org.apache.beam.sdk.transforms

Interface Aggregator<InputT,OutputT>

Type Parameters:

InputT - the type of input values

OutputT - the type of output values

public interface Aggregator<InputT,OutputT>

An Aggregator<InputT> enables monitoring of values of type InputT, to be combined across all bundles.

Aggregators are created by calling DoFn.createAggregator, typically from the DoFn constructor. Elements can be added to the Aggregator by calling addValue(InputT).

Aggregators are visible in the monitoring UI, when the pipeline is run using DataflowRunner or BlockingDataflowRunner, along with their current value. Aggregators may not become visible until the system begins executing the ParDo transform that created them and/or their initial value is changed.

Example:

 
 class MyDoFn extends DoFn {
   private Aggregator myAggregator;

   public MyDoFn() {
     myAggregator = createAggregator("myAggregator", new Sum.SumIntegerFn());
   }

Method Summary

Modifier and Type	Method and Description
void	addValue(InputT value) Adds a new value into the Aggregator.
Combine.CombineFn<InputT,?,OutputT>	getCombineFn() Returns the Combine.CombineFn, which combines input elements in the aggregator.
String	getName() Returns the name of the Aggregator.

Method Detail

addValue

void addValue(InputT value)

Adds a new value into the Aggregator.

getName

String getName()

Returns the name of the Aggregator.

getCombineFn

Combine.CombineFn<InputT,?,OutputT> getCombineFn()

Returns the Combine.CombineFn, which combines input elements in the aggregator.