Set default to prevent out of memory conditions

Change-Id: I00efd4784346adb89b137424ed35bdeafe9b6f24

ironic/conf/default.py

@@ -354,7 +354,7 @@ service_opts = [
                       'conductor and API services')),
     cfg.BoolOpt('minimum_memory_warning_only',
                 mutable=True,
-                default=True,
+                default=False,
                 help=_('Setting to govern if Ironic should only warn instead '
                        'of attempting to hold back the request in order to '
                        'prevent the exhaustion of system memory.')),

ironic/tests/unit/common/test_utils.py

@@ -452,7 +452,6 @@ class TempFilesTestCase(base.TestCase):
     @mock.patch.object(time, 'sleep', autospec=True)
     @mock.patch.object(psutil, 'virtual_memory', autospec=True)
     def test_is_memory_insufficent(self, mock_vm_check, mock_sleep):
-        self.config(minimum_memory_warning_only=False)
 
         class vm_check(object):
             available = 1000000000
@@ -465,7 +464,6 @@ class TempFilesTestCase(base.TestCase):
     @mock.patch.object(psutil, 'virtual_memory', autospec=True)
     def test_is_memory_insufficent_good(self, mock_vm_check,
                                         mock_sleep):
-        self.config(minimum_memory_warning_only=False)
 
         class vm_check(object):
             available = 3276700000
@@ -492,6 +490,19 @@ class TempFilesTestCase(base.TestCase):
         self.assertFalse(utils.is_memory_insufficent())
         self.assertEqual(3, mock_vm_check.call_count)
 
+    @mock.patch.object(time, 'sleep', autospec=True)
+    @mock.patch.object(psutil, 'virtual_memory', autospec=True)
+    def test_is_memory_insufficent_warning_only(self, mock_vm_check,
+                                                mock_sleep):
+        self.config(minimum_memory_warning_only=True)
+
+        class vm_check_bad(object):
+            available = 1023000000
+
+        mock_vm_check.side_effect = vm_check_bad
+        self.assertFalse(utils.is_memory_insufficent())
+        self.assertEqual(2, mock_vm_check.call_count)
+
 
 class GetUpdatedCapabilitiesTestCase(base.TestCase):
 

releasenotes/notes/conductor-now-waits-when-low-on-memory-d73892a79cde0516.yaml

@@ -0,0 +1,6 @@
+---
+features:
+  - |
+    By default Ironic will now not start new memory intensive work IF
+    insufficent system memory exists. This can be disabled by setting
+    the ``[DEFAULT]minimum_memory_warning_only`` value to ``True``.