os.fork() command distributed in windows Python27 (in SocketServer module)

[SamLobel]

BPO	25931
Nosy	@gpshead, @pfmoore, @tjguk, @bitdancer, @vadmium, @zware, @eryksun, @zooba, @applio, @antvalencia

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = <Date 2016-06-03.05:56:57.478>
created_at = <Date 2015-12-23.03:10:31.473>
labels = ['type-bug', 'docs']
title = 'os.fork() command distributed in windows Python27 (in SocketServer module)'
updated_at = <Date 2016-06-03.20:27:32.010>
user = 'https://bugs.python.org/SamLobel'

bugs.python.org fields:

activity = <Date 2016-06-03.20:27:32.010>
actor = 'berker.peksag'
assignee = 'docs@python'
closed = True
closed_date = <Date 2016-06-03.05:56:57.478>
closer = 'gregory.p.smith'
components = ['Documentation']
creation = <Date 2015-12-23.03:10:31.473>
creator = 'Sam Lobel'
dependencies = []
files = []
hgrepos = []
issue_num = 25931
keywords = []
message_count = 12.0
messages = ['256896', '256898', '266845', '266999', '267001', '267005', '267006', '267029', '267042', '267045', '267048', '267049']
nosy_count = 14.0
nosy_names = ['gregory.p.smith', 'paul.moore', 'tim.golden', 'r.david.murray', 'docs@python', 'python-dev', 'martin.panter', 'zach.ware', 'eryksun', 'steve.dower', 'davin', 'supriyanto maftuh', 'Sam Lobel', 'antvalencia']
pr_nums = []
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue25931'
versions = ['Python 2.7', 'Python 3.5', 'Python 3.6']

[SamLobel]

I ran into this bug while using multiprocessing in Flask, which deep down uses the SocketServer.py module.

There's a call to os.fork() in the windows version , which obviously doesn't work. So SocketServer.py can't be used on windows.

Maybe replace it with something from the multiprocessing module?

[eryksun]

Starting a Windows process is expensive. Who not use threading, e.g. SocketServer.ThreadingTCPServer?

It seems to me that it's a bug to even define ForkingMixIn, ForkingTCPServer, and ForkingUDPServer on Windows. Those should be conditionally defined depending on the existence of os.fork.

[bitdancer]

They aren't currently defined conditionally, though, and haven't ever been, so I'm not sure it is worth chaning that. However, we should probably add an 'availability' line, since they aren't (effectively) available on Windows.

[python-dev]

New changeset d772400a1211 by Gregory P. Smith in branch 'default':
Issue bpo-25931: Don't defining socketserver.Forking* names on platforms such
https://hg.python.org/cpython/rev/d772400a1211

[gpshead]

I made the change to not export the Forking names on Windows or other non-os.fork() supporting platforms in 3.6 only as it is arguably an API change, even though the names it removes would effectively be unusable on those platforms anyways.

the docs still need updating.

[bitdancer]

Your news entry says "don't defining". The doc note can say that the classes are only defined if the platform supports fork.

[bitdancer]

Well, defined for 3.6, and "functional" for 2.7 and 3.5 docs.

[vadmium]

This broke test_socketserver:

http://buildbot.python.org/all/builders/AMD64%20Windows7%20SP1%203.x/builds/7709/steps/test/logs/stdio
0:08:57 [193/400/1] test_socketserver failed
test test_socketserver crashed -- Traceback (most recent call last):
  File "C:\buildbot.python.org\3.x.kloth-win64\build\lib\test\test_socketserver.py", line 371, in <module>
    class ForkingErrorTestServer(socketserver.ForkingMixIn, BaseErrorTestServer):
AttributeError: module 'socketserver' has no attribute 'ForkingMixIn'

I am with David that it may not be worthwhile churning the API like this. Just document the existing (in 3.5) status that even though the classes exist, they need a working os.fork(). Otherwise, everyone that references ForkingMixIn but doesn’t use it (like test_socketserver) will have to update their code for 3.6.