DynamicSupervisor - problem with communication with the workers - erlang

Question

I have a problem with communication with the workers created in my dynamicSupervisor. after start all my workers i try make a call to one by pid and is generated one error (always).
At the beginning of the child I keep the pid with ets. Then when I want to make a call to this child I get the pid from the ets by an identifier. So far so good.
The problem is when I do the following:
GenServer.call(
pid,
{:action_project, %{project_id: project_id, pid: :erlang.pid_to_list(pid)}}
)
returns following error:
[error] GenServer #PID<0.606.0> terminating
** (RuntimeError) attempted to call GenServer #PID<0.606.0> but no handle_call/3 clause was provided
(backercamp) lib/gen_server.ex:693: MyApplication.ProjectWorker.handle_call/3
(stdlib) gen_server.erl:661: :gen_server.try_handle_call/4
(stdlib) gen_server.erl:690: :gen_server.handle_msg/6
(stdlib) proc_lib.erl:249: :proc_lib.init_p_do_apply/3
Last message (from #PID<0.680.0>): {:action_project, %{pid: '<0.606.0>', project_id: "23"}}
State: %{pid: '<0.606.0>', project_id: "23"}
Client #PID<0.680.0> is alive
(stdlib) gen.erl:169: :gen.do_call/4
(elixir) lib/gen_server.ex:921: GenServer.call/3
What's the problem with this call?
DynamicSupervisor code:
defmodule MyApplication.Supervisor do
use DynamicSupervisor
alias MyApplication.Management
def start_link(arg) do
DynamicSupervisor.start_link(__MODULE__, arg, name: __MODULE__)
end
def init(arg) do
DynamicSupervisor.init(arg)
end
def start_project_worker(project_id) do
spec = {MyApplication.ProjectWorker, %{project_id: project_id}}
DynamicSupervisor.start_child(__MODULE__, spec)
end
def start_all_project_workers() do
Enum.each(Management.list_all_projects(), fn %{id: project_id} ->
IO.puts("Started for project Id [#{project_id}]")
# 1s between workers
:timer.sleep(1000)
start_project_worker("#{project_id}")
end)
end
def action_project(pid, project_id) do
GenServer.call(
pid,
{:action_project, %{project_id: project_id, pid: :erlang.pid_to_list(pid)}}
)
end
end
Worker code:
defmodule MyApplication.ProjectWorker do
use GenServer, restart: :transient
alias MyApplication.Settings
alias MyApplication.Management
def start_link(state) do
GenServer.start_link(__MODULE__, state)
end
def init(state) do
schedule_action_project(Settings.get_frequency_ms())
state = Map.put(state, :pid, :erlang.pid_to_list(self()))
persist_state(state)
{:ok, state}
end
def handle_info(:schedule_action_project, %{project_id: _project_id, pid: _pid} = state) do
action_by_state(state)
{:noreply, state}
end
def handle_call({:action_project}, %{project_id: _project_id, pid: _pid} = state) do
case action_by_state(state) do
true ->
terminate(state)
false ->
{:reply, state, state}
end
end
defp persist_state(state) do
IO.puts(" :: Add project_id [#{state.project_id}] and pid #{state.pid}")
:ets.insert_new(:project_backup, {state.project_id, state.pid})
end
defp delete_persist_state(project_id) do
IO.puts(" :: Delete project_id [#{project_id}]")
:ets.delete(:project_backup, project_id)
end
defp schedule_action_project(time) do
IO.puts(" :: Schedule_action_project [#{time}]")
Process.send_after(self(), :schedule_action_project, time)
end
defp terminate(%{project_id: project_id, pid: _pid} = state) do
IO.puts(
" :: Stop processed, everything is done! project_id [#{state.project_id}] and pid #{
state.pid
}"
)
delete_persist_state(project_id)
{:stop, :normal, state}
end
defp action_by_state(%{project_id: _project_id, pid: _pid} = state) do
action_by_project(Management.get_project!(state.project_id))
end
defp action_by_project(%Project{} = project) do
#do something in project
end
end

Answer 1

The issue is within a handler. You messed all the arguments up. state is an internal state of GenServer, you do not pass it through, you receive it in the callback. The following signature will match if your state is a map having keys project_id and pid and you call it like GenServer.call(pid, {:action_project}).
def handle_call({:action_project}, %{project_id: _project_id, pid: _pid} = state)
You should change this handler to match your caller:
def handle_call(
{:action_project, %{project_id: _project_id, pid: _pid}},
_from,
state
)
Also note that handle_call callback receives three parameters (unlike handle_cast, the second one being the source of the message.
Sidenote: handle_info callback has the wrong signature as well.