Reproduce bug 1721652 in the functional test env

When bug 1709902 was fixed in I0df401a7c91f012fdb25cb0e6b344ca51de8c309
the fix assumed that when the _destroy_evacuated_instances() is called
during the init of the nova-compute service the resource tracker
already knows the compute node ids associated to the given compute
host. This is not true and therefore _destroy_evacuated_instances fails
with an exception and does not clean up the evacuated instance.

The solution for the original bug included a functional regression
test. However the functional test env is not capable of fully simulate
a nova-compute service restart. The service only stopped then started
again. This allows some in memory state of the compute service to
survive the simulated restart. This caused that the functional test
was not able to catch that the above described assumption is not
correct.

Related-Bug: #1721652
Related-Bug: #1709902
Change-Id: Icaf1bae8cb040b939f916a19ce026031ddb84af7

nova/tests/functional/test_servers.py

@@ -1613,6 +1613,20 @@ class ServerMovingTests(ProviderUsageBaseTestCase):
         self._delete_and_check_allocations(
             server, source_rp_uuid, dest_rp_uuid)
 
+    def _restart_compute_service(self, compute):
+        # NOTE(gibi): The service interface cannot be used to simulate a real
+        # service restart as the manager object will not be recreated after a
+        # service.stop() and service.start() therefore the manager state will
+        # survive. For example the resource tracker will not be recreated after
+        # a stop start. The service.kill() call cannot help as it deletes
+        # the service from the DB which is unrealistic and causes that some
+        # operation that refers to the killed host (e.g. evacuate) fails.
+        # So this helper method tries to simulate a better compute service
+        # restart by cleaning up some of the internal state of the compute
+        # manager.
+        compute.manager._resource_tracker = None
+        compute.start()
+
     def test_evacuate(self):
         source_hostname = self.compute1.host
         dest_hostname = self.compute2.host
@@ -1656,23 +1670,44 @@ class ServerMovingTests(ProviderUsageBaseTestCase):
         self.assertFlavorMatchesAllocation(self.flavor1, dest_allocation)
 
         # start up the source compute
-        self.compute1.start()
+        # NOTE(gibi): This is bug 1721652. The restart should go through
+        # without exception.
+        self.assertRaises(KeyError, self._restart_compute_service,
+                          self.compute1)
+
         self.admin_api.put_service(
             source_compute_id, {'forced_down': 'false'})
 
+        # NOTE(gibi): This is bug 1721652. After the source host is started up
+        # the allocation should be cleaned.
         source_usages = self._get_provider_usages(source_rp_uuid)
-        self.assertEqual({'VCPU': 0,
-                          'MEMORY_MB': 0,
-                          'DISK_GB': 0},
-                         source_usages)
+        self.assertFlavorMatchesAllocation(self.flavor1, source_usages)
 
         dest_usages = self._get_provider_usages(dest_rp_uuid)
         self.assertFlavorMatchesAllocation(self.flavor1, dest_usages)
 
         allocations = self._get_allocations_by_server_uuid(server['id'])
-        self.assertEqual(1, len(allocations))
+        self.assertEqual(2, len(allocations))
         dest_allocation = allocations[dest_rp_uuid]['resources']
         self.assertFlavorMatchesAllocation(self.flavor1, dest_allocation)
+        source_allocation = allocations[source_rp_uuid]['resources']
+        self.assertFlavorMatchesAllocation(self.flavor1, source_allocation)
+
+        # NOTE(gibi): Once the bug 1721652 is fixed this should be the expected
+        # behavior
+        # source_usages = self._get_provider_usages(source_rp_uuid)
+        # self.assertEqual({'VCPU': 0,
+        #                   'MEMORY_MB': 0,
+        #                   'DISK_GB': 0},
+        #                  source_usages)
+        #
+        # dest_usages = self._get_provider_usages(dest_rp_uuid)
+        # self.assertFlavorMatchesAllocation(self.flavor1, dest_usages)
+        #
+        # allocations = self._get_allocations_by_server_uuid(server['id'])
+        # self.assertEqual(1, len(allocations))
+        # dest_allocation = allocations[dest_rp_uuid]['resources']
+        # self.assertFlavorMatchesAllocation(self.flavor1, dest_allocation)
 
         self._delete_and_check_allocations(
             server, source_rp_uuid, dest_rp_uuid)