text: from django.http import HttpResponse
  from django.conf import settings
  from prometheus_client import multiprocess
  
  try:
      # Python 2
      from BaseHTTPServer import HTTPServer
  except ImportError:
      # Python 3
      from http.server import HTTPServer
  import socket
  import logging
  import os
  import prometheus_client
  import threading
  
  
  logger = logging.getLogger(__name__)
  
  
  def SetupPrometheusEndpointOnPort(port, addr=''):
      """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.
      """
      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)
  
  
  class PrometheusEndpointServer(threading.Thread):
      """A thread class that holds an http and makes it serve_forever()."""
      def __init__(self, httpd, *args, **kwargs):
          self.httpd = httpd
          super(PrometheusEndpointServer, self).__init__(*args, **kwargs)
  
      def run(self):
          self.httpd.serve_forever()
  
  
  def SetupPrometheusEndpointOnPortRange(port_range, addr=''):
      """Like SetupPrometheusEndpointOnPort, but tries several ports.
  
      This is useful when you're running Django as a WSGI application
      with multiple processes and you want Prometheus to discover all
      workers. Each worker will grab a port and you can use Prometheus
      to aggregate across workers.
  
      port_range may be any iterable object that contains a list of
      ports. Typically this would be an xrange of contiguous ports.
  
      As soon as one port is found that can serve, use this one and stop
      trying.
  
      The same caveats regarding autoreload apply. Do not use this when
      Django's autoreloader is active.
  
      """
      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.')
      for port in port_range:
          try:
              httpd = HTTPServer((addr, port), prometheus_client.MetricsHandler)
          except (OSError, socket.error):
              # Python 2 raises socket.error, in Python 3 socket.error is an
              # alias for OSError
              continue  # Try next port
          thread = PrometheusEndpointServer(httpd)
          thread.daemon = True
          thread.start()
          logger.info('Exporting Prometheus /metrics/ on port %s' % port)
          return  # Stop trying ports at this point
  
  
  def SetupPrometheusExportsFromConfig():
      """Exports metrics so Prometheus can collect them."""
      port = getattr(settings, 'PROMETHEUS_METRICS_EXPORT_PORT', None)
      port_range = getattr(
          settings, 'PROMETHEUS_METRICS_EXPORT_PORT_RANGE', None)
      addr = getattr(settings, 'PROMETHEUS_METRICS_EXPORT_ADDRESS', '')
      if port_range:
          SetupPrometheusEndpointOnPortRange(port_range, addr)
      elif port:
          SetupPrometheusEndpointOnPort(port, addr)
  
  
  def ExportToDjangoView(request):
      """Exports /metrics as a Django view.
  
      You can use django_prometheus.urls to map /metrics to this view.
      """
      if 'prometheus_multiproc_dir' in os.environ:
          registry = prometheus_client.CollectorRegistry()
          multiprocess.MultiProcessCollector(registry)
      else:
          registry = prometheus_client.REGISTRY
      metrics_page = prometheus_client.generate_latest(registry)
      return HttpResponse(
          metrics_page,
          content_type=prometheus_client.CONTENT_TYPE_LATEST)
  