cloud-swarm-join

A Docker image to automatically join a Docker Swarm. Designed to be used as part of the startup of a new Docker server for public & private clouds.

Usage

docker run --rm --net=host --env DISCOVERY_BACKEND="consul://consul.example.com:8500/" --volume /var/run/docker.sock:/var/run/docker.sock stuartc/cloud-swarm-join

This will advertise the default IP of the host to the Docker Swarm that can be found at the consul.example.com:8500 Consul server.

This container is designed to be started automatically as the host boots. One example is to use the cloud-init system for operating systems such as RancherOS:

rancher:
  services:
    cloud-swarm-join:
      image: stuartc/cloud-swarm-join
      environment:
        - "CONTAINER_NAME=swarm"
        - "DISCOVERY_BACKEND=consul://consul.example.com:8500/{{ Prefix }}"
        - "AWS_REGION=eu-west-1"
      volumes:
        - /var/run/docker.sock:/var/run/docker.sock

Using with Amazon EC2

There is also built in support for Amazon EC2. The internal IP address of the EC2 instance will be automatically looked up using an instance metadata lookup, so using host networking isn't required.

Additionally instance tags can be used to set some or all of the image options as well as for additional substitution variables.

Substitution Variables

Moustache style substitution tags (e.g. {{ Variable }}) can be used with all instance tags being available. Additionally those instance tags can be overridden via container environment variables (all upper-case equivalent of the tag name).

Configuration Settings

These can be set via EC2 instance tags (mixed case) or container environment variables (all upper-case).

ContainerName or CONTAINER_NAME The name to use for the Swarm node agent command container. Defaults to using an auto-generated name.

DiscoveryBackend or DISCOVERY_BACKEND The Swarm discovery backend details to use. Defaults to token://{{ Token }} which is not recommended for production use, but if used would expect either an instance tag called Token or a container environment variable called TOKEN to be set to the Swarm token.

DockerApiVersion or DOCKER_API_VERSION The Docker API version to use when connecting to the Docker daemon to start the Swarm agent container. Defaults to auto-detect.

DockerHost or DOCKER_HOST The Docker host to use when starting the Swarm agent container. Defaults to the Docker socket at /var/run/docker.sock which would need to be host volume mounted.

IpAddress or IP_ADDRESS Allows the IP address to advertise to Swarm to be set. Normally this wouldn't be used, with the IP address instead being detected via an instance metadata lookup (for Amazon EC2) or the default IP (you will need to set host networking for the container for that to work).

Options or SWARM_OPTIONS Additional options for passing to the Swarm join command, for example to set TTL settings.

The following are only available as container environment variables:

SKIP_METADATA If set to something true (y, yes, t, true, on or 1) don't try to find the host's IP address or instance tags via a metadata lookup. May speed things up slightly for non-EC2 hosts.

AWS_REGION AWS_ACCESS_KEY_ID AWS_SECRET_ACCESS_KEY The Amazon EC2 region & security details. If the access and secret keys aren't set an instance IAM profile can also be used. If the region isn't set it defaults to eu-west-1.