XenAPI support: Disk rates

Implemented inspect_disk_rates() to inspect the disk statistics as rates
for an instance.

Change-Id: I0220e612b156a967745ff281ce09329fa0d15a12
Implements: blueprint xenapi-support

ceilometer/compute/virt/xenapi/inspector.py

@@ -167,3 +167,27 @@ def inspect_vnic_rates(self, instance, duration=None):
                 tx_rate = float(vif_metrics_rec['io_write_kbs']) * units.Ki
                 stats = virt_inspector.InterfaceRateStats(rx_rate, tx_rate)
                 yield (interface, stats)
+
+    def inspect_disk_rates(self, instance, duration=None):
+        instance_name = util.instance_name(instance)
+        vm_ref = self._lookup_by_name(instance_name)
+        vbd_refs = self._call_xenapi("VM.get_VBDs", vm_ref)
+        if vbd_refs:
+            for vbd_ref in vbd_refs:
+                vbd_rec = self._call_xenapi("VBD.get_record", vbd_ref)
+                vbd_metrics_ref = self._call_xenapi("VBD.get_metrics",
+                                                    vbd_ref)
+                vbd_metrics_rec = self._call_xenapi("VBD_metrics.get_record",
+                                                    vbd_metrics_ref)
+
+                disk = virt_inspector.Disk(device=vbd_rec['device'])
+                # Stats provided from XenServer are in KB/s,
+                # converting it to B/s.
+                read_rate = float(vbd_metrics_rec['io_read_kbs']) * units.Ki
+                write_rate = float(vbd_metrics_rec['io_write_kbs']) * units.Ki
+                disk_rate_info = virt_inspector.DiskRateStats(
+                    read_bytes_rate=read_rate,
+                    read_requests_rate=0,
+                    write_bytes_rate=write_rate,
+                    write_requests_rate=0)
+                yield(disk, disk_rate_info)

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

@@ -139,3 +139,40 @@ def fake_xenapi_request(method, args):
             self.assertEqual('vif_mac', vnic0.mac)
             self.assertEqual(1024, info0.rx_bytes_rate)
             self.assertEqual(2048, info0.tx_bytes_rate)
+
+    def test_inspect_disk_rates(self):
+        fake_instance = {'OS-EXT-SRV-ATTR:instance_name': 'fake_instance_name',
+                         'id': 'fake_instance_id'}
+
+        def fake_xenapi_request(method, args):
+            vbd_rec = {
+                'device': 'xvdd'
+            }
+
+            vbd_metrics_rec = {
+                'io_read_kbs': '1',
+                'io_write_kbs': '2'
+            }
+            if method == 'VM.get_by_name_label':
+                return ['vm_ref']
+            elif method == 'VM.get_VBDs':
+                return ['vbd_ref']
+            elif method == 'VBD.get_record':
+                return vbd_rec
+            elif method == 'VBD.get_metrics':
+                return 'vbd_metrics_ref'
+            elif method == 'VBD_metrics.get_record':
+                return vbd_metrics_rec
+            else:
+                return None
+
+        session = self.inspector.session
+        with mock.patch.object(session, 'xenapi_request',
+                               side_effect=fake_xenapi_request):
+            disks = list(self.inspector.inspect_disk_rates(fake_instance))
+
+            self.assertEqual(1, len(disks))
+            disk0, info0 = disks[0]
+            self.assertEqual('xvdd', disk0.device)
+            self.assertEqual(1024, info0.read_bytes_rate)
+            self.assertEqual(2048, info0.write_bytes_rate)