Deprecate non-update_provider_tree compat code

With all in-tree virt drivers now implementing the
update_provider_tree interface, we can deprecate the
compatibility code in the ResourceTracker. This change
simply logs a warning if the driver does not implement
the upt interface and sets the timer for removal in the
U release at the earliest.

The resource tracker unit tests will need to be cleaned
up but that can happen in a separate change so it does
not slow down this deprecation.

Change-Id: I1eae47bce08f6292d38e893a2122289bcd6f4b58

nova/compute/resource_tracker.py

@@ -983,6 +983,13 @@ class ResourceTracker(object):
             traits = self._get_traits(nodename, provider_tree=prov_tree)
             prov_tree.update_traits(nodename, traits)
         except NotImplementedError:
+            # TODO(mriedem): Remove the compatibility code in the U release.
+            LOG.warning('Compute driver "%s" does not implement the '
+                        '"update_provider_tree" interface. Compatibility for '
+                        'non-update_provider_tree interfaces will be removed '
+                        'in a future release and result in an error to report '
+                        'inventory for this compute service.',
+                        CONF.compute_driver)
             # update_provider_tree isn't implemented yet - try get_inventory
             try:
                 inv_data = self.driver.get_inventory(nodename)

nova/tests/unit/compute/test_resource_tracker.py

@@ -445,6 +445,7 @@ def setup_rt(hostname, virt_resources=_VIRT_DRIVER_AVAIL_RESOURCES,
     virt_resources = copy.deepcopy(virt_resources)
     vd.get_available_resource.return_value = virt_resources
     vd.get_inventory.side_effect = NotImplementedError
+    # TODO(mriedem): Need to make this mocked virt driver implement upt.
     vd.update_provider_tree.side_effect = NotImplementedError
     vd.get_host_ip_addr.return_value = _NODENAME
     vd.estimate_instance_overhead.side_effect = estimate_overhead
@@ -1413,6 +1414,11 @@ class TestUpdateComputeNode(BaseTestCase):
         self.rt._update(mock.sentinel.ctx, new_compute)
         save_mock.assert_called_once_with()
         norm_mock.assert_called_once_with(mock.sentinel.inv_data, new_compute)
+        # Assert a warning was logged about using a virt driver that does not
+        # implement update_provider_tree.
+        self.assertIn('Compute driver "%s" does not implement the '
+                      '"update_provider_tree" interface.' %
+                      CONF.compute_driver, self.stdlog.logger.output)
 
     def test_existing_node_capabilities_as_traits(self):
         """The capabilities_as_traits() driver method returns traits

releasenotes/notes/train-deprecate-non-upt-compat-d061edf3f702eeec.yaml

@@ -0,0 +1,8 @@
+---
+deprecations:
+  - |
+    Compatibility code for compute drivers that do not implement the
+    `update_provider_tree`__ interface is deprecated and will be removed
+    in a future release.
+
+    __ https://docs.openstack.org/nova/latest/reference/update-provider-tree.html