Memory leak when using the old WMI

[Alin Balutoiu]

The Msvm_VirtualSystemManagementService WMI object is cached at the os-win level for performance reasons: https://github.com/openstack/os-win/blob/stable/ocata/os_win/utils/baseutils.py#L92-L97

It has been noticed that when the AddResourceSettings and ModifyResourceSettings are called on the previous object will leak the WMI objects passed as parameter to the mentioned functions. This will cause the Nova Python process to continue to eat more and more memory. It seems that the Python garbage collector is not able to free the respective memory until the cached object Msvm_VirtualSystemManagementService reference is deleted.

This issue does not affect if the PyMI module is being used. The old WMI is being used only on Windows Server 2012 for some operations where PyMI is not available. On Windows Server 2012r2 and Windows Server 2016 only PyMI is being used.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: stable/ocata
Review: https://review.openstack.org/475590

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/475590
Committed: https://git.openstack.org/cgit/openstack/os-win/commit/?id=938a99a7a7b1f55b7e31f0ff028d4f72ee0e2cdb
Submitter: Jenkins
Branch: stable/ocata

commit 938a99a7a7b1f55b7e31f0ff028d4f72ee0e2cdb
Author: Claudiu Belu <email address hidden>
Date: Tue Jun 13 16:07:58 2017 +0300

    Fixes cached old WMI service objects issue

    When using WMI, the resources passed to the
    Msvm_VirtualSystemManagementService are not cleaned up
    by the garbage collector if the Service object is still
    referenced (cached as a property in BaseUtilsVirt).

    PyMI doesn't have this issue, so the Service objects can be
    safely cached.

    This issue only affects Windows / Hyper-V Server 2012.

    Conflicts:
            os_win/tests/unit/utils/compute/test_migrationutils.py

    Closes-Bug: #1697389
    (cherry picked from commit 49a012e83c44d28ee533aace22c42b1781b8e5e2)

    tests: Sets baseutils.BaseUtilsVirt._old_wmi

    There is a race condition between tests, and because
    the _old_wmi is not set, it will try to load it, but since it
    is mocked, it cannot, and it shouldn't.

    Change-Id: Id029baf2e72f7b67eb6af3b3e66f998b902fd412

    Change-Id: If8df0bf0a2f13a9e94993dde8b2a18943f2e9f83

[OpenStack Infra (hudson-openstack)]

This issue was fixed in the openstack/os-win 1.4.2 release.

[OpenStack Infra (hudson-openstack)]

This issue was fixed in the openstack/os-win 2.1.0 release.