src/main/java/samza/examples/cookbook/TumblingPageViewCounterApp.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */
package samza.examples.cookbook;

import org.apache.samza.application.StreamApplication;
import org.apache.samza.config.Config;
import org.apache.samza.operators.MessageStream;
import org.apache.samza.operators.OutputStream;
import org.apache.samza.operators.StreamGraph;
import org.apache.samza.operators.functions.FoldLeftFunction;
import org.apache.samza.operators.windows.WindowPane;
import org.apache.samza.operators.windows.Windows;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.time.Duration;
import java.util.Collection;
import java.util.function.Function;

/**
 * In this example, we group a stream of page views by country, and compute the number of page views over a tumbling time
 * window.
 *
 * <p> Concepts covered: Performing Group-By style aggregations on tumbling time windows.
 *
 * <p> Tumbling windows divide a stream into a set of contiguous, fixed-sized, non-overlapping time intervals.
 *
 * To run the below example:
 *
 * <ol>
 *   <li>
 *     Ensure that the topic "pageview-tumbling-input" is created  <br/>
 *     ./kafka-topics.sh  --zookeeper localhost:2181 --create --topic pageview-tumbling-input --partitions 2 --replication-factor 1
 *   </li>
 *   <li>
 *     Run the application using the ./bin/run-app.sh script <br/>
 *     ./deploy/samza/bin/run-app.sh --config-factory=org.apache.samza.config.factories.PropertiesConfigFactory <br/>
 *     --config-path=file://$PWD/deploy/samza/config/tumbling-pageview-counter.properties)
 *   </li>
 *   <li>
 *     Produce some messages to the "pageview-tumbling-input" topic <br/>
       ./deploy/kafka/bin/kafka-console-producer.sh --topic pageview-tumbling-input --broker-list localhost:9092 <br/>
       user1,india,google.com <br/>
 *     user2,china,yahoo.com
 *   </li>
 *   <li>
 *     Consume messages from the "pageview-tumbling-output" topic (e.g. bin/kafka-console-consumer.sh)
 *     ./bin/kafka-console-consumer.sh --bootstrap-server localhost:9092 --topic pageview-tumbling-output --property print.key=true <br/>
 *   </li>
 * </ol>
 *
 */
public class TumblingPageViewCounterApp implements StreamApplication {

  private static final Logger LOG = LoggerFactory.getLogger(TumblingPageViewCounterApp.class);
  private static final String INPUT_TOPIC = "pageview-tumbling-input";
  private static final String OUTPUT_TOPIC = "pageview-tumbling-output";

  @Override
  public void init(StreamGraph graph, Config config) {

    MessageStream<String> pageViews = graph.<String, String, String>getInputStream(INPUT_TOPIC, (k, v) -> v);

    OutputStream<String, String, WindowPane<String, Integer>> outputStream = graph
        .getOutputStream(OUTPUT_TOPIC, m -> m.getKey().getKey(), m -> m.getMessage().toString());

    Function<String, String> keyFn = pageView -> new PageView(pageView).getCountry();

    pageViews
        .partitionBy(keyFn)
        .window(Windows.keyedTumblingWindow(keyFn, Duration.ofSeconds(3), () -> 0, (m, prevCount) -> prevCount + 1))
        .sendTo(outputStream);
  }
}