Hi good people,
I looking at an example from storm-starter project
https://github.com/apache/storm/blob/master/examples/storm-starter/src/jvm/org/apache/storm/starter/BasicDRPCTopology.java
If works for me, drpc replies with exclamation and everything is fine.
But now I modified it like this:
public class MyTopology {
public static class ExclamationBolt extends BaseBasicBolt {
@Override
public void declareOutputFields(OutputFieldsDeclarer declarer) {
declarer.declare(new Fields("id", "result"));
}
@Override
public void execute(Tuple tuple, BasicOutputCollector collector) {
String arg = tuple.getString(1);
for (int i = 0; i < 3; i++) {
String res = arg + "-> " + i;
System.out.println("emit -> " + res);
collector.emit(new Values(tuple.getValue(0), res));
}
}
}
public static void main(String ... args) throws InvalidTopologyException,
AuthorizationException, AlreadyAliveException {
LinearDRPCTopologyBuilder builder = new
LinearDRPCTopologyBuilder("exclamation");
LocalDRPC drpc = new LocalDRPC();
builder.addBolt(new ExclamationBolt(), 1);
Config config = new Config();
LocalCluster cluster = new LocalCluster();
cluster.submitTopology("mytopology", config,
builder.createLocalTopology(drpc));
System.out.println("drpc replies: " + drpc.execute("exclamation",
"aaa"));
}
}
As you can see I’ve added small loop into the bolt so it emits several tuples
per one input. But drpc.execute method returns only one tuple! In the logs I
see several emits:
emit -> aaa-> 0
emit -> aaa-> 1
emit -> aaa-> 2
But only one response:
drpc replies: aaa-> 0
Does it mean that each my bolt should emit only single output per input?
How can I get all three tuples in response?
Documentation suggest to use CoordinatedBolt directly, but I can’t find any
example…
P. s. I’ve also tried the same with manual drpc
(https://github.com/apache/storm/blob/master/examples/storm-starter/src/jvm/org/apache/storm/starter/ManualDRPC.java)
- same issue.
Thank you
