code: def SetupPrometheusEndpointOnPort(port, addr=''):
      
      assert os.environ.get('RUN_MAIN') != 'true', (
          'The thread-based exporter can\'t be safely used when django\'s '
          'autoreloader is active. Use the URL exporter, or start django '
          'with --noreload. See documentation/exports.md.')
      prometheus_client.start_http_server(port, addr=addr)
docs: Exports Prometheus metrics on an HTTPServer running in its own thread.
  
      The server runs on the given port and is by default listenning on
      all interfaces. This HTTPServer is fully independent of Django and
      its stack. This offers the advantage that even if Django becomes
      unable to respond, the HTTPServer will continue to function and
      export metrics. However, this also means that the features
      offered by Django (like middlewares or WSGI) can't be used.
  
      Now here's the really weird part. When Django runs with the
      auto-reloader enabled (which is the default, you can disable it
      with `manage.py runserver --noreload`), it forks and executes
      manage.py twice. That's wasteful but usually OK. It starts being a
      problem when you try to open a port, like we do. We can detect
      that we're running under an autoreloader through the presence of
      the RUN_MAIN environment variable, so we abort if we're trying to
      export under an autoreloader and trying to open a port.