Reverse role of synchronous_reader

Repaired the "synchronous_reader" modifier of enginefacade so that it
refers to the "writer" engine when set to True, thereby allowing
"synchronous" behavior with the writer.  When set to False, this is
"asynchronous", so this should be associated with the async engines.
The flag had the reverse behavior previously.

Change-Id: Id7fea7562ba90eb710176d497af103303f230531
Closes-bug: #1746116

oslo_db/sqlalchemy/enginefacade.py

@@ -393,7 +393,8 @@ class _TransactionFactory(object):
             self._start()
         if mode is _WRITER:
             return self._writer_engine.connect()
-        elif self.synchronous_reader or mode is _ASYNC_READER:
+        elif mode is _ASYNC_READER or \
+                (mode is _READER and not self.synchronous_reader):
             return self._reader_engine.connect()
         else:
             return self._writer_engine.connect()
@@ -408,7 +409,8 @@ class _TransactionFactory(object):
             kw['bind'] = bind
         if mode is _WRITER:
             return self._writer_maker(**kw)
-        elif self.synchronous_reader or mode is _ASYNC_READER:
+        elif mode is _ASYNC_READER or \
+                (mode is _READER and not self.synchronous_reader):
             return self._reader_maker(**kw)
         else:
             return self._writer_maker(**kw)

oslo_db/tests/sqlalchemy/test_enginefacade.py

@@ -135,15 +135,15 @@ class MockFacadeTest(oslo_test_base.BaseTestCase):
             async_reader_maker = writer_maker
 
         if self.synchronous_reader:
-            reader_conn = async_reader_conn
-            reader_engine = async_reader_engine
-            reader_session = async_reader_session
-            reader_maker = async_reader_maker
-        else:
             reader_conn = writer_conn
             reader_engine = writer_engine
             reader_session = writer_session
             reader_maker = writer_maker
+        else:
+            reader_conn = async_reader_conn
+            reader_engine = async_reader_engine
+            reader_session = async_reader_session
+            reader_maker = async_reader_maker
 
         self.connections = AssertDataSource(
             writer_conn, reader_conn, async_reader_conn
@@ -236,9 +236,9 @@ class MockFacadeTest(oslo_test_base.BaseTestCase):
             async_reader_engine = writer_engine
 
         if self.synchronous_reader:
-            reader_engine = async_reader_engine
-        else:
             reader_engine = writer_engine
+        else:
+            reader_engine = async_reader_engine
 
         engines = AssertDataSource(
             writer_engine, reader_engine, async_reader_engine)
@@ -333,9 +333,9 @@ class MockFacadeTest(oslo_test_base.BaseTestCase):
             async_reader_maker = writer_maker
 
         if self.synchronous_reader:
-            reader_maker = async_reader_maker
-        else:
             reader_maker = writer_maker
+        else:
+            reader_maker = async_reader_maker
 
         makers = AssertDataSource(
             writer_maker,

releasenotes/notes/fix_synchronous_reader-ca442ca9f07470ec.yaml

@@ -0,0 +1,8 @@
+---
+fixes:
+  - |
+    Repaired the "synchronous_reader" modifier of enginefacade so that it
+    refers to the "writer" engine when set to True, thereby allowing
+    "synchronous" behavior with the writer.  When set to False, this is
+    "asynchronous", so this should be associated with the async engines.
+    The flag had the reverse behavior previously.