add default conductor group capability

When creating nodes, previously there was no way to set a
default conductor group to create nodes with, thus forcing
a two step process, a dedicated conductor without a conductor
group to serve reqeusts for it.

With this change, an operator can set specific conductor_group
settings by API, allowing increased delineation with reduced
risk of misconfiguration or mis-step.

Story: 2010267
Task: 46183
Change-Id: I21d58750504b2eecf3368d2e03eaca050065c3d7

ironic/api/controllers/v1/node.py

@@ -2538,7 +2538,7 @@ class NodesController(rest.RestController):
         # NOTE(jroll) this is special-cased to "" and not None,
         # because it is used in hash ring calculations
         if not node.get('conductor_group'):
-            node['conductor_group'] = ''
+            node['conductor_group'] = CONF.default_conductor_group
 
         if node.get('name') is not None:
             error_msg = _("Cannot create node with invalid name '%(name)s'")

ironic/conf/default.py

@@ -81,6 +81,11 @@ api_opts = [
                mutable=True,
                help=_('Resource class to use for new nodes when no resource '
                       'class is provided in the creation request.')),
+    cfg.StrOpt('default_conductor_group',
+               mutable=True,
+               default="",
+               help=_('The conductor_group to use for new nodes when no '
+                      'conductor_group was defined in the creation request.')),
 ]
 
 driver_opts = [

ironic/tests/unit/api/controllers/v1/test_node.py

@@ -4495,6 +4495,27 @@ class TestPost(test_api_base.BaseApiTest):
                                headers={api_base.Version.string: "1.21"})
         self.assertEqual('class2', result['resource_class'])
 
+    def test_create_node_with_default_conductor_group(self):
+        self.config(default_conductor_group='magic')
+
+        ndict = test_api_utils.post_get_test_node()
+        self.post_json('/nodes', ndict)
+
+        # newer version is needed to see the resource_class field
+        result = self.get_json('/nodes/%s' % ndict['uuid'],
+                               headers={api_base.Version.string: "1.46"})
+        self.assertEqual('magic', result['conductor_group'])
+
+    def test_create_node_explicit_default_conductor_group(self):
+        self.config(default_conductor_group='meow')
+        ndict = test_api_utils.post_get_test_node(conductor_group='mouse')
+        self.post_json('/nodes', ndict,
+                       headers={api_base.Version.string: "1.46"})
+
+        result = self.get_json('/nodes/%s' % ndict['uuid'],
+                               headers={api_base.Version.string: "1.46"})
+        self.assertEqual('mouse', result['conductor_group'])
+
     def test_create_node_doesnt_contain_id(self):
         # FIXME(comstud): I'd like to make this test not use the
         # dbapi, however, no matter what I do when trying to mock

releasenotes/notes/add-default-conductor-group-a0355c5e9345a037.yaml

@@ -0,0 +1,7 @@
+---
+features:
+  - |
+    Adds the capability to define a ``default_conductor_group`` setting
+    which allows operators to assign a default conductor group to new nodes
+    created in Ironic if they do not otherwise have a ``conductor_group``
+    set upon creation. By default, this setting has no value.