class Fluent::SystemConfig

def attach(supervisor)
  system = self
  supervisor.instance_eval {
    SYSTEM_CONFIG_PARAMETERS.each do |param|
      case param
      when :rpc_endpoint, :enable_get_dump, :process_name, :file_permission, :dir_permission, :counter_server, :counter_client
        next # doesn't exist in command line options
      when :emit_error_log_interval
        system.emit_error_log_interval = @suppress_interval if @suppress_interval
      when :log_level
        ll_value = instance_variable_get("@log_level")
        # info level can't be specified via command line option.
        # log_level is info here, it is default value and <system>'s log_level should be applied if exists.
        if ll_value != Fluent::Log::LEVEL_INFO
          system.log_level = ll_value
        end
      else
        next unless instance_variable_defined?("@#{param}")
        supervisor_value = instance_variable_get("@#{param}")
        next if supervisor_value.nil? # it's not configured by command line options
        system.send("#{param}=", supervisor_value)
      end
    end
  }
end