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How does emit () and multiple tick sets act in a storm?

I have a topology and run it in local mode like Spout A

---> Bolt B

---> Bolt C

. Moreover, I am defining an object Object D

which is the value emitted from B to C. I have two questions:

  • I installed TOPOLOGY_TICK_TUPLE_FREQ_SECS

    in Bolt B

    and new Object D

    when Bolt B

    created. When TupleHelpers.isTickTuple(input)

    true

    , it emits Object D

    in Bolt C

    . I think the storm will clone Object D

    and generate a new one in Bolt C

    , however when I try to update the content Object D

    it still changes to Bolt B

    . What for? These two bolts can be on different servers and it is not possible to combine the same variables in memory between multiple bolts.

Bolt B

private final UserPreferBean userPrefer;
public FirstBolt() {
    this.keyword = "Default";
    this.userPrefer = new UserPreferBean();
    this.userPrefer.setAction("Action");
    this.userPrefer.setActor("Actor");
}
@Override
public void execute(Tuple input, BasicOutputCollector collector) {
    if (TupleHelpers.isTickTuple(input)) {
        System.out.println("FirstBolt.Tick.keyword= " + userPrefer.getAction());
        collector.emit(new Values(userPrefer));
    } else {
    }
}

Bolt C

@Override
public void execute(Tuple input, BasicOutputCollector collector) {
    UserPreferBean userPrefer = (UserPreferBean) input.getValue(0);
    System.out.println("SecondBolt.keyword= " + userPrefer.getAction());
    userPrefer.setAction("NewAction");
    System.out.println("SecondBolt.new.keyword= " + userPrefer.getAction());
}
  1. How does the storm work when I installed TOPOLOGY_TICK_TUPLE_FREQ_SECS

    in Bolt B

    and Bolt C

    . Since Bolt C

    after Bolt B

    , is it pointless to install TOPOLOGY_TICK_TUPLE_FREQ_SECS

    in several bolts?
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2 answers


For your first question, you must update the new Tuple data for each emit, as there is no guarantee that this data will be serialized for transport before you want to emit another tuple. You may end up chafing all previously released but uncommitted tuples if you don't. As for bolt C getting the same object that bolt B fired, I guess this is just an effect trick Storm uses when two bolts are in the same JVM. Obviously you won't get this if the two objects are on different machines. This is another reason for the appearance of new objects.



For your second question, the TOPOLOGY_TICK_TUPLE_FREQ_SECS configuration is used to send extra tick sets to your bolt - above any other tuples that are sent to the bolt using the side bolts. This means that you can send tick-tuples to any number of components, as long as it makes sense for your topology design.

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Tick ​​tuple is an additional tuple that will be automatically generated by the storm at the configured frequency time interval. If you want to release an object D from Bolt B to Bolt C when you receive a tick set, there is no need to set up a tick set in Bolt C. In your example, you have set:

TOPOLOGY_TICK_TUPLE_FREQ_SECS=10


In Bolt B. Thus, Bolt B will receive a tick-tuple every 10 seconds, and during this time you can create an object D in Bolt B and emit an object in Bolt C, and Bolt C will complete the task and select a tuple.

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