# File src/ruby_supportlib/phusion_passenger/debug_logging.rb, line 104
    def _output(level, message, nesting_level = 0)
      if @@log_level >= level
        if @@log_filename
          if !@@log_device || @@log_device.closed?
            @@log_device = File.open(@@log_filename, "a")
          end
          output = @@log_device
        else
          output = @@stderr_evaluator.call
        end
        location = caller[nesting_level].sub(/.*phusion_passenger\//, '')
        location.sub!(/(.*):.*/, '\1')
        now = Time.now
        time_str = now.strftime("%Y-%m-%d %H:%M:%S.")
        time_str << sprintf("%04d", now.usec / 100)

        current_thread = Thread.current
        if !(thread_id = current_thread[:id])
          current_thread.to_s =~ /:(0x[0-9a-f]+)/i
          thread_id = current_thread[:id] = $1 || '?'
        end
        if thread_name = current_thread[:name]
          thread_name = "(#{thread_name})"
        end

        output.write("[ #{time_str} #{$$}/#{thread_id}#{thread_name} #{location} ]: #{message}\n")
        output.flush
      end
    end