[Bug 1907081] Re: Clustered OVN database is not upgraded on package upgrade

[Frode Nordahl]

On Focal OVN central unit used to initialize a cluster (which means the db-*-clsuter-remote-addr parameters are set to blank):
# grep remote-addr= /etc/default/ovn-central 
    --db-nb-cluster-remote-addr= \
    --db-sb-cluster-remote-addr= \

I can then install the packages from -proposed:
# apt -y install ovn-common ovn-central

I can then confirm that the cluster is still healthy:
# ovn-appctl -t /var/run/ovn/ovnsb_db.ctl cluster/status OVN_Southbound
cd89
Name: OVN_Southbound
Cluster ID: d623 (d62321da-8009-4798-bd0a-171e5678a790)
Server ID: cd89 (cd8983cc-e19a-45ee-9247-34e130927eb6)
Address: ssl:10.247.39.51:6644
Status: cluster member
Role: follower
Term: 5
Leader: b941
Vote: unknown

Election timer: 4000
Log: [2, 7533]
Entries not yet committed: 0
Entries not yet applied: 0
Connections: ->b941 ->8c5f <-b941 <-8c5f
Servers:
    cd89 (cd89 at ssl:10.247.39.51:6644) (self)
    b941 (b941 at ssl:10.247.39.127:6644)
    8c5f (8c5f at ssl:10.247.39.149:6644)

Since the focal package currently does not contain any schema changes we
cannot do further checks as to the upgrade procedure actually working
for Focal. We will do that as part of validating Groovy.

** Tags removed: verification-needed-focal
** Tags added: verification-done-focal

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https://bugs.launchpad.net/bugs/1907081

Title:
  Clustered OVN database is not upgraded on package upgrade

Status in charm-ovn-central:
  Fix Released
Status in ovn package in Ubuntu:
  Fix Released
Status in ovn source package in Focal:
  Fix Committed
Status in ovn source package in Groovy:
  Fix Committed
Status in ovn source package in Hirsute:
  Fix Released

Bug description:
  [Impact]
  On upgrade of the OVN packages it may be necessary to perform a upgrade to the Northbound and Southbound databases.

  Failure to do so may lead to loss of connectivity between
  participating nodes as the software components will attempt to make
  use of columns that are not available in the database.

  The upgrade process has been performed automatically by the upstream
  init script by default since inception, both for a local and clustered
  setup. But as discussed below recent changes has inadvertently omitted
  this behavior for clustered databases.

  [Test Case]

  Non-clustered scenario as reference test:
  Install the ovn-central package in a container using the in-release focal package and start the database and ovn-northd services.

  Upgrade the container to the OVN packages from in-release Groovy and
  observe the package performing the database upgrade and subsequently
  ovn-northd service not complaining about missing columns in the
  database.

  Clustered scenario:
  Install the ovn-central charm across three containers and necessary dependencies. Perform package upgrade as outlined above and compare how in-relase and proposed packages behave.

  [Regression Potential]
  As we are restoring the intended behavior the regression potential is minimal.

  [Original Bug Report]
  In the systemd service we make use of the `ovn-ctl` script `run_nb_ovsdb` and `run_sb_ovsdb` sub-commands introduced in [0]. These sub-commands fit nicely with systemd's expectations of modern daemons to no longer detachand run in the background.

  However, the change in [0] has the side effect of disabling automatic
  upgrading of clustered databases. Previously this would have been done
  on every startup [1].

  A recent commit to master [2] addresses this and uses the combination
  of presence of `--db-*-cluster-local-addr` and non-presence of the
  `--db-*-cluster-remote-addr` to determine if the upgrade should be
  run.

  We should backport [2] to our supported OVN packages to prepare for
  supporting upgrades that require database schema changes. We may also
  need to change the behavior of the ovn-central charm to not set the
  `--db-*-cluster-remote-addr` argument on the leader unit.

  0: https://github.com/ovn-org/ovn/commit/6444059b5f9444ce06634794d275257f945a6ce5
  1: https://github.com/ovn-org/ovn/blob/5c2d311b8b7b4d5c3a619de72be6a433aa4c44db/utilities/ovn-ctl#L312-L314
  2: https://github.com/ovn-org/ovn/commit/67e2f386cc838d0b0f9b4b5da7fe611e1113b70c

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