code: void doBatchStart(String batch, Object args) {
      checkOpen();
      JsonObject message = createMessage(args)
          .putString("batch", batch)
          .putString("action", "startBatch");
      if (open && !paused) {
        if (log.isDebugEnabled()) {
          log.debug(String.format("%s - Batch start: Batch[batch=%s]", this, batch));
        }
        eventBus.send(inAddress, message);
      }
      checkFull();
    }
docs: Sends a batch start message.