- [bug] If conn.begin() fails when calling

"with engine.begin()", the newly acquired
Connection is closed explicitly before
propagating the exception onward normally.

3 files changed, 27 insertions, 1 deletions

diff --git a/CHANGES b/CHANGES
index 96383e1d7..633695d8d 100644
--- a/CHANGES
+++ b/CHANGES
@@ -48,6 +48,11 @@ CHANGES
     before SQLAlchemy modifies the state 
     of the cursor.
 
+  - [bug] If conn.begin() fails when calling
+    "with engine.begin()", the newly acquired
+    Connection is closed explicitly before 
+    propagating the exception onward normally.
+
 - mssql
   - [feature] Added interim create_engine flag
     supports_unicode_binds to PyODBC dialect,
diff --git a/lib/sqlalchemy/engine/base.py b/lib/sqlalchemy/engine/base.py
index 110ac4e8a..1d2511333 100644
--- a/lib/sqlalchemy/engine/base.py
+++ b/lib/sqlalchemy/engine/base.py
@@ -2355,7 +2355,11 @@ class Engine(Connectable, log.Identified):
 
         """
         conn = self.contextual_connect(close_with_result=close_with_result)
-        trans = conn.begin()
+        try:
+            trans = conn.begin()
+        except:
+            conn.close()
+            raise
         return Engine._trans_ctx(conn, trans, close_with_result)
 
     def transaction(self, callable_, *args, **kwargs):
diff --git a/test/engine/test_execute.py b/test/engine/test_execute.py
index 6bdbf4227..610f5e42b 100644
--- a/test/engine/test_execute.py
+++ b/test/engine/test_execute.py
@@ -358,6 +358,23 @@ class ConvenienceExecuteTest(fixtures.TablesTest):
         testing.run_as_contextmanager(ctx, fn, 5, value=8)
         self._assert_fn(5, value=8)
 
+    def test_transaction_engine_ctx_begin_fails(self):
+        engine = engines.testing_engine()
+        class MockConnection(Connection):
+            closed = False
+            def begin(self):
+                raise Exception("boom")
+
+            def close(self):
+                MockConnection.closed = True
+        engine._connection_cls = MockConnection
+        fn = self._trans_fn()
+        assert_raises(
+            Exception, 
+            engine.begin
+        )
+        assert MockConnection.closed
+
     def test_transaction_engine_ctx_rollback(self):
         fn = self._trans_rollback_fn()
         ctx = testing.db.begin()