Comment 2 for bug 1821362

Reviewed: https://review.openstack.org/645614
Committed: https://git.openstack.org/cgit/openstack/kolla-ansible/commit/?id=192dcd1e1b9baf7f3177a694c2b1ce8bd62d9159
Submitter: Zuul
Branch: master

commit 192dcd1e1b9baf7f3177a694c2b1ce8bd62d9159
Author: Mark Goddard <email address hidden>
Date: Fri Mar 22 14:59:41 2019 +0000

    Fix booting instances after nova-compute upgrade

    After upgrading from Rocky to Stein, nova-compute services fail to start
    new instances with the following error message:

    Failed to allocate the network(s), not rescheduling.

    Looking in the nova-compute logs, we also see this:

    Neutron Reported failure on event
    network-vif-plugged-60c05a0d-8758-44c9-81e4-754551567be5 for instance
    32c493c4-d88c-4f14-98db-c7af64bf3324: NovaException: In shutdown, no new
    events can be scheduled

    During the upgrade process, we send nova containers a SIGHUP to cause
    them to reload their object version state. Speaking to the nova team in
    IRC, there is a known issue with this, caused by oslo.service performing
    a full shutdown in response to a SIGHUP, which breaks nova-compute.
    There is a patch [1] in review to address this.

    The workaround employed here is to restart the nova compute service.

    [1] https://review.openstack.org/#/c/641907

    Change-Id: Ia4fcc558a3f62ced2d629d7a22d0bc1eb6b879f1
    Closes-Bug: #1821362