[Bug 2103413] Update Released

[Julian Andres Klode]

The verification of the Stable Release Update for nova has completed
successfully and the package is now being released to -updates.
Subsequently, the Ubuntu Stable Release Updates Team is being
unsubscribed and will not receive messages about this bug report.  In
the event that you encounter a regression using the package from
-updates please report a new bug using ubuntu-bug and tag the bug report
regression-update so we can easily find any regressions.

-- 
You received this bug notification because you are a member of Ubuntu
OpenStack, which is subscribed to nova in Ubuntu.
https://bugs.launchpad.net/bugs/2103413

Title:
  [SRU] Python3.13: Garbage collection due to attribute cache inlining

Status in OpenStack Compute (nova):
  Fix Released
Status in Release Notes for Ubuntu:
  Fix Released
Status in nova package in Ubuntu:
  Fix Released
Status in nova source package in Plucky:
  Fix Released

Bug description:
  [ Impact ]

   * Nova's neutron client wrapper fails under Python 3.13 due to a
  garbage collection bug in CPython that causes dictionary references to
  be prematurely cleared when one object's __dict__ is assigned to
  another object's __dict__. This completely prevents users from being
  able to spawn virtual VMs (or do other communication to Neutron that
  span multiple cpu cycles), which is the main purpose of Nova.

   * This bug fix stops ClientWrapper from inheriting clientv20.Client
  and directly referencing the base_client's __dict__. This allows
  ClientWrapper to act as a true proxy for clientv20.Client while
  preventing the cache inlining bug that leads to garbage collection.

  [ Test Plan ]

   * With a configured Nova, spawn a VM.
  To simplify testing, I've written a configuration script to help create a single node OpenStack cloud as VM: https://pastebin.ubuntu.com/p/JkHXBmKBbm/

  [ Where problems could occur ]

   * The change modifies how the ClientWrapper class accesses attributes
  from the underlying neutron client. If the __getattr__ implementation
  doesn't properly handle all attribute types or edge cases, it could
  result in AttributeError exceptions or unexpected behavior when
  accessing client methods or properties.

   * Since this changes the inheritance model (from inheritance to
  composition), any code that relies on isinstance() checks against
  clientv20.Client for the wrapper would fail.

  [ Other Info ]

   * This patch comes directly from upstream Nova and has been back-
  ported upstream to stable/2025.1, commit
  bdf62d0653c2e31ae291fc51e7016407b19f6ff4.

   * The fix specifically addresses Python 3.13 compatibility. The
  behavior is correct on Python 3.12 and earlier versions, but Python
  3.13 exhibits the dictionary clearing issue.

  Previous comment:
  https://bugs.launchpad.net/ubuntu/+source/nova/+bug/2103413/comments/0

To manage notifications about this bug go to:
https://bugs.launchpad.net/nova/+bug/2103413/+subscriptions