added gathering control to ansible, defaults to 'smart'

examples/ansible.cfg

@@ -24,6 +24,11 @@ transport      = smart
 remote_port    = 22
 module_lang    = C
 
+# controls implicit fact gathering (always, never or smart).
+# smart gathers only if not currently in memory.
+# does NOT affect explicit 'gather_facts' entries.
+gathering = smart
+
 # additional paths to search for roles in, colon separated
 #roles_path    = /etc/ansible/roles
 

lib/ansible/constants.py

@@ -134,6 +134,7 @@ DEFAULT_SU = get_config(p, DEFAULTS, 'su', 'ANSIBLE_SU', False, boolean=True)
 DEFAULT_SU_FLAGS = get_config(p, DEFAULTS, 'su_flags', 'ANSIBLE_SU_FLAGS', '')
 DEFAULT_SU_USER = get_config(p, DEFAULTS, 'su_user', 'ANSIBLE_SU_USER', 'root')
 DEFAULT_ASK_SU_PASS = get_config(p, DEFAULTS, 'ask_su_pass', 'ANSIBLE_ASK_SU_PASS', False, boolean=True)
+DEFAULT_GATHERING = get_config(p, DEFAULTS, 'gathering', 'ANSIBLE_GATHERING', 'smart').lower()
 
 DEFAULT_ACTION_PLUGIN_PATH     = get_config(p, DEFAULTS, 'action_plugins',     'ANSIBLE_ACTION_PLUGINS', '/usr/share/ansible_plugins/action_plugins')
 DEFAULT_CALLBACK_PLUGIN_PATH   = get_config(p, DEFAULTS, 'callback_plugins',   'ANSIBLE_CALLBACK_PLUGINS', '/usr/share/ansible_plugins/callback_plugins')

lib/ansible/playbook/__init__.py

@@ -479,11 +479,15 @@ class PlayBook(object):
     def _do_setup_step(self, play):
         ''' get facts from the remote system '''
 
-        if play.gather_facts is False:
-            return {}
-
         host_list = self._trim_unavailable_hosts(play._play_hosts)
 
+        if play.gather_facts is None and C.DEFAULT_GATHERING == 'smart':
+            host_list = [h for h in host_list if h not in self.SETUP_CACHE or 'module_setup' not in self.SETUP_CACHE[h]]
+            if len(host_list) == 0:
+                return {}
+        elif play.gather_facts is False or (play.gather_facts is None and C.DEFAULT_GATHERING == 'never'):
+            return {}
+
         self.callbacks.on_setup()
         self.inventory.restrict_to(host_list)
 

lib/ansible/playbook/play.py

@@ -117,7 +117,7 @@ class Play(object):
         self.sudo             = ds.get('sudo', self.playbook.sudo)
         self.sudo_user        = ds.get('sudo_user', self.playbook.sudo_user)
         self.transport        = ds.get('connection', self.playbook.transport)
-        self.gather_facts     = ds.get('gather_facts', True)
+        self.gather_facts     = ds.get('gather_facts', None)
         self.remote_port      = self.remote_port
         self.any_errors_fatal = utils.boolean(ds.get('any_errors_fatal', 'false'))
         self.accelerate       = utils.boolean(ds.get('accelerate', 'false'))