CODEWITHSUNDEEP
elixirerlang-supervisor
smoes
smoes

Reputation: 601

Elixir simple_one_for_one supervisor's start_child terminates with undefined handle_call/3

I am trying to create a supervisor using gproc for process registry. The following code defines the supervisor:

defmodule QueueSupervisor do
    use Supervisor

    def start_link do
        GenServer.start_link(__MODULE__, [], name: :model_queue)
    end

    def create_queue(name) do
        Supervisor.start_child(:model_queue, [name])
    end

    def init([]) do
        children = [
            worker(ModelQueueWriter, [])
        ]

        supervise(children, strategy: :simple_one_for_one)
    end

    def terminate(reason,_state) do
        Logger.info "terminating: #{inspect self}: #{inspect reason}"
        :ok
    end
end

The supervisor starts like a charm. However, when calling create_queue(:some_name), I get an undefined function error:

function QueueSupervisor.handle_call({:start_child, [:some_name]}, {#PID<0.2278.0>, #Reference<0.0.3.3361>}, {{:simple_one_for_one, 3, 5}, [{ModelQueueWriter, {ModelQueueWriter, :start_link, []}, :permanent, 5000, :worker, [ModelQueueWriter]}]}

ModelQueueWriter is a simple genserver, using gproc for naming:

defmodule ModelQueueWriter do
    use GenServer

    def start_link(queue_name) do
        GenServer.start_link(__MODULE__, [], name: via_tuple(queue_name))
    end

    defp via_tuple(queue_name) do
        {:via, :gproc, {:n, :l, {:model_queue, queue_name}}}
    end

    def init(_), do: %{:ok, []}
end

I am using elixir 1.4 and followed the doc for Supervisor, plus this example.

What am I missing?

Upon request the full error message:

** (exit) exited in: GenServer.call(:model_queue, {:start_child, [:some_name]}, :infinity)
    ** (EXIT) an exception was raised:
        ** (UndefinedFunctionError) function QueueSupervisor.handle_call/3 is undefined or private
        (ecohesion_web) QueueSupervisor.handle_call({:start_child, [:model_queue]}, {#PID<0.2278.0>, #Reference<0.0.1.8826>}, {{:simple_one_for_one, 3, 5}, [{ModelQueueWriter, {ModelQueueWriter, :start_link, []}, :permanent, 5000, :worker, [ModelQueueWriter]}]})
        (stdlib) gen_server.erl:629: :gen_server.try_handle_call/4
        (stdlib) gen_server.erl:661: :gen_server.handle_msg/5
        (stdlib) proc_lib.erl:240: :proc_lib.init_p_do_apply/3
11:01:17.094 [error] GenServer :model_queue terminating
** (UndefinedFunctionError) function QueueSupervisor.handle_call/3 is undefined or private
(ecohesion_web) QueueSupervisor.handle_call({:start_child, [:model_queue]}, {#PID<0.2278.0>, #Reference<0.0.1.8826>}, {{:simple_one_for_one, 3, 5}, [{ModelQueueWriter, {ModelQueueWriter, :start_link, []}, :permanent, 5000, :worker, [ModelQueueWriter]}]})
(stdlib) gen_server.erl:629: :gen_server.try_handle_call/4
(stdlib) gen_server.erl:661: :gen_server.handle_msg/5
(stdlib) proc_lib.erl:240: :proc_lib.init_p_do_apply/3
Last message: {:start_child, [mode_queue]}
State: {{:simple_one_for_one, 3, 5}, [{ModelQueueWriter, {ModelQueueWriter, :start_link, []}, :permanent, 5000, :worker, [ModelQueueWriter]}]}
       (elixir) lib/gen_server.ex:737: GenServer.call/3
(ecohesion_web) lib/ecohesion_web/archive_writer/queue_supervisor.ex:28: QueueSupervisor.create_queue/1

Upvotes: 1

Views: 980

Answers (1)

Dogbert
Dogbert

Reputation: 222040

You're starting a GenServer instead of Supervisor in QueueSupervisor.start_link/0. This should work:

defmodule QueueSupervisor do
  def start_link do
    Supervisor.start_link(__MODULE__, [], name: :model_queue)
  end
end

Why does that even start the supervisor properly?

It starts a GenServer; it's just that the arguments you've used are compatible with both Supervisor.start_link/3 and GenServer.start_link/3.

Upvotes: 1

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