---
upgrade:
  - |
    Internal backend modules have been renamed to **explicitly indicate that
    they are** private:

    * ``oslo_service.backend.common`` → ``oslo_service.backend._common``
    * ``oslo_service.backend.threading`` → ``oslo_service.backend._threading``
    * ``oslo_service.backend.eventlet`` → ``oslo_service.backend._eventlet``

    These modules were never intended to be used directly. **This change makes
    it clearer** that they are internal to ``oslo_service.backend``. Projects
    should only interact with the backend system via the public interface
    provided in ``oslo_service.backend.__init__``—**specifically through
    functions like** ``get_component()``, ``get_backend()``, and
    ``init_backend()``.

    **If your project was** directly importing any of these modules, please
    update the imports to use the public API instead.