docs: public void shutdownFetcher() {
  		running = false;
  
  		if (mainThread != null) {
  			mainThread.interrupt(); // the main thread may be sleeping for the discovery interval
  		}
  
  		if (LOG.isInfoEnabled()) {
  			LOG.info("Shutting down the shard consumer threads of subtask {} ...", indexOfThisConsumerSubtask);
  		}
  		shardConsumersExecutor.shutdownNow();
  	}