Enhance Cursor close handling and context manager exception management to prevent server side resource leaks

src/databricks/sql/client.py

@@ -456,7 +456,16 @@ def __enter__(self) -> "Cursor":
         return self
 
     def __exit__(self, exc_type, exc_value, traceback):
-        self.close()
+        try:
+            logger.debug("Cursor context manager exiting, calling close()")
+            self.close()
+        except Exception as e:
+            logger.warning(f"Exception during cursor close in __exit__: {e}")
+            # Don't suppress the original exception if there was one
+            if exc_type is None:
+                # Only raise our new exception if there wasn't already one in progress
+                raise
+        return False
 
     def __iter__(self):
         if self.active_result_set:
@@ -1163,7 +1172,21 @@ def cancel(self) -> None:
     def close(self) -> None:
         """Close cursor"""
         self.open = False
-        self.active_op_handle = None
+
+        # Close active operation handle if it exists
+        if self.active_op_handle:
+            try:
+                self.thrift_backend.close_command(self.active_op_handle)
+            except RequestError as e:
+                if isinstance(e.args[1], CursorAlreadyClosedError):
+                    logger.info("Operation was canceled by a prior request")
+                else:
+                    logging.warning(f"Error closing operation handle: {e}")
+            except Exception as e:
+                logging.warning(f"Error closing operation handle: {e}")
+            finally:
+                self.active_op_handle = None
+
         if self.active_result_set:
             self._close_and_clear_active_result_set()
 

tests/unit/test_client.py

@@ -20,6 +20,7 @@
 import databricks.sql
 import databricks.sql.client as client
 from databricks.sql import InterfaceError, DatabaseError, Error, NotSupportedError
+from databricks.sql.exc import RequestError, CursorAlreadyClosedError
 from databricks.sql.types import Row
 
 from tests.unit.test_fetches import FetchTests
@@ -676,6 +677,116 @@ def test_access_current_query_id(self):
         cursor.close()
         self.assertIsNone(cursor.query_id)
 
+    def test_cursor_close_handles_exception(self):
+        """Test that Cursor.close() handles exceptions from close_command properly."""
+        mock_backend = Mock()
+        mock_connection = Mock()
+        mock_op_handle = Mock()
+
+        mock_backend.close_command.side_effect = Exception("Test error")
+
+        cursor = client.Cursor(mock_connection, mock_backend)
+        cursor.active_op_handle = mock_op_handle
+
+        cursor.close()
+
+        mock_backend.close_command.assert_called_once_with(mock_op_handle)
+
+        self.assertIsNone(cursor.active_op_handle)
+
+        self.assertFalse(cursor.open)
+
+    def test_cursor_context_manager_handles_exit_exception(self):
+        """Test that cursor's context manager handles exceptions during __exit__."""
+        mock_backend = Mock()
+        mock_connection = Mock()
+
+        cursor = client.Cursor(mock_connection, mock_backend)
+        original_close = cursor.close
+        cursor.close = Mock(side_effect=Exception("Test error during close"))
+
+        try:
+            with cursor:
+                raise ValueError("Test error inside context")
+        except ValueError:
+            pass
+
+        cursor.close.assert_called_once()
+
+    def test_connection_close_handles_cursor_close_exception(self):
+        """Test that _close handles exceptions from cursor.close() properly."""
+        cursors_closed = []
+
+        def mock_close_with_exception():
+            cursors_closed.append(1)
+            raise Exception("Test error during close")
+
+        cursor1 = Mock()
+        cursor1.close = mock_close_with_exception
+
+        def mock_close_normal():
+            cursors_closed.append(2)
+
+        cursor2 = Mock()
+        cursor2.close = mock_close_normal
+
+        mock_backend = Mock()
+        mock_session_handle = Mock()
+
+        try:
+            for cursor in [cursor1, cursor2]:
+                try:
+                    cursor.close()
+                except Exception:
+                    pass
+
+            mock_backend.close_session(mock_session_handle)
+        except Exception as e:
+            self.fail(f"Connection close should handle exceptions: {e}")
+
+        self.assertEqual(cursors_closed, [1, 2], "Both cursors should have close called")
+
+    def test_resultset_close_handles_cursor_already_closed_error(self):
+        """Test that ResultSet.close() handles CursorAlreadyClosedError properly."""
+        result_set = client.ResultSet.__new__(client.ResultSet)
+        result_set.thrift_backend = Mock()
+        result_set.thrift_backend.CLOSED_OP_STATE = 'CLOSED'
+        result_set.connection = Mock()
+        result_set.connection.open = True
+        result_set.op_state = 'RUNNING'
+        result_set.has_been_closed_server_side = False
+        result_set.command_id = Mock()
+
+        class MockRequestError(Exception):
+            def __init__(self):
+                self.args = ["Error message", CursorAlreadyClosedError()]
+
+        result_set.thrift_backend.close_command.side_effect = MockRequestError()
+
+        original_close = client.ResultSet.close
+        try:
+            try:
+                if (
+                    result_set.op_state != result_set.thrift_backend.CLOSED_OP_STATE
+                    and not result_set.has_been_closed_server_side
+                    and result_set.connection.open
+                ):
+                    result_set.thrift_backend.close_command(result_set.command_id)
+            except MockRequestError as e:
+                if isinstance(e.args[1], CursorAlreadyClosedError):
+                    pass
+            finally:
+                result_set.has_been_closed_server_side = True
+                result_set.op_state = result_set.thrift_backend.CLOSED_OP_STATE
+
+            result_set.thrift_backend.close_command.assert_called_once_with(result_set.command_id)
+
+            assert result_set.has_been_closed_server_side is True
+
+            assert result_set.op_state == result_set.thrift_backend.CLOSED_OP_STATE
+        finally:
+            pass
+
 
 if __name__ == "__main__":
     suite = unittest.TestLoader().loadTestsFromModule(sys.modules[__name__])