Add generic reproducer for bug #1879878

No need for the libvirt driver in all its complexity here.

Changes:
  nova/tests/functional/regressions/test_bug_1879878.py

NOTE(stephenfin): The '_create_server' and '_delete_server' helpers
don't exist here, so we need to use the older helpers like
'_build_minimal_create_server_request'. Also, we need to support Python
2 here so we can't use 'super' without arguments :(

Change-Id: Ifea9a15fb01c0b25e9973024f4f61faecc56e1cd
Signed-off-by: Stephen Finucane <stephenfin@redhat.com>
(cherry picked from commit e1adbced92453329f7285ec38c1dc7821ebb52c7)
(cherry picked from commit 15da841ecb6cc6152f5e6dbcd63bf09725cac6fc)

1 files changed, 173 insertions, 0 deletions

diff --git a/nova/tests/functional/regressions/test_bug_1879878.py b/nova/tests/functional/regressions/test_bug_1879878.py
new file mode 100644
index 0000000000..b338d028ff
--- /dev/null
+++ b/nova/tests/functional/regressions/test_bug_1879878.py
@@ -0,0 +1,173 @@
+# Licensed under the Apache License, Version 2.0 (the "License"); you may
+# not use this file except in compliance with the License. You may obtain
+# a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+# License for the specific language governing permissions and limitations
+# under the License.
+
+import ddt
+
+from nova.compute import resource_tracker as rt
+from nova import context as nova_context
+from nova import objects
+from nova.tests.functional import integrated_helpers
+from nova.tests.unit.image import fake as fake_image
+
+
+@ddt.ddt
+class TestColdMigrationUsage(integrated_helpers.ProviderUsageBaseTestCase):
+    """Reproducer for bug #1879878.
+
+    Demonstrate the possibility of races caused by running the resource
+    tracker's periodic task between marking a migration as confirmed or
+    reverted and dropping the claim for that migration on the source or
+    destination host, respectively.
+    """
+    compute_driver = 'fake.MediumFakeDriver'
+
+    def setUp(self):
+        super(TestColdMigrationUsage, self).setUp()
+        # Start two computes so we can migrate between them.
+        self._start_compute('host1')
+        self._start_compute('host2')
+
+        self.ctxt = nova_context.get_admin_context()
+
+    def _create_server(self):
+        """Creates and return a server along with a source host and target
+        host.
+        """
+        server = self._build_minimal_create_server_request(
+            self.api, 'test-server',
+            image_uuid=fake_image.get_valid_image_id(), networks='none')
+        server = self.api.post_server({'server': server})
+        self.addCleanup(self.api.delete_server, server['id'])
+        server = self._wait_for_state_change(self.api, server, 'ACTIVE')
+        source_host = server['OS-EXT-SRV-ATTR:host']
+        target_host = 'host2' if source_host == 'host1' else 'host1'
+        return server, source_host, target_host
+
+    def assertUsage(self, hostname, usage):
+        """Assert VCPU usage for the given host."""
+        cn = objects.ComputeNode.get_by_nodename(self.ctxt, hostname)
+        # we could test anything, but vcpu is easy to grok
+        self.assertEqual(cn.vcpus_used, usage)
+
+    @ddt.data(True, False)
+    def test_migrate_confirm(self, drop_race):
+        server, src_host, dst_host = self._create_server()
+
+        # only one instance created, so usage on its host
+        self.assertUsage(src_host, 1)
+        self.assertUsage(dst_host, 0)
+
+        orig_drop_claim = rt.ResourceTracker.drop_move_claim
+
+        def fake_drop_move_claim(*args, **kwargs):
+            # run periodics after marking the migration confirmed, simulating a
+            # race between the doing this and actually dropping the claim
+
+            # check the usage, which should show usage on both hosts
+            self.assertUsage(src_host, 1)
+            self.assertUsage(dst_host, 1)
+
+            if drop_race:
+                self._run_periodics()
+
+                # FIXME(stephenfin): the periodic should not have dropped the
+                # records for the src yet
+                self.assertUsage(src_host, 0)
+                self.assertUsage(dst_host, 1)
+
+            return orig_drop_claim(*args, **kwargs)
+
+        self.stub_out(
+            'nova.compute.resource_tracker.ResourceTracker.drop_move_claim',
+            fake_drop_move_claim,
+        )
+
+        # TODO(stephenfin): Use a helper
+        self.api.post_server_action(server['id'], {'migrate': None})
+        self._wait_for_state_change(self.api, server, 'VERIFY_RESIZE')
+
+        # migration isn't complete so we should have usage on both hosts
+        self.assertUsage(src_host, 1)
+        self.assertUsage(dst_host, 1)
+
+        self._confirm_resize(server)
+
+        # migration is now confirmed so we should once again only have usage on
+        # one host
+        # FIXME(stephenfin): Our usage here should be 0 and 1 for source and
+        # dest respectively when confirming, but that won't happen until we run
+        # the periodic and rebuild our inventory from scratch
+        self.assertUsage(src_host, -1 if drop_race else 0)
+        self.assertUsage(dst_host, 1)
+
+        # running periodics shouldn't change things
+        self._run_periodics()
+
+        self.assertUsage(src_host, 0)
+        self.assertUsage(dst_host, 1)
+
+    @ddt.data(True, False)
+    def test_migrate_revert(self, drop_race):
+        server, src_host, dst_host = self._create_server()
+
+        # only one instance created, so usage on its host
+        self.assertUsage(src_host, 1)
+        self.assertUsage(dst_host, 0)
+
+        orig_drop_claim = rt.ResourceTracker.drop_move_claim
+
+        def fake_drop_move_claim(*args, **kwargs):
+            # run periodics after marking the migration reverted, simulating a
+            # race between the doing this and actually dropping the claim
+
+            # check the usage, which should show usage on both hosts
+            self.assertUsage(src_host, 1)
+            self.assertUsage(dst_host, 1)
+
+            if drop_race:
+                self._run_periodics()
+
+                # FIXME(stephenfin): the periodic should not have dropped the
+                # records for the src
+                self.assertUsage(src_host, 0)
+                self.assertUsage(dst_host, 1)
+
+            return orig_drop_claim(*args, **kwargs)
+
+        self.stub_out(
+            'nova.compute.resource_tracker.ResourceTracker.drop_move_claim',
+            fake_drop_move_claim,
+        )
+
+        # TODO(stephenfin): Use a helper
+        self.api.post_server_action(server['id'], {'migrate': None})
+        self._wait_for_state_change(self.api, server, 'VERIFY_RESIZE')
+
+        # migration isn't complete so we should have usage on both hosts
+        self.assertUsage(src_host, 1)
+        self.assertUsage(dst_host, 1)
+
+        self._revert_resize(server)
+
+        # migration is now reverted so we should once again only have usage on
+        # one host
+        # FIXME(stephenfin): Our usage here should always be 1 and 0 for source
+        # and dest respectively when reverting, but that won't happen until we
+        # run the periodic and rebuild our inventory from scratch
+        self.assertUsage(src_host, 0 if drop_race else 1)
+        self.assertUsage(dst_host, 1 if drop_race else 0)
+
+        # running periodics shouldn't change things
+        self._run_periodics()
+
+        self.assertUsage(src_host, 1)
+        self.assertUsage(dst_host, 0)