Only create a server group when affinity is set

Also adds docs so a user can find this behaviour easily.

Closes-Bug: #2071832
Change-Id: Iea3c4164f3e893c355ec21653f2e8f0e848941f0

blazar/plugins/instances/instance_plugin.py

@@ -317,7 +317,8 @@ class VirtualInstancePlugin(base.BasePlugin, nova.NovaClientWrapper):
 
         return {'added': added_host_ids, 'removed': removed_host_ids}
 
-    def _create_flavor(self, reservation_id, vcpus, memory, disk, group_id):
+    def _create_flavor(self, reservation_id, vcpus, memory, disk,
+                       group_id=None):
         flavor_details = {
             'flavorid': reservation_id,
             'name': RESERVATION_PREFIX + ":" + reservation_id,
@@ -333,9 +334,10 @@ class VirtualInstancePlugin(base.BasePlugin, nova.NovaClientWrapper):
         reservation_rc = "resources:CUSTOM_RESERVATION_" + rsv_id_rc_format
         extra_specs = {
             FLAVOR_EXTRA_SPEC: reservation_id,
-            "affinity_id": group_id,
             reservation_rc: "1"
             }
+        if group_id is not None:
+            extra_specs["affinity_id"] = group_id
         reserved_flavor.set_keys(extra_specs)
 
         return reserved_flavor
@@ -346,23 +348,31 @@ class VirtualInstancePlugin(base.BasePlugin, nova.NovaClientWrapper):
         ctx = context.current()
         user_client = nova.NovaClientWrapper()
 
-        reserved_group = user_client.nova.server_groups.create(
+        flavor_args = {
-            RESERVATION_PREFIX + ':' + reservation_id,
+            'reservation_id': reservation_id,
-            'affinity' if inst_reservation['affinity'] else 'anti-affinity'
+            'vcpus': inst_reservation['vcpus'],
-            )
+            'memory': inst_reservation['memory_mb'],
+            'disk': inst_reservation['disk_gb']
+        }
 
-        reserved_flavor = self._create_flavor(reservation_id,
-                                              inst_reservation['vcpus'],
-                                              inst_reservation['memory_mb'],
-                                              inst_reservation['disk_gb'],
-                                              reserved_group.id)
-
-        pool = nova.ReservationPool()
         pool_metadata = {
             RESERVATION_PREFIX: reservation_id,
             'filter_tenant_id': ctx.project_id,
-            'affinity_id': reserved_group.id
             }
+
+        if inst_reservation['affinity'] is not None:
+            reserved_group = user_client.nova.server_groups.create(
+                RESERVATION_PREFIX + ':' + reservation_id,
+                'affinity' if inst_reservation['affinity'] else 'anti-affinity'
+                )
+            flavor_args['group_id'] = reserved_group.id
+            pool_metadata['affinity_id'] = reserved_group.id
+        else:
+            reserved_group = None
+
+        reserved_flavor = self._create_flavor(**flavor_args)
+
+        pool = nova.ReservationPool()
         agg = pool.create(name=reservation_id, metadata=pool_metadata)
 
         self.placement_client.create_reservation_class(reservation_id)
@@ -483,9 +493,10 @@ class VirtualInstancePlugin(base.BasePlugin, nova.NovaClientWrapper):
             self.cleanup_resources(instance_reservation)
             raise mgr_exceptions.NovaClientError()
 
+        server_group_id = group.id if group is not None else None
         db_api.instance_reservation_update(instance_reservation['id'],
                                            {'flavor_id': flavor.id,
-                                            'server_group_id': group.id,
+                                            'server_group_id': server_group_id,
                                             'aggregate_id': pool.id})
 
         return instance_reservation['id']

blazar/tests/plugins/instances/test_instance_plugin.py

@@ -410,6 +410,61 @@ class TestVirtualInstancePlugin(tests.TestCase):
         expected_query = ['vcpus >= 2', 'memory_mb >= 2048', 'local_gb >= 100']
         mock_host_get_query.assert_called_once_with(expected_query)
 
