WMI object caching causes issues

[Lucian Petrut]

When WMI object caching is enabled and the vm ports get recreated (e.g. after a rebuild), the cache contains invalid entries (references of the old ports).

Because of those entries, some operations will not work as expected. For example, ports will not be connected to vswitches (as os-win will think that the ports are already bound, judging by the cached ports). Also, metrics will not be enabled for those ports (as this operation requires the ports to be connected to a vswitch), basically breaking the nova instance rebuild operation.

Trace: http://paste.openstack.org/show/733939/

os-win already provides a public method that recreates the cache, but none for removing ports from the cache. Besides, relying on os-win consumers to cleanup the cache whenever a port gets removed may be too much.

We should disable the cache by default, especially considering the countless issues we had because of it. Also, the config option description should provide a proper warning.

[OpenStack Infra (hudson-openstack)]

Related fix proposed to branch: master
Review: https://review.openstack.org/615570

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/615570
Committed: https://git.openstack.org/cgit/openstack/os-win/commit/?id=030df4e31005e28b71f549dbb888f3040e0a4457
Submitter: Zuul
Branch: master

commit 030df4e31005e28b71f549dbb888f3040e0a4457
Author: Lucian Petrut <email address hidden>
Date: Mon Nov 5 16:20:30 2018 +0200

    Disable wmi object caching by default

    Due to the known issues related to WMI object caching, it's safer
    if we just disable it by default.

    Change-Id: If859917af9a185fc612231002d252c9e0ac6ddd3
    Related-Bug: #1801701