classification
Title: Add socket.getblocking() method
Type: enhancement Stage: resolved
Components: Library (Lib) Versions: Python 3.7
process
Status: closed Resolution: fixed
Dependencies: Superseder:
Assigned To: yselivanov Nosy List: asvetlov, njs, pitrou, vstinner, yselivanov
Priority: normal Keywords: patch

Created on 2017-12-19 14:23 by yselivanov, last changed 2018-01-28 23:18 by yselivanov. This issue is now closed.

Pull Requests
URL Status Linked Edit
PR 4926 merged yselivanov, 2017-12-19 14:24
Messages (6)
msg308645 - (view) Author: Yury Selivanov (yselivanov) * (Python committer) Date: 2017-12-19 14:23
Currently we have the following methods:

* socket.settimeout(t) -- can set the socket in blocking mode, when t==0.
* socket.setblocking(flag) -- sets in blocking or non-blocking mode.
* socket.gettimeout() -- returns 0 when socket is in non-blocking mode.

socket.gettimeout() is the only easy way of checking if the socket is non-blocking or blocking, but it's not intuitive to use it.  It's especially strange that we have a setblocking() method without a corresponding getblocking().

I propose to add a 'socket.getblocking() -> bool' method.
msg308656 - (view) Author: Yury Selivanov (yselivanov) * (Python committer) Date: 2017-12-19 15:56
It looks like we have a bug with 'sock.settimeout()' and non-blocking/blocking modes (or maybe this is a feature?)

Currently:

* to make a socket non-blocking, we call 'sock.settimeout(0)'.

* to make a socket blocking, we call 'sock.settimeout(None)'.


What happens if we call sock.settimeout(t), where t > 0?  The internal timeout field of the socket object will simply be set to 't'.  What happens if the socket was in a non-blocking mode?  Nothing, it stays in non-blocking mode.

What it means: suppose you have a non-blocking socket.  You call socket.settimeout(10), and most likely you wanted to make it blocking again.  Because all operations on the socket become blocking from moment (sock_call_ex repeats on EWOULDBLOCK and EAGAIN).

Now is having a timeout and blocking send/recv methods on a non-blocking socket a feature? Or is this a bug?
msg308658 - (view) Author: Antoine Pitrou (pitrou) * (Python committer) Date: 2017-12-19 16:10
> Now is having a timeout and blocking send/recv methods on a non-blocking socket a feature? Or is this a bug?

I agree it's a bug (but should only be fixed in 3.7).

Also I agree with adding a socket.getblocking() method.
msg308663 - (view) Author: Andrew Svetlov (asvetlov) * (Python committer) Date: 2017-12-19 17:10
Agree, it's a bug.

+1 for getblocking()
msg308693 - (view) Author: Yury Selivanov (yselivanov) * (Python committer) Date: 2017-12-19 23:40
It appears the the timeouts situation is a bit more complex.  It's perfectly normal for a Python socket object to be in a "blocking" mode and for its FD to be in a non-blocking mode.  Read more about this in the latest docs update to the PR: https://github.com/python/cpython/pull/4926/commits/adcc91f93e1538f0d25645ebe0285b12137a3e3b
msg311019 - (view) Author: Yury Selivanov (yselivanov) * (Python committer) Date: 2018-01-28 22:27
New changeset f11b460d8717fc3a5810684713b8b818f68789e8 by Yury Selivanov in branch 'master':
bpo-32373: Add socket.getblocking() method. (#4926)
https://github.com/python/cpython/commit/f11b460d8717fc3a5810684713b8b818f68789e8
History
Date User Action Args
2018-01-28 23:18:40yselivanovsetstatus: open -> closed
resolution: fixed
stage: patch review -> resolved
2018-01-28 22:27:40yselivanovsetmessages: + msg311019
2017-12-19 23:40:15yselivanovsetmessages: + msg308693
2017-12-19 17:10:41asvetlovsetmessages: + msg308663
2017-12-19 16:10:04pitrousetmessages: + msg308658
2017-12-19 15:56:14yselivanovsetnosy: + pitrou, njs
messages: + msg308656
2017-12-19 14:24:57yselivanovsetkeywords: + patch
stage: patch review
pull_requests: + pull_request4820
2017-12-19 14:24:18yselivanovsetnosy: + vstinner, asvetlov
2017-12-19 14:23:24yselivanovcreate