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Hello,

Thanks Dims for raising the concern and Angus for reaching out. :)

Most of the time, python development on Windows is not too far off from Linux. But the two systems are quite different, which imply different modules (fcntl, pwd, grp modules do not exist in Windows) or different implementations of some modules (multiprocessing uses Popen instead of os.fork, os module is quite different) or some socket options and signals are different in Windows.

1.a. As I've said earlier, some modules do not exist in Windows. All, or at least most standard modules document the fact that they are strictly for Linux. [1][2][3]
b. At the very least, running the unit tests in a Windows environment can at least detect simple problems (e.g. imports). Secondly, there is a Hyper-V / Windows CI running on some of the OpenStack projects (nova, neutron, networking_hyperv, cinder) that can be checked before merging.

2. This is a bit more complicated question. Well, for functions, you could have separate modules for Linux specific functions and Windows specific functions. This has been done before: [4] As for object-oriented implementations, I'd suggest having the system-specific calls be done in private methods, which will be overriden by Windows / Linux subclasses with their specific implementations. We've done something like this before, but solutions were pretty much straight-forward; it might not be as simple for oslo_privsep, since it is very Linux-specific.

3. Typically, the OpenStack services on Hyper-V / Windows are run with users that have enough privileges to do their job. For example, the nova-compute service is run with a user that has Hyper-V Admin privileges and is not necessarily in the "Administrator" user group. We haven't used rootwrap in our usecases, it is disabled by default, plus, oslo.rootwrap imports pwd, which doesn't exist in Windows.

[1] https://docs.python.org/2/library/fcntl.html
[2] https://docs.python.org/2/library/pwd.html
[3] https://docs.python.org/2/library/grp.html
[4] https://github.com/openstack/neutron/blob/master/neutron/agent/common/utils.py
[5] https://github.com/openstack/oslo.rootwrap/blob/master/oslo_rootwrap/wrapper.py#L19

If you have any further questions, feel free to ask. :)

Best regards,
Claudiu Belu


________________________________
From: Angus Lees [gus at inodes.org]
Sent: Tuesday, November 24, 2015 6:18 AM
To: OpenStack Development Mailing List (not for usage questions); Claudiu Belu
Subject: [hyper-v] oslo.privsep vs Windows

Dims has just raised[1] the excellent concern that oslo.privsep will need to at least survive on Windows, because hyper-v.  I have no real experience coding on windows (I wrote a windows C program once, but I only ever ran it under wine ;) and certainly none within an OpenStack/python context:

1) How can I test whatever I'm working on to see if I have mistakenly introduced something Linux-specific?  Surely this is a challenge common across every project in the nova/oslo/hyper-v stack.

2) What predicate should I use to guard the inevitable Linux-specific or Windows-specific code branches?

and I guess:
3) What does a typical OpenStack/hyper-v install even look like? Do we run rootwrap with some sudo-like-thing, or just run everything as the superuser?
What _should_ oslo.privsep do for this environment?

[1] https://review.openstack.org/#/c/244984<https://review.openstack.org/#/c/244984/1>

 - Gus
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