Fix resource tracker VCPU counting

The resource track is double counting the number of
vcpus used because it counts the virt driver's view
and the resource tracker's view. It should reset
the count to 0 before counting the resourcet racker's
view. this is done for other resources (memory, disk)
in _update_usage_from_instances().

This was not caught in unit tests because they always
provide a virt driver view with no resource used for
tests that assume instances are already running.

This patch adds the reset to 0 and modifies the
tests to provide correct counts of used resources
from the virt driver.

Change-Id: I21acfd7d5b5ed442cd1e9049c986a06bd2b59b81
Closes-Bug: #1519001

nova/compute/resource_tracker.py

@@ -862,6 +862,7 @@ class ResourceTracker(object):
         # set some initial values, reserve room for host/hypervisor:
         self.compute_node.local_gb_used = CONF.reserved_host_disk_mb / 1024
         self.compute_node.memory_mb_used = CONF.reserved_host_memory_mb
+        self.compute_node.vcpus_used = 0
         self.compute_node.free_ram_mb = (self.compute_node.memory_mb -
                                          self.compute_node.memory_mb_used)
         self.compute_node.free_disk_gb = (self.compute_node.local_gb -

nova/tests/unit/compute/test_tracker.py

@@ -538,7 +538,14 @@ class TestUpdateAvailableResources(BaseTestCase):
                                           get_cn_mock):
         self.flags(reserved_host_disk_mb=0,
                    reserved_host_memory_mb=0)
-        self._setup_rt()
+
+        # Setup virt resources to match used resources to number
+        # of defined instances on the hypervisor
+        virt_resources = copy.deepcopy(_VIRT_DRIVER_AVAIL_RESOURCES)
+        virt_resources.update(vcpus_used=1,
+                              memory_mb_used=128,
+                              local_gb_used=1)
+        self._setup_rt(virt_resources=virt_resources)
 
         get_mock.return_value = _INSTANCE_FIXTURES
         migr_mock.return_value = []
@@ -583,7 +590,12 @@ class TestUpdateAvailableResources(BaseTestCase):
                                               get_cn_mock):
         self.flags(reserved_host_disk_mb=0,
                    reserved_host_memory_mb=0)
-        self._setup_rt()
+
+        # Setup virt resources to match used resources to number
+        # of defined instances on the hypervisor
+        virt_resources = copy.deepcopy(_VIRT_DRIVER_AVAIL_RESOURCES)
+        virt_resources.update(memory_mb_used=64)
+        self._setup_rt(virt_resources=virt_resources)
 
         get_mock.return_value = []
         migr_mock.return_value = []
@@ -660,7 +672,14 @@ class TestUpdateAvailableResources(BaseTestCase):
         # node in case of a revert of the resize.
         self.flags(reserved_host_disk_mb=0,
                    reserved_host_memory_mb=0)
-        self._setup_rt()
+
+        # Setup virt resources to match used resources to number
+        # of defined instances on the hypervisor
+        virt_resources = copy.deepcopy(_VIRT_DRIVER_AVAIL_RESOURCES)
+        virt_resources.update(vcpus_used=4,
+                              memory_mb_used=128,
+                              local_gb_used=1)
+        self._setup_rt(virt_resources=virt_resources)
 
         get_mock.return_value = []
         migr_obj = _MIGRATION_FIXTURES['source-only']
@@ -723,7 +742,14 @@ class TestUpdateAvailableResources(BaseTestCase):
         # node in case of a confirm of the resize.
         self.flags(reserved_host_disk_mb=0,
                    reserved_host_memory_mb=0)
-        self._setup_rt()
+
+        # Setup virt resources to match used resources to number
+        # of defined instances on the hypervisor
+        virt_resources = copy.deepcopy(_VIRT_DRIVER_AVAIL_RESOURCES)
+        virt_resources.update(vcpus_used=2,
+                              memory_mb_used=256,
+                              local_gb_used=5)
+        self._setup_rt(virt_resources=virt_resources)
 
         get_mock.return_value = []
         migr_obj = _MIGRATION_FIXTURES['dest-only']
@@ -780,7 +806,14 @@ class TestUpdateAvailableResources(BaseTestCase):
         # is in progress, but not finished yet.
         self.flags(reserved_host_disk_mb=0,
                    reserved_host_memory_mb=0)
-        self._setup_rt()
+
+        # Setup virt resources to match used resources to number
+        # of defined instances on the hypervisor
+        virt_resources = copy.deepcopy(_VIRT_DRIVER_AVAIL_RESOURCES)
+        virt_resources.update(vcpus_used=2,
+                              memory_mb_used=256,
+                              local_gb_used=5)
+        self._setup_rt(virt_resources=virt_resources)
 
         get_mock.return_value = []
         migr_obj = _MIGRATION_FIXTURES['dest-only-evac']
@@ -842,7 +875,14 @@ class TestUpdateAvailableResources(BaseTestCase):
         # resize instance types as taking up space on the node.
         self.flags(reserved_host_disk_mb=0,
                    reserved_host_memory_mb=0)
-        self._setup_rt()
+
+        # Setup virt resources to match used resources to number
+        # of defined instances on the hypervisor
+        virt_resources = copy.deepcopy(_VIRT_DRIVER_AVAIL_RESOURCES)
+        virt_resources.update(vcpus_used=4,
+                              memory_mb_used=512,
+                              local_gb_used=7)
+        self._setup_rt(virt_resources=virt_resources)
 
         migr_obj = _MIGRATION_FIXTURES['source-and-dest']
         migr_mock.return_value = [migr_obj]