@Override
      public LlapClusterStateForCompile call() throws Exception {
        LOG.info("Creating cluster info for " + userName + ":" + nodes);
        return new LlapClusterStateForCompile(conf, CLUSTER_UPDATE_INTERVAL_MS);
      }
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