What’s new in Tornado 2.2

Jan 30, 2012


  • Updated and expanded WebSocket support.
  • Improved compatibility in the Twisted/Tornado bridge.
  • Template errors now generate better stack traces.
  • Better exception handling in tornado.gen.

Security fixes

  • tornado.simple_httpclient now disables SSLv2 in all cases. Previously SSLv2 would be allowed if the Python interpreter was linked against a pre-1.0 version of OpenSSL.

Backwards-incompatible changes

  • tornado.process.fork_processes now raises SystemExit if all child processes exit cleanly rather than returning None. The old behavior was surprising and inconsistent with most of the documented examples of this function (which did not check the return value).
  • On Python 2.6, tornado.simple_httpclient only supports SSLv3. This is because Python 2.6 does not expose a way to support both SSLv3 and TLSv1 without also supporting the insecure SSLv2.
  • tornado.websocket no longer supports the older “draft 76” version of the websocket protocol by default, although this version can be enabled by overriding tornado.websocket.WebSocketHandler.allow_draft76.


  • SimpleAsyncHTTPClient no longer hangs on HEAD requests, responses with no content, or empty POST/PUT response bodies.
  • SimpleAsyncHTTPClient now supports 303 and 307 redirect codes.
  • tornado.curl_httpclient now accepts non-integer timeouts.
  • tornado.curl_httpclient now supports basic authentication with an empty password.


  • HTTPServer with xheaders=True will no longer accept X-Real-IP headers that don’t look like valid IP addresses.
  • HTTPServer now treats the Connection request header as case-insensitive.

tornado.ioloop and tornado.iostream

  • IOStream.write now works correctly when given an empty string.
  • IOStream.read_until (and read_until_regex) now perform better when there is a lot of buffered data, which improves peformance of SimpleAsyncHTTPClient when downloading files with lots of chunks.
  • SSLIOStream now works correctly when ssl_version is set to a value other than SSLv23.
  • Idle IOLoops no longer wake up several times a second.
  • tornado.ioloop.PeriodicCallback no longer triggers duplicate callbacks when stopped and started repeatedly.


  • Exceptions in template code will now show better stack traces that reference lines from the original template file.
  • {# and #} can now be used for comments (and unlike the old {% comment %} directive, these can wrap other template directives).
  • Template directives may now span multiple lines.



Other modules