private synchronized String getNextTableNameToPrewarm() {
      return tableNames.pop();
    }
This method is only used for testing. Test method will init a new cache and use the new handle to query the cache
to get content in the cache. In production, no code would/should call this method, because SharedCache should be
a singleton.
standalone-metastore/metastore-server/src/main/java/org/apache/hadoop/hive/metastore/cache/CachedStore.java