Update resources once in update_available_resource

This change ensures that resources are updated only once per
update_available_resource() call.

Compute resources were previously updated during host
object initialization and at the end of
update_available_resource(). It could cause inconsistencies
in resource tracking between compute host and DB for couple
of second when final _update() at the end of
update_available_resource() is being called.

For example: nova-api shows that host uses 10GB of RAM, but
in fact its 12GB because DB doesn't have resources that belongs
to shutdown instance.

Because of that fact nova-scheduler (CachingScheduler) could
choose (based on imcomplete information) host which is already full.

For more informations please see realted bug: #1729621

Change-Id: I120a98cc4c11772f24099081ef3ac44a50daf71d
Closes-Bug: #1729621

nova/compute/resource_tracker.py

@@ -561,7 +561,6 @@ def _init_compute_node(self, context, resources):
             cn = self.compute_nodes[nodename]
             self._copy_resources(cn, resources)
             self._setup_pci_tracker(context, cn, resources)
-            self._update(context, cn)
             return
 
         # now try to get the compute node record from the
@@ -571,7 +570,6 @@ def _init_compute_node(self, context, resources):
             self.compute_nodes[nodename] = cn
             self._copy_resources(cn, resources)
             self._setup_pci_tracker(context, cn, resources)
-            self._update(context, cn)
             return
 
         if self._check_for_nodes_rebalance(context, resources, nodename):
@@ -590,7 +588,6 @@ def _init_compute_node(self, context, resources):
                  {'host': self.host, 'node': nodename, 'uuid': cn.uuid})
 
         self._setup_pci_tracker(context, cn, resources)
-        self._update(context, cn)
 
     def _setup_pci_tracker(self, context, compute_node, resources):
         if not self.pci_tracker:

nova/tests/unit/compute/test_resource_tracker.py

@@ -573,6 +573,7 @@ def test_no_instances_no_migrations_no_reserved(self, get_mock, migr_mock,
         actual_resources = update_mock.call_args[0][1]
         self.assertTrue(obj_base.obj_equal_prims(expected_resources,
                                                  actual_resources))
+        update_mock.assert_called_once()
 
     @mock.patch('nova.objects.InstancePCIRequests.get_by_instance',
                 return_value=objects.InstancePCIRequests(requests=[]))
@@ -613,6 +614,7 @@ def test_no_instances_no_migrations_reserved_disk_ram_and_cpu(
         actual_resources = update_mock.call_args[0][1]
         self.assertTrue(obj_base.obj_equal_prims(expected_resources,
                                                  actual_resources))
+        update_mock.assert_called_once()
 
     @mock.patch('nova.compute.utils.is_volume_backed_instance')
     @mock.patch('nova.objects.InstancePCIRequests.get_by_instance',
@@ -662,6 +664,7 @@ def test_some_instances_no_migrations(self, get_mock, migr_mock,
         actual_resources = update_mock.call_args[0][1]
         self.assertTrue(obj_base.obj_equal_prims(expected_resources,
                                                  actual_resources))
+        update_mock.assert_called_once()
 
     @mock.patch('nova.objects.InstancePCIRequests.get_by_instance',
                 return_value=objects.InstancePCIRequests(requests=[]))
@@ -725,6 +728,7 @@ def test_orphaned_instances_no_migrations(self, get_mock, migr_mock,
         actual_resources = update_mock.call_args[0][1]
         self.assertTrue(obj_base.obj_equal_prims(expected_resources,
                                                  actual_resources))
+        update_mock.assert_called_once()
 
     @mock.patch('nova.objects.InstancePCIRequests.get_by_instance',
                 return_value=objects.InstancePCIRequests(requests=[]))
@@ -787,6 +791,7 @@ def test_no_instances_source_migration(self, get_mock, get_inst_mock,
         actual_resources = update_mock.call_args[0][1]
         self.assertTrue(obj_base.obj_equal_prims(expected_resources,
                                                  actual_resources))
+        update_mock.assert_called_once()
 
     @mock.patch('nova.objects.InstancePCIRequests.get_by_instance',
                 return_value=objects.InstancePCIRequests(requests=[]))
@@ -846,6 +851,7 @@ def test_no_instances_dest_migration(self, get_mock, get_inst_mock,
         actual_resources = update_mock.call_args[0][1]
         self.assertTrue(obj_base.obj_equal_prims(expected_resources,
                                                  actual_resources))
+        update_mock.assert_called_once()
 
     @mock.patch('nova.objects.InstancePCIRequests.get_by_instance',
                 return_value=objects.InstancePCIRequests(requests=[]))
@@ -902,6 +908,7 @@ def test_no_instances_dest_evacuation(self, get_mock, get_inst_mock,
         actual_resources = update_mock.call_args[0][1]
         self.assertTrue(obj_base.obj_equal_prims(expected_resources,
                                                  actual_resources))
+        update_mock.assert_called_once()
 
     @mock.patch('nova.compute.utils.is_volume_backed_instance')
     @mock.patch('nova.objects.InstancePCIRequests.get_by_instance',
@@ -973,6 +980,7 @@ def test_some_instances_source_and_dest_migration(self, get_mock,
         actual_resources = update_mock.call_args[0][1]
         self.assertTrue(obj_base.obj_equal_prims(expected_resources,
                                                  actual_resources))
+        update_mock.assert_called_once()
 
 
 class TestInitComputeNode(BaseTestCase):
@@ -998,7 +1006,7 @@ def test_no_op_init_compute_node(self, update_mock, get_mock, service_mock,
         self.assertFalse(get_mock.called)
         self.assertFalse(create_mock.called)
         self.assertTrue(pci_mock.called)
-        self.assertTrue(update_mock.called)
+        self.assertFalse(update_mock.called)
 
     @mock.patch('nova.objects.PciDeviceList.get_by_compute_node',
                 return_value=objects.PciDeviceList())
@@ -1022,7 +1030,7 @@ def fake_get_node(_ctx, host, node):
         get_mock.assert_called_once_with(mock.sentinel.ctx, _HOSTNAME,
                                          _NODENAME)
         self.assertFalse(create_mock.called)
-        self.assertTrue(update_mock.called)
+        self.assertFalse(update_mock.called)
 
     @mock.patch('nova.objects.ComputeNodeList.get_by_hypervisor')
     @mock.patch('nova.objects.PciDeviceList.get_by_compute_node',
@@ -1187,7 +1195,7 @@ def set_cn_id():
         self.assertTrue(obj_base.obj_equal_prims(expected_compute, cn))
         pci_tracker_mock.assert_called_once_with(mock.sentinel.ctx,
                                                  42)
-        self.assertTrue(update_mock.called)
+        self.assertFalse(update_mock.called)
 
     @mock.patch('nova.objects.ComputeNodeList.get_by_hypervisor')
     @mock.patch('nova.objects.PciDeviceList.get_by_compute_node',