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Clarify that flow control works for datagrams, except on BSD.

This commit is contained in:
Guido van Rossum 2014-02-24 14:31:25 -08:00
parent 8920e915fa
commit 3e97585b3e
1 changed files with 11 additions and 2 deletions
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13
Doc/library/asyncio-protocol.rst
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@ -376,8 +376,8 @@ The following callbacks are called on :class:`DatagramProtocol` instances.
Flow control callbacks
----------------------
These callbacks may be called on :class:`Protocol` and
:class:`SubprocessProtocol` instances:
These callbacks may be called on :class:`Protocol`,
:class:`DatagramProtocol` and :class:`SubprocessProtocol` instances:
.. method:: BaseProtocol.pause_writing()
@ -402,6 +402,15 @@ buffer size reaches the low-water mark.
are important to ensure that things go as expected when either
mark is zero.
.. note::
On BSD systems (OS X, FreeBSD, etc.) flow control is not supported
for :class:`DatagramProtocol`, because send failures caused by
writing too many packets cannot be detected easily. The socket
always appears 'ready' and excess packets are dropped; an
:class:`OSError` with errno set to :const:`errno.ENOBUFS` may or
may not be raised; if it is raised, it will be reported to
:meth:`DatagramProtocol.error_received` but otherwise ignored.
Coroutines and protocols
------------------------