private static final class RecordingSubscriberExceptionHandler
      implements SubscriberExceptionHandler {
    private SubscriberExceptionContext context;
    private Throwable exception;

    @Override
    public void handleException(Throwable exception, SubscriberExceptionContext context) {
      this.exception = exception;
      this.context = context;
    }
  }

  private static final class RecordingSubscriberExceptionHandler
      implements SubscriberExceptionHandler {
    private SubscriberExceptionContext context;
    private Throwable exception;

    @Override
    public void handleException(Throwable exception, SubscriberExceptionContext context) {
      this.exception = exception;
      this.context = context;
    }
  }

    @Override
    public void handleException(Throwable exception, SubscriberExceptionContext context) {
      Logger logger = logger(context);
      if (logger.isLoggable(Level.SEVERE)) {
        logger.log(Level.SEVERE, message(context), exception);
      }
    }

    private static Logger logger(SubscriberExceptionContext context) {