Comment 15 for bug 1414895

Reviewed: https://review.openstack.org/627958
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=8c678ae57299076a5013f0be985621e064acfee0
Submitter: Zuul
Branch: stable/rocky

commit 8c678ae57299076a5013f0be985621e064acfee0
Author: Lee Yarwood <email address hidden>
Date: Mon Dec 3 09:03:26 2018 +0000

    libvirt: Add workaround to cleanup instance dir when using rbd

    At present all virt drivers provide a cleanup method that takes a single
    destroy_disks boolean to indicate when the underlying storage of an
    instance should be destroyed.

    When cleaning up after an evacuation or revert resize the value of
    destroy_disks is determined by the compute layer calling down both into
    the check_instance_shared_storage_local method of the local virt driver
    and remote check_instance_shared_storage method of the virt driver on
    the host now running the instance.

    For the Libvirt driver the initial local call will return None when
    using the shared block RBD imagebackend as it is assumed all instance
    storage is shared resulting in destroy_disks always being False when
    cleaning up. This behaviour is wrong as the instance disks are stored
    separately to the instance directory that still needs to be cleaned up
    on the host. Additionally this directory could also be shared
    independently of the disks on a NFS share for example and would need to
    also be checked before removal.

    This change introduces a backportable workaround configurable for the
    Libvirt driver with which operators can ensure that the instance
    directory is always removed during cleanup when using the RBD
    imagebackend. When enabling this workaround operators will need to
    ensure that the instance directories are not shared between computes.

    Future work will allow for the removal of this workaround by separating
    the shared storage checks from the compute to virt layers between the
    actual instance disks and any additional storage required by the
    specific virt backend.

    Related-Bug: #1761062
    Partial-Bug: #1414895
    Change-Id: I8fd6b9f857a1c4919c3365951e2652d2d477df77
    (cherry picked from commit d6c1f6a1032ed2ea99f3d8b70ccf38065163d785)