Trying to learn Storm

[Thiago Souza]

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