Apache Storm-用另一个螺栓组成一个螺栓

Question

I am using Apache Storm and I am wondering is it possible to compose a bolt with another bolt like this:

public class MyNewBolt extends BaseRichBolt {
    private MyOldBolt bolt; // MyOldBolt also extends BaseRichBolt

    public MyNewBolt(MyOldBolt bolt) {
        this.bolt = bolt;
    }

    @Override 
    public void prepare(Map map, TopologyContext topologyContext, OutputCollector outputCollector) {
        bolt.prepare(map, topologyContext, outputCollector);
        //Prepare other stuff
    }

    @Override
    public void execute(Tuple tuple) {
        bolt.execute(tuple);
        bolt.someOtherMethod();
        //Do some other stuff
    }

    @Override
    public void declareOutputFields(OutputFieldsDeclarer outputFieldsDeclarer) {
        bolt.declareOutputFields(outputFieldsDeclarer);
    }
}

After this I would submit the bolt:

public static void main(String[] args) throws Exception {
                         .
                         .
                         .
    TopologyBuilder builder = new TopologyBuilder();
    BaseRichBolt bolt = new MyNewBolt(new MyOldBolt());
    builder.setBolt("bolt-id", bolt).someGrouping(....);
                         .
                         .
                         .
}

This works when I run it in local mode but would it actually work in remote mode? How does Storm treat bolt serialization-deserialization in this case? How many tasks are now created?

Answer 1

I would suggest you take another approach (which coincidentally is the approach I use). Instead of treating the bolt as a reusable class, factor the bolt's business logic out into a pure-Java class. Then if you want to reuse that logic in another bolt, it's much easier to do so.

I'll also suggest that you factor all behavior related to a specific stream (knowledge of names, types and order of values in the tuple, etc.) out into another class. The implementation of your bolt classes should be fairly minimal.