Comment 12 for bug 1868607

Reviewed: https://review.opendev.org/731120
Committed: https://git.openstack.org/cgit/openstack/tripleo-heat-templates/commit/?id=05f19f2c596149c19f5005b4b31ccfdb11bc388d
Submitter: Zuul
Branch: stable/ussuri

commit 05f19f2c596149c19f5005b4b31ccfdb11bc388d
Author: Rodolfo Alonso Hernandez <email address hidden>
Date: Tue May 26 13:59:42 2020 +0000

    Force container deletion if namespace does not exist in service_kill

    When a service is stopped using "service_kill" script and the
    namespace where the container is running does not exist, the
    container process should be forced to stop from the root namespace.

    A namespace where a process is running, can be deleted whitout
    stopping the mentioned process. "ip netns identify <PID>" then
    returns an empty string (root namespace).

    If the namespace where a container was executed is deleted,
    "service_kill" script should execute a container related command
    from the root namespace. To access to the root namespace from
    inside a container, running in another namespace, it is necessary
    to gain access via "nsenter", specifying the parameter "--all" to
    access to all namespaces of the target process.

    This patch will prevent an endless loop in Neutron DHCP agent. As
    reported in the related bug, when a DHCP agent is resync, the DHCP
    helper (metadata proxy) is stopped. In case this process stop raises
    an exception (for example if the namespace does not exist), schedules
    again a resync, creating an endless loop.

    This patch combines [1] and [2] in this repository.
    [1]https://review.opendev.org/#/c/714517/
    [2]https://review.opendev.org/#/c/730657/

    Change-Id: Ifb7dbfb93a7cf0b50ef15652d83d87f65bdb6221
    Closes-Bug: #1868607
    (cherry picked from commit 0bc1383a60c4ab249d16402c37adcea988b84c53)