[Storm DRPC] Using RetunResult to aggregate output of Bolts

[Rahul R <ra...@gmail.com>]

Hey Guys,

I have a drpc spout sending data to all the bolts which connect to
ReturnResult bolt

DrpcSpout -> (T1 .... Tn)  -> ReturnResult

The following is the code

==================
DRPCSpout spout = new DRPCSpout("update_cache");
builder.setSpout("drpc", spout,1);
builder.setBolt("TransformBolt", new TransformationBolt(), 2)
                .allGrouping("drpc");
builder.setBolt("return", new ReturnResults(),
1).noneGrouping("TransformBolt","drpc_stream");
=====================

I want the ReturnResult bolt send me total no of TransformationBolt
executed drpc command.

For example,  when Transformation Bolt receives the data. Based on some
logic, It tells, whether its processing is Ok or NOK  and forward the
result to ReturnResult.

I want ReturnResult to aggregate the output and give me the count of OK it
receives for a DRPC call.  In this case, if both the transformationbolt are
processing it fine. The output should be "2" .  How do I go about doing
that ?

Thanks,
./Rahul