Define testing runtime for 2027.1 release

Indri is a SLURP release. Ubuntu 24.04 is retained
for SLURP upgrade testing from Gazpacho (2026.1).

Python 3.11 remains the minimum supported version.
It does not reach end-of-life until October 2027,
well after Indri ships. Dropping it prematurely
in a SLURP release that users will stay on longer
is not warranted.

Python 3.14 is now the upper bound of required
testing, with full tempest coverage expected via
Ubuntu 26.04 where it is the default runtime.

Python 3.15 is expected to release in October 2026
and is included as advance/optional testing. Project
teams are encouraged to begin testing early so that
3.15 can become mandatory in the next cycle.

Change-Id: I7b67b00c31d1fa40edc0d3184b83320cb4f2bbfd
Signed-off-by: Goutham Pacha Ravi <gouthampravi@gmail.com>

reference/runtimes/2027.1.rst

@@ -0,0 +1,95 @@
+.. _2027-1-testing-runtime:
+
+===================================
+Tested Runtimes for 2027.1 (Indri)
+===================================
+
+Linux Distribution
+==================
+
+At the start of the 2027.1 development cycle, the current :ref:`LTS or stable
+distribution <pti-linux-distros>` versions are:
+
+* Ubuntu 26.04
+* Debian 13
+
+Additional testing for a smooth upgrade
+---------------------------------------
+
+* Ubuntu 24.04 (Supported in previous SLURP release 2026.1)
+
+  At least one tempest job should run on Ubuntu 24.04 to ensure that the
+  SLURP release upgrade path (from 2026.1 to 2027.1) works.
+
+Python
+======
+
+It is the :doc:`policy <../../resolutions/20181024-python-update-process>` that
+each OpenStack release cycle will target the latest available version of
+Python; default Python runtime on the distributions listed above; and versions
+used in integration tests at the start of the cycle, at least until the point
+when all projects have migrated to a later version.
+
+As per the Python testing requirements defined in :ref:`pti-python`,
+projects should avoid removing Python versions that have not reached EOL
+without a solid reason.
+
+Based on the criteria above, all Python-based projects must target and test
+against, at a minimum:
+
+* Python 3.11
+
+  Python 3.11 is the minimum supported version for 2027.1. Supporting
+  Python 3.11 does not require full tempest testing, but py311 unit tests
+  are expected as a minimum requirement for all Python projects.
+
+* Python 3.12 (available as default in Ubuntu 24.04)
+
+  We have not seen significant incompatible changes between Python 3.11 and
+  3.12 in previous cycles. Projects may skip dedicated py312 test jobs if
+  they are already testing on 3.11 and 3.13. Periodic testing is sufficient.
+
+* Python 3.13 (available as default in Debian 13)
+
+  We have not seen significant incompatible changes between Python 3.12 and
+  3.13 in previous cycles. Projects may skip dedicated py313 test jobs if
+  they are already testing on 3.11 and 3.14. Periodic testing is sufficient.
+
+* Python 3.14 (available as default in Ubuntu 26.04)
+
+  This is the upper bound of required testing for 2027.1. Python 3.14 is the
+  default on Ubuntu 26.04, our primary tested distribution. Full tempest
+  testing coverage is expected on this version.
+
+* Python 3.15 (expected release October 2026)
+
+  Testing with Python 3.15 is not mandatory for the 2027.1 release.
+
+  .. warning::
+
+     Project teams should begin testing with Python 3.15 in this cycle,
+     starting with linting and unit test jobs and extending to end-to-end
+     tempest jobs where possible. Incompatibilities should be identified
+     and fixed early. Python 3.15 will likely become mandatory in a future
+     release.
+
+More details on Python requirements can be found in :ref:`pti-python`.
+
+Advance/Unstable Testing
+========================
+
+The following distributions and Python versions are candidates for advance
+or unstable testing in OpenStack CI/CD. They are not part of integrated
+testing and may be tested as non-blockers or periodically. This list can
+be updated during any phase of the development cycle.
+
+* CentOS Stream 10
+* Rocky Linux 10
+* AlmaLinux 10
+
+  AlmaLinux 10's continued support for x86_64_v2 makes it a
+  compelling option for project teams due to greater CI node
+  availability. We may need to work through additional packaging
+  deficiencies occasionally. We do not expect any other major
+  differences between these Enterprise Linux distributions.
+  Project teams can make a choice based on their needs.