test_utils: Ensure diverse placement of test instances

Use the Nova Server Groups API to influence placement of test
instances.

Fixes #641

zaza/openstack/charm_tests/test_utils.py

@@ -733,14 +733,20 @@ def setUpClass(cls, application_name=None, model_alias=None):
     def resource_cleanup(self):
         """Remove test resources."""
         try:
-            logging.info('Removing instances launched by test ({}*)'
+            logging.info('Removing resources created by test ({}*)'
                          .format(self.RESOURCE_PREFIX))
             for server in self.nova_client.servers.list():
                 if server.name.startswith(self.RESOURCE_PREFIX):
                     openstack_utils.delete_resource(
                         self.nova_client.servers,
                         server.id,
                         msg="server")
+            for server_group in self.nova_client.server_groups.list():
+                if server_group.name.startswith(self.RESOURCE_PREFIX):
+                    openstack_utils.delete_resource(
+                        self.nova_client.server_groups,
+                        server_group.id,
+                        msg="server group")
         except AssertionError as e:
             # Resource failed to be removed within the expected time frame,
             # log this fact and carry on.
@@ -752,7 +758,8 @@ def resource_cleanup(self):
 
     def launch_guest(self, guest_name, userdata=None, use_boot_volume=False,
                      instance_key=None, flavor_name=None,
-                     attach_to_external_network=False):
+                     attach_to_external_network=False,
+                     scheduler_hints=None):
         """Launch one guest to use in tests.
 
         Note that it is up to the caller to have set the RESOURCE_PREFIX class
@@ -772,6 +779,9 @@ def launch_guest(self, guest_name, userdata=None, use_boot_volume=False,
         :param attach_to_external_network: Attach instance directly to external
                                            network.
         :type attach_to_external_network: bool
+        :param scheduler_hints: arbitrary key-value pairs specified by the
+                                client to help boot an instance.
+        :type scheduler_hints: Optional[Dict[str,str]]
         :returns: Nova instance objects
         :rtype: Server
         """
@@ -801,7 +811,8 @@ def launch_guest(self, guest_name, userdata=None, use_boot_volume=False,
                     use_boot_volume=use_boot_volume,
                     userdata=userdata,
                     flavor_name=flavor_name,
-                    attach_to_external_network=attach_to_external_network)
+                    attach_to_external_network=attach_to_external_network,
+                    scheduler_hints=scheduler_hints)
 
     def launch_guests(self, userdata=None, attach_to_external_network=False,
                       flavor_name=None):
@@ -818,14 +829,18 @@ def launch_guests(self, userdata=None, attach_to_external_network=False,
         :returns: List of launched Nova instance objects
         :rtype: List[Server]
         """
+        server_group = configure_guest.create_server_group(
+            self.RESOURCE_PREFIX, policy='anti-affinity')
+
         launched_instances = []
         for guest_number in range(1, 2+1):
             launched_instances.append(
                 self.launch_guest(
                     guest_name='ins-{}'.format(guest_number),
                     userdata=userdata,
                     attach_to_external_network=attach_to_external_network,
-                    flavor_name=flavor_name))
+                    flavor_name=flavor_name,
+                    scheduler_hints={'group': server_group.id}))
         return launched_instances
 
     def retrieve_guest(self, guest_name):

zaza/openstack/configure/guest.py

@@ -50,10 +50,33 @@
         'bootstring': 'finished at'}}
 
 
+def create_server_group(name, policy=None):
+    """Create a server group for influencing instance placement.
+
+    :param name: Name of server group.
+    :type name: str
+    :param policy: Policy for group, one of ('affinity', 'anti-affinity',
+                   'soft-affinity', 'soft-anti-affinity').  Default: 'affinity'
+    :type policy: Optional[str]
+    :param rules
+    :returns: ServerGroup resource.
+    :rtype: novaclient.v2.server_groups.ServerGroup
+    :raises: ValueError
+    """
+    if policy and policy not in ('affinity', 'anti-affinity', 'soft-affinity',
+                                 'soft-anti-affinity'):
+        raise ValueError
+
+    keystone_session = openstack_utils.get_overcloud_keystone_session()
+    nova_client = openstack_utils.get_nova_session_client(keystone_session)
+    return nova_client.server_groups.create(name, policy)
+
+
 def launch_instance(instance_key, use_boot_volume=False, vm_name=None,
                     private_network_name=None, image_name=None,
                     flavor_name=None, external_network_name=None, meta=None,
-                    userdata=None, attach_to_external_network=False):
+                    userdata=None, attach_to_external_network=False,
+                    scheduler_hints=None):
     """Launch an instance.
 
     :param instance_key: Key to collect associated config data with.
@@ -79,6 +102,9 @@ def launch_instance(instance_key, use_boot_volume=False, vm_name=None,
     :param attach_to_external_network: Attach instance directly to external
                                        network.
     :type attach_to_external_network: bool
+    :param scheduler_hints: arbitrary key-value pairs specified by the client
+                            to help boot an instance.
+    :type scheduler_hints: Optional[Dict[str,str]]
     :returns: the created instance
     :rtype: novaclient.Server
     """
@@ -131,7 +157,8 @@ def launch_instance(instance_key, use_boot_volume=False, vm_name=None,
         key_name=nova_utils.KEYPAIR_NAME,
         meta=meta,
         nics=nics,
-        userdata=userdata)
+        userdata=userdata,
+        scheduler_hints=scheduler_hints)
 
     # Test Instance is ready.
     logging.info('Checking instance is active')