Mastering Apache Storm

ReducerAggregator

The ReducerAggregator first runs the global repartitioning operation on the input stream to combine all the partitions of the same batch into a single partition, and then runs the aggregation function on each batch. The ReducerAggregator<T> interface contains the following methods:

• init(): This method returns the initial value
• Reduce(T curr, TridentTuple tuple): This method iterates over the input tuples and emits a single tuple with a single value

This example shows how we can implement Sum using the ReducerAggregator:

public static class Sum implements ReducerAggregator<Long> { private static final long serialVersionUID = 1L; /** return the initial value zero */ public Long init() { return 0L; } /** Iterates on the input ...