Return HTTP 200 on list for invalid status

The server listing API raises a 500 error if you pass an invalid status
filter for admin user. In the case of a non-admin user, it simply
returns an empty list. In the case of an admin user, it fetches extended
server attributes, so a condition was added to get extended server
attributes only when servers list is not empty.

This change simply removes the cause of the 500 exception. A subsequent
patch with a microversion bump will modify the behavior so that a 400
Bad Request will be raised for an invalid status, for both admin and
non-admin alike.

Co-Authored-By: Dinesh Bhor <dinesh.bhor@nttdata.com>

Closes-Bug: #1579706

Change-Id: I10bde78f0a9ac59b8646d58f62fa5056f989f54f
(cherry picked from commit ee4d69e28d)

nova/api/openstack/compute/extended_server_attributes.py

@@ -89,18 +89,21 @@ class ExtendedServerAttributesController(wsgi.Controller):
             authorize_host_status = True
         if authorize_extend or authorize_host_status:
             servers = list(resp_obj.obj['servers'])
-            instances = req.get_db_instances()
-            # Instances is guaranteed to be in the cache due to
-            # the core API adding it in its 'detail' method.
-            if authorize_host_status:
-                host_statuses = self.compute_api.get_instances_host_statuses(
-                                instances.values())
-            for server in servers:
-                if authorize_extend:
-                    instance = instances[server['id']]
-                    self._extend_server(context, server, instance, req)
+            # NOTE(dinesh-bhor): Skipping fetching of instances from cache as
+            # servers list can be empty if invalid status is provided to the
+            # core API 'detail' method.
+            if servers:
+                instances = req.get_db_instances()
                 if authorize_host_status:
-                    server['host_status'] = host_statuses[server['id']]
+                    host_statuses = (
+                        self.compute_api.get_instances_host_statuses(
+                                instances.values()))
+                for server in servers:
+                    if authorize_extend:
+                        instance = instances[server['id']]
+                        self._extend_server(context, server, instance, req)
+                    if authorize_host_status:
+                        server['host_status'] = host_statuses[server['id']]
 
 
 class ExtendedServerAttributes(extensions.V21APIExtensionBase):

nova/tests/unit/api/openstack/compute/test_extended_server_attributes.py

@@ -13,6 +13,7 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
+import mock
 from oslo_config import cfg
 from oslo_serialization import jsonutils
 import webob
@@ -130,6 +131,17 @@ class ExtendedServerAttributesTestV21(test.TestCase):
                                     node='node-%s' % (i + 1),
                                     instance_name=NAME_FMT % (i + 1))
 
+    @mock.patch.object(compute.api.API, 'get_all')
+    def test_detail_empty_instance_list_invalid_status(self,
+                                                       mock_get_all_method):
+        mock_get_all_method.return_value = objects.InstanceList(objects=[])
+
+        url = "%s%s" % (self.fake_url, '/servers/detail?status=invalid_status')
+        res = self._make_request(url)
+        # check status code 200 with empty instance list
+        self.assertEqual(200, res.status_int)
+        self.assertEqual(0, len(self._get_servers(res.body)))
+
     def test_no_instance_passthrough_404(self):
 
         def fake_compute_get(*args, **kwargs):

releasenotes/notes/list-server-bad-status-fix-7db504b38c8d732f.yaml

@@ -0,0 +1,7 @@
+---
+fixes:
+  - |
+    Fixed bug #1579706: "Listing nova instances with invalid status raises 500
+    InternalServerError for admin user". Now passing an invalid status as a
+    filter will return an empty list. A subsequent patch will then correct this
+    to raise a 400 Bad Request when an invalid status is received.