code: public synchronized void formatJournal() throws IOException {
      if (mDeployMode == DeployMode.EMBEDDED) {
        for (Master master : mMasters) {
          File journalDir = new File(master.getConf().get(PropertyKey.MASTER_JOURNAL_FOLDER));
          FileUtils.deleteDirectory(journalDir);
          journalDir.mkdirs();
        }
        return;
      }
      try (Closeable c = new ConfigurationRule(mProperties, ServerConfiguration.global())
          .toResource()) {
        Format.format(Format.Mode.MASTER, ServerConfiguration.global());
      } catch (IOException e) {
        throw new RuntimeException(e);
      }
    }
docs: Formats the cluster journal.