Add blocker alembic migration for null root_provider_ids

This adds an alembic migration script which will block a db_sync
if the online data migration has not been run.

Change-Id: I74c49d286dfc62f49af24303ed1cb18489e7e89d
Story: 2005613
Task: 30921

placement/db/sqlalchemy/alembic/versions/611cd6dffd7b_block_on_null_root_provider_id.py

@@ -0,0 +1,42 @@
+#    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.
+
+"""Block on null root_provider_id
+
+Revision ID: 611cd6dffd7b
+Revises: b4ed3a175331
+Create Date: 2019-05-09 13:57:04.874293
+
+"""
+from alembic import context
+import sqlalchemy as sa
+from sqlalchemy import func as sqlfunc
+from sqlalchemy import MetaData, Table, select
+
+# revision identifiers, used by Alembic.
+revision = '611cd6dffd7b'
+down_revision = 'b4ed3a175331'
+branch_labels = None
+depends_on = None
+
+
+def upgrade():
+    connection = context.get_bind()
+    metadata = MetaData(bind=connection)
+    resource_providers = Table('resource_providers', metadata, autoload=True)
+    query = select([sqlfunc.count()]).select_from(resource_providers).where(
+        resource_providers.c.root_provider_id == sa.null())
+    if connection.scalar(query):
+        raise Exception('There is at least one resource provider table '
+                        'record which is missing its root provider id. '
+                        'Run the "placement-manage db '
+                        'online_data_migrations" command.')

placement/tests/functional/db/test_migrations.py

@@ -28,8 +28,11 @@ from alembic import script
 import mock
 from oslo_db.sqlalchemy import test_fixtures
 from oslo_db.sqlalchemy import test_migrations
+from oslo_db.sqlalchemy import utils as db_utils
 from oslo_log import log as logging
+from oslo_utils.fixture import uuidsentinel as uuids
 from oslotest import base as test_base
+import six
 import testtools
 
 from placement.db.sqlalchemy import migration
@@ -164,6 +167,32 @@ class MigrationCheckersMixin(object):
         v2 = self.migration_api.version()
         self.assertNotEqual(v1, v2)
 
+    def test_block_on_null_root_provider_id(self):
+        """Upgrades the schema to b4ed3a175331 (initial), injects a resource
+        provider with no root provider and then tries to upgrade to head which
+        should fail on the 611cd6dffd7b blocker migration.
+        """
+        # Upgrade to populate the schema.
+        self.migration_api.upgrade('b4ed3a175331')
+        # Now insert a resource provider with no root.
+        rps = db_utils.get_table(self.engine, 'resource_providers')
+        rp_id = rps.insert(values={
+            'name': 'fake-rp-name', 'uuid': uuids.rp_uuid
+        }).execute().inserted_primary_key[0]
+        # Now run the blocker migration and it should raise an error.
+        ex = self.assertRaises(  # noqa H202
+            Exception, self.migration_api.upgrade, '611cd6dffd7b')
+        # Make sure it's the error we expect.
+        self.assertIn('There is at least one resource provider table '
+                      'record which is missing its root provider id.',
+                      six.text_type(ex))
+        # Now update the resource provider with a root_provider_id.
+        rps.update(
+            values={'root_provider_id': rp_id}).where(
+            rps.c.id == rp_id).execute()
+        # Re-run the upgrade and it should be OK.
+        self.migration_api.upgrade('611cd6dffd7b')
+
 
 class PlacementOpportunisticFixture(object):
     def get_enginefacade(self):