JavaKafka流：从应用程序每个实例中的所有分区读取

Question

使用KTable时，当实例/使用者的数量等于分区的数量时，Kafka streams不允许实例从特定主题的多个分区读取。我尝试使用GlobalKTable实现这一点，但问题是数据将被覆盖，聚合也无法应用于此

假设我有一个名为“data_in”的主题，有3个分区（P1、P2、P3）。当我运行Kafka流应用程序的3个实例（I1、I2、I3）时，我希望每个实例从“data_in”的所有分区读取数据。我的意思是I1可以从P1，P2和P3中读取，I2可以从P1，P2和P3中读取，I2等等等等

EDIT：请记住，生产者可以在“data_in”中将两个相似的ID发布到两个不同的分区中。因此，当运行两个不同的实例时，GlobalKtable将被覆盖

请问，如何做到这一点？这是我代码的一部分

private KTable<String, theDataList> globalStream() {

    // KStream of records from data-in topic using String and theDataSerde deserializers
    KStream<String, Data> trashStream = getBuilder().stream("data_in",Consumed.with(Serdes.String(), SerDes.theDataSerde));

    // Apply an aggregation operation on the original KStream records using an intermediate representation of a KStream (KGroupedStream)
    KGroupedStream<String, Data> KGS = trashStream.groupByKey();

    Materialized<String, theDataList, KeyValueStore<Bytes, byte[]>> materialized = Materialized.as("agg-stream-store");
    materialized = materialized.withValueSerde(SerDes.theDataDataListSerde);

    // Return a KTable
    return KGS.aggregate(() -> new theDataList(), (key, value, aggregate) -> {
        if (!value.getValideData())
            aggregate.getList().removeIf((t) -> t.getTimestamp() <= value.getTimestamp());
        else
            aggregate.getList().add(value);
        return aggregate;
    }, materialized);
}

Answer 1

将输入主题“data_in”的分区数更改为1个分区，或者使用GlobalKtable从主题中的所有分区获取数据，然后您可以将流与之连接。这样，您的应用程序实例就不必再位于不同的消费者组中

代码如下所示：

private GlobalKTable<String, theDataList> globalStream() {

   // KStream of records from data-in topic using String and theDataSerde deserializers
  KStream<String, Data> trashStream = getBuilder().stream("data_in", Consumed.with(Serdes.String(), SerDes.theDataSerde));

  thrashStream.to("new_data_in"); // by sending to an other topic you're forcing a repartition on that topic

  KStream<String, Data> newTrashStream = getBuilder().stream("new_data_in", Consumed.with(Serdes.String(), SerDes.theDataSerde));

  // Apply an aggregation operation on the original KStream records using an intermediate representation of a KStream (KGroupedStream)
  KGroupedStream<String, Data> KGS = newTrashStream.groupByKey();

  Materialized<String, theDataList, KeyValueStore<Bytes, byte[]>> materialized = Materialized.as("agg-stream-store");
  materialized = materialized.withValueSerde(SerDes.theDataDataListSerde);

// Return a KTable
  KGS.aggregate(() -> new theDataList(), (key, value, aggregate) -> {
      if (!value.getValideData())
          aggregate.getList().removeIf((t) -> t.getTimestamp() <= value.getTimestamp());
      else
        aggregate.getList().add(value);
      return aggregate;
  }, materialized)
  .to("agg_data_in");

  return getBuilder().globalTable("agg_data_in");
}

编辑：我编辑了上面的代码，以强制对名为“new_data_in”的主题进行重新分区