Find subordinates reading from top level tree.

This patch changes the way subordinates are filtered, since juju-2.9
doesn't populate the 'charm' key within the 'subordinates' key in the
principal, so instead this change uses the unit id to get the app name
and read the 'charm' value from the 'applications' section.

This functionality is behind a feature a flag, if the environment
variable TEST_ZAZA_BUG_LP1987332 is set to anything that evaluates to
true, then this new code path is executed.

Related-Bug: #1987332
(cherry picked from commit fc26818)

.github/workflows/tox.yaml

@@ -50,6 +50,8 @@ jobs:
             bundle: first
           - juju_channel: 2.8/stable
             bundle: second
+    env:
+      TEST_ZAZA_BUG_LP1987332: "on"  # http://pad.lv/1987332
     needs: build
     steps:
     - uses: actions/checkout@v1

unit_tests/utilities/test_zaza_utilities_juju.py

@@ -13,6 +13,7 @@
 # limitations under the License.
 
 import mock
+import os
 import unit_tests.utils as ut_utils
 from zaza.utilities import juju as juju_utils
 
@@ -411,6 +412,51 @@ def test_get_subordinate_units(self):
                 status=juju_status),
             ['cinder-ceph/3'])
 
+    def test_get_subordinate_units_lp1987332(self):
+        juju_status = mock.MagicMock()
+        juju_status.applications = {
+            'nova-compute': {
+                'charm': 'ch:amd64/focal/nova-compute-1',
+                'units': {
+                    'nova-compute/0': {
+                        'subordinates': {
+                            'neutron-openvswitch/2': {
+                                'charm': ''}}}}},
+            'cinder': {
+                'charm': 'ch:amd64/focal/cinder-2',
+                'units': {
+                    'cinder/1': {
+                        'subordinates': {
+                            'cinder-hacluster/0': {
+                                'charm': ''},
+                            'cinder-ceph/3': {
+                                'charm': ''}}}}},
+            'cinder-hacluster': {
+                'charm': 'ch:amd64/focal/hacluster-3',
+            },
+            'cinder-ceph': {
+                'charm': 'ch:amd64/focal/cinder-ceph-4',
+            },
+            'neutron-openvswitch': {
+                'charm': 'ch:amd64/focal/neutron-openvswitch-5',
+            },
+        }
+        self.model.get_status.return_Value = juju_status
+        with mock.patch.dict(os.environ,
+                             {'TEST_ZAZA_BUG_LP1987332': '1'}):
+            self.assertEqual(
+                sorted(juju_utils.get_subordinate_units(
+                    ['nova-compute/0', 'cinder/1'],
+                    status=juju_status)),
+                sorted(['neutron-openvswitch/2', 'cinder-hacluster/0',
+                        'cinder-ceph/3']))
+            self.assertEqual(
+                juju_utils.get_subordinate_units(
+                    ['nova-compute/0', 'cinder/1'],
+                    charm_name='ceph',
+                    status=juju_status),
+                ['cinder-ceph/3'])
+
     def test_get_application_ip(self):
         self.model.get_application_config.return_value = {
             'vip': {'value': '10.0.0.10'}}

zaza/utilities/juju.py

@@ -480,9 +480,14 @@ def get_subordinate_units(unit_list, charm_name=None, status=None,
         subs = status.applications[app_name]['units'][unit_name].get(
             'subordinates') or {}
         if charm_name:
-            for unit_name, unit_data in subs.items():
-                if charm_name in unit_data['charm']:
-                    sub_units.append(unit_name)
+            for subordinate_name, unit_data in subs.items():
+                if os.environ.get('TEST_ZAZA_BUG_LP1987332'):
+                    sub_app = subordinate_name.split('/')[0]
+                    charm = status.applications[sub_app]['charm']
+                else:
+                    charm = unit_data['charm']
+                if charm_name in charm:
+                    sub_units.append(subordinate_name)
         else:
             sub_units.extend([n for n in subs.keys()])
     return sub_units