public static void initialize(HiveConf conf) throws IOException {
    if (!inited.getAndSet(true)) {
      try {
        instance = new QueryResultsCache(conf);

        Metrics metrics = MetricsFactory.getInstance();
        if (metrics != null) {
          registerMetrics(metrics, instance);
        }
      } catch (Exception err) {
        inited.set(false);
        throw err;
      }
    }
  }
Wait for the cache entry to go from PENDING to VALID status.
@return true if the cache entry successfully changed to VALID status,
        false if the status changes from PENDING to INVALID
ql/src/java/org/apache/hadoop/hive/ql/cache/results/QueryResultsCache.java