oslo-specs/specs/liberty/windows-oslo-service-workers.rst

Oslo Service Workers for Windows

https://blueprints.launchpad.net/oslo.service/+spec/ windows-oslo-service-workers

The goal of this blueprint is implement a way which will allow OpenStack services to run under Windows.

Problem description

Currently, oslo_service project has a couple of Linux specific implementations, which makes it impossible to use under Windows. A few examples would be service.ProcessLauncher, which uses:

• eventlet.greenio.GreenPipe, which it cannot be used, as it tries to set the pipe as non-blocking, mechanism that does not exist in Windows. [1]
• os.fork, which does not exist in Windows. [2]

Proposed change

An alternative option for forking would be spawning subprocesses by using the multiprocessing module, which avoids the GIL problem. [3]

Multiprocessing module still forks the process on Linux systems, which means that the behaviour will remain consistent with the current implementation.

The proposed change is that service.ProcessLauncher to spawn mutliprocessing.Process objects as service workers instead.

Alternatives

Cygwin can be used under Windows [3], which is a collection of tools providing similar functionality to a "Linux distribution on Windows".

The problem is, forking in Cygwin is known to be problematic and inefficient, as it does not map well on top of the WIN32 API. [4]

Impact on Existing APIs

None

Security impact

None

Performance Impact

None, functionality and performance should not change for Linux.

Configuration Impact

None

Developer Impact

None

Testing Impact

Unit tests.

CI testing will be performed by Jenkins for Linux and Hyper-V CI for Windows.

Testing should be done for both Python 2.7 and 3.4, as the implementation of the multiprocessing module differs greatly. Needed in order not to introduce regressions for a certain Python version.

Implementation

Assignee(s)

Primary assignee:

Claudiu Belu <cbelu@cloudbasesolutions.com>

Milestones

Target Milestone for completion:

Work Items

As per Proposed Change.

Incubation

Adoption

The current services that use the oslo_services module.

Library

oslo_service

Anticipated API Stabilization

None

Documentation Impact

None

Dependencies

multiprocessing

Version might be different for Python 2.7 and 3.4.

References

[1] GreenIO exception

http://paste.openstack.org/show/284115/

[2] os.fork available only on Unix.

https://docs.python.org/2/library/os.html#os.fork

[3] multiprocessing module

http://sebastianraschka.com/Articles/2014_multiprocessing_intro.html

[4] Cygwin

https://www.cygwin.com/

[5] Cygwin fork issues:

http://cygwin.com/cygwin-ug-net/highlights.html#ov-hi-process

Note

This work is licensed under a Creative Commons Attribution 3.0 Unported License. http://creativecommons.org/licenses/by/3.0/legalcode