Tornado – Error Handling

Web development often calls for gracefully handling of non-existent pages or broken links that users request for. A simple way to achieve error handling in Tornado is with:

• tornado.web.HTTPError - Exception handler that can used to generate error code of specified type. 
  It is often used to raise an exception as we would see in the example below

• send_error - Generates an error page of the status code provided along with error description if debug=True

In the example below, when user generates a GET request on http://127.0.0.1:8888/articles/, articles along with author names are shown up.

But when GET request is made on http://127.0.0.1:8888/articles/1, since there is no Id implementation for articles page, error is handled with self.send_error(500) or raise tornado.web.HTTPError(404, ‘Page Not Found Error!!’)

Case1: raise tornado.web.HTTPError(404, ‘Page Not Found Error!!’) is enabled

• Traceback (most recent call last):                                          —– Traceback is noticed on web page
  File “/home/ubuntu/tornado-2.2/tornado/web.py”, line 988, in _execute
  getattr(self, self.request.method.lower())(*args, **kwargs)
  File “errorhandling.py”, line 12, in get
  raise tornado.web.HTTPError(400, ‘Page Not Found Error!!’)
  HTTPError: HTTP 400: Bad Request (Page Not Found Error!!)

• WARNING:root:400 GET /articles/1 (127.0.0.1): Page Not Found Error!!     —– Error description where web server is running
  WARNING:root:400 GET /articles/1 (127.0.0.1) 10.68ms

Case2: self.send_error(500) is enabled

• ‘500: Internal Server Error’ web page shows up

• ERROR:root:500 GET /articles/1 (127.0.0.1) 0.41ms error line is generated where web server is running

Example:
https://gist.github.com/3249999.js