BasicDRPCTopology.java

package storm.starter;

import backtype.storm.Config;
import backtype.storm.LocalCluster;
import backtype.storm.LocalDRPC;
import backtype.storm.StormSubmitter;
import backtype.storm.drpc.LinearDRPCTopologyBuilder;
import backtype.storm.task.TopologyContext;
import backtype.storm.topology.BasicOutputCollector;
import backtype.storm.topology.OutputFieldsDeclarer;
import backtype.storm.topology.base.BaseBasicBolt;
import backtype.storm.tuple.Fields;
import backtype.storm.tuple.Tuple;
import backtype.storm.tuple.Values;
import java.util.Map;

/**
 * This topology is a basic example of doing distributed RPC on top of Storm. It implements a function
 * that appends a "!" to any string you send the DRPC function.
 * 
 * See https://github.com/nathanmarz/storm/wiki/Distributed-RPC for more information on 
 * doing distributed RPC on top of Storm.
 */
public class BasicDRPCTopology {
    public static class ExclaimBolt extends BaseBasicBolt {
        @Override
        public void execute(Tuple tuple, BasicOutputCollector collector) {
            String input = tuple.getString(1);
            collector.emit(new Values(tuple.getValue(0), input + "!"));
        }

        @Override
        public void declareOutputFields(OutputFieldsDeclarer declarer) {
            declarer.declare(new Fields("id", "result"));
        }
    
    }
    
    public static void main(String[] args) throws Exception {
        LinearDRPCTopologyBuilder builder = new LinearDRPCTopologyBuilder("exclamation");
        builder.addBolt(new ExclaimBolt(), 3);
        
        Config conf = new Config();
        
        if(args==null || args.length==0) {
            LocalDRPC drpc = new LocalDRPC();
            LocalCluster cluster = new LocalCluster();
            
            cluster.submitTopology("drpc-demo", conf, builder.createLocalTopology(drpc));

            for(String word: new String[] {"hello", "goodbye"}) {
                System.out.println("Result for \"" + word + "\": "
                        + drpc.execute("exclamation", word));
            }
            
            cluster.shutdown();
            drpc.shutdown();
        } else {
            conf.setNumWorkers(3);
            StormSubmitter.submitTopology(args[0], conf, builder.createRemoteTopology());
        }
    }
}