Swarm webhook

Quick start

Create a docker-compose.yaml file with the following content:

version: "3"

services:
  webhook:
    image: ghcr.io/zazuko/swarm-webhook
    volumes:
      - "/var/run/docker.sock:/var/run/docker.sock"
    ports:
      - 3000:3000
    environment:
      - SERVER_HOST=0.0.0.0
      - SERVER_PORT=3000
    deploy:
      placement:
        constraints:
          - node.role == manager

  nginx:
    image: nginx:1.21-alpine
    deploy:
      mode: replicated
      replicas: 0
      labels:
        - swarm.webhook.enabled=true
        - swarm.webhook.name=nginx
      restart_policy:
        condition: none

  nginx-two:
    image: nginx:1.21-alpine
    deploy:
      mode: replicated
      replicas: 0
      labels:
        - swarm.webhook.enabled=true
        - swarm.webhook.name=nginx-two
      restart_policy:
        condition: none

Make sure you have a Swarm cluster (docker swarm init), and run the stack using:

docker stack deploy -c docker-compose.yaml swarm-webhook

Some actions:

• http://127.0.0.1:3000/ : list all containers with webhook enabled
• http://127.0.0.1:3000/start/nginx : start the container for the nginx service
• http://127.0.0.1:3000/stop/nginx : stop the container for the nginx service
• http://127.0.0.1:3000/start/nginx-two : start the container for the nginx-two service
• http://127.0.0.1:3000/stop/nginx-two : stop the container for the nginx-two service

You can use docker ps to see the containers that are running.

To remove the stack, use:

docker stack rm swarm-webhook

Use it in your stack

Deploying the webhook service

You have to deploy the webhook service:

webhook:
  image: ghcr.io/zazuko/swarm-webhook
  volumes:
    - "/var/run/docker.sock:/var/run/docker.sock"
  ports:
    - 3000:3000
  environment:
    - SERVER_HOST=0.0.0.0
    - SERVER_PORT=3000
  deploy:
    placement:
      constraints:
        - node.role == manager

You can use following environment variables:

• SERVER_PORT: configure the server port (default: 3000)
• SERVER_HOST: configure the server host (default: ::)

Configure your services

You will have to edit the deploy part of your services to have something like the following:

your-service:
  # …
  deploy:
    mode: replicated
    replicas: 0
    labels:
      - swarm.webhook.enabled=true
      - swarm.webhook.name=your-service
    restart_policy:
      condition: none

The swarm.webhook.enabled=true is useful to filter only on services having this label.

You will also have to add the swarm.webhook.name=your-service label (by changing your-service with something which is unique). This will be the part you should provide in the URL: WEBHOOK_URL/start/your-service.

If you want to run multiple instances for a specific service, you can add the following label: swarm.webhook.replicas=2 (replace 2 with the desired number of replicas). The default value is 1.