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From "Cody A. Ray" <>
Subject Re: Topology Suggestion Required for Batching
Date Tue, 06 May 2014 22:58:16 GMT
Can you tell us more about this use case? I don't really understand, but
given what you've said so far, I might create a trident topology something
like this:

    TridentTopology topology = new TridentTopology();
    StormTopology = topology.newStream("spout1", spout)
        .each(new Fields("request_id"), new CsvReader(), new
Fields("csv_field1", "csv_field2", "csv_fieldN"));
        .groupBy(new Fields("csv_field1"))
        .... do something on the GroupedStream

    public class CsvReader extends BaseFunction {
        public CsvReader() {

        public void execute(TridentTuple tuple, TridentCollector collector)
            long requestId = tuple.getLong(0);
            // do something with this requestId to figure out which CSV
file to read ???
            /* PSEUDOCODE
            for (each line in the CSV) {
                 // emit one tuple per line with all the fields
                collector.emit(new Values(line[0], line[1], line[N]));

(Trident makes working with batches a lot easier. :)

In general though, I'm not sure where you're getting the CSV files. I don't
think reading CSV files off of the worker nodes' disks directly would be a
good practice in Storm. It'd probably be better if your spouts emitted the
data themselves or something.


On Tue, May 6, 2014 at 1:13 AM, Kiran Kumar <>wrote:

> Hi Padma,
> Firstly, thanks for responding.
> Here is how i am defining my topology conceptually..
> - Spout waits for a request signal..
> - once spout got a signal, it generates a request_id and broadcasts that
> request_id to 10 csv reader bolts..
> - 10 csv reader bolts reads csv files line-by-line and emits those tuples,
> respectively..
> - Now (this is the place where i need suggestion in technical/syntactical)
> i need to batch up those tuples from all the 10 csv reader bolts on
> specified fields..
> - finally, batch-ed tuples will be processed by final bolts.
> What i need is a technical approach.
>   On Tuesday, 6 May 2014 11:10 AM, padma priya chitturi <
>> wrote:
> Hi,
>  You can define spouts and bolts in  such a way that, input streams read
> by spouts would be grouped on specified fields and these could be processed
> by specific bolts. This way, you could make batches of input stream.
> On Tue, May 6, 2014 at 11:02 AM, Kiran Kumar <>wrote:
> Hi,
>  Can anyone suggest me a topology that makes batches of the input stream
> on specified fields. so that the batch will be forwarded to a function that
> processes it.
> Regards,
>  Kiran Kumar Dasari.

Cody A. Ray, LEED AP

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