Blocker Description
An interrupt along with a HiveProcessor.abort call is made when attempting to preempt a task.
In this specific case, the task was in the middle of HDFS IO - which 'handled' the interrupt by retrying. As a result the interrupt status on the thread was reset - so instead of skipping the future.get in completeInitialization - the task ended up blocking there.
End result - a single executor slot permanently blocked in LLAP. Depending on what else is running - this can cause a cluster level deadlock.