ClusterHcloud

This is a Hetzner Cloud clustering strategy for libcluster.

The labels strategy queries the hcloud API using HTTPoison and Jason to find nodes by given label selectors.

Quick example

config :libcluster,
  topologies: [
    labels_example: [
      strategy: Elixir.ClusterHcloud.Strategy.Labels,
      config: [
        hcloud_api_access_token: "xxx",
        label_selector: "mylabel",
        app_prefix: "app",
        show_debug: false,
        private_network_name: "my-network",
        polling_interval: 10_000]]],

You can define your topologies in the location where you start the Cluster.Supervisor as well. If you use the above, remember that you still have to add Cluster.Supervisor to the supervision tree. You can get the configuration using Application.get_env(:libcluster, :topologies).

For further details on configuration, see the documentation.

To practically use this on Hetzner Cloud, you need to make sure you run your application appropriately, i.e., you have to make sure you run your nodes with a name allowing for external connections. This means it has to be run with the Erlang start parameter --name {app_prefix}@{private_ip} or --name {app_prefix}@{public_ip}! If you are using Mix Releases, the documentation of mix-release is a good read.

TL;DR e.g. for use with mix release you need to set the environment variables RELEASE_DISTRIBUTION=name and RELEASE_NODE={app_prefix}@{private_ip|public_ip} when running you release.

Installation

The package can be installed by adding libcluster_hcloud to your list of dependencies in mix.exs:

def deps do
  [
    {:libcluster_hcloud, "~> 0.1.0"}
  ]
end

Acknowledgments

This package is heavily based on libcluster_ec2 by kyleaa.