---
prelude: |
  The Kolla ``21.0.0`` (Flamingo) release modernises the base operating
  systems and core infrastructure shipped by the containers. Highlights
  include:

  * Rocky Linux 10 replaces Rocky Linux 9 as the only supported Rocky base
    image, removing the Delorean/CentOS Cloud SIG dependency and tightening RPM
    repository handling via ``repos.yaml`` (including a new versioned Erlang
    source for aarch64).
  * Data-plane services received major upgrades: ``MariaDB`` now tracks the
    11.4 LTS series with the upstream health check script and the legacy
    clustercheck image removed, ``ProxySQL`` moves to 3.x, ``Bifrost`` consumes
    Ansible 11, ``RabbitMQ`` advances to 4.1, and ``Gnocchi`` is updated to
    4.7.0.
  * Observability components were refreshed with ``Fluentd`` 6.x LTS,
    ``OpenSearch``/``OpenSearch Dashboards`` 3.x, broad ``Prometheus`` exporter
    and infrastructure bumps (``etcd``, ``helm``, ``letsencrypt-lego``), and the
    retirement of the ``collectd``, ``telegraf``, and ``prometheus-ovn-exporter``
    images.
  * The container portfolio was streamlined: support landed for the
    ``ironic-pxe-filter`` image and ``neutron-metadata-agent`` wrapper scripts,
    while dormant services such as ``ironic-inspector`` and ``Venus`` were
    dropped.