hourly-tips/src/solution/java/org/apache/flink/training/solutions/hourlytips/HourlyTipsSolution.java

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 * to you under the Apache License, Version 2.0 (the
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package org.apache.flink.training.solutions.hourlytips;

import org.apache.flink.api.java.tuple.Tuple3;
import org.apache.flink.api.java.utils.ParameterTool;
import org.apache.flink.streaming.api.TimeCharacteristic;
import org.apache.flink.streaming.api.datastream.DataStream;
import org.apache.flink.streaming.api.environment.StreamExecutionEnvironment;
import org.apache.flink.streaming.api.functions.windowing.ProcessWindowFunction;
import org.apache.flink.streaming.api.windowing.time.Time;
import org.apache.flink.streaming.api.windowing.windows.TimeWindow;
import org.apache.flink.training.exercises.common.datatypes.TaxiFare;
import org.apache.flink.training.exercises.common.sources.TaxiFareSource;
import org.apache.flink.training.exercises.common.utils.ExerciseBase;
import org.apache.flink.util.Collector;

/**
 * Java reference implementation for the "Hourly Tips" exercise of the Flink training in the docs.
 *
 * <p>The task of the exercise is to first calculate the total tips collected by each driver, hour by hour, and
 * then from that stream, find the highest tip total in each hour.
 *
 * <p>Parameters:
 * -input path-to-input-file
 */
public class HourlyTipsSolution extends ExerciseBase {

	/**
	 * Main method.
	 *
	 * <p>Parameters:
	 * -input path-to-input-file
	 *
	 * @throws Exception which occurs during job execution.
	 */
	public static void main(String[] args) throws Exception {

		// read parameters
		ParameterTool params = ParameterTool.fromArgs(args);
		final String input = params.get("input", ExerciseBase.PATH_TO_FARE_DATA);

		final int maxEventDelay = 60;       // events are out of order by max 60 seconds
		final int servingSpeedFactor = 600; // events of 10 minutes are served in 1 second

		// set up streaming execution environment
		StreamExecutionEnvironment env = StreamExecutionEnvironment.getExecutionEnvironment();
		env.setStreamTimeCharacteristic(TimeCharacteristic.EventTime);
		env.setParallelism(ExerciseBase.parallelism);

		// start the data generator
		DataStream<TaxiFare> fares = env.addSource(fareSourceOrTest(new TaxiFareSource(input, maxEventDelay, servingSpeedFactor)));

		// compute tips per hour for each driver
		DataStream<Tuple3<Long, Long, Float>> hourlyTips = fares
				.keyBy((TaxiFare fare) -> fare.driverId)
				.timeWindow(Time.hours(1))
				.process(new AddTips());

		DataStream<Tuple3<Long, Long, Float>> hourlyMax = hourlyTips
				.timeWindowAll(Time.hours(1))
				.maxBy(2);

//		You should explore how this alternative behaves. In what ways is the same as,
//		and different from, the solution above (using a timeWindowAll)?

// 		DataStream<Tuple3<Long, Long, Float>> hourlyMax = hourlyTips
// 			.keyBy(0)
// 			.maxBy(2);

		printOrTest(hourlyMax);

		// execute the transformation pipeline
		env.execute("Hourly Tips (java)");
	}

	/*
	 * Wraps the pre-aggregated result into a tuple along with the window's timestamp and key.
	 */
	public static class AddTips extends ProcessWindowFunction<
			TaxiFare, Tuple3<Long, Long, Float>, Long, TimeWindow> {
		@Override
		public void process(Long key, Context context, Iterable<TaxiFare> fares, Collector<Tuple3<Long, Long, Float>> out) {
			float sumOfTips = 0F;
			for (TaxiFare f : fares) {
				sumOfTips += f.tip;
			}
			out.collect(Tuple3.of(context.window().getEnd(), key, sumOfTips));
		}
	}
}