1,DRPC原理
客户端给DRPC服务器发送要履行的方法的名字，和这个方法的参数。实现了这个函数的topology使用DRPCSpout从DRPC服务器接收函 数调用流。每一个函数调用被DRPC服务器标记了1个唯1的id。 这个topology然后计算结果，在topology的最后1个叫做ReturnResults的bolt会连接到DRPC服务器，并且把这个调用的结
果发送给DRPC服务器(通过那个唯1的id标识)。DRPC服务器用那个唯1id来跟等待的客户端匹配上，唤醒这个客户端并且把结果发送给它。
2，例子
package storm.starter;
import backtype.storm.Config;
import backtype.storm.LocalCluster;
import backtype.storm.LocalDRPC;
import backtype.storm.drpc.DRPCSpout;
import backtype.storm.drpc.ReturnResults;
import backtype.storm.topology.BasicOutputCollector;
import backtype.storm.topology.OutputFieldsDeclarer;
import backtype.storm.topology.TopologyBuilder;
import backtype.storm.topology.base.BaseBasicBolt;
import backtype.storm.tuple.Fields;
import backtype.storm.tuple.Tuple;
import backtype.storm.tuple.Values;
public class ManualDRPC {
public static class ExclamationBolt extends BaseBasicBolt {
@Override
public void declareOutputFields(OutputFieldsDeclarer declarer) {
declarer.declare(new Fields("result", "return-info"));
}
@Override
public void execute(Tuple tuple, BasicOutputCollector collector) {
String arg = tuple.getString(0);
Object retInfo = tuple.getValue(1);
collector.emit(new Values(arg + "!!!", retInfo));
}
}
public static void main(String[] args) {
TopologyBuilder builder = new TopologyBuilder();
LocalDRPC drpc = new LocalDRPC();
DRPCSpout spout = new DRPCSpout("exclamation", drpc);
builder.setSpout("drpc", spout);
builder.setBolt("exclaim", new ExclamationBolt(), 3).shuffleGrouping("drpc");
builder.setBolt("return", new ReturnResults(), 3).shuffleGrouping("exclaim");
LocalCluster cluster = new LocalCluster();
Config conf = new Config();
cluster.submitTopology("exclaim", conf, builder.createTopology());
System.out.println(drpc.execute("exclamation", "aaa"));
System.out.println(drpc.execute("exclamation", "bbb"));
}
}
备注：DRPCSpout的名字与drpc.execute指定运行的名字1致