Elixir GenServer handle_cast not being invoked - erlang

Question

I am having an issue with Handle Cast. After the module loads it calls periodic_comm which after every 5 seconds calls the save_data method. In my save_data method the logs are being printed but the statement does nothing.
GenServer.cast(__MODULE__, {:save_load_data, data})
The handle cast method is defined here
def handle_cast({:save_load_data, data}, state) do
Logger.error("uin saving data====================================")
# state = Map.put_new(state, :load_data, data)
# Logger.debug "updated state : #{inspect state}"
{:noreply, state}
end
The entire file looks like this
defmodule Core.Inverter.Manager do
# core inverter process that handles the inverter communication
use GenServer
require Logger
def start_link(_) do
Logger.info("putting some string")
GenServer.start_link(__MODULE__, %{}, name: __MODULE__)
end
#impl true
def init(_) do
Logger.info("inverter Manager init'ed")
{:ok, %{configs: nil, inverter_connection: nil, inverter_impl: nil}}
end
# public api
# initialize the inverter and start periodic comm
def init_inverter(configs) do
GenServer.cast(__MODULE__, {:init_inverter, configs})
GenServer.cast(__MODULE__, {:start_periodic_comm, configs})
end
def inverter_off() do
GenServer.call(__MODULE__, :inverter_off)
end
#impl true
def handle_cast({:init_inverter, configs}, state) do
Logger.debug("initializing the inverter")
# fetching inverter type/configurations
inverter_impl = get_inverter_impl(configs)
# initializing inverter comm channel
inverter_connection = inverter_impl.init(configs)
state = %{
configs: configs,
inverter_connection: inverter_connection,
inverter_impl: inverter_impl
}
Logger.warn("inverter type #{state.inverter_impl}")
{:noreply, state}
end
def handle_cast({:start_periodic_comm, configs}, state) do
Logger.warn(
"Actually Starting inverter periodic COMM with inverter type #{state.inverter_impl}"
)
start_periodic_comm(state)
{:noreply, state}
end
#impl true
def handle_call(
:inverter_off,
_from,
%{inverter_impl: inverter_impl, inverter_connection: inverter_connection} = state
) do
{:ok, inverter_connection} = inverter_impl.inverter_off(inverter_connection)
{:reply, :ok, %{state | inverter_connection: inverter_connection}}
end
def handle_cast({:save_load_data, data}, state) do
Logger.error("uin saving data====================================")
# state = Map.put_new(state, :load_data, data)
# Logger.debug "updated state : #{inspect state}"
{:noreply, state}
end
defp start_periodic_comm(state) do
periodic_comm(state)
end
defp periodic_comm(state) do
# call functions from the inverter_type module, e.g infit.ex
receive do
after
5000 ->
{:ok, data} = state.inverter_impl.get_load_data(state)
save_data(data)
end
periodic_comm(state)
end
# defp save_data() do end
def save_data(data) do
Logger.debug("saving data")
Logger.debug("in savinf data data is : #{inspect(data)}")
GenServer.cast(__MODULE__, {:save_load_data, data})
end
defp get_inverter_impl(configs) do
# add case statements here
Core.Inverter.Infini
end
end

Answer 1

I'm not so familiar with elixir's syntax, but it seems to me that periodic_comm is looping:
defp periodic_comm(state) do
# call functions from the inverter_type module, e.g infit.ex
receive do
after
5000 ->
{:ok, data} = state.inverter_impl.get_load_data(state)
save_data(data)
end
periodic_comm(state)
end
regardless of the result of save_data, the thread is endlessly looping over calls to periodic_comm, so it gets no chance to receive and execute the save_load_data message.
In order to fix it, you should refactor the server to have the logic in handle_X without looping, which receive all kind of messages. You can use erlang:start_timer (I don't know the elixir's counterpart) or rely on the Timeout in the gen_server return values to receive timeout messages.