Verify equivalent VMs share one candidate host lookup

The grouping could have been disabled and every test would still have
passed. Asserts the expensive call is made once for two interchangeable
VMs.

Signed-off-by: Brad House <bhouse@nexthop.ai>

Author: bhouse-nexthop

server/src/test/java/org/apache/cloudstack/cluster/ClusterDrsServiceImplTest.java

@@ -1139,4 +1139,57 @@ public void testNonStrictAntiAffinityIsHonoured() {
         assertFalse("a preferred host must stay available",
                 excludes.getHostsToAvoid().contains(31L));
     }
-}
+
+    @Test
+    public void testEquivalentVmsShareOneCandidateHostLookup() throws ConfigurationException {
+        // the expensive call is listHostsForMigrationOfVM. Two interchangeable VMs must cost one
+        // pass, not two - otherwise the grouping is not actually doing anything.
+        ClusterVO cluster = Mockito.mock(ClusterVO.class);
+        Mockito.when(cluster.getId()).thenReturn(1L);
+        Mockito.when(cluster.getAllocationState()).thenReturn(Grouping.AllocationState.Enabled);
+
+        HostVO host1 = Mockito.mock(HostVO.class);
+        Mockito.when(host1.getId()).thenReturn(1L);
+
+        List<VMInstanceVO> vmList = new ArrayList<>();
+        for (long id : new long[] {1L, 2L}) {
+            VMInstanceVO vm = Mockito.mock(VMInstanceVO.class);
+            Mockito.when(vm.getId()).thenReturn(id);
+            Mockito.when(vm.getHostId()).thenReturn(1L);
+            Mockito.when(vm.getType()).thenReturn(VirtualMachine.Type.User);
+            Mockito.when(vm.getState()).thenReturn(VirtualMachine.State.Running);
+            Mockito.when(vm.getServiceOfferingId()).thenReturn(9L);
+            Mockito.lenient().when(vm.getTemplateId()).thenReturn(8L);
+            vmList.add(vm);
+        }
+
+        ServiceOfferingVO offering = Mockito.mock(ServiceOfferingVO.class);
+        Mockito.when(offering.isDynamic()).thenReturn(false);
+        Mockito.when(serviceOfferingDao.findByIdIncludingRemoved(Mockito.anyLong(), Mockito.anyLong()))
+                .thenReturn(offering);
+        Mockito.when(vmInstanceDetailsDao.listDetailsKeyPairs(Mockito.anyLong()))
+                .thenReturn(Collections.emptyMap());
+        Mockito.when(volumeDao.findCreatedByInstance(Mockito.anyLong())).thenReturn(Collections.emptyList());
+
+        HostJoinVO hostJoin1 = Mockito.mock(HostJoinVO.class);
+        Mockito.when(hostJoin1.getId()).thenReturn(1L);
+        Mockito.when(hostJoin1.getCpus()).thenReturn(4);
+        Mockito.when(hostJoin1.getSpeed()).thenReturn(1000L);
+        Mockito.when(hostJoin1.getTotalMemory()).thenReturn(8192L);
+
+        Mockito.when(hostDao.findByClusterId(1L)).thenReturn(List.of(host1));
+        Mockito.when(vmInstanceDao.listByClusterId(1L)).thenReturn(vmList);
+        Mockito.when(hostJoinDao.searchByIds(Mockito.any())).thenReturn(List.of(hostJoin1));
+        Mockito.when(balancedAlgorithm.needsDrs(Mockito.any(), Mockito.anyMap(), Mockito.anyMap(), Mockito.anyMap()))
+                .thenReturn(false);
+        Mockito.when(managementServer.listHostsForMigrationOfVM(Mockito.any(), Mockito.anyLong(),
+                        Mockito.anyLong(), Mockito.any(), Mockito.anyList()))
+                .thenReturn(new Ternary<>(new Pair<>(Collections.emptyList(), 0),
+                        List.of(host1), Collections.emptyMap()));
+
+        clusterDrsService.getDrsPlan(cluster, 5);
+
+        Mockito.verify(managementServer, Mockito.times(1)).listHostsForMigrationOfVM(
+                Mockito.any(), Mockito.anyLong(), Mockito.anyLong(), Mockito.any(), Mockito.anyList());
+    }
+}