unused images are always deleted (add to in-tree hper-v code)

This is to apply changes applied to openstack/computer-hyperv
to the in-tree hyper-v code.

Change-Id: Ib89c2e407bea5168f2eebb12cfb2d50e4566ff7a
Closes-Bug: #1773342

nova/tests/unit/virt/hyperv/test_imagecache.py

@@ -15,6 +15,7 @@
 
 import os
 
+import ddt
 import fixtures
 import mock
 from oslo_config import cfg
@@ -32,6 +33,7 @@ from nova.virt.hyperv import imagecache
 CONF = cfg.CONF
 
 
+@ddt.ddt
 class ImageCacheTestCase(test_base.HyperVBaseTestCase):
     """Unit tests for the Hyper-V ImageCache class."""
 
@@ -184,7 +186,10 @@ class ImageCacheTestCase(test_base.HyperVBaseTestCase):
         self.imagecache._vhdutils.get_vhd_info.assert_called_once_with(
             expected_vhd_path)
 
-    def test_age_and_verify_cached_images(self):
+    @ddt.data(True, False)
+    def test_age_and_verify_cached_images(self, remove_unused_base_images):
+        self.flags(remove_unused_base_images=remove_unused_base_images)
+
         fake_images = [mock.sentinel.FAKE_IMG1, mock.sentinel.FAKE_IMG2]
         fake_used_images = [mock.sentinel.FAKE_IMG1]
 
@@ -201,8 +206,12 @@ class ImageCacheTestCase(test_base.HyperVBaseTestCase):
 
         self.imagecache._update_image_timestamp.assert_called_once_with(
             mock.sentinel.FAKE_IMG1)
-        self.imagecache._remove_if_old_image.assert_called_once_with(
-            mock.sentinel.FAKE_IMG2)
+
+        if remove_unused_base_images:
+            self.imagecache._remove_if_old_image.assert_called_once_with(
+                mock.sentinel.FAKE_IMG2)
+        else:
+            self.imagecache._remove_if_old_image.assert_not_called()
 
     @mock.patch.object(imagecache.os, 'utime')
     @mock.patch.object(imagecache.ImageCache, '_get_image_backing_files')

nova/virt/hyperv/imagecache.py

@@ -171,7 +171,7 @@ class ImageCache(imagecache.ImageCacheManager):
                 # change the timestamp on the image so as to reflect the last
                 # time it was used
                 self._update_image_timestamp(img)
-            else:
+            elif CONF.remove_unused_base_images:
                 self._remove_if_old_image(img)
 
     def _update_image_timestamp(self, image):

releasenotes/notes/bug-1773342-52b6a1460c7bee64.yaml

@@ -0,0 +1,8 @@
+---
+fixes:
+  - |
+    Fixes `bug 1773342`_ where the Hyper-v driver always deleted unused images
+    ignoring ``remove_unused_images`` config option. This change will now allow
+    deployers to disable the auto-removal of old images.
+
+    .. _bug 1773342: https://bugs.launchpad.net/nova/+bug/1773342