protected Config getConfig() {
    if (config == null) {
      config = this.loggingContextHolder.getConfig();
    }
    return this.config;
  }
This should only be called after verifying that the {@link LoggingContextHolder} has the config.
samza-log4j2/src/main/java/org/apache/samza/logging/log4j2/StreamAppender.java