Adds memory stats meter to libvirt inspector

Uses libvirt 'virDomainMemoryStats' to retrive the memory
that is used by domain, implements 'inspect_memory_usage'
function in libvirt inspector.

Change-Id: I5bf17d51d82d10d2f31b9c81583f53b81c1c5268
Implements: blueprint libvirt-memory-utilization-inspector

ceilometer/compute/virt/libvirt/inspector.py

@@ -18,8 +18,10 @@
 
 from lxml import etree
 from oslo.config import cfg
+from oslo.utils import units
 import six
 
+from ceilometer.compute.pollsters import util
 from ceilometer.compute.virt import inspector as virt_inspector
 from ceilometer.openstack.common.gettextutils import _
 from ceilometer.openstack.common import log as logging
@@ -178,3 +180,35 @@ class LibvirtInspector(virt_inspector.Inspector):
                                              write_bytes=block_stats[3],
                                              errors=block_stats[4])
             yield (disk, stats)
+
+    def inspect_memory_usage(self, instance, duration=None):
+        instance_name = util.instance_name(instance)
+        domain = self._lookup_by_name(instance_name)
+        state = domain.info()[0]
+        if state == libvirt.VIR_DOMAIN_SHUTOFF:
+            LOG.warn(_('Failed to inspect memory usage of %(instance_name)s, '
+                       'domain is in state of SHUTOFF'),
+                     {'instance_name': instance_name})
+            return
+
+        try:
+            memory_stats = domain.memoryStats()
+            if (memory_stats and
+                    memory_stats.get('available') and
+                    memory_stats.get('unused')):
+                memory_used = (memory_stats.get('available') -
+                               memory_stats.get('unused'))
+                # Stat provided from libvirt is in KB, converting it to MB.
+                memory_used = memory_used / units.Ki
+                return virt_inspector.MemoryUsageStats(usage=memory_used)
+            else:
+                LOG.warn(_('Failed to inspect memory usage of '
+                           '%(instance_name)s, can not get info from libvirt'),
+                         {'instance_name': instance_name})
+        # memoryStats might launch an exception if the method
+        # is not supported by the underlying hypervisor being
+        # used by libvirt
+        except libvirt.libvirtError as e:
+            LOG.warn(_('Failed to inspect memory usage of %(instance_name)s, '
+                       'can not get info from libvirt: %(error)s'),
+                     {'instance_name': instance_name, 'error': e})

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

@@ -22,6 +22,7 @@ import contextlib
 
 import fixtures
 import mock
+from oslo.utils import units
 from oslotest import base
 
 from ceilometer.compute.virt import inspector as virt_inspector
@@ -245,6 +246,44 @@ class TestLibvirtInspection(base.BaseTestCase):
             disks = list(self.inspector.inspect_disks(self.instance_name))
             self.assertEqual(disks, [])
 
+    def test_inspect_memory_usage(self):
+        fake_memory_stats = {'available': 51200L, 'unused': 25600L}
+        connection = self.inspector.connection
+        with mock.patch.object(connection, 'lookupByName',
+                               return_value=self.domain):
+            with mock.patch.object(self.domain, 'info',
+                                   return_value=(0L, 0L, 51200L,
+                                                 2L, 999999L)):
+                with mock.patch.object(self.domain, 'memoryStats',
+                                       return_value=fake_memory_stats):
+                    memory = self.inspector.inspect_memory_usage(
+                        self.instance_name)
+                    self.assertEqual(25600L / units.Ki, memory.usage)
+
+    def test_inspect_memory_usage_with_domain_shutoff(self):
+        connection = self.inspector.connection
+        with mock.patch.object(connection, 'lookupByName',
+                               return_value=self.domain):
+            with mock.patch.object(self.domain, 'info',
+                                   return_value=(5L, 0L, 0L,
+                                                 2L, 999999L)):
+                memory = self.inspector.inspect_memory_usage(
+                    self.instance_name)
+                self.assertIsNone(memory)
+
+    def test_inspect_memory_usage_with_empty_stats(self):
+        connection = self.inspector.connection
+        with mock.patch.object(connection, 'lookupByName',
+                               return_value=self.domain):
+            with mock.patch.object(self.domain, 'info',
+                                   return_value=(0L, 0L, 51200L,
+                                                 2L, 999999L)):
+                with mock.patch.object(self.domain, 'memoryStats',
+                                       return_value={}):
+                    memory = self.inspector.inspect_memory_usage(
+                        self.instance_name)
+                    self.assertIsNone(memory)
+
 
 class TestLibvirtInspectionWithError(base.BaseTestCase):
 

doc/source/measurements.rst

@@ -71,7 +71,7 @@ Name                             Type*  Unit       Resource  Origin**  Support**
 instance                         g      instance   inst ID   both      1, 2, 3, 4     Existence of instance
 instance:<type>                  g      instance   inst ID   both      1, 2, 3, 4     Existence of instance <type> (openstack types)
 memory                           g      MB         inst ID   n         1, 2           Volume of RAM allocated in MB
-memory.usage                     g      MB         inst ID   p         3, 4           Volume of RAM used in MB
+memory.usage                     g      MB         inst ID   p         1, 3, 4        Volume of RAM used in MB
 cpu                              c      ns         inst ID   p         1, 2           CPU time used
 cpu_util                         g      %          inst ID   p         1, 2, 3, 4     Average CPU utilisation
 vcpus                            g      vcpu       inst ID   n         1, 2           Number of VCPUs
@@ -118,6 +118,12 @@ network.outgoing.packets.rate    g      packet/s   iface ID  p         1, 2, 3,
   [3]: Vsphere support
   [4]: XenAPI support
 
+.. note:: To enable the libvirt memory.usage supporting, you need libvirt
+   version 1.1.1+, qemu version 1.5+, and you need to prepare suitable balloon
+   driver in the image, particularly for Windows guests, most modern Linuxes
+   have it built in. The memory.usage meters can't be fetched without image
+   balloon driver.
+
 Contributors are welcome to extend other virtualization backends' meters
 or complete the existing ones.