IBasicBolt IRichBolt

In fact, a lot of people using JStorm/Storm don't know the difference between IBasicBolt and IRichBolt. We suggest using IBasicBolt as much as possible.

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IRichBolt extends from IBolt that uses OutputCollector to emit tuple.

public interface IBolt extends Serializable {
...
  void prepare(Map stormConf, TopologyContext context, OutputCollector collector);
...
}

OutputCollector has two kinds of methods to emit tuple:

//the next component's tasks will send Ack response to Acker.
List<Integer> emit(String streamId, Tuple anchor, List<Object> tuple)
//the next component's tasks won't send Ack response to Acker.
List<Integer> emit(String streamId, List<Object> tuple) {

IBasicBolt uses BasicOutputCollector to emit tuple.

public interface IBasicBolt extends IComponent {
...
void execute(Tuple input, BasicOutputCollector collector);
...
}

BasicOutputCollector only has the second emit method, but this method wraps the OutputCollector's first one to do the job.

//out is a OutputCollector instance.
List<Integer> emit(String streamId, List<Object> tuple) {
        return out.emit(streamId, inputTuple, tuple);
    }

So in IBasicBolt, emit(String streamId, List<Object> tuple) is a reliable method to process tuple, but in IRichBolt, it is not.

If you want to process tuple reliability when you use IRichBolt, you should call emit(String streamId, Tuple anchor, List<Object> tuple) explicitly.