db: Add tests to ensure we keep migrations in sync

Our database migrations were previously out of sync with the models
used. These issues are now resolved, but we want to prevent this
happening again. Add tests to do just that. oslo.db does most of the
heavy lifting here and we simply use the tests that this provides.

Change-Id: Iad51e8c4c78f9ed813cb44ad4e13d0d1c84cfc40
Signed-off-by: Stephen Finucane <stephenfin@redhat.com>

cinder/tests/unit/db/test_migrations.py

@@ -27,16 +27,104 @@ from oslo_db.sqlalchemy import enginefacade
 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.fixture import logging_error as log_fixture
 from oslotest import base as test_base
 import sqlalchemy
 from sqlalchemy.engine import reflection
 
 import cinder.db.legacy_migrations
 from cinder.db import migration
+from cinder.db.sqlalchemy import models
+from cinder.tests import fixtures as cinder_fixtures
 from cinder.tests.unit import utils as test_utils
 from cinder.volume import volume_types
 
 
+class CinderModelsMigrationsSync(test_migrations.ModelsMigrationsSync):
+    """Test sqlalchemy-migrate migrations."""
+
+    def setUp(self):
+        # Ensure BaseTestCase's ConfigureLogging fixture is disabled since
+        # we're using our own (StandardLogging).
+        with fixtures.EnvironmentVariable('OS_LOG_CAPTURE', '0'):
+            super().setUp()
+
+        self.useFixture(log_fixture.get_logging_handle_error_fixture())
+        self.useFixture(cinder_fixtures.WarningsFixture())
+        self.useFixture(cinder_fixtures.StandardLogging())
+
+        self.engine = enginefacade.writer.get_engine()
+
+    def db_sync(self, engine):
+        migration.db_sync(engine=self.engine)
+
+    def get_engine(self):
+        return self.engine
+
+    def get_metadata(self):
+        return models.BASE.metadata
+
+    def include_object(self, object_, name, type_, reflected, compare_to):
+        if type_ == 'table':
+            # migrate_version is a sqlalchemy-migrate control table and
+            # isn't included in the model
+            if name == 'migrate_version':
+                return False
+
+        return True
+
+    def filter_metadata_diff(self, diff):
+        # Overriding the parent method to decide on certain attributes
+        # that maybe present in the DB but not in the models.py
+
+        def include_element(element):
+            """Determine whether diff element should be excluded."""
+            if element[0] == 'modify_nullable':
+                table_name, column = element[2], element[3]
+                return (table_name, column) not in {
+                    # NOTE(stephenfin): This field has nullable=True set, but
+                    # since it's also a primary key (primary_key=True) the
+                    # resulting schema will still end up being "NOT NULL". This
+                    # weird combination was deemed necessary because MySQL will
+                    # otherwise set this to "NOT NULL DEFAULT ''" which may be
+                    # harmless but is inconsistent with other models. See the
+                    # migration for more information.
+                    ('encryption', 'encryption_id'),
+                    # NOTE(stephenfin): The nullability of these fields is
+                    # dependent on the backend, for some reason
+                    ('encryption', 'provider'),
+                    ('encryption', 'control_location'),
+                }
+
+            return True
+
+        return [element for element in diff if include_element(element[0])]
+
+
+class TestModelsSyncSQLite(
+    CinderModelsMigrationsSync,
+    test_fixtures.OpportunisticDBTestMixin,
+    test_base.BaseTestCase,
+):
+    pass
+
+
+class TestModelsSyncMySQL(
+    CinderModelsMigrationsSync,
+    test_fixtures.OpportunisticDBTestMixin,
+    test_base.BaseTestCase,
+):
+    FIXTURE = test_fixtures.MySQLOpportunisticFixture
+
+
+class TestModelsSyncPostgreSQL(
+    CinderModelsMigrationsSync,
+    test_fixtures.OpportunisticDBTestMixin,
+    test_base.BaseTestCase,
+):
+    FIXTURE = test_fixtures.PostgresqlOpportunisticFixture
+
+
 class MigrationsWalk(
     test_fixtures.OpportunisticDBTestMixin, test_base.BaseTestCase,
 ):