code: public synchronized void abort()
      {
          if (done)
              return;
  
          done = true;
          for (SSTableWriter writer : sstables)
              writer.abort();
          sstables.clear();
      }
docs: Abort this task.
  If the task already received all files and
  {@link org.apache.cassandra.streaming.StreamReceiveTask.OnCompletionRunnable} task is submitted,
  then task cannot be aborted.