Comment 3 for bug 1777608

Reviewed: https://review.opendev.org/c/openstack/nova/+/813263
Committed: https://opendev.org/openstack/nova/commit/7f81cf28bf21ad2afa98accfde3087c83b8e269b
Submitter: "Zuul (22348)"
Branch: master

commit 7f81cf28bf21ad2afa98accfde3087c83b8e269b
Author: Julia Kreger <email address hidden>
Date: Fri Oct 8 14:35:00 2021 -0700

    Ignore plug_vifs on the ironic driver

    When the nova-compute service starts, by default it attempts to
    startup instance configuration states for aspects such as networking.
    This is fine in most cases, and makes a lot of sense if the
    nova-compute service is just managing virtual machines on a hypervisor.

    This is done, one instance at a time.

    However, when the compute driver is ironic, the networking is managed
    as part of the physical machine lifecycle potentially all the way into
    committed switch configurations. As such, there is no need to attempt
    to call ``plug_vifs`` on every single instance managed by the
    nova-compute process which is backed by Ironic.

    Additionally, using ironic tends to manage far more physical machines
    per nova-compute service instance then when when operating co-installed
    with a hypervisor. Often this means a cluster of a thousand machines,
    with three controllers, will see thousands of un-needed API calls upon
    service start, which elongates the entire process and negatively
    impacts operations.

    In essence, nova.virt.ironic's plug_vifs call now does nothing,
    and merely issues a debug LOG entry when called.

    Closes-Bug: #1777608
    Change-Id: Iba87cef50238c5b02ab313f2311b826081d5b4ab