Transactional Topologies - Getting Started with Storm - page 86

public int numPartitions () {
return 4 ;
}
@Override
public void close () {
}
}
The most interesting method is emitPartitionBatch , which receives the previous com-
mitted metadata. You should use that information to generate a batch of tuples. This
batch won't be necessarily the same, as was said earlier, you might not be able to re-
produce the same batch. The rest of the job is handled by the committer bolts, which
use the previous state.