Until HDFS-4882 and HDFS-7306 get real fixes, operations teams need a way to force close files. DNs are essentially held hostage by broken clients that never close. This situation will get worse as longer/permanently running jobs start increasing.
is related to
HDFS-7306can't decommission w/under construction blocks
HDFS-4882Prevent the Namenode's LeaseManager from looping forever in checkLeases