Apache Flink: Count window with timeout

Question

Here is a simple code example to illustrate my question:

case class Record( key: String, value: Int )

object Job extends App
{
  val env = StreamExecutionEn         


        

Answer 1

I think you can implement this use case using ProcessFunction

In which you have count property and windowEnd property. Using that you can decide when to collect the data.

public class TimeCountWindowProcessFunction extends ProcessFunction {

    protected long windowStart;
    protected long windowEnd;
    protected long count;
    private ValueState state;

    public TimeCountWindowProcessFunction(long windowSize, long count) {

    this.windowSize = windowSize;
    this.count = count;

    }

@Override
    public void open(Configuration parameters) {

    TypeInformation typeInformation = TypeInformation.of(new TypeHint() {
    });
    ValueStateDescriptor descriptor = new ValueStateDescriptor("test", typeInformation);

    state = getRuntimeContext().getState(descriptor);
}


    @Override
    public void processElement(CountPojo input, Context ctx, Collector out)
            throws Exception {

    long timestamp = ctx.timestamp();
        windowStart = timestamp - (timestamp % windowSize);
        windowEnd = windowStart + windowSize;

        // retrieve the current count
        CountPojo current = (CountPojo) state.value();

        if (current == null) {

            current = new CountPojo();
        current.count = 1;

            ctx.timerService().registerEventTimeTimer(windowEnd);
        } else {

            current.count += 1;
        }

        if(current.count >= count) {
        out.collect(current);
    }

        // set the state's timestamp to the record's assigned event time timestamp
        current.setLastModified(ctx.timestamp());

        // write the state back
        state.update(current);
    }


    @Override
    public void onTimer(long timestamp, OnTimerContext ctx, Collector out)
            throws Exception {


        if (windowEnd == timestamp) {

            out.collect(state.value());
        }

        state.clear();
    }
}

I hope this will helpful to you.