How we configure lager for logging

setup_lager_logging.erl

setup_lager_logging() ->
  application:load(lager),

  ConsoleFormat = [time, " ", pid, {pid, [" "], ""}, 
    {module, [module, ":", line, " "], ""},
    message, "\n"
  ],
  FileFormat = [date, " "] ++ ConsoleFormat,

  LogDir = os:getenv("LOGDIR"),

  {FileLogger, CrashLogger} = case LogDir of
    false ->
      {[], undefined};
    _ ->
      {[
        {lager_file_backend, [{file,LogDir++"/flussonic.log"},{level,info},{size,2097152},{date,"$D04"}, {count,40},
                              {formatter,lager_default_formatter},{formatter_config,FileFormat}]}
      ], LogDir++"/crash.log"}
  end,

  application:set_env(lager,handlers,[
    {lager_console_backend,[info,{lager_default_formatter, ConsoleFormat}]}
  ] ++ FileLogger),
  application:set_env(lager,error_logger_redirect,false),
  application:set_env(lager,crash_log,CrashLogger),
  application:set_env(lager,crash_log_msg_size,16384),
  application:set_env(lager,error_logger_hwm,200),
  application:set_env(lager,crash_log_size,1048576),
  application:set_env(lager,crash_log_date,"$D04"),
  application:set_env(lager,crash_log_count,5),
  if 
    is_list(LogDir) -> application:set_env(lager,log_dir, LogDir);
    LogDir == false -> ok
  end,

  [error_logger:delete_report_handler(X) || X <- gen_event:which_handlers(error_logger)],
  {ok, HighWaterMark} = application:get_env(lager, error_logger_hwm),
  lager:start(),
  supervisor:start_child(lager_handler_watcher_sup, [error_logger, error_logger_flu, [HighWaterMark]]),
  lager:notice("Flussonic version ~s is booting", [flu:version()]),
  ok.