private void join() throws InterruptedException {
    for (int i = 0; i < writerThreads.length; ++i)
      writerThreads[i].join();
  }
Used to shut down the cache -or- turn it off in the case of something broken.
hbase-server/src/main/java/org/apache/hadoop/hbase/io/hfile/bucket/BucketCache.java