private boolean isUpdateNeeded() {
    Long lastUpdateLocal = lastClusterUpdateNs;
    if (lastUpdateLocal == null) return true;
    long elapsed = System.nanoTime() - lastUpdateLocal;
    return (elapsed >= updateIntervalNs);
  }
Synchronizes the actual update from the cluster; only one thread at a time.
ql/src/java/org/apache/hadoop/hive/ql/optimizer/physical/LlapClusterStateForCompile.java