Kafka流固定窗口不按键分组。

Question

我得到一个单一的Kafka流。我怎样才能不考虑key，积累特定时间窗口的消息？

我的用例是每10分钟从一个流中写一个文件，而不考虑密钥。

Answer 1

你需要使用 Transformer 有国营商店和 预约打标点电话 每隔10分钟翻阅一次仓库并发出记录。 变压器应返回 null 因为您正在收集状态存储中的记录，所以您还需要在变换器之后进行过滤，以忽略任何的 null 记录。

这里有一个快速的例子，我认为是接近你所要求的东西。让我知道它是如何去。

class WindowedTransformerExample {

  public static void main(String[] args) {
    final StreamsBuilder builder = new StreamsBuilder();

    final String stateStoreName = "stateStore";
    final StoreBuilder<KeyValueStore<String, String>> keyValueStoreBuilder =
        Stores.keyValueStoreBuilder(Stores.inMemoryKeyValueStore(stateStoreName),
            Serdes.String(),
            Serdes.String());

    builder.addStateStore(keyValueStoreBuilder);

       builder.<String, String>stream("topic").transform(new WindowedTransformer(stateStoreName), stateStoreName)
        .filter((k, v) -> k != null && v != null)
           // Here's where you do something with records emitted after 10 minutes
        .foreach((k, v)-> System.out.println());
  }


  static final class WindowedTransformer implements TransformerSupplier<String, String, KeyValue<String, String>> {

    private final String storeName;

    public WindowedTransformer(final String storeName) {
         this.storeName = storeName;
    }

    @Override
    public Transformer<String, String, KeyValue<String, String>> get() {
      return new Transformer<String, String, KeyValue<String, String>>() {
        private KeyValueStore<String, String> keyValueStore;
        private ProcessorContext processorContext;

        @Override
        public void init(final ProcessorContext context) {
          processorContext = context;
          keyValueStore = (KeyValueStore<String, String>) context.getStateStore(storeName);
          // could change this to PunctuationType.STREAM_TIME if needed
          context.schedule(Duration.ofMinutes(10), PunctuationType.WALL_CLOCK_TIME, (ts) -> {
            try(final KeyValueIterator<String, String> iterator = keyValueStore.all()) {
                while (iterator.hasNext()) {
                  final KeyValue<String, String> keyValue = iterator.next();
                  processorContext.forward(keyValue.key, keyValue.value);
                }
            }
          });
        }

        @Override
        public KeyValue<String, String> transform(String key, String value) {
          if (key != null) {
            keyValueStore.put(key, value);
          }
          return null;
        }

        @Override
        public void close() {

        }
      };
    }
  }
}