control.erl

#!/usr/bin/env escript
%%
%%! -env ERL_LIBS _build/default/lib

main(Args) ->
  inet_db:set_lookup([file, dns]),
  inet_db:add_host({127,0,0,1}, ["server.l"]),
  ensure_epmd_is_working(),
  Names = case net_adm:names("server.l") of
    {error, _} -> [];
    {ok, NameList} -> NameList
  end,
  GoodName = first_good_name(Names),
  {ok, _} = net_kernel:start([GoodName, longnames]),

  {ok, CookieBin} = file:read_file("/etc/myservice/.erlang.cookie"),
  erlang:set_cookie(erlang:node(), binary_to_atom(CookieBin,latin1)),
  
  Node = 'streamer@server.l',
  M = ..,
  F = ..,
  A = ..,
  ok = rpc:call(Node, M, F, A),
  ok.

  
  
ensure_epmd_is_working() ->
  ensure_epmd_is_working(20).

ensure_epmd_is_working(0) ->
  ok;
ensure_epmd_is_working(N) ->
  case net_adm:names("server.l") of
    {error, _} -> timer:sleep(100), ensure_epmd_is_working(N-1);
    {ok, _} -> ok
  end.


ensure_streamer_working(#{} = Opts) ->
  case is_running(Opts) of
    false ->
      io:format("Server is down\n"),
      erlang:halt(2);
    _ ->
      ok
  end.



first_good_name(Names) ->
  first_good_name(Names, 0).

first_good_name(_Names, N) when N > 10 ->
  error_logger:error_msg("Too many launched control nodes"),
  timer:sleep(1000),
  erlang:halt(5);

first_good_name(Names, N) ->
  CheckName = "control" ++ integer_to_list(N),
  case lists:keymember(CheckName, 1, Names) of
    true -> first_good_name(Names, N+1);
    false -> list_to_atom(CheckName++"@server.l")
  end.