Kafka中的“Correlation ID in Header”

在Kafka中添加“Correlation ID in Header”可以通过以下步骤实现：

1. 首先，需要创建一个自定义的ProducerInterceptor和ConsumerInterceptor来处理消息的header。下面是一个示例：

import org.apache.kafka.clients.consumer.ConsumerInterceptor;
import org.apache.kafka.clients.consumer.ConsumerRecords;
import org.apache.kafka.clients.consumer.OffsetAndMetadata;
import org.apache.kafka.common.Cluster;
import org.apache.kafka.common.TopicPartition;
import org.apache.kafka.common.header.Header;
import org.apache.kafka.common.header.Headers;
import org.apache.kafka.common.header.internals.RecordHeader;
import org.apache.kafka.common.serialization.Deserializer;
import org.apache.kafka.common.serialization.Serializer;

import java.util.Map;

public class CorrelationIdInterceptor<K, V> implements ConsumerInterceptor<K, V> {

    private static final String CORRELATION_ID_HEADER = "correlation-id";

    @Override
    public ConsumerRecords<K, V> onConsume(ConsumerRecords<K, V> records) {
        return records;
    }

    @Override
    public void onCommit(Map<TopicPartition, OffsetAndMetadata> offsets) {
    }

    @Override
    public void close() {
    }

    @Override
    public void configure(Map<String, ?> configs) {
    }

    @Override
    public ConsumerRecords<K, V> onConsume(ConsumerRecords<K, V> records, Deserializer<K> keyDeserializer, Deserializer<V> valueDeserializer) {
        return records;
    }

    @Override
    public void onCommit(Map<TopicPartition, OffsetAndMetadata> offsets, Exception exception) {
    }

    @Override
    public void onConsume(ConsumerRecords<K, V> records, ConsumerInterceptor<K, V>.ConsumerRecordsInterceptorCallback interceptCallback) {
        for (ConsumerRecord<K, V> record : records) {
            Headers headers = record.headers();
            Header correlationIdHeader = headers.lastHeader(CORRELATION_ID_HEADER);
            if (correlationIdHeader != null) {
                String correlationId = new String(correlationIdHeader.value());
                // 在这里处理相关的逻辑
            }
        }
        interceptCallback.onConsume(records);
    }

    @Override
    public void onCommit(Map<TopicPartition, OffsetAndMetadata> offsets, ConsumerInterceptor<K, V>.OffsetCommitCallback commitCallback) {
        commitCallback.onComplete(offsets, null);
    }

}

2. 在Producer中，可以使用以下代码将correlation id添加到消息的header中：

import org.apache.kafka.clients.producer.ProducerRecord;
import org.apache.kafka.clients.producer.RecordMetadata;
import org.apache.kafka.common.header.Header;
import org.apache.kafka.common.header.internals.RecordHeader;

import java.util.concurrent.Future;

public class CorrelationIdProducer {

    private static final String CORRELATION_ID_HEADER = "correlation-id";

    private KafkaProducer<String, String> producer;

    public CorrelationIdProducer() {
        Properties props = new Properties();
        props.put("bootstrap.servers", "localhost:9092");
        props.put("key.serializer", "org.apache.kafka.common.serialization.StringSerializer");
        props.put("value.serializer", "org.apache.kafka.common.serialization.StringSerializer");
        this.producer = new KafkaProducer<>(props);
    }

    public Future<RecordMetadata> send(String topic, String key, String value, String correlationId) {
        Header header = new RecordHeader(CORRELATION_ID_HEADER, correlationId.getBytes());
        ProducerRecord<String, String> record = new ProducerRecord<>(topic, null, key, value, Collections.singletonList(header));
        return producer.send(record);
    }

    public void close() {
        producer.close();
    }

}

3. 在Consumer中，可以使用ConsumerInterceptor来解析消息的header并获取correlation id。以下是一个示例：

import org.apache.kafka.clients.consumer.ConsumerRecord;
import org.apache.kafka.clients.consumer.ConsumerRecords;
import org.apache.kafka.clients.consumer.KafkaConsumer;
import org.apache.kafka.common.header.Header;
import org.apache.kafka.common.header.Headers;
import org.apache.kafka.common.header.internals.RecordHeader;

import java.time.Duration;
import java.util.Collections;
import java.util.Properties;

public class CorrelationIdConsumer {

    private static final String CORRELATION_ID_HEADER = "correlation-id";

    private KafkaConsumer<String, String> consumer;

    public CorrelationIdConsumer() {
        Properties props = new Properties();
        props.put("bootstrap.servers", "localhost:9092");
        props.put("group.id", "test-group");
        props.put("key.deserializer", "org.apache.kafka.common.serialization.StringDeserializer");
        props.put("value.deserializer", "org.apache.kafka.common.serialization.StringDeserializer");
        this.consumer = new KafkaConsumer<>(props);
    }

    public void consume(String topic) {
        consumer.subscribe(Collections.singletonList