Ensure access to neutron db on a late joining cloud-compute relation.

hooks/nova_compute_hooks.py

@@ -92,12 +92,15 @@ def amqp_changed():
 
 
 @hooks.hook('shared-db-relation-joined')
-def db_joined():
-    relation_set(database=config('database'), username=config('database-user'),
-                 hostname=unit_get('private-address'))
+def db_joined(rid=None):
+    relation_set(relation_id=rid,
+                 nova_database=config('database'),
+                 nova_username=config('database-user'),
+                 nova_hostname=unit_get('private-address'))
     if network_manager() in ['quantum', 'neutron']:
         # XXX: Renaming relations from quantum_* to neutron_* here.
-        relation_set(neutron_database=config('neutron-database'),
+        relation_set(relation_id=rid,
+                     neutron_database=config('neutron-database'),
                      neutron_username=config('neutron-database-user'),
                      neutron_hostname=unit_get('private-address'))
 
@@ -145,6 +148,10 @@ def compute_changed():
     CONFIGS.write_all()
     import_authorized_keys()
     import_keystone_ca_cert()
+    if network_manager() in ['quantum', 'neutron']:
+        # in case we already have a database relation, need to request
+        # access to the additional neutron database.
+        [db_joined(rid) for rid in relation_ids('shared-db')]
 
 
 @hooks.hook('ceph-relation-joined')

hooks/nova_compute_utils.py

@@ -50,7 +50,7 @@ BASE_RESOURCE_MAP = {
     '/etc/nova/nova.conf': {
         'services': ['nova-compute'],
         'contexts': [context.AMQPContext(),
-                     context.SharedDBContext(),
+                     context.SharedDBContext(relation_prefix='nova'),
                      context.ImageServiceContext(),
                      context.OSConfigFlagContext(),
                      CloudComputeContext(),

unit_tests/test_nova_compute_hooks.py

@@ -136,8 +136,27 @@ class NovaComputeRelationsTests(CharmTestCase):
     def test_db_joined(self):
         self.unit_get.return_value = 'nova.foohost.com'
         hooks.db_joined()
-        self.relation_set.assert_called_with(database='nova', username='nova',
-                                             hostname='nova.foohost.com')
+        self.relation_set.assert_called_with(relation_id=None,
+                                             nova_database='nova',
+                                             nova_username='nova',
+                                             nova_hostname='nova.foohost.com')
+        self.unit_get.assert_called_with('private-address')
+
+    def test_db_joined_quantum(self):
+        self.unit_get.return_value = 'nova.foohost.com'
+        self.network_manager.return_value = 'quantum'
+        hooks.db_joined(rid='shared-db:0')
+        calls = [call(nova_database='nova',
+                      nova_username='nova',
+                      nova_hostname='nova.foohost.com',
+                      relation_id='shared-db:0'),
+                 call(neutron_database='neutron',
+                      neutron_username='neutron',
+                      neutron_hostname='nova.foohost.com',
+                      relation_id='shared-db:0'),
+]
+        [self.assertIn(c, self.relation_set.call_args_list)
+         for c in calls]
         self.unit_get.assert_called_with('private-address')
 
     @patch.object(hooks, 'CONFIGS')