In case ambari API doesn't help. You can use following SQL queries to abort hung/queued/pending operations directly from ambari database.   1) Stop Ambari-Server   ambari-server stop   2) Take backup of ambari database before making any changes to ambari db 3) Check IN_PROGRESS, QUEUED and PENDING operations.   ambari=> select task_id,role,role_command from host_role_command where status='IN_PROGRESS'; ambari=> select task_id,role,role_command from host_role_command where status='QUEUED' limit 100; ambari=> select task_id,role,role_command from host_role_command where status='PENDING';   4) Abort Operations   ambari=> update host_role_command set status='ABORTED' where status='QUEUED'; ambari=> update host_role_command set status='ABORTED' where status='PENDING'; ambari=> update host_role_command set status='ABORTED' where status='IN_PROGRESS';   5) Start ambari-server   ambari-server start       ... View more