I saw this in the official 3.4rc1 doc. The doc says, that flow-control callbacks are valid for Protocols and SubprocessProtocols, but DatagramProtocol is not specified.
Though I'm happy that Datagram control flow is officially supported I have now an other problem which is directly connected with this issue. Using OSX10.9.1 and python 3.3 sending a lot of udp packets actually does not cause the flow-control to be activated but throws an OSError(55 *No buffer space available)* . After googling around for hours I found out that this is a BSD(probably OS X only) thing. On linux the control-flow works as expected. I listed an issue for this in your tulip repo: Issue 153 <https://code.google.com/p/tulip/issues/detail?id=153> I think that this is really not a python bug, but the way BSD/OSX handles too much udp packets (the socket sdnbuf option is kind of ignored by OSX). I've read that windows actually handles udp overload in a similiar way as BSD does. Though i don't have a windows machine this should probably be tested to confirm or disprove this issue. PS: 18.5.3.2.5. Flow control callbacks<http://docs.python.org/3.4/library/asyncio-protocol.html#flow-control-callbacks> These callbacks may be called on Protocol<http://docs.python.org/3.4/library/asyncio-protocol.html#asyncio.Protocol> and SubprocessProtocol<http://docs.python.org/3.4/library/asyncio-protocol.html#asyncio.SubprocessProtocol> instances: BaseProtocol.pause_writing()<http://docs.python.org/3.4/library/asyncio-protocol.html#asyncio.BaseProtocol.pause_writing> Called when the transport’s buffer goes over the high-water mark. BaseProtocol.resume_writing()<http://docs.python.org/3.4/library/asyncio-protocol.html#asyncio.BaseProtocol.resume_writing> Called when the transport’s buffer drains below the low-water mark. Am Sonntag, 23. Februar 2014 18:56:42 UTC+1 schrieb Guido van Rossum: > > This looks like a bug in the docs; the intention is that datagram > protocols also support flow control. Where does it say so in the docs? Is > it the PEP or the CPython Doc tree? > > > On Sat, Feb 22, 2014 at 5:12 PM, Christopher Probst < > [email protected] <javascript:>> wrote: > >> Hi, >> >> after looking into the implementation I saw that, for instance, >> _SelectorDatagramTransport calls _maybe_pause_protocol and it's >> counterpart, but the doc says that only Protocol and SubprocessProtocol has >> flow-control support and DatagramProtocol does not. >> >> I know that udp flow-control is not the same as tcp flow-control, but I'm >> concerned about filling up the internal buffer when writing a lot of >> datagrams. If this is not supported, I would argue that the udp support >> is pretty much broken for data intense application because how would the >> writer know when the internal buffer (and/or kernel level buffer) are full ? >> >> So, is the doc just not up-to-date or is it an implementation detail of >> tulip ? >> >> And other question that came up: Are there any plans for coroutine >> methods for udp (like StreamWriter/Reader for TCP) ? >> >> Also, are there any "dirty" corners somebody heavily working with udp >> have to know ? I'm implementing reliable udp and I would like to use the >> coroutine style instead of callbacks. >> >> >> Regards, >> Chris >> >> > > > -- > --Guido van Rossum (python.org/~guido) >
