code: @Async
      public void send(String topic, String content) {
          try {
              if (!StringUtils.isBlank(content)) {
                  log.debug("Sending kafka event with data {} to topic {}", content, topic);
                  template.send(topic, content);
              }
          } catch (Exception e) {
              log.error("Error send timeline event", e);
              throw e;
          }
      }
docs: Send event to kafka.
  
  @param topic   the kafka topic
  @param content the event content