java - Transformer Kafka 中的 ManagedChannel 是线程安全的吗

Question

这是我的变压器:

public class DataEnricher implements Transformer < byte[], EnrichedData, KeyValue < byte[], EnrichedData >> {

    private ManagedChannel channel;
    private InfoClient infoclient;
    private LRUCacheCollector < String,
    InfoResponse > cache;


    public DataEnricher() {}

    @Override
    public void init(ProcessorContext context) {
        channel = ManagedChannelBuilder.forAddress("localhost", 50051).usePlaintext().build();
        infoclient = new InfoClient(channel);
    }

    @Override
    public KeyValue < byte[],
    EnrichedData > transform(byte[] key, EnrichedData request) {
        InfoResponse infoResponse = null;
        String someInfo = request.getSomeInfo();
        try {
            infoResponse = infoclient.getMoreInfo(someInfo);
        } catch (Exception e) {
            logger.warn("An exception has occurred during retrieval.", e.getMessage());
        }
        EnrichedData enrichedData = EnrichedDataBuilder.addExtraInfo(request, infoResponse);
        return new KeyValue < > (key, enrichedData);
    }

    @Override
    public KeyValue < byte[],
    DataEnricher > punctuate(long timestamp) {
        return null;
    }

    @Override
    public void close() {
        client.shutdown();
    }
}

在 Kafka Streams 中，每个流线程都会初始化自己的流拓扑副本，然后按 ProcessorContext(即每个任务，即每个分区)实例化该拓扑。那么 init() 不会被调用并覆盖/泄漏每个分区的 channel 吗？而且由于我们有多个线程，甚至会与 channel/client 的创建发生竞争？有没有办法防止这种情况发生？

这在 run() 方法中调用:

public KafkaStreams createStreams() {
    final Properties streamsConfiguration = new Properties();
    //other configuration is setup here
    streamsConfiguration.put(StreamsConfig.DEFAULT_TIMESTAMP_EXTRACTOR_CLASS_CONFIG, WallclockTimestampExtractor.class.getName());
    streamsConfiguration.put(
        StreamsConfig.NUM_STREAM_THREADS_CONFIG,
        3);

    StreamsBuilder streamsBuilder = new StreamsBuilder();

    RequestJsonSerde requestSerde = new RequestJsonSerde();
    DataEnricher dataEnricher = new DataEnricher();
    // Get the stream of requests
    final KStream < byte[], EnrichedData > requestsStream = streamsBuilder
        .stream(requestsTopic, Consumed.with(Serdes.ByteArray(), requestSerde));
    final KStream < byte[], EnrichedData > enrichedRequestsStream = requestsStream
        .filter((key, request) - > {
            return Objects.nonNull(request);
        }
        .transform(() - > dataEnricher);

    enrichedRequestsStream.to(enrichedRequestsTopic, Produced.with(Serdes.ByteArray()));

    return new KafkaStreams(streamsBuilder.build(), new StreamsConfig(streamsConfiguration));
}

Answer 1

与ManagedChannel无关，但您必须在TransformerSupplier中为每个ProcessContext提供新的DataEnricher实例。

KStream.transform(DataEnricher::new);

一旦我遇到一些与此相关的 Kafka 流异常，我将尝试重新创建它。

在我看来，如果您不使用标点符号向下游发送更多记录，并且新 key 与输入记录相同，您应该使用 transformValues() 因为 transform() 当应用聚合、连接等基于键的操作时，可能会导致重新分区。