Implement watcher datamodel list in watcher-decision-engine

1. Add datamodel list endpoint and rpc process.
2. Add datamodel list parased and return.
3. Add related unittest.

Partially Implements:blueprint show-datamodel-api

Change-Id: I758b7ca2bc3d8d596d3457277744336c6629bc4e

watcher/decision_engine/messaging/data_model_endpoint.py

@@ -0,0 +1,60 @@
+# -*- encoding: utf-8 -*-
+# Copyright 2019 ZTE corporation.
+# 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.
+#
+from watcher.common import exception
+from watcher.common import utils
+from watcher.decision_engine.model.collector import manager
+from watcher import objects
+
+
+class DataModelEndpoint(object):
+    def __init__(self, messaging):
+        self._messaging = messaging
+
+    def get_audit_scope(self, context, audit=None):
+        scope = None
+        try:
+            if utils.is_uuid_like(audit) or utils.is_int_like(audit):
+                audit = objects.Audit.get(
+                    context, audit)
+            else:
+                audit = objects.Audit.get_by_name(
+                    context, audit)
+        except exception.AuditNotFound:
+            raise exception.InvalidIdentity(identity=audit)
+        if audit:
+            scope = audit.scope
+        else:
+            scope = []
+        return scope
+
+    def get_data_model_info(self, context, data_model_type='compute',
+                            audit=None):
+        if audit is not None:
+            scope = self.get_audit_scope(context, audit)
+        else:
+            scope = []
+        collector_manager = manager.CollectorManager()
+        collector = collector_manager.get_cluster_model_collector(
+            data_model_type)
+        audit_scope_handler = collector.get_audit_scope_handler(
+            audit_scope=scope)
+        available_data_model = audit_scope_handler.get_scoped_model(
+            collector.get_latest_cluster_data_model())
+        if not available_data_model:
+            return {"context": []}
+        return {"context": available_data_model.to_list()}