@Override
  protected void addReaderThreads(int numThreads) throws IOException {
    for (int i = 0; i < numThreads; ++i) {
      HBaseReaderThread reader = new HBaseReaderThreadWithACL(i);
      readers.add(reader);
    }
  }
Maps user with Table instance. Because the table instance has to be created per user inorder to
work in that user's context
hbase-diagnostics/src/main/java/org/apache/hadoop/hbase/util/MultiThreadedReaderWithACL.java