code: public static void main(String[] args) {
      if (args.length != 0) {
        LOG.info("java -cp {} {}", RuntimeConstants.ALLUXIO_JAR,
            AlluxioJobMasterMonitor.class.getCanonicalName());
        LOG.warn("ignoring arguments");
      }
      AlluxioConfiguration conf = new InstancedConfiguration(ConfigurationUtils.defaults());
      HealthCheckClient client;
      // Only the primary master serves RPCs, so if we're configured for HA, fall back to simply
      // checking for the running process.
      if (ConfigurationUtils.isHaMode(conf)) {
        client = new MasterHealthCheckClient.Builder(conf)
            .withAlluxioMasterType(MasterHealthCheckClient.MasterType.JOB_MASTER)
            .build();
      } else {
        client = new JobMasterRpcHealthCheckClient(NetworkAddressUtils
            .getConnectAddress(NetworkAddressUtils.ServiceType.JOB_MASTER_RPC, conf),
            AlluxioMasterMonitor.TWO_MIN_EXP_BACKOFF, conf);
      }
  
      if (!client.isServing()) {
        System.exit(1);
      }
      System.exit(0);
    }
docs: Starts the Alluxio job_master monitor.
  
  @param args command line arguments, should be empty