presto-hive/src/main/java/io/prestosql/plugin/hive/HdfsConfigurationInitializer.java/NoOpDNSToSwitchMapping/reloadCachedMappings
class NoOpDNSToSwitchMapping:        @Override
        public void reloadCachedMappings(List<String> names)
        {
            // no-op
        }