What’s new in Tornado 4.1

Feb 7, 2015

Highlights

• If a Future contains an exception but that exception is never examined or re-raised (e.g. by yielding the Future), a stack trace will be logged when the Future is garbage-collected.
• New class tornado.gen.WaitIterator provides a way to iterate over Futures in the order they resolve.
• The tornado.websocket module now supports compression via the “permessage-deflate” extension. Override WebSocketHandler.get_compression_options to enable on the server side, and use the compression_options keyword argument to websocket_connect on the client side.
• When the appropriate packages are installed, it is possible to yield asyncio.Future or Twisted Defered objects in Tornado coroutines.

Backwards-compatibility notes

• HTTPServer now calls start_request with the correct arguments. This change is backwards-incompatible, afffecting any application which implemented HTTPServerConnectionDelegate by following the example of Application instead of the documented method signatures.

tornado.concurrent

• If a Future contains an exception but that exception is never examined or re-raised (e.g. by yielding the Future), a stack trace will be logged when the Future is garbage-collected.
• Future now catches and logs exceptions in its callbacks.

tornado.curl_httpclient

• tornado.curl_httpclient now supports request bodies for PATCH and custom methods.
• tornado.curl_httpclient now supports resubmitting bodies after following redirects for methods other than POST.
• curl_httpclient now runs the streaming and header callbacks on the IOLoop.
• tornado.curl_httpclient now uses its own logger for debug output so it can be filtered more easily.

tornado.gen

• New class tornado.gen.WaitIterator provides a way to iterate over Futures in the order they resolve.
• When the singledispatch library is available (standard on Python 3.4, available via pip install singledispatch on older versions), the convert_yielded function can be used to make other kinds of objects yieldable in coroutines.
• New function tornado.gen.sleep is a coroutine-friendly analogue to time.sleep.
• gen.engine now correctly captures the stack context for its callbacks.

tornado.httpclient

• tornado.httpclient.HTTPRequest accepts a new argument raise_error=False to suppress the default behavior of raising an error for non-200 response codes.

tornado.httpserver

• HTTPServer now calls start_request with the correct arguments. This change is backwards-incompatible, afffecting any application which implemented HTTPServerConnectionDelegate by following the example of Application instead of the documented method signatures.
• HTTPServer now tolerates extra newlines which are sometimes inserted between requests on keep-alive connections.
• HTTPServer can now use keep-alive connections after a request with a chunked body.
• HTTPServer now always reports HTTP/1.1 instead of echoing the request version.

tornado.httputil

• New function tornado.httputil.split_host_and_port for parsing the netloc portion of URLs.
• The context argument to HTTPServerRequest is now optional, and if a context is supplied the remote_ip attribute is also optional.
• HTTPServerRequest.body is now always a byte string (previously the default empty body would be a unicode string on python 3).
• Header parsing now works correctly when newline-like unicode characters are present.
• Header parsing again supports both CRLF and bare LF line separators.
• Malformed multipart/form-data bodies will always be logged quietly instead of raising an unhandled exception; previously the behavior was inconsistent depending on the exact error.

tornado.ioloop

• The kqueue and select IOLoop implementations now report writeability correctly, fixing flow control in IOStream.
• When a new IOLoop is created, it automatically becomes “current” for the thread if there is not already a current instance.
• New method PeriodicCallback.is_running can be used to see whether the PeriodicCallback has been started.

tornado.iostream

• IOStream.start_tls now uses the server_hostname parameter for certificate validation.
• SSLIOStream will no longer consume 100% CPU after certain error conditions.
• SSLIOStream no longer logs EBADF errors during the handshake as they can result from nmap scans in certain modes.

tornado.options

• parse_config_file now always decodes the config file as utf8 on Python 3.
• tornado.options.define more accurately finds the module defining the option.

tornado.platform.asyncio

• It is now possible to yield asyncio.Future objects in coroutines when the singledispatch library is available and tornado.platform.asyncio has been imported.
• New methods tornado.platform.asyncio.to_tornado_future and to_asyncio_future convert between the two libraries’ Future classes.

tornado.platform.twisted

• It is now possible to yield Deferred objects in coroutines when the singledispatch library is available and tornado.platform.twisted has been imported.

tornado.tcpclient

• TCPClient will no longer raise an exception due to an ill-timed timeout.

tornado.tcpserver

• TCPServer no longer ignores its read_chunk_size argument.

tornado.testing

• AsyncTestCase has better support for multiple exceptions. Previously it would silently swallow all but the last; now it raises the first and logs all the rest.
• AsyncTestCase now cleans up Subprocess state on tearDown when necessary.

tornado.web

• The asynchronous decorator now understands concurrent.futures.Future in addition to tornado.concurrent.Future.
• StaticFileHandler no longer logs a stack trace if the connection is closed while sending the file.
• RequestHandler.send_error now supports a reason keyword argument, similar to tornado.web.HTTPError.
• RequestHandler.locale now has a property setter.
• Application.add_handlers hostname matching now works correctly with IPv6 literals.
• Redirects for the Application default_host setting now match the request protocol instead of redirecting HTTPS to HTTP.
• Malformed _xsrf cookies are now ignored instead of causing uncaught exceptions.
• Application.start_request now has the same signature as HTTPServerConnectionDelegate.start_request.

tornado.websocket

• The tornado.websocket module now supports compression via the “permessage-deflate” extension. Override WebSocketHandler.get_compression_options to enable on the server side, and use the compression_options keyword argument to websocket_connect on the client side.
• WebSocketHandler no longer logs stack traces when the connection is closed.
• WebSocketHandler.open now accepts *args, **kw for consistency with RequestHandler.get and related methods.
• The Sec-WebSocket-Version header now includes all supported versions.
• websocket_connect now has a on_message_callback keyword argument for callback-style use without read_message().