Follow-up patch of 8e5e69869d

This patch is a follow-up patch of
8e5e69869d addressing some the remaining
comments after the patch was merged. The changes are:

* Optimize the code by generating the list of reserved words for the
  nodes controller only once.

* List the reserved words in the release note.

* Improve the error string when someone tries to name a node using a
  reserved word.

* Add a comment for future reference indicating how we should try to
  model the API in case a new sub-controller needs to be added to the
  nodes controller class.

Change-Id: I43d6d9e2e92cc941a7839c60d9cd361cd94b6208

ironic/api/controllers/v1/node.py

@@ -96,6 +96,16 @@ PROVISION_ACTION_STATES = (ir_states.VERBS['manage'],
                            ir_states.VERBS['provide'],
                            ir_states.VERBS['abort'])
 
+_NODES_CONTROLLER_RESERVED_WORDS = None
+
+
+def get_nodes_controller_reserved_names():
+    global _NODES_CONTROLLER_RESERVED_WORDS
+    if _NODES_CONTROLLER_RESERVED_WORDS is None:
+        _NODES_CONTROLLER_RESERVED_WORDS = (
+            api_utils.get_controller_reserved_names(NodesController))
+    return _NODES_CONTROLLER_RESERVED_WORDS
+
 
 def hide_fields_in_newer_versions(obj):
     # if requested version is < 1.3, hide driver_internal_info
@@ -924,6 +934,12 @@ class NodeMaintenanceController(rest.RestController):
 class NodesController(rest.RestController):
     """REST controller for Nodes."""
 
+    # NOTE(lucasagomes): For future reference. If we happen
+    # to need to add another sub-controller in this class let's
+    # try to make it a parameter instead of an endpoint due
+    # https://bugs.launchpad.net/ironic/+bug/1572651, e.g, instead of
+    # v1/nodes/(ident)/detail we could have v1/nodes/(ident)?detail=True
+
     states = NodeStatesController()
     """Expose the state controller action as a sub-element of nodes"""
 
@@ -1033,8 +1049,7 @@ class NodesController(rest.RestController):
         if not api_utils.allow_node_logical_names():
             raise exception.NotAcceptable()
 
-        reserved_names = api_utils.get_controller_reserved_names(
+        reserved_names = get_nodes_controller_reserved_names()
-            NodesController)
         for name in names:
             if not api_utils.is_valid_node_name(name):
                 raise wsme.exc.ClientSideError(
@@ -1043,7 +1058,7 @@ class NodesController(rest.RestController):
             if name in reserved_names:
                 raise wsme.exc.ClientSideError(
                     'The word "%(name)s" is reserved and can not be used as a '
-                    'node name. Other reserved words are: %(reserved)s' %
+                    'node name. Reserved words are: %(reserved)s.' %
                     {'name': name,
                      'reserved': ', '.join(reserved_names)},
                     status_code=http_client.BAD_REQUEST)

releasenotes/notes/reserved-node-names-67a08012ed1131ae.yaml

@@ -2,4 +2,5 @@
 fixes:
   - Fixes a problem which allowed nodes to be named with some reserved
     words that are implicitly not allowed due the way the Ironic API
-    works.
+    works. The reserved words are "maintenance", "management", "ports",
+    "states", "vendor_passthru", "validate" and "detail".