Cannot add discovered server

[gelato]

controller_1 | 2017-08-24 23:16:04 [INFO ] ( taskpool.py:132 ): Management process for task 599f5e31553bed00102743fc (execution_id: 0458c2e5-fc8c-4fca-a84a-9b5e9246d996) with PID 361 has stopped with exit code 4 controller_1 | 2017-08-24 23:16:04 [INFO ] (playbook_plugin.py:248 ): Execute post-run step for server_discovery controller_1 | 2017-08-24 23:16:04 [INFO ] ( plugin.py:95 ): Do not execute anything because of Process exit with code 4: <class 'ChildProcessError'> controller_1 | 2017-08-24 23:16:04 [INFO ] (playbook_plugin.py:251 ): Finish execution of post-run step for server_discovery controller_1 | 2017-08-24 23:16:04 [DEBUG ] ( taskpool.py:61 ): Finish execution of task 599f5e31553bed00102743fc (execution_id: 0458c2e5-fc8c-4fca-a84a-9b5e9246d996) controller_1 | 2017-08-24 23:16:04 [ERROR ] ( taskpool.py:69 ): Fail task 599f5e31553bed00102743fc (execution_id: 0458c2e5-fc8c-4fca-a84a-9b5e9246d996): Process exit with code 4 controller_1 | Traceback (most recent call last): controller_1 | File "/usr/lib/python3.5/concurrent/futures/thread.py", line 55, in run controller_1 | result = self.fn(*self.args, **self.kwargs) controller_1 | File "/usr/local/lib/python3.5/dist-packages/decapod_controller/taskpool.py", line 137, in execute controller_1 | "Process exit with code {0}".format(process.returncode)) controller_1 | ChildProcessError: Process exit with code 4 controller_1 | 2017-08-24 23:16:04 [DEBUG ] ( taskpool.py:81 ): Removed finished task 599f5e31553bed00102743fc (execution_id: 0458c2e5-fc8c-4fca-a84a-9b5e9246d996). Current active tasks 0

I really dunno what does this mean. It is after i manually run rc.local