This is a Tornado base handler that implements CORS support to a REST API

tornado_base_handler_cors.py

class BaseHandler(tornado.web.RequestHandler):

    """
    Base handler setting up the default headers for CORS
    """
    def set_default_headers(self):
        self.set_header("Access-Control-Allow-Origin", "*")
        self.set_header("Access-Control-Allow-Headers", "x-requested-with")
        self.set_header('Access-Control-Allow-Methods', 'POST, GET, DELETE, PUT')

    """
    Base handler preparing requests and redirect to HTTPS
    """
    def prepare(self):
        if self.request.protocol == 'http':
            self.redirect('https://' + self.request.host, permanent=False)
    """
    Base handler to be used instead of RequestHandler
    """
    def write_error(self, status_code, **kwargs):
      if status_code in [403, 404, 500, 503]:
        self.write('Error %s' % status_code)
      else:
        self.write('BOOM!')