org.apache.kafka.streams.examples.pipe.PipeDemo Maven / Gradle / Ivy

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/*
 * 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.pipe;

import org.apache.kafka.clients.consumer.ConsumerConfig;
import org.apache.kafka.common.serialization.Serdes;
import org.apache.kafka.streams.KafkaStreams;
import org.apache.kafka.streams.StreamsBuilder;
import org.apache.kafka.streams.StreamsConfig;

import java.util.Properties;
import java.util.concurrent.CountDownLatch;

/**
 * Demonstrates, using the high-level KStream DSL, how to read data from a source (input) topic and how to
 * write data to a sink (output) topic.
 *
 * In this example, we implement a simple "pipe" program that reads from a source topic "streams-plaintext-input"
 * and writes the data as-is (i.e. unmodified) into a sink topic "streams-pipe-output".
 *
 * Before running this example you must create the input topic and the output topic (e.g. via
 * bin/kafka-topics.sh --create ...), and write some data to the input topic (e.g. via
 * bin/kafka-console-producer.sh). Otherwise you won't see any data arriving in the output topic.
 */
public class PipeDemo {

    public static void main(final String[] args) {
        final Properties props = new Properties();
        props.put(StreamsConfig.APPLICATION_ID_CONFIG, "streams-pipe");
        props.put(StreamsConfig.BOOTSTRAP_SERVERS_CONFIG, "localhost:9092");
        props.put(StreamsConfig.DEFAULT_KEY_SERDE_CLASS_CONFIG, Serdes.StringSerde.class);
        props.put(StreamsConfig.DEFAULT_VALUE_SERDE_CLASS_CONFIG, Serdes.StringSerde.class);

        // setting offset reset to earliest so that we can re-run the demo code with the same pre-loaded data
        props.put(ConsumerConfig.AUTO_OFFSET_RESET_CONFIG, "earliest");

        final StreamsBuilder builder = new StreamsBuilder();

        builder.stream("streams-plaintext-input").to("streams-pipe-output");

        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-pipe-shutdown-hook") {
            @Override
            public void run() {
                streams.close();
                latch.countDown();
            }
        });

        try {
            streams.start();
            latch.await();
        } catch (final Throwable e) {
            System.exit(1);
        }
        System.exit(0);
    }
}