[Bug 1940043] Re: Upgrade from OVN 20.03 to newer OVN version will cause data plane outage

[Frode Nordahl]

** Also affects: ovn (Ubuntu)
   Importance: Undecided
       Status: New

** Description changed:

  The upstream recommendation for upgrades of OVN is to first upgrade the
  data plane components (chassis aka. ovn-controller), and then upgrade
  the central components (the database schema and ovn-northd). The
  rationale for this is that the new version of the ovn-controller is
  required to cope with any changes to database schema or how northd
  programs flows.
  
  However, during the course of rapid OVN development there has also been
  introduced changes that make the new ovn-controller not cope with a old
  database schema, breaking the recommended upgrade procedure.
  
  To cope with this upstream has introduced a new optional configuration
  for the ovn-controller that allows it to detect version inconsistencies,
  and when they are present stop it from making changes to the data plane
  until the version inconsistency is resolved [0].
  
- The charms should enable this option to allow upgrades to progress with
- less data plane outage.
+ For the above mentioned configuration to be effective we also need the
+ package to call ``ovn-ctl stop_controller`` with the --restart option so
+ that the ovn-controller does not flush the installed flows on exit.
+ 
+ We should make required changes to packages and charms to allow upgrades
+ to progress with less data plane outage.
  
  0: https://github.com/ovn-
  org/ovn/commit/1dd27ea7aea40122c1edbff845e14abaa70c0413

** Also affects: ovn (Ubuntu Hirsute)
   Importance: Undecided
       Status: New

** Also affects: ovn (Ubuntu Focal)
   Importance: Undecided
       Status: New

** Also affects: ovn (Ubuntu Impish)
   Importance: Undecided
       Status: New

** Changed in: ovn (Ubuntu Impish)
       Status: New => In Progress

** Changed in: ovn (Ubuntu Impish)
   Importance: Undecided => High

** Changed in: ovn (Ubuntu Impish)
     Assignee: (unassigned) => Frode Nordahl (fnordahl)

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https://bugs.launchpad.net/bugs/1940043

Title:
  Upgrade from OVN 20.03 to newer OVN version will cause data plane
  outage

Status in charm-ovn-chassis:
  In Progress
Status in ovn package in Ubuntu:
  In Progress
Status in ovn source package in Focal:
  New
Status in ovn source package in Hirsute:
  New
Status in ovn source package in Impish:
  In Progress

Bug description:
  The upstream recommendation for upgrades of OVN is to first upgrade
  the data plane components (chassis aka. ovn-controller), and then
  upgrade the central components (the database schema and ovn-northd).
  The rationale for this is that the new version of the ovn-controller
  is required to cope with any changes to database schema or how northd
  programs flows.

  However, during the course of rapid OVN development there has also
  been introduced changes that make the new ovn-controller not cope with
  a old database schema, breaking the recommended upgrade procedure.

  To cope with this upstream has introduced a new optional configuration
  for the ovn-controller that allows it to detect version
  inconsistencies, and when they are present stop it from making changes
  to the data plane until the version inconsistency is resolved [0].

  For the above mentioned configuration to be effective we also need the
  package to call ``ovn-ctl stop_controller`` with the --restart option
  so that the ovn-controller does not flush the installed flows on exit.

  We should make required changes to packages and charms to allow
  upgrades to progress with less data plane outage.

  0: https://github.com/ovn-
  org/ovn/commit/1dd27ea7aea40122c1edbff845e14abaa70c0413

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