@Override
  public void shutdown() {
    disableCache();
    LOG.info("Shutdown bucket cache: IO persistent=" + ioEngine.isPersistent() + "; path to write="
      + persistencePath);
    if (ioEngine.isPersistent() && persistencePath != null) {
      try {
        join();
        if (cachePersister != null) {
          LOG.info("Shutting down cache persister thread.");
          cachePersister.shutdown();
          while (cachePersister.isAlive()) {
            Thread.sleep(10);
          }
        }
        persistToFile();
      } catch (IOException ex) {
        LOG.error("Unable to persist data on exit: " + ex.toString(), ex);
      } catch (InterruptedException e) {
        LOG.warn("Failed to persist data on exit", e);
      }
    }
  }
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