docs.facundoitest.space

To recall how to deploy a Swarm service, you might use a command like:

history | grep deploy

Here’s an example of a command to remove and deploy a Swarm service:

docker service rm homepage_homepage && docker stack deploy -c /home/facundo/homepage/docker-compose.yml homepage

The contents of the `docker-compose.yml` are as follows:

version: "3.3"
services:

  homepage:
    image: ghcr.io/gethomepage/homepage:latest
    restart: always
    ports:
      - 3080:3000
    volumes:
      - /mnt/swarm/homepage:/app/config # Make sure your local config directory exists
    deploy:
      replicas: 1
      restart_policy:
        condition: on-failure
      placement:
        constraints: [node.role != manager]

When you run the deployment command, you might see the following output:

Ignoring unsupported options: restart

Since --detach=false was not specified, tasks will be created in the background.
In a future release, --detach=false will become the default.
Creating service homepage_homepage

1. Command Breakdown

• `docker service rm homepage_homepage`:
  1. This command removes the existing service named `homepage_homepage`. This is useful to ensure a clean state before deploying the new service.

• `docker stack deploy -c /home/facundo/homepage/docker-compose.yml homepage`:
  1. This command deploys a stack using the specified Compose file (`docker-compose.yml`). The stack is named `homepage`.

2. YAML File Breakdown

version: "3.3" # Specifies the version of the Docker Compose file format

services: # Defines the services that make up the application

  homepage: # Name of the service
    image: ghcr.io/gethomepage/homepage:latest # Specifies the Docker image to use
    restart: always # This option is ignored in Swarm mode (only used in standalone Docker)
    ports:
      - 3080:3000 # Maps port 3080 on the host to port 3000 in the container
    volumes:
      - /mnt/swarm/homepage:/app/config # Mounts a volume from the host to the container
    deploy:
      replicas: 1 # Specifies the number of service replicas to run
      restart_policy:
        condition: on-failure # Defines the restart policy for failed tasks
      placement:
        constraints: [node.role != manager] # Ensures that the service runs only on worker nodes, not on the manager

3. Ignored Options and Output Explanation

• Ignoring unsupported options: restart:
  1. The `restart: always` option is used in standalone Docker configurations and is not supported in Swarm mode. In Swarm mode, restart policies are defined within the `deploy` section.

• Since –detach=false was not specified, tasks will be created in the background.:
  1. By default, `docker stack deploy` creates tasks in the background. This message indicates that the tasks are being created asynchronously. If you want to wait for the service to be fully deployed, you can use the `–detach=false` flag.

4. Why This Works

• Service Removal: By removing the existing service with `docker service rm`, you ensure that any previous configurations or issues are cleared before deploying the new service.

• Stack Deployment: The `docker stack deploy` command reads the specified Compose file and creates the defined services as part of a stack. It handles the deployment and orchestration of the services.

• YAML Configuration: The YAML file specifies the service details, including the image to use, port mappings, volume mounts, number of replicas, restart policy, and placement constraints. Docker Swarm uses this configuration to deploy and manage the service.

• Review Docker Swarm Documentation: Familiarize yourself with Docker Swarm concepts and commands. The official documentation is a great resource: [Docker Swarm Documentation](https://docs.docker.com/engine/swarm/).

• Monitoring and Logging: Consider setting up monitoring and logging for your Swarm services to keep track of their health and performance. Tools like Prometheus, Grafana, and the ELK stack (Elasticsearch, Logstash, Kibana) are popular choices.

• Backup and Recovery: Ensure that you have a backup strategy for your configurations and data. Regularly back up your volume mounts and configuration files.

• Security: Implement security best practices for your Docker Swarm setup, such as using secrets to manage sensitive data, setting resource limits, and ensuring your Docker daemon is securely configured.