anchor.diff:        # Zoom the map to the bounding box
         map.zoom_to_box(bbox)
   
  +      # Fork so that we can handle crashes rendering the map
  +      pid = os.fork()
  +
         # Render the map
  -      if form.getvalue("format") == "png":
  -        image = mapnik.Image(map.width, map.height)
  -        mapnik.render(map, image)
  -        png = image.tostring("png")
  -        output_headers("image/png", "map.png", len(png))
  -        sys.stdout.write(png)
  -      elif form.getvalue("format") == "jpeg":
  -        image = mapnik.Image(map.width, map.height)
  -        mapnik.render(map, image)
  -        jpeg = image.tostring("jpeg")
  -        output_headers("image/jpeg", "map.jpg", len(jpeg))
  -        sys.stdout.write(jpeg)
  -      elif form.getvalue("format") == "svg":
  -        file = tempfile.NamedTemporaryFile(prefix = "export")
  -        surface = cairo.SVGSurface(file.name, map.width, map.height)
  -        mapnik.render(map, surface)
  -        surface.finish()
  -        output_headers("image/svg+xml", "map.svg", file_size(file))
  -        output_file(file)
  -      elif form.getvalue("format") == "pdf":
  -        file = tempfile.NamedTemporaryFile(prefix = "export")
  -        surface = cairo.PDFSurface(file.name, map.width, map.height)
  -        mapnik.render(map, surface)
  -        surface.finish()
  -        output_headers("application/pdf", "map.pdf", file_size(file))
  -        output_file(file)
  -      elif form.getvalue("format") == "ps":
  -        file = tempfile.NamedTemporaryFile(prefix = "export")
  -        surface = cairo.PSSurface(file.name, map.width, map.height)
  -        mapnik.render(map, surface)
  -        surface.finish()
  -        output_headers("application/postscript", "map.ps", file_size(file))
  -        output_file(file)
  +      if pid == 0:
  +        if form.getvalue("format") == "png":
  +          image = mapnik.Image(map.width, map.height)
  +          mapnik.render(map, image)
  +          png = image.tostring("png")
  +          output_headers("image/png", "map.png", len(png))
  +          sys.stdout.write(png)
  +        elif form.getvalue("format") == "jpeg":
  +          image = mapnik.Image(map.width, map.height)
  +          mapnik.render(map, image)
  +          jpeg = image.tostring("jpeg")
  +          output_headers("image/jpeg", "map.jpg", len(jpeg))
  +          sys.stdout.write(jpeg)
  +        elif form.getvalue("format") == "svg":
  +          file = tempfile.NamedTemporaryFile(prefix = "export")
  +          surface = cairo.SVGSurface(file.name, map.width, map.height)
  +          mapnik.render(map, surface)
  +          surface.finish()
  +          output_headers("image/svg+xml", "map.svg", file_size(file))
  +          output_file(file)
  +        elif form.getvalue("format") == "pdf":
  +          file = tempfile.NamedTemporaryFile(prefix = "export")
  +          surface = cairo.PDFSurface(file.name, map.width, map.height)
  +          mapnik.render(map, surface)
  +          surface.finish()
  +          output_headers("application/pdf", "map.pdf", file_size(file))
  +          output_file(file)
  +        elif form.getvalue("format") == "ps":
  +          file = tempfile.NamedTemporaryFile(prefix = "export")
  +          surface = cairo.PSSurface(file.name, map.width, map.height)
  +          mapnik.render(map, surface)
  +          surface.finish()
  +          output_headers("application/postscript", "map.ps", file_size(file))
  +          output_file(file)
  +        else:
  +          output_error("Unknown format '%s'" % form.getvalue("format"))
         else:
  -        output_error("Unknown format '%s'" % form.getvalue("format"))
  +        pid, status = os.waitpid(pid, 0)
  +        if status & 0xff == signal.SIGXCPU:
  +          output_error("CPU time limit exceeded", "509 Resource Limit Exceeded")
  +        elif status & 0xff == signal.SIGSEGV:
  +          output_error("Memory limit exceeded", "509 Resource Limit Exceeded")
  +        elif status != 0:
  +          output_error("Internal server error", "500 Internal Server Error")
  
positive.code: # Process the request
  if idletime < 0.2:
    # Abort if the CPU idle time on the machine is too low
    print "Status: 503 Service Unavailable"
    output_error("The server is too busy at the moment. Please wait a few minutes before trying again.")
  <% @blocks["user_agents"].each do |user_agent| -%>
  elif os.environ['HTTP_USER_AGENT'] == '<%= user_agent %>':
    # Block scraper
    print "Status: 503 Service Unavailable"
    output_error("The server is too busy at the moment. Please wait a few minutes before trying again.")
  <% end -%>
  elif not form.has_key("bbox"):
    # No bounding box specified
  
negative.code:   return os.fstat(file.fileno()).st_size
  
  # Routine to report an error
  def output_error(message, status = "400 Bad Request"):
    print "Status: %s" % status
    output_headers("text/html")
    print "<html>"
    print "<head>"
  