code: private String getEffectiveUser(final Props jobProps) {
      String effectiveUser = null;
      if (jobProps.containsKey(JobProperties.USER_TO_PROXY)) {
        effectiveUser = jobProps.getString(JobProperties.USER_TO_PROXY);
      } else if (jobProps.containsKey(CommonJobProperties.SUBMIT_USER)) {
        effectiveUser = jobProps.getString(CommonJobProperties.SUBMIT_USER);
      } else {
        throw new RuntimeException(
            "Internal Error: No user.to.proxy or submit.user in the jobProps");
      }
      info("effective user is: " + effectiveUser);
      return effectiveUser;
    }
docs: <pre>
  Determines what user id should the process job run as, in the following order of precedence:
  1. USER_TO_PROXY
  2. SUBMIT_USER
  </pre>
  
  @return the user that Azkaban is going to execute as