM_TASK: await resolve4(SWARM_TASK).catch(as_err),
              SWARM_PEERS: await resolve4(SWARM_PEERS).catch(as_err),
            }}, null, 2))
        })
        .listen(3001, "0.0.0.0", ()=> {})

    ports: ["3001:3001"]
    deploy:
      replicas: 5

Do you have one where you can get the computed hostname so it can be embedded in a variable?