tornado-problem-details 0.0.4

RFC-7807 Error documents for Tornado

This library provides a version of tornado.web.RequestHandler.send_error that speaks application/problem+json instead of HTML. The easiest way to use this library is to inherit from problemdetails.ErrorWriter and call send_error() with additional parameters.

from tornado import web
import problemdetails


class MyHandler(problemdetails.ErrorWriter, web.RequestHandler):
   def get(self):
      try:
         self.do_something_hard()
      except SomeException as error:
         self.send_error(500, title="Failed to do_something_hard")

HTTP/1.1 500 Internal Server Error
Content-Type: application/problem+json

{
   "title": "Failed to do_something_hard",
   "type": "https://tools.ietf.org/html/rfc7231#section-6.6.1"
}

As an alternative, you can raise a problemdetails.Problem instance and let the Tornado exception handling take care of eventually calling write_error. The following snippet produces the same output as the previous example.

from tornado import web
import problemdetails


class MyHandler(problemdetails.ErrorWriter, web.RequestHandler):
   def get(self):
      if not self.do_something_hard():
         raise problemdetails.Problem(status_code=500,
                                      title='Failed to do_something_hard')

The problemdetails.Problem instance passes all of the keyword parameters through in the resulting message so it is very easy to add fields. The interface of tornado.web.RequestHandler.send_error is less expressive since keyword parameters may be swallowed by intervening code.