Understanding Storm Internals by Examples - Real-time Analytics with Storm and Cassandra - page 57

method (the tuple). In this arrangement, if a failure occurs the tuple being
anchored at the root of the tree would be replayed by the spout.
• collector.ack : Here we are informing Storm that tuple has been processed
successfully by this bolt. In the event of a failure, the programmer can explicitly
call a fail method, or Storm internally calls it, as in the case of timeout events
so that it can be replayed.
• declarer.declare : This is the method called to specify the stream on which
successfully processed tuples would be emitted. Notice that we have used the
same word stream in the _collector.emit method. Similarly, if you look
into the WordCount topology's Builder method, you'd find another piece in
overall integration of word stream, which is as follows:
builder.setBolt("count", new WordCount(),
12).fieldsGrouping("split", new Fields(" word "));