code: public static void main(String[] args) {
      if (!parseInputArgs(args)) {
        usage();
        System.exit(EXIT_FAILED);
      }
      if (sHelp) {
        usage();
        System.exit(EXIT_SUCCEEDED);
      }
  
      List<String> masters = new ArrayList<>();
      for (MasterFactory factory : ServiceUtils.getMasterServiceLoader()) {
        masters.add(factory.getName());
      }
  
      for (String master : masters) {
        Upgrader upgrader = new Upgrader(master,
            new InstancedConfiguration(ConfigurationUtils.defaults()));
        try {
          upgrader.upgrade();
        } catch (IOException e) {
          LOG.error("Failed to upgrade the journal for {}.", master, e);
          System.exit(EXIT_FAILED);
        }
      }
    }
docs: Reads a journal via
  {@code java -cp \
  assembly/server/target/alluxio-assembly-server-<ALLUXIO-VERSION>-jar-with-dependencies.jar \
  alluxio.master.journal.JournalUpgrader -master BlockMaster}.
  
  @param args arguments passed to the tool