mnesiac / libcluters / kube dns

db-application.ex

defmodule Db.Application do
  @moduledoc false

  use Application
  require Logger

  def start(_type, _args) do
    import Supervisor.Spec, warn: false

    init_cluster(System.get_env("CLUSTER_DNS"), System.get_env("CLUSTER"))

    children = [
      supervisor(Db.Repo, [])
    ]

    opts = [strategy: :one_for_one, name: Db.Supervisor]
    Supervisor.start_link(children, opts)
  end

  defp init_cluster(nil, _),
    do: Logger.warn("Cluster not initiated, missing service configuration")

  defp init_cluster(_, nil),
    do: Logger.warn("Cluster not initiated, missing application configuration")

  defp init_cluster(service, application) do
    topology = [
      myapp: [
        strategy: Elixir.Cluster.Strategy.Kubernetes.DNS,
        config: [
          service: service,
          application_name: application,
          polling_interval: 10_000
        ]
      ]
    ]

    Application.put_env(:libcluster, :topologies, topology)

    children = [{Cluster.Supervisor, [topology, [name: Db.LibclusterSupervisor]]}]
    opts = [strategy: :one_for_one, name: Db.ClusterSupervisor]
    Supervisor.start_link(children, opts)
  end
end

web-application.ex

defmodule Web.Application do
  @moduledoc false

  use Application

  def start(_type, _args) do
    import Supervisor.Spec, warn: false

    # Define workers and child supervisors to be supervised
    children = [
      {Mnesiac.Supervisor, [Node.list(), [name: Web.MnesiacSupervisor]]},
      supervisor(Web.Endpoint, [])
    ]

    opts = [strategy: :one_for_one, name: Web.Supervisor]
    Supervisor.start_link(children, opts)
  end
  
  ...
end