A repo that contains your Rancher stack (I put mine inside of a folder called 'stack' -- docker-compose.yml -- rancher-compose.yml
Rancher Environment set-up with at least one active host
Rancher Environment set-up with a stack (empty or not)
Rancher Environment Access and Secret Keys

Parameter Reference

The plugin requires the following:

image: dubc/drone-rancher-stack-v1
url: The url where your rancher resides. E.g rancher.domain.com
stack: This stack must already exist in your rancher environment. E.g app-staging
accesskey: Your Rancher environment Access_Key
secretkey: Your Rancher environment Secret_Key
pull: Makes sure you get the latest plugin version. E.g true

Drone Pipeline Example

pipeline:
  compile-javascript:
    image: node:8.9.4
    commands:
      - yarn
      - yarn build
      - git clone 'https://github.com/USERNAME/app-rancher-stack.git' rancher

  docker-registry-push:
    image: plugins/docker
    repo: registry.domain.com:5000/app
    registry: registry.domain.com:5000
    username: REGISTRY_USERNAME
    password: REGISTRY_PASSWORD
    insecure: true
    pull: true
        
  rancher-v1-staging-upgrade:
    image: dubc/drone-rancher-stack-v1
    url: rancher.domain.com
    stack: app-staging        
    accesskey: RANCHER_ACCESS_KEY
    secretkey: RANCHER_SECRET_KEY
    pull: true

Drone Step Output

rancher-compose.yml @ /drone/src/github.com/USERNAME/app/rancher/stack/rancher-compose.yml
version: "2"
services:
  app:
    scale: 1
    start_on_create: true

docker-compose.yml @ /drone/src/github.com/USERNAME/app/rancher/stack/docker-compose.yml
version: "2"
services:
  app:
    ports:
    - "80:80/tcp"
    expose:
    - "80"
    labels:
      io.rancher.container.pull_image: always
    image: registry.domain.com:5000/app:latest

Deploying Rancher Stack with force upgrade
time="2018-07-01T00:51:38Z" level=debug msg="Environment Context from file : map[]" 
time="2018-07-01T00:51:38Z" level=debug msg="Opening compose files: /drone/src/github.com/USERNAME/app/rancher/stack/docker-compose.yml" 
time="2018-07-01T00:51:38Z" level=debug msg="Opening rancher-compose file: /drone/src/github.com/USERNAME/app/rancher/stack/rancher-compose.yml" 
time="2018-07-01T00:51:38Z" level=debug msg="[0/1] [app]: Adding " 
time="2018-07-01T00:51:38Z" level=debug msg="Looking for stack app-staging" 
time="2018-07-01T00:51:38Z" level=debug msg="Found stack: app-staging(1st92)" 
time="2018-07-01T00:51:38Z" level=debug msg="Launching action for app" 
time="2018-07-01T00:51:38Z" level=debug msg="Project [app-staging]: Creating project " 
time="2018-07-01T00:51:38Z" level=info msg="[0/1] [app]: Creating " 
time="2018-07-01T00:51:38Z" level=debug msg="Finding service app" 
time="2018-07-01T00:51:38Z" level=debug msg="Found service app" 
time="2018-07-01T00:51:38Z" level=info msg="[0/1] [app]: Created " 
time="2018-07-01T00:51:38Z" level=debug msg="Project [app-staging]: Project created " 
time="2018-07-01T00:51:38Z" level=debug msg="Launching action for app" 
time="2018-07-01T00:51:38Z" level=debug msg="Project [app-staging]: Starting project " 
time="2018-07-01T00:51:38Z" level=info msg="[0/1] [app]: Starting " 
time="2018-07-01T00:51:38Z" level=debug msg="Finding service app" 
time="2018-07-01T00:51:38Z" level=debug msg="Found service app" 
time="2018-07-01T00:51:41Z" level=info msg="Finished pulling registry.domain.com:5000/app:latest" 
time="2018-07-01T00:51:41Z" level=debug msg="Finding service app" 
time="2018-07-01T00:51:41Z" level=debug msg="Found service app" 
time="2018-07-01T00:51:41Z" level=info msg="Updating app" 
time="2018-07-01T00:51:41Z" level=info msg="Upgrading app" 
time="2018-07-01T00:51:46Z" level=debug msg="Finding service app" 
time="2018-07-01T00:51:46Z" level=debug msg="Found service app" 
time="2018-07-01T00:51:46Z" level=info msg="[1/1] [app]: Started " 
time="2018-07-01T00:51:46Z" level=debug msg="Project [app-staging]: Project started "

Notes

Rancher compose is pre-configured to force stack upgrade which will also create the stack if it doesn't exist
Rancher Compose is baked into the plugin container and isn't configurable as it is the latest for the Rancher 1.6 stable
Future versions will not take into account Rancher 2.1, I will create a new plugin for it called dubc/drone-rancher-stack-v2