presto-hive/src/main/java/io/prestosql/plugin/hive/HdfsConfigurationInitializer.java/NoOpDNSToSwitchMapping/resolve
class NoOpDNSToSwitchMapping:        @Override
        public List<String> resolve(List<String> names)
        {
            // dfs client expects an empty list as an indication that the host->switch mapping for the given names are not known
            return ImmutableList.of();
        }