+    def test_pickup_host_with_anti_affinity(self):
+        def fake_get_reservation_by_host(host_id, start, end):
+            if host_id in ['host-1', 'host-3']:
+                return [
+                    {'id': '1',
+                     'resource_type': instances.RESOURCE_TYPE},
+                    {'id': '2',
+                     'resource_type': instances.RESOURCE_TYPE}
+                    ]
+            else:
+                return []
+
+        plugin = instance_plugin.VirtualInstancePlugin()
+
+        mock_host_allocation_get = self.patch(
+            db_api, 'host_allocation_get_all_by_values')
+        mock_host_allocation_get.return_value = []
+
+        mock_host_get_query = self.patch(db_api,
+                                         'reservable_host_get_all_by_queries')
+        hosts_list = [self.generate_host_info('host-1', 8, 8192, 1000),
+                      self.generate_host_info('host-2', 2, 2048, 500)]
+        mock_host_get_query.return_value = hosts_list
+
+        mock_get_reservations = self.patch(db_utils,
+                                           'get_reservations_by_host_id')
+
+        mock_get_reservations.side_effect = fake_get_reservation_by_host
+
+        mock_max_usages = self.patch(plugin, 'max_usages')
+        mock_max_usages.return_value = (0, 0, 0)
+
+        mock_reservation_get = self.patch(db_api, 'reservation_get')
+        mock_reservation_get.return_value = {
+            'status': 'pending'
+            }
+
+        params = {
+            'vcpus': 2,
+            'memory_mb': 2048,
+            'disk_gb': 100,
+            'amount': 2,
+            'affinity': False,
+            'resource_properties': '',
+            'start_date': datetime.datetime(2030, 1, 1, 8, 00),
+            'end_date': datetime.datetime(2030, 1, 1, 12, 00)
+            }
+
+        expected = {'added': ['host-1', 'host-2'], 'removed': []}
+        ret = plugin.pickup_hosts('reservation-id1', params)
+
+        self.assertEqual(expected, ret)
+        expected_query = ['vcpus >= 2', 'memory_mb >= 2048', 'local_gb >= 100']
+        mock_host_get_query.assert_called_once_with(expected_query)
+
     @ddt.data('None', 'none', None)
     def test_pickup_host_with_no_affinity(self, value):
         def fake_get_reservation_by_host(host_id, start, end):

doc/source/cli/instance-reservation.rst

@@ -166,3 +166,20 @@ Result:
     openstack server create --flavor db83d6fd-c69c-4259-92cf-012db2e55a58 --image <image> --network <network> <server-name>
 
 ..
+
+
+Affinity
+--------
+
+A lease can be created with the optional ``--affinity`` parameter. This
+provides the following behavior:
+
+* ``affinity=True``: Instances will be deployed on the same host for this
+  reservation, by adding them to a server group with an affinity policy.
+
+* ``affinity=False``: Instances will be deployed on different hosts for this
+  reservation, by adding them to a server group with an anti-affinity policy.
+
+* ``affinity=None`` (default): Instances can be deployed on any host,
+  regardless of other instances in this reservation. No server group is
+  created.

releasenotes/notes/update-affinity-behaviour-a03231e461bd2b21.yaml

@@ -0,0 +1,14 @@
+---
+upgrade:
+  - |
+    Instance reservations will no longer create a server group when the
+    ``affinity`` parameter is not set. This means that instances can be
+    deployed on any host. To achieve the old behaviour, you must now explicity
+    set ``--affinity=false``.
+    `LP#2071832 <https://launchpad.net/bugs/2071832>`__
+fixes:
+  - |
+    Instance reservations will no longer create a server group when the
+    ``affinity`` parameter is not set. This means that instances can be
+    deployed on any host.
+    `LP#2071832 <https://launchpad.net/bugs/2071832>`__