nova-status: Add hw_machine_type check for libvirt instances

This change introduces a new nova-status check to ensure a machine type
has been recorded for each instance within an environment.

nova-status will fail with a warning when instances are found, directing
the operator to use the previously added nova-manage list_unset and
update commands to set a machine type for these instances. The logic for
this check comes entirely from the list_unset command.

It is noted in the warning output that this can be ignored if no libvirt
or HyperV based computes are present in the environment as
hw_machine_type is only used by these two virt drivers at present.

blueprint: libvirt-default-machine-type
Change-Id: Ic3ae48c57e61c4e45883fbae1328a448be025953

doc/source/cli/nova-status.rst

@@ -146,6 +146,7 @@ Upgrade
   **23.0.0 (Wallaby)**
 
   * Checks for computes older than the previous major release
+  * Checks for any instances without ``hw_machine_type`` set.
 
 See Also
 ========

nova/cmd/status.py

@@ -36,9 +36,14 @@ from nova.db.sqlalchemy import api as db_session
 from nova import exception
 from nova.i18n import _
 from nova.objects import cell_mapping as cell_mapping_obj
+# NOTE(lyarwood): The following are imported as machine_type_utils expects them
+# to be registered under nova.objects when called via _check_machine_type_set
+from nova.objects import image_meta as image_meta_obj  # noqa: F401
+from nova.objects import instance as instance_obj  # noqa: F401
 from nova import policy
 from nova import utils
 from nova import version
+from nova.virt.libvirt import machine_type_utils
 from nova.volume import cinder
 
 CONF = nova.conf.CONF
@@ -307,6 +312,19 @@ class UpgradeCommands(upgradecheck.UpgradeCommands):
 
         return upgradecheck.Result(upgradecheck.Code.SUCCESS)
 
+    def _check_machine_type_set(self):
+        ctxt = nova_context.get_admin_context()
+        if machine_type_utils.get_instances_without_type(ctxt):
+            msg = (_("""
+Instances found without hw_machine_type set. This warning can be ignored if
+your environment does not contain libvirt based compute hosts.
+Use the `nova-manage machine_type list_unset` command to list these instances.
+For more details see the following:
+https://docs.openstack.org/latest/nova/admin/hw_machine_type.html"""))
+            return upgradecheck.Result(upgradecheck.Code.WARNING, msg)
+
+        return upgradecheck.Result(upgradecheck.Code.SUCCESS)
+
     # The format of the check functions is to return an upgradecheck.Result
     # object with the appropriate upgradecheck.Code and details set. If the
     # check hits warnings or failures then those should be stored in the
@@ -329,7 +347,9 @@ class UpgradeCommands(upgradecheck.UpgradeCommands):
             (common_checks.check_policy_json, {'conf': CONF})
         ),
         # Added in Wallaby
-        (_('Older than N-1 computes'), _check_old_computes)
+        (_('Older than N-1 computes'), _check_old_computes),
+        # Added in Wallaby
+        (_('hw_machine_type unset'), _check_machine_type_set),
     )
 
 

nova/tests/unit/cmd/test_status.py

@@ -476,3 +476,30 @@ class TestUpgradeCheckOldCompute(test.NoDBTestCase):
                 return_value=too_old):
             result = self.cmd._check_old_computes()
             self.assertEqual(upgradecheck.Code.WARNING, result.code)
+
+
+class TestCheckMachineTypeUnset(test.NoDBTestCase):
+
+    def setUp(self):
+        super().setUp()
+        self.cmd = status.UpgradeCommands()
+
+    @mock.patch(
+        'nova.virt.libvirt.machine_type_utils.get_instances_without_type',
+        new=mock.Mock(return_value=[mock.Mock(spec=objects.Instance)]))
+    def test_instances_found_without_hw_machine_type(self):
+        result = self.cmd._check_machine_type_set()
+        self.assertEqual(
+            upgradecheck.Code.WARNING,
+            result.code
+        )
+
+    @mock.patch(
+        'nova.virt.libvirt.machine_type_utils.get_instances_without_type',
+        new=mock.Mock(return_value=[]))
+    def test_instances_not_found_without_hw_machine_type(self):
+        result = self.cmd._check_machine_type_set()
+        self.assertEqual(
+            upgradecheck.Code.SUCCESS,
+            result.code
+        )

releasenotes/notes/libvirt-store-and-change-default-machine-type-bf86b4973c4dee4c.yaml

@@ -46,3 +46,8 @@ upgrade:
     This command will list instance UUIDs that do not have a machine type
     recorded. An optional cell UUID can be provided to list on instances
     without a machine type from that cell.
+
+    A new ``nova-status`` check has been introduced to help operators
+    identify if any instances within their environment have ``hw_machine_type``
+    unset before they attempt to change the ``[libvirt]hw_machine_type``
+    configurable.