Deprecated Noisy Neighbor strategy

Noisy neighbor strategy is a proof of concept strategy that was
built based on LLC metric, which is not available in Nova since
Victoria release[1].
This patch marks this strategy as deprecated, to be removed in
future releases.

[1] https://docs.openstack.org/releasenotes/nova/victoria.html#relnotes-22-0-0-unmaintained-victoria-upgrade-notes

Change-Id: I940b88555007312c76a86706bd44a38fbcf7701e

releasenotes/notes/deprecate-noisy-neighbor-strat-7da910837ae8fa80.yaml

@@ -0,0 +1,6 @@
+---
+deprecations:
+  - |
+    Noisy Neighbor strategy is deprecated and will be removed in a future release.
+    This strategy relies on Last Level Cache metrics that are not available in Nova
+    since `Victoria release <https://docs.openstack.org/releasenotes/nova/victoria.html>`_.

requirements.txt

@@ -2,6 +2,7 @@
 # date but we do not test them so no guarantee of having them all correct. If
 # you find any incorrect lower bounds, let us know or propose a fix.
 apscheduler>=3.5.1 # MIT License
+debtcollector>=1.2.0 # Apache-2.0
 eventlet>=0.27.0 # MIT
 jsonpatch>=1.21 # BSD
 keystoneauth1>=3.4.0 # Apache-2.0

watcher/decision_engine/strategy/strategies/noisy_neighbor.py

@@ -16,8 +16,10 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 #
+from debtcollector import removals
 from oslo_config import cfg
 from oslo_log import log
+import warnings
 
 from watcher._i18n import _
 from watcher.decision_engine.strategy.strategies import base
@@ -25,7 +27,11 @@ from watcher.decision_engine.strategy.strategies import base
 LOG = log.getLogger(__name__)
 CONF = cfg.CONF
 
+warnings.simplefilter('always')
 
+
+@removals.removed_class("NoisyNeighbor", version="2025.2",
+                        removal_version="2026.2")
 class NoisyNeighbor(base.NoisyNeighborBaseStrategy):
     """Noisy Neighbor strategy using live migration