Add get_node_by_name

We want to set the value of uuid field of Watcher ComputeNode
to hypversion id(as uuid). We need a method to get compute
node by name.

Change-Id: I0975500f359de92b6d6fdea2e01614cf0ba73f05
Related-Bug: #1835192

watcher/decision_engine/model/model_root.py

@@ -149,6 +149,19 @@ class ModelRoot(nx.DiGraph, base.Model):
         except exception.ComputeResourceNotFound:
             raise exception.ComputeNodeNotFound(name=uuid)
 
+    @lockutils.synchronized("model_root")
+    def get_node_by_name(self, name):
+        try:
+            node_list = [cn['attr'] for uuid, cn in self.nodes(data=True)
+                         if (isinstance(cn['attr'], element.ComputeNode) and
+                         cn['attr']['hostname'] == name)]
+            if node_list:
+                return node_list[0]
+            else:
+                raise exception.ComputeResourceNotFound
+        except exception.ComputeResourceNotFound:
+            raise exception.ComputeNodeNotFound(name=name)
+
     @lockutils.synchronized("model_root")
     def get_instance_by_uuid(self, uuid):
         try:

watcher/tests/decision_engine/model/test_model.py

@@ -122,6 +122,32 @@ class TestModel(base.TestCase):
         node.state = element.ServiceState.OFFLINE.value
         self.assertIn(node.state, [el.value for el in element.ServiceState])
 
+    def test_get_node_by_name(self):
+        model = model_root.ModelRoot()
+        uuid_ = "{0}".format(uuidutils.generate_uuid())
+        name = 'test_node'
+        node = element.ComputeNode()
+        node.uuid = uuid_
+        node.hostname = name
+        model.add_node(node)
+        compute_node = model.get_node_by_name(name)
+        model.assert_node(compute_node)
+        self.assertEqual(name, compute_node['hostname'])
+        self.assertEqual(uuid_, compute_node['uuid'])
+
+    def test_node_from_name_raise(self):
+        model = model_root.ModelRoot()
+        uuid_ = "{0}".format(uuidutils.generate_uuid())
+        name = 'test_node'
+        node = element.ComputeNode()
+        node.uuid = uuid_
+        node.hostname = name
+        model.add_node(node)
+
+        fake_name = 'fake_node'
+        self.assertRaises(exception.ComputeNodeNotFound,
+                          model.get_node_by_name, fake_name)
+
     def test_node_from_uuid_raise(self):
         model = model_root.ModelRoot()
         uuid_ = "{0}".format(uuidutils.generate_uuid())