What’s new in the next version of Tornado

In progress

Backwards-compatibility notes

• Authors of alternative IOLoop implementations should see the changes to IOLoop.add_handler in this release.
• tornado.concurrent.Future is no longer thread-safe; use concurrent.futures.Future when thread-safety is needed.
• Tornado now depends on the certifi package instead of bundling its own copy of the Mozilla CA list. This will be installed automatically when using pip or easy_install.

tornado.concurrent

• tornado.concurrent.Future is now always thread-unsafe (previously it would be thread-safe if the concurrent.futures package was available). This improves performance and provides more consistent semantics. The parts of Tornado that accept Futures will accept both Tornado’s thread-unsafe Futures and the thread-safe concurrent.futures.Future.
• tornado.concurrent.Future now includes all the functionality of the old TracebackFuture class. TracebackFuture is now simply an alias for Future.

tornado.gen

• The internals of the tornado.gen module have been rewritten to improve performance when using Futures, at the expense of some performance degradation for the older YieldPoint interfaces.
• Performance of coroutines has been improved.
• Coroutines no longer generate StackContexts by default, but they will be created on demand when needed.
• New function with_timeout wraps a Future and raises an exception if it doesn’t complete in a given amount of time.

tornado.http1connection

• New module contains the HTTP implementation shared by tornado.httpserver and tornado.simple_httpclient.

tornado.httpclient

• The command-line HTTP client (python -m tornado.httpclient $URL) now works on Python 3.

tornado.httpserver

• tornado.httpserver.HTTPRequest has moved to tornado.httputil.HTTPServerRequest.
• HTTP implementation has been unified with tornado.simple_httpclient in tornado.http1connection.
• Now supports Transfer-Encoding: chunked for request bodies.
• Now supports Content-Encoding: gzip for request bodies if gzip=True is passed to the HTTPServer constructor.
• The connection attribute of HTTPServerRequest is now documented for public use; applications are expected to write their responses via the HTTPConnection interface.
• The HTTPServerRequest.write and HTTPServerRequest.finish methods are now deprecated.
• HTTPServer now supports HTTPServerConnectionDelegate in addition to the old request_callback interface. The delegate interface supports streaming of request bodies.
• HTTPServer now detects the error of an application sending a Content-Length error that is inconsistent with the actual content.
• New constructor arguments max_header_size and max_body_size allow separate limits to be set for different parts of the request. max_body_size is applied even in streaming mode.
• New constructor argument chunk_size can be used to limit the amount of data read into memory at one time per request.
• New constructor arguments idle_connection_timeout and body_timeout allow time limits to be placed on the reading of requests.

tornado.httputil

• HTTPServerRequest was moved to this module from tornado.httpserver.
• New base classes HTTPConnection, HTTPServerConnectionDelegate, and HTTPMessageDelegate define the interaction between applications and the HTTP implementation.

tornado.ioloop

• IOLoop.add_handler and related methods now accept file-like objects in addition to raw file descriptors. Passing the objects is recommended (when possible) to avoid a garbage-collection-related problem in unit tests.
• New method IOLoop.clear_instance makes it possible to uninstall the singleton instance.
• IOLoop.add_timeout is now a bit more efficient.

tornado.iostream

• The callback argument to most IOStream methods is now optional. When called without a callback the method will return a Future for use with coroutines.
• No longer gets confused when an IOError or OSError without an errno attribute is raised.
• BaseIOStream.read_bytes now accepts a partial keyword argument, which can be used to return before the full amount has been read. This is a more coroutine-friendly alternative to streaming_callback.
• BaseIOStream.read_until and read_until_regex now acept a max_bytes keyword argument which will cause the request to fail if it cannot be satisfied from the given number of bytes.
• IOStream no longer reads from the socket into memory if it does not need data to satisfy a pending read. As a side effect, the close callback will not be run immediately if the other side closes the connection while there is unconsumed data in the buffer.
• The default chunk_size has been increased to 64KB (from 4KB)

tornado.netutil

• When bind_sockets chooses a port automatically, it will now use the same port for IPv4 and IPv6.
• TLS compression is now disabled by default on Python 3.3 and higher (it is not possible to change this option in older versions.

tornado.options

• It is now possible to disable the default logging configuration by setting options.logging to None instead of the string “none”.

tornado.platform.asyncio

• Now works on Python 2.6.

tornado.simple_httpclient

• Improved default cipher suite selection (Python 2.7+).
• HTTP implementation has been unified with tornado.httpserver in tornado.http1connection
• Streaming request bodies are now supported via the body_producer keyword argument to tornado.httpclient.HTTPRequest.
• The expect_100_continue keyword argument to tornado.httpclient.HTTPRequest allows the use of the HTTP Expect: 100-continue feature.

tornado.stack_context

• The stack context system now has less performance overhead when no stack contexts are active.

tornado.testing

• AsyncTestCase now attempts to detect test methods that are generators but were not run with @gen_test or any similar decorator (this would previously result in the test silently being skipped).
• Better stack traces are now displayed when a test times out.
• Fixed the test suite when unittest2 is installed on Python 3.

tornado.web

• When gzip support is enabled, all text/* mime types will be compressed, not just those on a whitelist.
• Application now implements the HTTPMessageDelegate interface.
• It is now possible to support streaming request bodies with the stream_request_body decorator and the new RequestHandler.data_received method.
• RequestHandler.flush now returns a Future if no callback is given.

tornado.websocket

• WebSocketHandler.close and WebSocketClientConnection.close now support code and reason arguments to send a status code and message to the other side of the connection when closing. Both classes also have close_code and close_reason attributes to receive these values when the other side closes.
• The C speedup module now builds correctly with MSVC, and can support messages larger than 2GB on 64-bit systems.
• The fallback mechanism for detecting a missing C compiler now works correctly on Mac OS X.
• Arguments to WebSocketHandler.open are now decoded in the same way as arguments to RequestHandler.get and similar methods.

tornado.wsgi

• New class WSGIAdapter supports running a Tornado Application on a WSGI server in a way that is more compatible with Tornado’s non-WSGI HTTPServer. WSGIApplication is deprecated in favor of using WSGIAdapter with a regular Application.
• WSGIAdapter now supports gzipped output.