将 KTable 与 KStream 连接起来，输出主题中没有任何内容

Question

我用 KTable 左连接了一个 KStream，但是我没有看到输出主题的任何输出：

  val stringSerde: Serde[String] = Serdes.String()
  val longSerde: Serde[java.lang.Long] = Serdes.Long()
  val genericRecordSerde: Serde[GenericRecord] = new GenericAvroSerde()

  val builder = new KStreamBuilder()

  val networkImprStream: KStream[Long, GenericRecord] = builder
    .stream(dfpGcsNetworkImprEnhanced)

  // Create a global table for advertisers. The data from this global table
  // will be fully replicated on each instance of this application.
  val advertiserTable: GlobalKTable[java.lang.Long, GenericRecord]= builder.globalTable(advertiserTopicName, "advertiser-store")

  // Join the network impr stream to the advertiser global table. As this is global table
  // we can use a non-key based join with out needing to repartition the input stream
  val networkImprWithAdvertiserNameKStream: KStream[java.lang.Long, GenericRecord] = networkImprStream.leftJoin(advertiserTable,
    (_, networkImpr) => {
      println(networkImpr)
      networkImpr.get("advertiserId").asInstanceOf[java.lang.Long]
    },
    (networkImpr: GenericRecord, adertiserIdToName: GenericRecord) => {
      println(networkImpr)
      networkImpr.put("advertiserName", adertiserIdToName.get("name"))
      networkImpr
    }
  )

  networkImprWithAdvertiserNameKStream.to(networkImprProcessed)

  val streams = new KafkaStreams(builder, streamsConfiguration)
  streams.cleanUp()
  streams.start()
  // usually the stream application would be running forever,
  // in this example we just let it run for some time and stop since the input data is finite.
  Thread.sleep(15000L)

如果我绕过连接并直接将输入主题输出到输出，我会看到消息到达。我已经将连接更改为左连接，添加了一些 printlns 以查看何时提取密钥（虽然控制台上没有打印任何内容）。此外，我每次都使用 kafka 流重置工具，所以从头开始。我运行没主意了。我还添加了一些对商店的测试访问，它可以工作并包含来自流的键（尽管这不应该因为左连接而禁止任何输出）。

Answer 1

在我的源流中，键为空。虽然我不是用这个key来加入table这个key不能为null。因此，使用虚拟密钥创建中间流是可行的。所以即使我在这里有一个全局 KTable，流消息的键的限制也适用于这里： http://docs.confluent.io/current/streams/developer-guide.html#kstream-ktable-join

Input records for the stream with a null key or a null value are ignored and do not trigger the join.

将 KTable 与 KStream 连接起来，输出主题中没有任何内容

Joining a KTable with a KStream and nothing arrives in the output topic

apache-kafka

apache-kafka-streams