Deprecate filters that have been replaced by placement filters

This change deprecates the AZ filters which is no longer required.

This also enable the use of placement for AZ enforcement by default and
deprecates the config option for removal.

Change-Id: I92b0386432444fc8bdf852de4bdb6cebb370a8ca

6 files changed, 59 insertions, 21 deletions

diff --git a/doc/source/admin/availability-zones.rst b/doc/source/admin/availability-zones.rst
index 95cc44e10c..678aff2c5a 100644
--- a/doc/source/admin/availability-zones.rst
+++ b/doc/source/admin/availability-zones.rst
@@ -65,7 +65,7 @@ placement aggregates that match the membership and UUID of nova host aggregates
 that you assign as availability zones. The same key in aggregate metadata used
 by the `AvailabilityZoneFilter` filter controls this function, and is enabled by
 setting :oslo.config:option:`scheduler.query_placement_for_availability_zone`
-to ``True``.
+to ``True``. As of 24.0.0 (Xena), this is the default.
 
 .. code-block:: console
 
@@ -102,11 +102,9 @@ to ``True``.
 
   $ openstack --os-placement-api-version=1.2 resource provider aggregate set --aggregate 019e2189-31b3-49e1-aff2-b220ebd91c24 815a5634-86fb-4e1e-8824-8a631fee3e06
 
-With the above configuration, the `AvailabilityZoneFilter` filter can be
-disabled in :oslo.config:option:`filter_scheduler.enabled_filters` while
-retaining proper behavior (and doing so with the higher performance of
-placement's implementation).
-
+Without the above configuration, the `AvailabilityZoneFilter` filter must be
+enabled in :oslo.config:option:`filter_scheduler.enabled_filters` to retain
+proper behavior.
 
 Implications for moving servers
 -------------------------------
diff --git a/doc/source/admin/configuration/schedulers.rst b/doc/source/admin/configuration/schedulers.rst
index 78539c0be6..f992230703 100644
--- a/doc/source/admin/configuration/schedulers.rst
+++ b/doc/source/admin/configuration/schedulers.rst
@@ -18,7 +18,7 @@ Compute is configured with the following default scheduler options in the
 
    [filter_scheduler]
    available_filters = nova.scheduler.filters.all_filters
-   enabled_filters = AvailabilityZoneFilter, ComputeFilter, ComputeCapabilitiesFilter, ImagePropertiesFilter, ServerGroupAntiAffinityFilter, ServerGroupAffinityFilter
+   enabled_filters = ComputeFilter, ComputeCapabilitiesFilter, ImagePropertiesFilter, ServerGroupAntiAffinityFilter, ServerGroupAffinityFilter
 
 By default, the scheduler ``driver`` is configured as a filter scheduler, as
 described in the next section. In the default configuration, this scheduler
@@ -341,8 +341,12 @@ This is a no-op filter. It does not eliminate any of the available hosts.
 AvailabilityZoneFilter
 ----------------------
 
-Filters hosts by availability zone. You must enable this filter for the
-scheduler to respect availability zones in requests.
+.. deprecated:: 24.0.0 (Xena)
+
+   The functionality of this filter has been replaced by
+   :ref:`availability-zones-with-placement`.
+
+Filters hosts by availability zone.
 
 Refer to :doc:`/admin/availability-zones` for more information.
 
diff --git a/nova/conf/scheduler.py b/nova/conf/scheduler.py
index eb927b262e..3b7e518eb5 100644
--- a/nova/conf/scheduler.py
+++ b/nova/conf/scheduler.py
@@ -150,7 +150,18 @@ Related options:
 - ``[scheduler] placement_aggregate_required_for_tenants``
 """),
     cfg.BoolOpt("query_placement_for_availability_zone",
-        default=False,
+        default=True,
+        deprecated_for_removal=True,
+        deprecated_since='24.0.0',
+        deprecated_reason="""
+Since the introduction of placement pre-filters in 18.0.0 (Rocky), we have
+supported tracking Availability Zones either natively in placement or using the
+legacy ``AvailabilityZoneFilter`` scheduler filter. In 24.0.0 (Xena), the
+filter-based approach has been deprecated for removal in favor of the
+placement-based approach. As a result, this config option has also been
+deprecated and will be removed when the ``AvailabilityZoneFilter`` filter is
+removed.
+""",
         help="""
 Use placement to determine availability zones.
 
@@ -164,8 +175,9 @@ operation. If no host aggregate with the `availability_zone` key is
 found, or that aggregate does not match one in placement, the result will
 be the same as not finding any suitable hosts.
 
