[Bug 2074309] Re: upgrade 22.04 -> 24.04 won't start due to feature flags

[Andreas Hasenack]

I added an ubuntu-release-upgrader task because we might consider
blocking the release upgrade there if the conditions for this bug are
found to be present.

Those conditions might be as simple as "is rabbitmq-server installed
(and running)?". Or perhaps a more generic one, carefully checking the
version number jump between jammy and noble, because in the future we
might have a newer version in jammy exactly because of this bug.

** Also affects: ubuntu-release-upgrader (Ubuntu)
   Importance: Undecided
       Status: New

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https://bugs.launchpad.net/bugs/2074309

Title:
  upgrade 22.04 -> 24.04 won't start due to feature flags

Status in Release Notes for Ubuntu:
  New
Status in rabbitmq-server package in Ubuntu:
  Confirmed
Status in ubuntu-release-upgrader package in Ubuntu:
  New
Status in rabbitmq-server source package in Noble:
  Confirmed
Status in ubuntu-release-upgrader source package in Noble:
  New
Status in rabbitmq-server source package in Oracular:
  Confirmed
Status in ubuntu-release-upgrader source package in Oracular:
  New

Bug description:
  Hi,

  I was just doing an upgrade from ubuntu 22.04 server to 24.04 server.

  After upgrading, the rabbitmq-server cannot be started anymore.

  
  Reason: 

  See 
  https://www.rabbitmq.com/blog/2022/07/20/required-feature-flags-in-rabbitmq-3.11

  
  Higher versions of rabbitmq require feature flags to be set *before* upgrade. In my rabbitmq installation these features had not been set, therefore the the rabbitmq server would not start. They ask you to downgerade to an earlier version and do the upgrade. 

  
  I therefore used LXD to run a Ubuntu 22.04 machine with rabbitmq 3.9 to set the missing feature flags and achieved:

  rabbitmqctl  enable_feature_flag all

  rabbitmqctl list_feature_flags
  Listing feature flags ...
  name    state
  implicit_default_bindings       enabled
  maintenance_mode_status enabled
  quorum_queue    enabled
  stream_queue    enabled
  user_limits     enabled
  virtual_host_metadata   enabled


  But it still does not work, it still complains about  one feature
  missing:

  classic_mirrored_queue_version


  unfortunately, this is required by rabbitmq 3.12 coming with Ubuntu
  24.04, but is not known and thus cannot be set by rabbitmq 3.9 coming
  with Ubuntu 22.04.


  Now the problem is: There is no Ubuntu coming with 3.9 or 3.10. Ubuntu
  jumps directly from rabbitmq 3.9 to rabbitmq 3.12, although there is
  no upgrade path from 3.9 to 3.12.


  Three nasty options:

  - loose your data and configuration and run from scratch
  - run an old version in either docker or LXD
  - try some upgrade path with docker/podman and non-ubuntu versions of rabbitmq

  Unfortunately,

  https://hub.docker.com/_/rabbitmq

  does not list versions older than 3.12, but they still seem to be
  available, so this might by some migration/workaround path.

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