\c - - - :master_port
-- do some setup
CREATE TABLE tab(a int, b int);
SELECT create_distributed_table('tab', 'a');
 create_distributed_table
---------------------------------------------------------------------

(1 row)

INSERT INTO tab (a, b) VALUES (1, 1);
INSERT INTO tab (a, b) VALUES (1, 2);
\c - - - :follower_master_port
RESET citus.task_executor_type;
SELECT * FROM tab;
 a | b
---------------------------------------------------------------------
 1 | 1
 1 | 2
(2 rows)

SET citus.task_executor_type TO 'task-tracker';
SELECT * FROM tab;
ERROR:  task tracker queries are not allowed while citus.use_secondary_nodes is 'always'
HINT:  try setting citus.task_executor_type TO 'adaptive'
-- clean up
\c - - - :master_port
DROP TABLE tab;