protected final int sizeInternal() {
    // not using the path child cache here as there could be more than 1 path per host (worker and slot znodes)
    return nodeToInstanceCache.size();
  }
Get the ensemble server addresses from the configuration. The format is: host1:port,
host2:port..

@param conf configuration
llap-client/src/java/org/apache/hadoop/hive/registry/impl/ZkRegistryBase.java