docs: public AtomicLong getNextIndex(String virtualHostname, boolean secure) {
          Map<String, VipIndexSupport> index = (secure) ? secureVirtualHostNameAppMap : virtualHostNameAppMap;
          return Optional.ofNullable(index.get(virtualHostname.toUpperCase(Locale.ROOT)))
                  .map(VipIndexSupport::getRoundRobinIndex)
                  .orElse(null);
      }