Placement: constants

Introduce a constants file for later use for symbols in Placement,
including constants for:

* custom trait prefixes
* resource class names (though that should be replaced as soon as we
  have an os-resource-classes package)
* known inventory parameters to validate config options

Change-Id: I3a5afd04ce8b5919efdb7591e3717742dd27151e
Partial-Bug: #1578989
See-Also: https://review.openstack.org/502306 (nova spec)
See-Also: https://review.openstack.org/508149 (neutron spec)

neutron_lib/placement/constants.py

@@ -0,0 +1,33 @@
+# Copyright 2018 Ericsson
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# trait prefixes to be used after CUSTOM_
+TRAIT_PREFIX_VNIC_TYPE = 'VNIC_TYPE_'
+TRAIT_PREFIX_PHYSNET = 'PHYSNET_'
+
+# resource classes
+CLASS_NET_BW_EGRESS_KBPS = 'NET_BANDWIDTH_EGRESS_KILOBITS_PER_SECOND'
+CLASS_NET_BW_INGRESS_KBPS = 'NET_BANDWIDTH_INGRESS_KILOBITS_PER_SECOND'
+
+# Optionally reported inventory parameters. Mandatory parameters like 'total'
+# are left out intentionally. See also:
+# https://developer.openstack.org/api-ref/placement
+#        /#update-resource-provider-inventory
+INVENTORY_OPTIONS = set([
+    'allocation_ratio',
+    'max_unit',
+    'min_unit',
+    'reserved',
+    'step_size',
+    ])

releasenotes/notes/placement-constants-f2629b98f6fe148f.yaml

@@ -0,0 +1,4 @@
+---
+features:
+  - |
+    New constants module for Placement: ``neutron_lib.placement.constants``.