-Note that if you enable this flag, you can disable the (less efficient)
-AvailabilityZoneFilter in the scheduler.
+Note that if you disable this flag, you **must** enable the (less efficient)
+``AvailabilityZoneFilter`` in the scheduler in order to availability zones to
+work correctly.
 
 Possible values:
 
@@ -355,7 +367,6 @@ Related options:
         # Tempest's scheduler_enabled_filters to keep the default values in
         # sync.
         default=[
-            "AvailabilityZoneFilter",
             "ComputeFilter",
             "ComputeCapabilitiesFilter",
             "ImagePropertiesFilter",
diff --git a/nova/scheduler/filters/availability_zone_filter.py b/nova/scheduler/filters/availability_zone_filter.py
index f48a9f3571..a0f4a669b0 100644
--- a/nova/scheduler/filters/availability_zone_filter.py
+++ b/nova/scheduler/filters/availability_zone_filter.py
@@ -37,6 +37,21 @@ class AvailabilityZoneFilter(filters.BaseHostFilter):
 
     RUN_ON_REBUILD = False
 
+    def __init__(self):
+        super().__init__()
+        if CONF.scheduler.query_placement_for_availability_zone:
+            LOG.warning(
+                "The 'AvailabilityZoneFilter' is deprecated since the 24.0.0 "
+                "(Xena) release. Since the 18.0.0 (Rocky) release, nova "
+                "has supported mapping AZs to placement aggregates. "
+                "The feature is enabled by the "
+                "'query_placement_for_availability_zone' config option and "
+                "is now enabled by default. As such, the "
+                "'AvailabilityZoneFilter' is no longer required. Nova is "
+                "currently configured to use both placement and the "
+                "AvailabilityZoneFilter for AZ enforcement."
+            )
+
     def host_passes(self, host_state, spec_obj):
         availability_zone = spec_obj.availability_zone
 
diff --git a/nova/tests/functional/test_aggregates.py b/nova/tests/functional/test_aggregates.py
index 60c2d20a14..508c435f54 100644
--- a/nova/tests/functional/test_aggregates.py
+++ b/nova/tests/functional/test_aggregates.py
@@ -444,13 +444,6 @@ class AvailabilityZoneFilterTest(AggregateRequestFiltersTest):
         # Use custom weigher to make sure that we have a predictable
         # scheduling sort order.
         self.useFixture(nova_fixtures.HostNameWeigherFixture())
-
-        # NOTE(danms): Do this before calling setUp() so that
-        # the scheduler service that is started sees the new value
-        filters = CONF.filter_scheduler.enabled_filters
-        filters.remove('AvailabilityZoneFilter')
-        self.flags(enabled_filters=filters, group='filter_scheduler')
-
         super(AvailabilityZoneFilterTest, self).setUp()
 
     def test_filter_with_az(self):
@@ -729,7 +722,6 @@ class TestAggregateFiltersTogether(AggregateRequestFiltersTest):
         # NOTE(danms): Do this before calling setUp() so that
         # the scheduler service that is started sees the new value
         filters = CONF.filter_scheduler.enabled_filters
-        filters.remove('AvailabilityZoneFilter')
 
         # NOTE(shilpasd): To test `isolate_aggregates` request filter, removed
         # following filters which also filters hosts based on aggregate
diff --git a/releasenotes/notes/deprecate-AZ-filter-28406abc0135c1c3.yaml b/releasenotes/notes/deprecate-AZ-filter-28406abc0135c1c3.yaml
new file mode 100644
index 0000000000..2e258ad38c
--- /dev/null
+++ b/releasenotes/notes/deprecate-AZ-filter-28406abc0135c1c3.yaml
@@ -0,0 +1,18 @@
+---
+deprecations:
+  - |
+    The ``AvailabilityZoneFilter`` scheduler filters is now deprecated
+    for removal in a future release. The functionality of the
+    ``AvailabilityZoneFilter`` has been replaced by the
+    ``map_az_to_placement_aggregate`` pre-filter which was introduced in
+    18.0.0 (Rocky). This pre-filter is now enabled by default and will be
+    mandatory in a future release.
+upgrades:
+  - |
+    The ``AvailabilityZoneFilter``  has been removed from the default
+    ``[scheduler] enabled_filters`` list. The ``AvailabilityZoneFilter``
+    is replaced by an optional placement pre-filter which is enabled by
+    ``[scheduler] query_placement_for_availability_zone``.
+    The pre-filter is now enabled by default. If you choose to disable the
+    AZ pre-filter, you will need to re-add ``AvailabilityZoneFilter`` to the
+    ``[scheduler] enabled_filters`` config value.