Fixing a few bugs in the HostVars performance areas

* Also refresh inventory in the HostVars manager process when things
  are changed via add_host/group_by
* Raise j2undefined rather than return it

lib/ansible/executor/task_queue_manager.py

@@ -198,11 +198,13 @@ class TaskQueueManager:
             'hostvars',
             callable=lambda: hostvars,
             # FIXME: this is the list of exposed methods to the DictProxy object, plus our
-            #        one special one (set_variable_manager). There's probably a better way
+            #        special ones (set_variable_manager/set_inventory). There's probably a better way
             #        to do this with a proper BaseProxy/DictProxy derivative
-            exposed=('set_variable_manager', '__contains__', '__delitem__', '__getitem__',
-                     '__len__', '__setitem__', 'clear', 'copy', 'get', 'has_key', 'items',
-                     'keys', 'pop', 'popitem', 'setdefault', 'update', 'values'),
+            exposed=(
+                'set_variable_manager', 'set_inventory', '__contains__', '__delitem__',
+                '__getitem__', '__len__', '__setitem__', 'clear', 'copy', 'get', 'has_key',
+                'items', 'keys', 'pop', 'popitem', 'setdefault', 'update', 'values'
+            ),
         )
         self._hostvars_manager = HostVarsManager()
         self._hostvars_manager.start()

lib/ansible/plugins/strategy/__init__.py

@@ -246,11 +246,13 @@ class StrategyBase:
                     new_host_info = result_item.get('add_host', dict())
 
                     self._add_host(new_host_info, iterator)
+                    self._tqm._hostvars_manager.hostvars().set_inventory(self._inventory)
 
                 elif result[0] == 'add_group':
                     host = result[1]
                     result_item = result[2]
                     self._add_group(host, result_item)
+                    self._tqm._hostvars_manager.hostvars().set_inventory(self._inventory)
 
                 elif result[0] == 'notify_handler':
                     task_result  = result[1]

lib/ansible/vars/__init__.py

@@ -119,7 +119,7 @@ class VariableManager:
         self._host_vars_files = data.get('host_vars_files', defaultdict(dict))
         self._group_vars_files = data.get('group_vars_files', defaultdict(dict))
         self._omit_token = data.get('omit_token', '__omit_place_holder__%s' % sha1(os.urandom(64)).hexdigest())
-        self._inventory = None
+        self._inventory = data.get('inventory', None)
 
     def _get_cache_entry(self, play=None, host=None, task=None):
         play_id = "NONE"

lib/ansible/vars/hostvars.py

@@ -57,13 +57,16 @@ class HostVars(collections.Mapping):
     def set_variable_manager(self, variable_manager):
         self._variable_manager = variable_manager
 
+    def set_inventory(self, inventory):
+        self._inventory = inventory
+
     def _find_host(self, host_name):
         return self._inventory.get_host(host_name)
 
     def __getitem__(self, host_name):
         host = self._find_host(host_name)
         if host is None:
-            return j2undefined
+            raise j2undefined
 
         data = self._variable_manager.get_vars(loader=self._loader, host=host, play=self._play, include_hostvars=False)