Add placement service versions discovery

Some tempest tests require placement service microversions to be
specified, e.g. MinBwAllocationPlacementTest. This patch adds
discovery of the placement service min and max microversions.

Change-Id: I639cbf0d63cc2a3235615762d61347b9bb0c5e6f

config_tempest/services/base.py

@@ -180,16 +180,16 @@ class VersionedService(Service):
                 versions.append(version)
         return list(map(lambda x: x['id'], versions))
 
-    def filter_api_microversions(self):
+    def filter_api_microversions(self, max_version='version'):
         min_microversion = ''
         max_microversion = ''
         for version in self.versions_body['versions']:
             if version['status'] != "DEPRECATED":
                 if max_microversion == '':
-                    max_microversion = version['version']
+                    max_microversion = version[max_version]
                 else:
                     max_microversion = max(max_microversion,
-                                           version['version'])
+                                           version[max_version])
                 if 'min_version' not in version:
                     continue
                 if min_microversion == '':

config_tempest/services/placement.py

@@ -0,0 +1,42 @@
+# Copyright 2020 Red Hat, Inc.
+# All Rights Reserved.
+#
+# 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.
+
+import json
+
+from config_tempest.services.base import VersionedService
+
+
+class PlacementService(VersionedService):
+    def set_versions(self):
+        url, top_level = self.no_port_cut_url()
+        body = self.do_get(url, top_level=top_level,
+                           top_level_path='placement')
+        self.versions_body = json.loads(body)
+
+    def set_default_tempest_options(self, conf):
+        # set microversions
+        m_versions = self.filter_api_microversions(max_version='max_version')
+        conf.set(
+            'placement', 'min_microversion', m_versions['min_microversion'])
+        conf.set(
+            'placement', 'max_microversion', m_versions['max_microversion'])
+
+    @staticmethod
+    def get_service_type():
+        return ['placement']
+
+    @staticmethod
+    def get_codename():
+        return 'placement'

releasenotes/notes/discover-placement-service-bbd6522424e4eee4.yaml

@@ -0,0 +1,8 @@
+---
+features:
+  - |
+    discover-tempest-config can now automatically set the following 2 tempest
+    options:
+    * CONF.placement.min_microversion
+    * CONF.placement.max_microversion
+    The mentioned options are set based on the placement service response.