Detect not-started _TransactionFactory in legacy3.2.0

When LegacyEngineFacade is passed a _TransactionFactory
that is not started, or one that fails to start, the
_start() method should be called again each time the
factory is called upon; this ensures that the failed
start either can be made to succeed, or at least re-raises
the same error as earlier, instead of falling into attribute
access for non-existent attributes.

Change-Id: I7484f837d455c1f69c448e5ccadc277d19af47e7
Closes-Bug: #1515326

2 files changed, 32 insertions, 0 deletions

diff --git a/oslo_db/sqlalchemy/enginefacade.py b/oslo_db/sqlalchemy/enginefacade.py
index 111f033..7f64acc 100644
--- a/oslo_db/sqlalchemy/enginefacade.py
+++ b/oslo_db/sqlalchemy/enginefacade.py
@@ -952,6 +952,10 @@ class LegacyEngineFacade(object):
                 _conf, connection=sql_connection,
                 slave_connection=slave_connection)
 
+    def _check_factory_started(self):
+        if not self._factory._started:
+            self._factory._start()
+
     def get_engine(self, use_slave=False):
         """Get the engine instance (note, that it's shared).
 
@@ -962,6 +966,7 @@ class LegacyEngineFacade(object):
         :type use_slave: bool
 
         """
+        self._check_factory_started()
         if use_slave:
             return self._factory._reader_engine
         else:
@@ -982,6 +987,7 @@ class LegacyEngineFacade(object):
         was created). See SQLAlchemy Session docs for details.
 
         """
+        self._check_factory_started()
         if use_slave:
             return self._factory._reader_maker(**kwargs)
         else:
@@ -994,6 +1000,7 @@ class LegacyEngineFacade(object):
         be temporarily injected with some state such as a specific connection.
 
         """
+        self._check_factory_started()
         if use_slave:
             return self._factory._reader_maker
         else:
diff --git a/oslo_db/tests/sqlalchemy/test_enginefacade.py b/oslo_db/tests/sqlalchemy/test_enginefacade.py
index 62e3fa9..9226c05 100644
--- a/oslo_db/tests/sqlalchemy/test_enginefacade.py
+++ b/oslo_db/tests/sqlalchemy/test_enginefacade.py
@@ -997,6 +997,31 @@ class LegacyIntegrationtest(test_base.DbTestCase):
 
         self.assertNotEqual(legacy1, legacy2)
 
+    def test_legacy_not_started(self):
+
+        factory = enginefacade._TransactionFactory()
+
+        self.assertRaises(
+            exception.CantStartEngineError,
+            factory.get_legacy_facade
+        )
+
+        legacy_facade = factory.get_legacy_facade()
+        self.assertRaises(
+            exception.CantStartEngineError,
+            legacy_facade.get_session
+        )
+
+        self.assertRaises(
+            exception.CantStartEngineError,
+            legacy_facade.get_session
+        )
+
+        self.assertRaises(
+            exception.CantStartEngineError,
+            legacy_facade.get_engine
+        )
+
 
 class ThreadingTest(test_base.DbTestCase):
     """Test copy/pickle on new threads using real connections and sessions."""