com.google.cloud.dataflow.sdk.transforms

Interface Aggregator<VI>

Type Parameters:

VI - the type of input values

public interface Aggregator<VI>

An Aggregator enables arbitrary monitoring in user code.

Aggregators are created by calling DoFn.Context.createAggregator(java.lang.String, com.google.cloud.dataflow.sdk.transforms.Combine.CombineFn<? super AI, AA, AO>), typically from DoFn.startBundle(com.google.cloud.dataflow.sdk.transforms.DoFn<I, O>.Context). Elements can be added to the Aggregator by calling addValue(VI).

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

Example:

 class MyDoFn extends DoFn<String, String> {
   private Aggregator<Integer> myAggregator;

   {@literal @}Override
   public void startBundle(Context c) {
     myAggregator = c.createAggregator("myCounter", new Sum.SumIntegerFn());
   }

   {@literal @}Override
   public void processElement(ProcessContext c) {
     myAggregator.addValue(1);
   }
 }
  

Method Summary

Methods

Modifier and Type	Method and Description
void	addValue(VI value) Adds a new value into the Aggregator.

Method Detail

addValue

void addValue(VI value)

Adds a new value into the Aggregator.