Practical Real-time Data Processing and Analytics

Reducer aggregator

The following are the characteristics of the reducer aggregator:

• It produces a single value
• It executes an init function only once to get the init value
• It executes an reduce function on all tuples
• It transfers all tuples over the network and then performs the reduce function
• Less optimized compared to the combiner aggregator
• Interface available in package:

public interface ReducerAggregator<T> extends Serializable {  T init();  T reduce(T curr, TridentTuple tuple);}

Example:

public class Count implements ReducerAggregator<Long> {  public Long init() {    return 0L;  }  public Long reduce(Long curr, TridentTuple tuple) {    return curr + 1;  }}