The tuples emitted from the join must have these fields:
1. First, the fields you are joining on.
2. Next, the other fields, in the same order as the streams passed to the
join method and in the same order as the input tuple fields.
For your example, the join output tuple fields would be
new Fields("messageId", "datatype", "provider")
On Thu, Oct 16, 2014 at 7:25 AM, Thiago Souza <[email protected]> wrote:
> I'm a Storm newbie trying to learn it. Could someone please help me?
> Consider the following snippet:
>
> TridentTopology builder = new TridentTopology();
>
> // Random data generated with a random 'messageId'
> Stream inputStream = builder.newStream("data-supply", new
> RandomDataGenerator() /* this extends BaseRichSpout */);
>
> // Load 'Datatype' referenced by datatypeId from external source
>
> Stream datatypeStream = inputStream.each(new Fields("datatypeId"),
> new DatatypeLoader(), new Fields("datatype")).
>
> project(new Fields("messageId", "datatype"));
>
> // Load 'Provider' referenced by providerId from external source
>
> Stream providerStream = inputStream.each(new Fields("providerId"),
> new ProviderLoader(), new Fields("provider")).
>
> project(new Fields("messageId", "provider"));
>
> // Join both streams on original 'messageId'
> builder.join(providerStream, new Fields("messageId"),
> datatypeStream, new Fields("messageId"),
> new Fields("datatype", "provider")).
>
> each(new Fields("datatype", "provider"), new Print()); // Print the
> result
>
>
> I expected to get a Tuple with both 'Datatype' and 'Provider' previoulsy
> loaded, but what I get is a Tuple with either one, depending on which is
> the first argument of the 'join' method (in this case 'providerStream').
>
> Am I doing something wrong or maybe with a misconcept of how storm works?
>
> Thanks,
> Thiago Souza
>
