Extend invalidate_rp to only invalidate cache

This makes invalidate_resource_provider() have a cacheonly flag that
only invalidates our cache, but does not remove the provider from the
tree for efficiency.

Related to blueprint one-time-use-devices

Change-Id: I04dd5e984c5671d866804c258422e4230fce37b7

nova/scheduler/client/report.py

@@ -2389,15 +2389,18 @@ class SchedulerReportClient(object):
                 #  left a no-op for backward compatibility.
                 pass
 
-    def invalidate_resource_provider(self, name_or_uuid):
+    def invalidate_resource_provider(self, name_or_uuid, cacheonly=False):
         """Invalidate the cache for a resource provider.
 
         :param name_or_uuid: Name or UUID of the resource provider to look up.
+        :param cacheonly: Only reset the cache but do not remove the provider
+                          from the tree
         """
-        try:
-            self._provider_tree.remove(name_or_uuid)
-        except ValueError:
-            pass
+        if not cacheonly:
+            try:
+                self._provider_tree.remove(name_or_uuid)
+            except ValueError:
+                pass
         self._association_refresh_time.pop(name_or_uuid, None)
 
     def get_provider_by_name(self, context, name):

nova/tests/unit/scheduler/client/test_report.py

@@ -2811,6 +2811,36 @@ class TestProviderOperations(SchedulerReportClientTestCase):
             self.client.get_resource_provider_name,
             self.context, uuids.rp)
 
+    def test_invalidate_full(self):
+        self._init_provider_tree()
+        rp_uuid = self.compute_node.uuid
+        self.client._association_refresh_time[rp_uuid] = time.time()
+
+        # Initially, cache is not stale and our provider exists
+        self.assertFalse(self.client._associations_stale(rp_uuid))
+        self.assertTrue(self.client._provider_tree.exists(rp_uuid))
+
+        # A full invalidation means our cache is stale (i.e. needs update)
+        # and our provider is gone from the tree
+        self.client.invalidate_resource_provider(rp_uuid)
+        self.assertTrue(self.client._associations_stale(rp_uuid))
+        self.assertFalse(self.client._provider_tree.exists(rp_uuid))
+
+    def test_invalidate_cache_only(self):
+        self._init_provider_tree()
+        rp_uuid = self.compute_node.uuid
+        self.client._association_refresh_time[rp_uuid] = time.time()
+
+        # Initially, cache is not stale and our provider exists
+        self.assertFalse(self.client._associations_stale(rp_uuid))
+        self.assertTrue(self.client._provider_tree.exists(rp_uuid))
+
+        # After a cache-only validation, our cache is stale (i.e. needs update)
+        # but the provider still exists in our tree
+        self.client.invalidate_resource_provider(rp_uuid, cacheonly=True)
+        self.assertTrue(self.client._associations_stale(rp_uuid))
+        self.assertTrue(self.client._provider_tree.exists(rp_uuid))
+
 
 class TestAggregates(SchedulerReportClientTestCase):
     def test_get_provider_aggregates_found(self):