Question

我正在尝试将Kafka与Heron拓扑集成在一起。但是，我找不到最新版本的Heron（0.17.5）的任何示例。是否有任何可以共享的示例或有关如何实现自定义Kafka Spout和Kafka Bolt的任何建议？

编辑1：

我相信 KafkaSpout 和 KafkaBolt 在Heron中已被弃用，以让路给新的 Streamlet API 。我目前正在查看是否可以使用Streamlet API构建 KafkaSource 和 KafkaSink 。但是，当我尝试在来源中创建 KafkaConsumer 时，出现了以下异常。

Caused by: java.io.NotSerializableException: org.apache.kafka.clients.consumer.KafkaConsumer
at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1184)
at java.io.ObjectOutputStream.defaultWriteFields(ObjectOutputStream.java:1548)
at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1509)
at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1432)
at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1178)
at java.io.ObjectOutputStream.defaultWriteFields(ObjectOutputStream.java:1548)
at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1509)
at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1432)
at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1178)
at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:348)
at com.twitter.heron.api.utils.Utils.serialize(Utils.java:97)

编辑2：

解决了以上问题。我在构造函数中初始化KafkaConsumer，这是错误的。在setup()方法中进行初始化可以解决此问题。

Answer 1

我设法使用适用于苍鹭的Streamlet API来完成此任务。我在这里张贴相同。希望它可以帮助其他面临相同问题的人。

Kafka来源

public class KafkaSource implements Source {

    private String streamName;

    private Consumer<String, String> kafkaConsumer;
    private List<String> kafkaTopic;

    private static final Logger LOGGER = Logger.getLogger("KafkaSource");

    @Override
    public void setup(Context context) {

        this.streamName = context.getStreamName();

        kafkaTopic = Arrays.asList(KafkaProperties.KAFKA_TOPIC);

        Properties props = new Properties();
        props.put("bootstrap.servers", KafkaProperties.BOOTSTRAP_SERVERS);
        props.put("group.id", KafkaProperties.CONSUMER_GROUP_ID);
        props.put("enable.auto.commit", KafkaProperties.ENABLE_AUTO_COMMIT);
        props.put("auto.commit.interval.ms", KafkaProperties.AUTO_COMMIT_INTERVAL_MS);
        props.put("session.timeout.ms", KafkaProperties.SESSION_TIMEOUT);
        props.put("key.deserializer", KafkaProperties.KEY_DESERIALIZER);
        props.put("value.deserializer", KafkaProperties.VALUE_DESERIALIZER);
        props.put("auto.offset.reset", KafkaProperties.AUTO_OFFSET_RESET);
        props.put("max.poll.records", KafkaProperties.MAX_POLL_RECORDS);
        props.put("max.poll.interval.ms", KafkaProperties.MAX_POLL_INTERVAL_MS);

        this.kafkaConsumer = new KafkaConsumer<>(props);

        kafkaConsumer.subscribe(kafkaTopic);
    }

    @Override
    public Collection get() {

        List<String> kafkaRecords = new ArrayList<>();

        ConsumerRecords<String, String> records = kafkaConsumer.poll(Long.MAX_VALUE);

        for (ConsumerRecord<String, String> record : records) {
            String rVal = record.value();
            kafkaRecords.add(rVal);
        }

        return kafkaRecords;
    }

    @Override
    public void cleanup() {
        kafkaConsumer.wakeup();
    }
}

Apache Heron中的Kafka集成

1 个答案: