Comment 4 for bug 1940043

Reviewed: https://review.opendev.org/c/x/charm-ovn-dedicated-chassis/+/804744
Committed: https://opendev.org/x/charm-ovn-dedicated-chassis/commit/33ed06cb238ea6b7f031a6500c054d522d538d88
Submitter: "Zuul (22348)"
Branch: master

commit 33ed06cb238ea6b7f031a6500c054d522d538d88
Author: Frode Nordahl <email address hidden>
Date: Mon Aug 16 15:27:46 2021 +0200

    Improve handling of major version upgrades

    Setting the external_ids:ovn-match-northd-version value to
    'true' will make the ovn-controller refrain from making updates to
    the data plane tables in the event of a version mismatch.

    This in combination with stopping the ovn-controller with the
    ovn-ctl stop_controller --restart command will allow upgrades
    to progress with little or no data plane downtime.
    (Note that we will accomplish this by a separate proposal to the
    OVN package itself in Ubuntu.)

    As soon as the central components are upgraded ovn-controller will
    notice and resume (re-)programming of the local Open vSwitch data
    plane.

    Closes-Bug: #1940043
    Change-Id: I16fedbc455e25bec0de4a475a9daa55b700ab3a0