[stable/xena] Ensure get_requests_for_local_unit doesn't fail on inco…

…mplete relation (#824)

If the certificates relation has been set from a consuming charm for
certificates, but the provider hasn't supplied a certificate, and the
request is in the 'legacy' form, then the get_request_for_local_unit()
function in cert_utils fails on accessing the (non-existant) 'ca'
parameter in the databag.  This patch ensures that if the 'ca' key is
missing that the processing moves on to the next relation.

(cherry-picked from: c8f4720)
Closes LP#2028683

charmhelpers/contrib/openstack/cert_utils.py

@@ -414,18 +414,27 @@ def get_requests_for_local_unit(relation_name=None):
         is_legacy_request = set(sent).intersection(legacy_keys)
         for unit in related_units(rid):
             data = relation_get(rid=rid, unit=unit)
-            if data.get(raw_certs_key):
-                bundles.append({
-                    'ca': data['ca'],
-                    'chain': data.get('chain'),
-                    'certs': json.loads(data[raw_certs_key])})
-            elif is_legacy_request:
-                bundles.append({
-                    'ca': data['ca'],
-                    'chain': data.get('chain'),
-                    'certs': {sent['common_name']:
-                              {'cert': data.get(local_name + '.server.cert'),
-                               'key': data.get(local_name + '.server.key')}}})
+            # Note: Bug#2028683 - data may not be available if the certificates
+            # relation hasn't been populated by the providing charm. If no 'ca'
+            # in the data then don't attempt the bundle at all.
+            if data.get('ca'):
+                if data.get(raw_certs_key):
+                    bundles.append({
+                        'ca': data['ca'],
+                        'chain': data.get('chain'),
+                        'certs': json.loads(data[raw_certs_key])
+                    })
+                elif is_legacy_request:
+                    bundles.append({
+                        'ca': data['ca'],
+                        'chain': data.get('chain'),
+                        'certs': {
+                            sent['common_name']: {
+                                'cert': data.get(local_name + '.server.cert'),
+                                'key': data.get(local_name + '.server.key')
+                            }
+                        }
+                    })
 
     return bundles
 

tests/contrib/openstack/test_cert_utils.py

@@ -616,6 +616,30 @@ def fake_relation_get(rid, unit):
                 'chain': 'MYCHAIN'}]
         )
 
+    @mock.patch.object(cert_utils, 'local_unit')
+    @mock.patch.object(cert_utils, 'related_units')
+    @mock.patch.object(cert_utils, 'relation_ids')
+    @mock.patch.object(cert_utils, 'relation_get')
+    def test_get_requests_for_local_unit_half_done(
+            self, relation_get, relation_ids, related_units, local_unit):
+        local_unit.return_value = 'rabbitmq-server/2'
+
+        def fake_relation_get(rid, unit):
+            if unit == 'rabbitmq-server/2':
+                # i.e. legacy request
+                return {'certificate_name':
+                        'eb32103b-27c8-4feb-8771-c7097c7314e8',
+                        'common_name': 'juju-cd4bb3-5.lxd',
+                        'sans': '["10.5.100.11", "10.5.0.32"]'}
+            else:
+                return {}
+
+        relation_ids.return_value = ['certificates:12']
+        related_units.return_value = ['vault/0']
+        relation_get.side_effect = fake_relation_get
+        self.assertEqual(
+            cert_utils.get_requests_for_local_unit(), [])
+
     @mock.patch.object(cert_utils, 'get_requests_for_local_unit')
     def test_get_bundle_for_cn(self, get_requests_for_local_unit):
         get_requests_for_local_unit.return_value = [{