What's new in Tornado 4.4

Jul 15, 2016

General


* Tornado now requires Python 2.7 or 3.3+; versions 2.6 and 3.2 are no
  longer supported. Pypy3 is still supported even though its latest
  release is mainly based on Python 3.2.
* The `monotonic <https://pypi.python.org/pypi/monotonic>`_ package is
  now supported as an alternative to `Monotime
  <https://pypi.python.org/pypi/Monotime>`_ for monotonic clock support
  on Python 2.

``tornado.curl_httpclient``

Failures in _curl_setup_request no longer cause the max_clients pool to be exhausted.
Non-ascii header values are now handled correctly.

tornado.gen


* `.with_timeout` now accepts any yieldable object (except
  ``YieldPoint``), not just `tornado.concurrent.Future`.

`tornado.httpclient`

The errors raised by timeouts now indicate what state the request was in; the error message is no longer simply "599 Timeout".
Calling repr on a tornado.httpclient.HTTPError no longer raises an error.

tornado.httpserver


* Int-like enums (including `http.HTTPStatus`) can now be used as
  status codes.
* Responses with status code ``204 No Content`` no longer emit a
  ``Content-Length: 0`` header.

`tornado.ioloop`
~~~~~~~~~~~~~~~~

* Improved performance when there are large numbers of active timeouts.

`tornado.netutil`
~~~~~~~~~~~~~~~~~

* All included `.Resolver` implementations raise `IOError` (or a
  subclass) for any resolution failure.

`tornado.options`
~~~~~~~~~~~~~~~~~

* Options can now be modified with subscript syntax in addition to
  attribute syntax.
* The special variable ``__file__`` is now available inside config files.

``tornado.simple_httpclient``

HTTP/1.0 (not 1.1) responses without a Content-Length header now work correctly.

tornado.tcpserver


* `.TCPServer.bind` now accepts a ``reuse_port`` argument.

`tornado.testing`
~~~~~~~~~~~~~~~~~

* Test sockets now always use ``127.0.0.1`` instead of ``localhost``.
  This avoids conflicts when the automatically-assigned port is
  available on IPv4 but not IPv6, or in unusual network configurations
  when ``localhost`` has multiple IP addresses.

`tornado.web`
~~~~~~~~~~~~~

* ``image/svg+xml`` is now on the list of compressible mime types.
* Fixed an error on Python 3 when compression is used with multiple
  ``Vary`` headers.

`tornado.websocket`

WebSocketHandler.__init__ now uses super, which improves support for multiple inheritance.