What's new in Tornado 4.5
=========================

Apr 16, 2017
------------

Backwards-compatibility warning
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

- The `tornado.websocket` module now imposes a limit on the size of incoming
  messages, which defaults to 10MiB.

New module
~~~~~~~~~~

- `tornado.routing` provides a more flexible routing system than the one built in
  to `.Application`.

General changes
~~~~~~~~~~~~~~~

- Reduced the number of circular references, reducing memory usage and
  improving performance.

`tornado.auth`
~~~~~~~~~~~~~~

* The `tornado.auth` module has been updated for compatibility with `a
  change to Facebook's access_token endpoint
  <https://github.com/tornadoweb/tornado/pull/1977>`_. This includes both
  the changes initially released in Tornado 4.4.3 and an additional change
  to support the ```session_expires`` field in the new format.
  The ``session_expires`` field is currently a string; it should be accessed
  as ``int(user['session_expires'])`` because it will change from a string to
  an int in Tornado 5.0.


`tornado.autoreload`
~~~~~~~~~~~~~~~~~~~~

- Autoreload is now compatible with the `asyncio` event loop.
- Autoreload no longer attempts to close the `.IOLoop` and all registered
  file descriptors before restarting; it relies on the ``CLOEXEC`` flag
  being set instead.

`tornado.concurrent`
~~~~~~~~~~~~~~~~~~~~

- Suppressed some "'NoneType' object not callback" messages that could
  be logged at shutdown.

`tornado.gen`
~~~~~~~~~~~~~

- ``yield None`` is now equivalent to ``yield gen.moment``.
  `~tornado.gen.moment` is deprecated. This improves compatibility with
  `asyncio`.
- Fixed an issue in which a generator object could be garbage
  collected prematurely (most often when weak references are used.
- New function `.is_coroutine_function` identifies functions wrapped
  by `.coroutine` or ``engine``.

``tornado.http1connection``
~~~~~~~~~~~~~~~~~~~~~~~~~~~

- The ``Transfer-Encoding`` header is now parsed case-insensitively.

`tornado.httpclient`
~~~~~~~~~~~~~~~~~~~~

- ``SimpleAsyncHTTPClient`` now follows 308 redirects.
- ``CurlAsyncHTTPClient`` will no longer accept protocols other than
  ``http`` and ``https``. To override this, set ``pycurl.PROTOCOLS``
  and ``pycurl.REDIR_PROTOCOLS`` in a ``prepare_curl_callback``.
- ``CurlAsyncHTTPClient`` now supports digest authentication for proxies
  (in addition to basic auth) via the new ``proxy_auth_mode`` argument.
- The minimum supported version of ``libcurl`` is now ``7.22.0``.

`tornado.httpserver`
~~~~~~~~~~~~~~~~~~~~

- `.HTTPServer` now accepts the keyword argument
  ``trusted_downstream`` which controls the parsing of
  ``X-Forwarded-For`` headers. This header may be a list or set of IP
  addresses of trusted proxies which will be skipped in the
  ``X-Forwarded-For`` list.
- The ``no_keep_alive`` argument works again.

`tornado.httputil`
~~~~~~~~~~~~~~~~~~

- `.url_concat` correctly handles fragments and existing query arguments.

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

- Fixed 100% CPU usage after a callback returns an empty list or dict.
- `.IOLoop.add_callback` now uses a lockless implementation which
  makes it safe for use from ``__del__`` methods. This improves
  performance of calls to `~.IOLoop.add_callback` from the `.IOLoop`
  thread, and slightly decreases it for calls from other threads.

`tornado.iostream`
~~~~~~~~~~~~~~~~~~

- `memoryview` objects are now permitted as arguments to `~.BaseIOStream.write`.
- The internal memory buffers used by `.IOStream` now use `bytearray`
  instead of a list of `bytes`, improving performance.
- Futures returned by `~.BaseIOStream.write` are no longer orphaned if a second
  call to ``write`` occurs before the previous one is finished.

`tornado.log`
~~~~~~~~~~~~~

- Colored log output is now supported on Windows if the
  `colorama <https://pypi.python.org/pypi/colorama>`_ library
  is installed  and the application calls ``colorama.init()`` at
  startup.
- The signature of the `.LogFormatter` constructor has been changed to
  make it compatible with `logging.config.dictConfig`.

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

- Worked around an issue that caused "LookupError: unknown encoding:
  latin1" errors on Solaris.

`tornado.process`
~~~~~~~~~~~~~~~~~

- `.Subprocess` no longer causes "subprocess still running" warnings on Python 3.6.
- Improved error handling in `.cpu_count`.

`tornado.tcpclient`
~~~~~~~~~~~~~~~~~~~

- `.TCPClient` now supports a ``source_ip`` and ``source_port`` argument.
- Improved error handling for environments where IPv6 support is incomplete.

`tornado.tcpserver`
~~~~~~~~~~~~~~~~~~~

- `.TCPServer.handle_stream` implementations may now be native coroutines.
- Stopping a `.TCPServer` twice no longer raises an exception.

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

- `.RedirectHandler` now supports substituting parts of the matched
  URL into the redirect location using `str.format` syntax.
- New methods `.RequestHandler.render_linked_js`,
  `.RequestHandler.render_embed_js`,
  `.RequestHandler.render_linked_css`, and
  `.RequestHandler.render_embed_css` can be overridden to customize
  the output of `.UIModule`.


`tornado.websocket`
~~~~~~~~~~~~~~~~~~~

- `.WebSocketHandler.on_message` implementations may now be
  coroutines. New messages will not be processed until the previous
  ``on_message`` coroutine has finished.
- The ``websocket_ping_interval`` and ``websocket_ping_timeout``
  application settings can now be used to enable a periodic ping of
  the websocket connection, allowing dropped connections to be
  detected and closed.
- The new ``websocket_max_message_size`` setting defaults to 10MiB.
  The connection will be closed if messages larger than this are received.
- Headers set by `.RequestHandler.prepare` or
  `.RequestHandler.set_default_headers` are now sent as a part of the
  websocket handshake.
- Return values from `.WebSocketHandler.get_compression_options` may now include
  the keys ``compression_level`` and ``mem_level`` to set gzip parameters.
  The default compression level is now 6 instead of 9.

Demos
~~~~~

- A new file upload demo is available in the `file_upload
  <https://github.com/tornadoweb/tornado/tree/master/demos/file_upload>`_
  directory.
- A new `.TCPClient` and `.TCPServer` demo is available in the
  `tcpecho <https://github.com/tornadoweb/tornado/tree/master/demos/tcpecho>`_ directory.
- Minor updates have been made to several existing demos, including
  updates to more recent versions of jquery.

Credits
~~~~~~~

The following people contributed commits to this release:

- A\. Jesse Jiryu Davis
- Aaron Opfer
- Akihiro Yamazaki
- Alexander
- Andreas Røsdal
- Andrew Rabert
- Andrew Sumin
- Antoine Pietri
- Antoine Pitrou
- Artur Stawiarski
- Ben Darnell
- Brian Mego
- Dario
- Doug Vargas
- Eugene Dubovoy
- Iver Jordal
- JZQT
- James Maier
- Jeff Hunter
- Leynos
- Mark Henderson
- Michael V. DePalatis
- Min RK
- Mircea Ulinic
- Ping
- Ping Yang
- Riccardo Magliocchetti
- Samuel Chen
- Samuel Dion-Girardeau
- Scott Meisburger
- Shawn Ding
- TaoBeier
- Thomas Kluyver
- Vadim Semenov
- matee
- mike820324
- stiletto
- zhimin
- 依云
