Allow the server name limit to be configurable

For some deployments 53 may be to high of a value and
a lower value may be used (ie for registration into active
directory, which has lower name limits) so add the ability
to reduce the valid length of server names (but
preserve the current limits by default).

Change-Id: Icd06aba14dbf156b9164b0e25233f2df7099fc9b

heat/common/config.py

@@ -132,6 +132,13 @@ engine_opts = [
                help=_('Number of times to retry when a client encounters an '
                       'expected intermittent error. Set to 0 to disable '
                       'retries.')),
+    # Server host name limit to 53 characters by due to typical default
+    # linux HOST_NAME_MAX of 64, minus the .novalocal appended to the name
+    cfg.IntOpt('max_server_name_length',
+               default=53,
+               max=53,
+               help=_('Maximum length of a server name to be used '
+                      'in nova.')),
     cfg.IntOpt('max_interface_check_attempts',
                min=1,
                default=10,

heat/engine/resources/aws/ec2/instance.py

@@ -13,9 +13,12 @@
 
 import copy
 
+from oslo_config import cfg
 from oslo_log import log as logging
 import six
 
+cfg.CONF.import_opt('max_server_name_length', 'heat.common.config')
+
 from heat.common import exception
 from heat.common.i18n import _
 from heat.common.i18n import _LI
@@ -340,9 +343,7 @@ class Instance(resource.Resource, sh.SchedulerHintsMixin):
         ),
     }
 
-    # Server host name limit to 53 characters by due to typical default
-    # linux HOST_NAME_MAX of 64, minus the .novalocal appended to the name
-    physical_resource_name_limit = 53
+    physical_resource_name_limit = cfg.CONF.max_server_name_length
 
     default_client_name = 'nova'
 

heat/engine/resources/openstack/nova/server.py

@@ -38,6 +38,7 @@ from heat.engine import translation
 from heat.rpc import api as rpc_api
 
 cfg.CONF.import_opt('default_software_config_transport', 'heat.common.config')
+cfg.CONF.import_opt('max_server_name_length', 'heat.common.config')
 
 LOG = logging.getLogger(__name__)
 
@@ -577,9 +578,7 @@ class Server(stack_user.StackUser, sh.SchedulerHintsMixin,
         ),
     }
 
-    # Server host name limit to 53 characters by due to typical default
-    # linux HOST_NAME_MAX of 64, minus the .novalocal appended to the name
-    physical_resource_name_limit = 53
+    physical_resource_name_limit = cfg.CONF.max_server_name_length
 
     default_client_name = 'nova'
 

releasenotes/notes/configurable-server-name-limit-947d9152fe9b43ee.yaml

@@ -0,0 +1,6 @@
+---
+features:
+    - Adds new 'max_server_name_length' configuration option
+      which defaults to the prior upper bound (53) and can be
+      lowered by users (if they need to, for example due to
+      ldap or other internal name limit restrictions).