Centralize sqlite FK constraint enforcement

There's a TODO in the code to centralize foreign key constraint
enforcement for sqlite for unit and functional tests and we're missing
enforcement of FK constraints in a couple of test classes that should
have it.

This resolves the TODO and turns on FK constraint enforcement where it
is missing. Do this to enhance testing in preparation for a proposed
change to the database archiving logic later in this patch series.

Conflicts:
    nova/test.py

NOTE(melwitt): The conflicts are because of the following changes not
in Victoria:

  * Ib2c406327fef2fb4868d8050fc476a7d17706e23 (Remove six.moves)
  * Ide65686cf02463045f5c32771ca949802b19636f (Remove
    six.binary_type/integer_types/string_types)

Change-Id: Idcf026d020e63e4e6ece1db46e4cdc7b7742b76f
(cherry picked from commit 172024d)

Author: melwitt

nova/test.py

@@ -51,10 +51,12 @@
 from oslotest import mock_fixture
 import six
 from six.moves import builtins
+from sqlalchemy.dialects import sqlite
 import testtools
 
 from nova.compute import rpcapi as compute_rpcapi
 from nova import context
+from nova.db.sqlalchemy import api as sqlalchemy_api
 from nova import exception
 from nova import objects
 from nova.objects import base as objects_base
@@ -376,6 +378,22 @@ def flags(self, **kw):
         for k, v in kw.items():
             CONF.set_override(k, v, group)
 
+    def enforce_fk_constraints(self, engine=None):
+        if engine is None:
+            engine = sqlalchemy_api.get_engine()
+        dialect = engine.url.get_dialect()
+        if dialect == sqlite.dialect:
+            # We're seeing issues with foreign key support in SQLite 3.6.20
+            # SQLAlchemy doesn't support it at all with < SQLite 3.6.19
+            # It works fine in SQLite 3.7.
+            # So return early to skip this test if running SQLite < 3.7
+            import sqlite3
+            tup = sqlite3.sqlite_version_info
+            if tup[0] < 3 or (tup[0] == 3 and tup[1] < 7):
+                self.skipTest(
+                    'sqlite version too old for reliable SQLA foreign_keys')
+            engine.connect().execute("PRAGMA foreign_keys = ON")
+
     def start_service(self, name, host=None, cell_name=None, **kwargs):
         # Disallow starting multiple scheduler services
         if name == 'scheduler' and self._service_fixture_count[name]:

nova/tests/functional/db/test_archive.py

@@ -17,7 +17,6 @@
 
 from dateutil import parser as dateutil_parser
 from oslo_utils import timeutils
-from sqlalchemy.dialects import sqlite
 from sqlalchemy import func
 from sqlalchemy import MetaData
 from sqlalchemy import select
@@ -33,22 +32,7 @@ class TestDatabaseArchive(integrated_helpers._IntegratedTestBase):
 
     def setUp(self):
         super(TestDatabaseArchive, self).setUp()
-        # TODO(mriedem): pull this out so we can re-use it in
-        # test_archive_deleted_rows_fk_constraint
-        # SQLite doesn't enforce foreign key constraints without a pragma.
-        engine = sqlalchemy_api.get_engine()
-        dialect = engine.url.get_dialect()
-        if dialect == sqlite.dialect:
-            # We're seeing issues with foreign key support in SQLite 3.6.20
-            # SQLAlchemy doesn't support it at all with < SQLite 3.6.19
-            # It works fine in SQLite 3.7.
-            # So return early to skip this test if running SQLite < 3.7
-            import sqlite3
-            tup = sqlite3.sqlite_version_info
-            if tup[0] < 3 or (tup[0] == 3 and tup[1] < 7):
-                self.skipTest(
-                    'sqlite version too old for reliable SQLA foreign_keys')
-            engine.connect().execute("PRAGMA foreign_keys = ON")
+        self.enforce_fk_constraints()
 
     def test_archive_deleted_rows(self):
         # Boots a server, deletes it, and then tries to archive it.

nova/tests/functional/test_nova_manage.py

@@ -1767,6 +1767,7 @@ class TestDBArchiveDeletedRows(integrated_helpers._IntegratedTestBase):
 
     def setUp(self):
         super(TestDBArchiveDeletedRows, self).setUp()
+        self.enforce_fk_constraints()
         self.cli = manage.DbCommands()
         self.output = StringIO()
         self.useFixture(fixtures.MonkeyPatch('sys.stdout', self.output))
@@ -1812,6 +1813,7 @@ class TestDBArchiveDeletedRowsMultiCell(integrated_helpers.InstanceHelperMixin,
 
     def setUp(self):
         super(TestDBArchiveDeletedRowsMultiCell, self).setUp()
+        self.enforce_fk_constraints()
         self.useFixture(nova_fixtures.NeutronFixture(self))
         self.useFixture(nova_fixtures.GlanceFixture(self))
         self.useFixture(func_fixtures.PlacementFixture())

nova/tests/unit/db/test_db_api.py

@@ -39,7 +39,6 @@
 import six
 from six.moves import range
 from sqlalchemy import Column
-from sqlalchemy.dialects import sqlite
 from sqlalchemy.exc import OperationalError
 from sqlalchemy.exc import SQLAlchemyError
 from sqlalchemy import inspect
@@ -6440,18 +6439,7 @@ def test_archive_deleted_rows_shadow_insertions_equals_deletions(self):
 
     def _check_sqlite_version_less_than_3_7(self):
         # SQLite doesn't enforce foreign key constraints without a pragma.
-        dialect = self.engine.url.get_dialect()
-        if dialect == sqlite.dialect:
-            # We're seeing issues with foreign key support in SQLite 3.6.20
-            # SQLAlchemy doesn't support it at all with < SQLite 3.6.19
-            # It works fine in SQLite 3.7.
-            # So return early to skip this test if running SQLite < 3.7
-            import sqlite3
-            tup = sqlite3.sqlite_version_info
-            if tup[0] < 3 or (tup[0] == 3 and tup[1] < 7):
-                self.skipTest(
-                    'sqlite version too old for reliable SQLA foreign_keys')
-            self.conn.execute("PRAGMA foreign_keys = ON")
+        self.enforce_fk_constraints(engine=self.engine)
 
     def test_archive_deleted_rows_for_migrations(self):
         # migrations.instance_uuid depends on instances.uuid