I’m running a Phoenix app on Fly. I have a GenServer I’m starting as a child in my Application.start/2 function under my MyApp.Supervisor.

I had it crash within the GenServer.init/1 function when the app was starting for a deploy. In the logs there was:

{exit,terminating,[{application_controller,call,2,[{file,"application_controller.erl"},{line,511}]},{application,enqueue_or_start,6,[{file,"application.erl"},{line,380}]},{application,ensure_all_started,3,[{file,"application.erl"},{line,359}]},{elixir,start_cli,0,[{file,"src/elixir.erl"},{line,195}]},{init,start_it,1,[]},{init,start_em,1,[]},{init,do_boot,3,[]}]}
Runtime terminating during boot (terminating)

However, the cause of the crash was not in the logs. When I tested it more, if I try to log in GenServer.init/1 during a successful start with Logger.error("Test log") it also doesn’t end up in the production logs.

The crash and logs show up when I try all these scenarios in dev using either mix or a release.

I found How do I get Phoenix or Elixir to print more detailed logs on a crash? and added:

config :logger, 
   handle_otp_reports: true, 
   handle_sasl_reports: true,
   ...

That gave me more information about the supervisor starting its children, but I still didn’t get any logs from the GenServer init function in production.

My config/prod.exs is:

config :logger,
  level: :info,
  backends: [:console, {Appsignal.Logger.Backend, [group: "phoenix"]}],
  handle_otp_reports: true,
  handle_sasl_reports: true

my config/config.exs is:

config :logger, :console,
  format: "$time $metadata[$level] $message\n",
  metadata: [:request_id]

Any idea why I’m not getting these logs in production (either AppSignal or the console)?