XenAPI support: Memory Usage

Implemented inspect_memory_usage() to inspect the memory usage statistics
for an instance.

Change-Id: I0a8549e9e80ffeab18acc3b236c8fdc63d970783
Implements: blueprint xenapi-support

ceilometer/compute/virt/xenapi/inspector.py

@@ -17,6 +17,7 @@
 
 from eventlet import timeout
 from oslo.config import cfg
+from oslo.utils import units
 try:
     import XenAPI as api
 except ImportError:
@@ -134,3 +135,13 @@ class XenapiInspector(virt_inspector.Inspector):
             utils += vcpus_utils.get(str(num))
         utils = utils / int(vcpus_number) * 100
         return virt_inspector.CPUUtilStats(util=utils)
+
+    def inspect_memory_usage(self, instance, duration=None):
+        instance_name = util.instance_name(instance)
+        vm_ref = self._lookup_by_name(instance_name)
+        metrics_ref = self._call_xenapi("VM.get_metrics", vm_ref)
+        metrics_rec = self._call_xenapi("VM_metrics.get_record",
+                                        metrics_ref)
+        # Stat provided from XenServer is in B, converting it to MB.
+        memory = long(metrics_rec['memory_actual']) / units.Mi
+        return virt_inspector.MemoryUsageStats(usage=memory)

ceilometer/tests/compute/virt/xenapi/test_inspector.py

@@ -74,3 +74,28 @@ class TestXenapiInspection(base.BaseTestCase):
                                side_effect=fake_xenapi_request):
             cpu_util_stat = self.inspector.inspect_cpu_util(fake_instance)
             self.assertEqual(fake_stat, cpu_util_stat)
+
+    def test_inspect_memory_usage(self):
+        fake_instance = {'OS-EXT-SRV-ATTR:instance_name': 'fake_instance_name',
+                         'id': 'fake_instance_id'}
+        fake_stat = virt_inspector.MemoryUsageStats(usage=128)
+
+        def fake_xenapi_request(method, args):
+            metrics_rec = {
+                'memory_actual': '134217728',
+            }
+
+            if method == 'VM.get_by_name_label':
+                return ['vm_ref']
+            elif method == 'VM.get_metrics':
+                return 'metrics_ref'
+            elif method == 'VM_metrics.get_record':
+                return metrics_rec
+            else:
+                return None
+
+        session = self.inspector.session
+        with mock.patch.object(session, 'xenapi_request',
+                               side_effect=fake_xenapi_request):
+            memory_stat = self.inspector.inspect_memory_usage(fake_instance)
+            self.assertEqual(fake_stat, memory_stat)