Update glance pollster to use cache

Save the images being scanned by the glance
pollster to the cache.

blueprint one-meter-per-plugin

Change-Id: I7fc808e7b6f0c0ca93a10319574cbb865a69a424
Signed-off-by: Doug Hellmann <doug.hellmann@dreamhost.com>

2 files changed, 19 insertions, 5 deletions

diff --git a/ceilometer/image/glance.py b/ceilometer/image/glance.py
index e96a9a23..9efe2559 100644
--- a/ceilometer/image/glance.py
+++ b/ceilometer/image/glance.py
@@ -40,8 +40,7 @@ class _Base(plugin.PollsterBase):
         return glanceclient.Client('1', endpoint,
                                    token=ksclient.auth_token)
 
-    def iter_images(self, ksclient):
-        """Iterate over all images."""
+    def _get_images(self, ksclient):
         client = self.get_glance_client(ksclient)
         #TODO(eglynn): use pagination to protect against unbounded
         #              memory usage
@@ -70,6 +69,12 @@ class _Base(plugin.PollsterBase):
                 imageIdSet -= set([image.id])
                 yield image
 
+    def _iter_images(self, ksclient, cache):
+        """Iterate over all images."""
+        if 'images' not in cache:
+            cache['images'] = list(self._get_images(ksclient))
+        return iter(cache['images'])
+
     @staticmethod
     def extract_image_metadata(image):
         return dict((k, getattr(image, k))
@@ -100,7 +105,7 @@ class ImagePollster(_Base):
         return ['image', 'image.size']
 
     def get_counters(self, manager, cache):
-        for image in self.iter_images(manager.keystone):
+        for image in self._iter_images(manager.keystone, cache):
             yield counter.Counter(
                 name='image',
                 type=counter.TYPE_GAUGE,
diff --git a/tests/image/test_glance.py b/tests/image/test_glance.py
index f1618b8b..6d00f03a 100644
--- a/tests/image/test_glance.py
+++ b/tests/image/test_glance.py
@@ -133,12 +133,21 @@ class TestImagePollster(base.TestCase):
         self.stubs.Set(glance._Base, 'get_glance_client',
                        self.fake_get_glance_client)
 
-    # Tests whether the iter_images method returns an unique image list.
     def test_iter_images(self):
+        # Tests whether the iter_images method returns an unique image
+        # list when there is nothing in the cache
         images = list(glance.ImagePollster().
-                      iter_images(self.manager.keystone))
+                      _iter_images(self.manager.keystone, {}))
         self.assertEqual(len(images), len(set(image.id for image in images)))
 
+    def test_iter_images_cached(self):
+        # Tests whether the iter_images method returns the values from
+        # the cache
+        cache = {'images': []}
+        images = list(glance.ImagePollster().
+                      _iter_images(self.manager.keystone, cache))
+        self.assertEqual(images, [])
+
     def test_glance_image_counter(self):
         counters = list(glance.ImagePollster().get_counters(self.manager, {}))
         self.assertEqual(len(counters), 6)