KAFKA-5454: Add a new Kafka Streams example IoT oriented

Added a Kafka Streams example (IoT oriented) using "tumbling" window

Author: Paolo Patierno <ppatierno@live.com>
Author: ppatierno <ppatierno@live.com>

Reviewers: Guozhang Wang <wangguoz@gmail.com>, Michael G. Noll <michael@confluent.io>

Closes #3352 from ppatierno/stream-temperature-example

streams/examples/src/main/java/org/apache/kafka/streams/examples/temperature/TemperatureDemo.java

@@ -0,0 +1,144 @@
+/*
+ * 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 org.apache.kafka.streams.examples.temperature;
+
+import org.apache.kafka.clients.consumer.ConsumerConfig;
+import org.apache.kafka.common.serialization.Serde;
+import org.apache.kafka.common.serialization.Serdes;
+import org.apache.kafka.common.utils.Exit;
+import org.apache.kafka.streams.KafkaStreams;
+import org.apache.kafka.streams.StreamsBuilder;
+import org.apache.kafka.streams.StreamsConfig;
+import org.apache.kafka.streams.kstream.KStream;
+import org.apache.kafka.streams.kstream.KeyValueMapper;
+import org.apache.kafka.streams.kstream.Predicate;
+import org.apache.kafka.streams.kstream.Reducer;
+import org.apache.kafka.streams.kstream.TimeWindows;
+import org.apache.kafka.streams.kstream.Windowed;
+import org.apache.kafka.streams.kstream.internals.WindowedDeserializer;
+import org.apache.kafka.streams.kstream.internals.WindowedSerializer;
+
+import java.util.Properties;
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.TimeUnit;
+
+/**
+ * Demonstrates, using the high-level KStream DSL, how to implement an IoT demo application
+ * which ingests temperature value processing the maximum value in the latest TEMPERATURE_WINDOW_SIZE seconds (which
+ * is 5 seconds) sending a new message if it exceeds the TEMPERATURE_THRESHOLD (which is 20)
+ *
+ * In this example, the input stream reads from a topic named "iot-temperature", where the values of messages
+ * represent temperature values; using a TEMPERATURE_WINDOW_SIZE seconds "tumbling" window, the maximum value is processed and
+ * sent to a topic named "iot-temperature-max" if it exceeds the TEMPERATURE_THRESHOLD.
+ *
+ * Before running this example you must create the input topic for temperature values in the following way :
+ *
+ * bin/kafka-topics.sh --create --zookeeper localhost:2181 --replication-factor 1 --partitions 1 --topic iot-temperature
+ *
+ * and at same time the output topic for filtered values :
+ *
+ * bin/kafka-topics.sh --create --zookeeper localhost:2181 --replication-factor 1 --partitions 1 --topic iot-temperature-max
+ *
+ * After that, a console consumer can be started in order to read filtered values from the "iot-temperature-max" topic :
+ *
+ * bin/kafka-console-consumer.sh --bootstrap-server localhost:9092 --topic iot-temperature-max --from-beginning
+ *
+ * On the other side, a console producer can be used for sending temperature values (which needs to be integers)
+ * to "iot-temperature" typing them on the console :
+ *
+ * bin/kafka-console-producer.sh --broker-list localhost:9092 --topic iot-temperature
+ * > 10
+ * > 15
+ * > 22
+ */
+public class TemperatureDemo {
+
+    // threshold used for filtering max temperature values
+    private static final int TEMPERATURE_THRESHOLD = 20;
+    // window size within which the filtering is applied
+    private static final int TEMPERATURE_WINDOW_SIZE = 5;
+
+    public static void main(String[] args) throws Exception {
+
+        Properties props = new Properties();
+        props.put(StreamsConfig.APPLICATION_ID_CONFIG, "streams-temperature");
+        props.put(StreamsConfig.BOOTSTRAP_SERVERS_CONFIG, "localhost:9092");
+        props.put(StreamsConfig.DEFAULT_KEY_SERDE_CLASS_CONFIG, Serdes.String().getClass());
+        props.put(StreamsConfig.DEFAULT_VALUE_SERDE_CLASS_CONFIG, Serdes.String().getClass());
+
+        props.put(ConsumerConfig.AUTO_OFFSET_RESET_CONFIG, "earliest");
+        props.put(StreamsConfig.CACHE_MAX_BYTES_BUFFERING_CONFIG, 0);
+
+        StreamsBuilder builder = new StreamsBuilder();
+
+        KStream<String, String> source = builder.stream("iot-temperature");
+
+        KStream<Windowed<String>, String> max = source
+                // temperature values are sent without a key (null), so in order
+                // to group and reduce them, a key is needed ("temp" has been chosen)
+                .selectKey(new KeyValueMapper<String, String, String>() {
+                    @Override
+                    public String apply(String key, String value) {
+                        return "temp";
+                    }
+                })
+                .groupByKey()
+                .reduce(new Reducer<String>() {
+                    @Override
+                    public String apply(String value1, String value2) {
+                        if (Integer.parseInt(value1) > Integer.parseInt(value2))
+                            return value1;
+                        else
+                            return value2;
+                    }
+                }, TimeWindows.of(TimeUnit.SECONDS.toMillis(TEMPERATURE_WINDOW_SIZE)))
+                .toStream()
+                .filter(new Predicate<Windowed<String>, String>() {
+                    @Override
+                    public boolean test(Windowed<String> key, String value) {
+                        return Integer.parseInt(value) > TEMPERATURE_THRESHOLD;
+                    }
+                });
+
+        WindowedSerializer<String> windowedSerializer = new WindowedSerializer<>(Serdes.String().serializer());
+        WindowedDeserializer<String> windowedDeserializer = new WindowedDeserializer<>(Serdes.String().deserializer());
+        Serde<Windowed<String>> windowedSerde = Serdes.serdeFrom(windowedSerializer, windowedDeserializer);
+
+        // need to override key serde to Windowed<String> type
+        max.to(windowedSerde, Serdes.String(), "iot-temperature-max");
+
+        final KafkaStreams streams = new KafkaStreams(builder.build(), props);
+        final CountDownLatch latch = new CountDownLatch(1);
+
+        // attach shutdown handler to catch control-c
+        Runtime.getRuntime().addShutdownHook(new Thread("streams-temperature-shutdown-hook") {
+            @Override
+            public void run() {
+                streams.close();
+                latch.countDown();
+            }
+        });
+
+        try {
+            streams.start();
+            latch.await();
+        } catch (Throwable e) {
+            Exit.exit(1);
+        }
+        Exit.exit(0);
+    }
+}