Stop creating a context manager during db._api module import

This patch exposes accessors methods for the context manager,
pulls latest changes according to bp/enginefacade-switch, and
publishes a Sql fixture.

Original-commit: I28b741bfa27bf04cbe273586e6e3e00e14fbe683
Co-authored-by: Ann Taraday <akamyshnikova@mirantis.com>
Change-Id: I6e923e9b228ba20a8b782e787504239da713c652

neutron_lib/context.py

@@ -18,9 +18,8 @@ import datetime
 from oslo_context import context as oslo_context
 from oslo_db.sqlalchemy import enginefacade
 
-# TODO(HenryG): replace db/_api.py with the real db/api.py
 from neutron_lib import _policy as policy
-from neutron_lib.db import _api as db_api
+from neutron_lib.db import api as db_api
 
 
 class ContextBase(oslo_context.RequestContext):
@@ -144,7 +143,8 @@ class Context(ContextBaseWithSession):
         if hasattr(super(Context, self), 'session'):
             return super(Context, self).session
         if self._session is None:
-            self._session = db_api.get_session()
+            self._session = db_api.get_writer_session()
+
         return self._session
 
 

neutron_lib/db/_api.py

@@ -1,26 +0,0 @@
-#    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.
-
-from oslo_db.sqlalchemy import enginefacade
-
-
-context_manager = enginefacade.transaction_context()
-context_manager.configure(sqlite_fk=True)
-
-
-# TODO(akamyshnikova): when all places in the code, which use sessions/
-# connections will be updated, this won't be needed
-def get_session(autocommit=True, expire_on_commit=False, use_slave=False):
-    """Helper method to grab session."""
-    return context_manager.get_legacy_facade().get_session(
-        autocommit=autocommit, expire_on_commit=expire_on_commit,
-        use_slave=use_slave)

neutron_lib/db/api.py

@@ -0,0 +1,54 @@
+#    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.
+
+from oslo_concurrency import lockutils
+from oslo_db.sqlalchemy import enginefacade
+
+_synchronized = lockutils.synchronized_with_prefix("neutron-")
+_CTX_MANAGER = None
+
+
+@_synchronized("context-manager")
+def _create_context_manager():
+    global _CTX_MANAGER
+    if _CTX_MANAGER is None:
+        _CTX_MANAGER = enginefacade.transaction_context()
+        _CTX_MANAGER.configure(sqlite_fk=True)
+
+    return _CTX_MANAGER
+
+
+def get_context_manager():
+    """Transaction Context Manager accessor.
+
+    :returns: The transaction context manager.
+    """
+    if _CTX_MANAGER is None:
+        return _create_context_manager()
+
+    return _CTX_MANAGER
+
+
+def get_reader_session():
+    """Helper to get reader session.
+
+    :returns: The reader session.
+    """
+    return get_context_manager().reader.get_sessionmaker()()
+
+
+def get_writer_session():
+    """Helper to get writer session.
+
+    :returns: The writer session.
+    """
+    return get_context_manager().writer.get_sessionmaker()()

neutron_lib/fixture.py

@@ -14,6 +14,8 @@ import fixtures
 
 from neutron_lib.callbacks import manager
 from neutron_lib.callbacks import registry
+from neutron_lib.db import api as db_api
+from neutron_lib.db import model_base
 from neutron_lib.plugins import directory
 
 
@@ -59,3 +61,24 @@ class CallbackRegistryFixture(fixtures.Fixture):
 
     def _restore(self):
         registry._CALLBACK_MANAGER = self._orig_manager
+
+
+class SqlFixture(fixtures.Fixture):
+
+    # flag to indicate that the models have been loaded
+    _TABLES_ESTABLISHED = False
+
+    def _setUp(self):
+        # Register all data models
+        engine = db_api.get_context_manager().writer.get_engine()
+        if not SqlFixture._TABLES_ESTABLISHED:
+            model_base.BASEV2.metadata.create_all(engine)
+            SqlFixture._TABLES_ESTABLISHED = True
+
+        def clear_tables():
+            with engine.begin() as conn:
+                for table in reversed(
+                        model_base.BASEV2.metadata.sorted_tables):
+                    conn.execute(table.delete())
+
+        self.addCleanup(clear_tables)

neutron_lib/tests/unit/db/_base.py

@@ -15,37 +15,12 @@ Base classes for unit tests needing DB backend.
 Only sqlite is supported in neutron-lib.
 """
 
-import fixtures
-
-from neutron_lib.db import _api as db_api
-from neutron_lib.db import model_base
-
+from neutron_lib import fixture
 from neutron_lib.tests import _base as base
 
 
-class SqlFixture(fixtures.Fixture):
-
-    # flag to indicate that the models have been loaded
-    _TABLES_ESTABLISHED = False
-
-    def _setUp(self):
-        # Register all data models
-        engine = db_api.context_manager.get_legacy_facade().get_engine()
-        if not SqlFixture._TABLES_ESTABLISHED:
-            model_base.BASEV2.metadata.create_all(engine)
-            SqlFixture._TABLES_ESTABLISHED = True
-
-        def clear_tables():
-            with engine.begin() as conn:
-                for table in reversed(
-                        model_base.BASEV2.metadata.sorted_tables):
-                    conn.execute(table.delete())
-
-        self.addCleanup(clear_tables)
-
-
 class SqlTestCase(base.BaseTestCase):
 
     def setUp(self):
         super(SqlTestCase, self).setUp()
-        self.useFixture(SqlFixture())
+        self.useFixture(fixture.SqlFixture())

neutron_lib/tests/unit/test_context.py

@@ -22,7 +22,7 @@ class TestNeutronContext(_base.BaseTestCase):
 
     def setUp(self):
         super(TestNeutronContext, self).setUp()
-        db_api = 'neutron_lib.db._api.get_session'
+        db_api = 'neutron_lib.db.api.get_writer_session'
         self._db_api_session_patcher = mock.patch(db_api)
         self.db_api_session = self._db_api_session_patcher.start()
 

neutron_lib/tests/unit/test_fixture.py

@@ -12,9 +12,12 @@
 
 import mock
 
+from oslo_config import cfg
+from oslo_db import options
 from oslotest import base
 
 from neutron_lib.callbacks import registry
+from neutron_lib.db import model_base
 from neutron_lib import fixture
 from neutron_lib.plugins import directory
 
@@ -43,3 +46,16 @@ class CallbackRegistryFixtureTestCase(base.BaseTestCase):
     def test_fixture(self):
         registry.notify('a', 'b', self)
         self.assertTrue(self.manager.notify.called)
+
+
+class SqlFixtureTestCase(base.BaseTestCase):
+
+    def setUp(self):
+        super(SqlFixtureTestCase, self).setUp()
+        options.set_defaults(
+            cfg.CONF,
+            connection='sqlite://')
+        self.useFixture(fixture.SqlFixture())
+
+    def test_fixture(self):
+        self.assertIsNotNone(model_base.BASEV2.metadata.sorted_tables)

releasenotes/notes/context-manager-23538670cd9c701f.yaml

@@ -0,0 +1,7 @@
+---
+features:
+  - |
+    ``neutron_lib.db`` has a public module ``api`` that provides
+    accessor functions for transactional context manager services.
+  - |
+    ``neutron_lib.fixture`` has a new ``SqlFixture`` available.