I had this error too. Only solution I found was to shut down and reboot. Apparently sometimes when you shut down the spark context in zeppelin it still somehow persists and hangs. Workaround for me was to stop all services in ambari, reboot the system and start again. Then the session is flushed. (Found it here: https://stackoverflow.com/questions/35515120/why-does-sparkcontext-randomly-close-and-how-do-you-restart-it-from-zeppelin ) ... View more