public String getSystemName() {
    String log4jSystem = get(TASK_LOG4J_SYSTEM, null);
    if (log4jSystem == null) {
      throw new ConfigException("Missing " + TASK_LOG4J_SYSTEM + " configuration. Can't figure out the system name to use.");
    }
    return log4jSystem;
  }
Get the log4j system name from the config.
If it's not defined, throw a ConfigException

@return log4j system name
samza-log4j2/src/main/java/org/apache/samza/config/Log4jSystemConfig.java