@Override
  public boolean evictBlock(BlockCacheKey cacheKey) {
    try {
      cacheStats.evict();
      return client.delete(cacheKey.toString()).get();
    } catch (InterruptedException e) {
      LOG.warn("Error deleting " + cacheKey.toString(), e);
      Thread.currentThread().interrupt();
    } catch (ExecutionException e) {
      if (LOG.isDebugEnabled()) {
        LOG.debug("Error deleting " + cacheKey.toString(), e);
      }
    }
    return false;
  }
Statistics thread schedule pool (for heavy debugging, could remove)
hbase-external-blockcache/src/main/java/org/apache/hadoop/hbase/io/hfile/MemcachedBlockCache.java