** (ArgumentError) unknown registry: Registry.MongoConnectionRegistry

application.ex

defmodule Wrangler.Application do
  # See https://hexdocs.pm/elixir/Application.html
  # for more information on OTP Applications
  @moduledoc false

  use Application

  @registry Registry.MongoConnectionRegistry

  @impl true
  def start(_type, _args) do
    children = [
      # Start the Ecto repository
      Wrangler.Repo,
      # Start the Telemetry supervisor
      WranglerWeb.Telemetry,
      # Start the PubSub system
      {Phoenix.PubSub, name: Wrangler.PubSub},
      # Start the Endpoint (http/https)
      WranglerWeb.Endpoint,
      {Task.Supervisor, name: Wrangler.BackgroundTask},
      {Oban, oban_config()},
      {Finch, name: Swoosh.Finch},
      {Registry, keys: :unique, name: @registry}
    ]

    register_mongo_connection()

    [{_pid, mongo_connection_pid}] = Registry.lookup(@registry, "open5gs_conn")

    dbg(mongo_connection_pid)

    # See https://hexdocs.pm/elixir/Supervisor.html
    # for other strategies and supported options
    opts = [strategy: :one_for_one, name: Wrangler.Supervisor]
    Supervisor.start_link(children, opts)
  end

  # Tell Phoenix to update the endpoint configuration
  # whenever the application is updated.
  @impl true
  def config_change(changed, _new, removed) do
    WranglerWeb.Endpoint.config_change(changed, removed)
    :ok
  end

  # Conditionally disable queues or plugins here.
  defp oban_config do
    Application.fetch_env!(:wrangler, Oban)
  end

  defp register_mongo_connection() do
    if Mix.env() == :dev do
      # mix/dev
      {:ok, conn} = Mongo.start_link(url: "mongodb://localhost:27017/open5gs")

      Registry.register(@registry, "open5gs_conn", conn)
    else
      # docker/prod
      {:ok, conn} =
        Mongo.start_link(
          url: "mongodb://mongodb:27017/open5gs",
          username: "secret",
          password: "secret",
          auth_source: "admin"
        )

      Registry.register(@registry, "open5gs_conn", conn)
    end
  end
end

** (Mix) Could not start application wrangler: exited in: Wrangler.Application.start(:normal, [])
    ** (EXIT) an exception was raised:
        ** (ArgumentError) unknown registry: Registry.MongoConnectionRegistry
            (elixir 1.14.0) lib/registry.ex:1373: Registry.info!/1
            (elixir 1.14.0) lib/registry.ex:989: Registry.register/3
            (wrangler 1.4.1) lib/wrangler/application.ex:27: Wrangler.Application.start/2
            (kernel 8.4) application_master.erl:293: :application_master.start_it_old/4