Re: non-working Agent reload code

gistfile1.txt

Tracing RefData.Server.start_link/0, I found that it isn't getting run
after the exit.  So, I probably have a problem in the Supervision setup.
I will look into this, but meanwhile, here is my current setup:

=========================================================

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

  use Application

  def start(_type, _args) do
    # List all child processes to be supervised
    children = [
      # Start the endpoint when the application starts
      PhxHttpWeb.Endpoint
      # Starts a worker by calling: PhxHttp.Worker.start_link(arg)
      # {PhxHttp.Worker, arg},
    ]

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

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

=========================================================

defmodule RefData.Application do

  use Application

  @doc """
  Load the TOML file tree, then fold in the index.
  """

  def start(_type, _args) do
    import Supervisor.Spec, warn: false
    
    children = [
      worker(RefData.Server, []),
    ]
    
    options = [
      name:     RefData.Supervisor,
      strategy: :one_for_one,
    ]
    
    Supervisor.start_link(children, options)
  end

end

=========================================================

While it's a valid strategy to have two different applications to separate these concerns, go ahead and just use one Application for now and treat your RefData.Server as a kind of library:

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

  use Application

  def start(_type, _args) do
    # List all child processes to be supervised
    children = [
      # Start the endpoint when the application starts
      PhxHttpWeb.Endpoint,
      %{id: RefData.Server, start: {RefData.Server, :start_link, []}}, # <-- see notes below about child_spec
      # Starts a worker by calling: PhxHttp.Worker.start_link(arg)
      # {PhxHttp.Worker, arg},
    ]

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

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

I've added a child_spec so that you can explicitly have an ID for RefData.Server, which is necessary to look it up in the supervisor. An ID can actually be any valid atom (or maybe even any valid term). Check out the documentation for Supervisor for more information on that.

Now at this point, you should be able to call this:

:ok = Supervisor.terminate_child(PhxHttp.Supervisor, RefData.Server)
{:ok, _pid} = Supervisor.restart_child(PhxHttp.Supervisor, RefData.Server)

without any problems