code: public void stop() {
          MessageBatcher batcher = null;
          for (String originalAppenderName : originalAsyncAppenderNameMap.keySet()) {
              String batcherName = AsyncAppender.class.getName() + "." + originalAppenderName;
              batcher = BatcherFactory.getBatcher(batcherName);
              if (batcher == null) {
                  continue;
              }
              batcher.stop();
          }
          
          for (String originalAppenderName : originalAsyncAppenderNameMap.keySet()) {
              String batcherName = AsyncAppender.class.getName() + "." + originalAppenderName;
              batcher = BatcherFactory.getBatcher(batcherName);
              if (batcher == null) {
                  continue;
              }
              BatcherFactory.removeBatcher(batcherName);
          }
      }
docs: Shuts down blitz4j cleanly by flushing out all the async related
  messages.