code: public void authorize() {
      if (this.isSecurityEnabled) {
        try {
          login(this.keytabPrincipal, this.keytabPath);
        } catch (final IOException e) {
          log.error(e);
          throw new AzkabanException(String.format(
              "Error: Unable to authorize to Hadoop. Principal: %s Keytab: %s", this.keytabPrincipal,
              this.keytabPath));
        }
      }
    }
docs: API to authorize HDFS access. This logins in the configured user via the keytab. If the user is
  already logged in then it renews the TGT.