Question

我正在使用最近由lightbend开源的新Kafka-scala-streams api。而我正试图运行两个流。但是发生的事情是其中两个不能同时运行而且我没有得到所需的输出。

package in.internity

import java.util.Properties
import java.util.concurrent.TimeUnit

import com.lightbend.kafka.scala.streams.{KStreamS, StreamsBuilderS}
import org.apache.kafka.common.serialization.Serdes
import org.apache.kafka.streams.kstream.Produced
import org.apache.kafka.streams.{StreamsConfig, _}
import org.json4s.DefaultFormats
import org.json4s.native.JsonMethods.parse
import org.json4s.native.Serialization.write

import scala.util.Try

/**
  * @author Shivansh <shiv4nsh@gmail.com>
  * @since 8/1/18
  */
object Boot extends App {
  implicit val formats: DefaultFormats.type = DefaultFormats
  val config: Properties = {
    val p = new Properties()
    p.put(StreamsConfig.APPLICATION_ID_CONFIG, "wordcount-application")
    p.put(StreamsConfig.BOOTSTRAP_SERVERS_CONFIG, "localhost:9092")
    p.put(StreamsConfig.DEFAULT_KEY_SERDE_CLASS_CONFIG, Serdes.String().getClass)
    p.put(StreamsConfig.DEFAULT_VALUE_SERDE_CLASS_CONFIG, Serdes.String().getClass)
    p
  }

  val streams1 = wordSplit("lines", "wordCount")
  val streams2 = readAndWriteJson("person", "personName")

  private def wordSplit(intopic: String, outTopic: String) = {
    val builder = new StreamsBuilderS()
    val produced = Produced.`with`(Serdes.String(), Serdes.String())
    val textLines: KStreamS[String, String] = builder.stream(intopic)
    val data: KStreamS[String, String] = textLines.flatMapValues(value => value.toLowerCase.split("\\W+").toIterable)
    data.to(outTopic, produced)

    val streams: KafkaStreams = new KafkaStreams(builder.build(), config)
    streams
  }

  private def readAndWriteJson(intopic: String, outTopic: String) = {
    val builder = new StreamsBuilderS()
    val produced = Produced.`with`(Serdes.String(), Serdes.String())
    val textLines: KStreamS[String, String] = builder.stream(intopic)
    val data: KStreamS[String, String] = textLines.mapValues(value => {
      val person = Try(parse(value).extract[Person]).toOption
      println("1::", person)
      val personNameAndEmail = person.map(a => PersonNameAndEmail(a.name, a.email))
      println("2::", personNameAndEmail)
      write(personNameAndEmail)
    })
    data.to(outTopic, produced)

    val streams: KafkaStreams = new KafkaStreams(builder.build(), config)
    streams
  }

  streams1.start()
  streams2.start()
  Runtime.getRuntime.addShutdownHook(new Thread(() => {
    streams2.close(10, TimeUnit.SECONDS)
    streams1.close(10, TimeUnit.SECONDS)
  }))
}

case class Person(name: String, age: Int, email: String)

case class PersonNameAndEmail(name: String, email: String)

当我运行此主题并在主题person上生成消息时，它们不会被消耗掉。但是当我改变他们的开始顺序时，即

streams2.start()
streams1.start()

工作正常。那么为什么一个流的启动会阻塞另一个流。我们不能同时运行多个流。

Answer 1

让它工作，似乎我试图用不同的方法自己初始化流两次（愚蠢的我：P）

工作代码：

package in.internity

import java.util.Properties
import java.util.concurrent.TimeUnit

import com.lightbend.kafka.scala.streams.{KStreamS, StreamsBuilderS}
import org.apache.kafka.common.serialization.Serdes
import org.apache.kafka.streams.kstream.Produced
import org.apache.kafka.streams.{StreamsConfig, _}
import org.json4s.DefaultFormats
import org.json4s.native.JsonMethods.parse
import org.json4s.native.Serialization.write

import scala.util.Try

/**
  * @author Shivansh <shiv4nsh@gmail.com>
  * @since 8/1/18
  */
object Boot extends App {
  implicit val formats: DefaultFormats.type = DefaultFormats
  val config: Properties = {
    val p = new Properties()
    p.put(StreamsConfig.APPLICATION_ID_CONFIG, "wordcount-application")
    p.put(StreamsConfig.BOOTSTRAP_SERVERS_CONFIG, "localhost:9092")
    p.put(StreamsConfig.DEFAULT_KEY_SERDE_CLASS_CONFIG, Serdes.String().getClass)
    p.put(StreamsConfig.DEFAULT_VALUE_SERDE_CLASS_CONFIG, Serdes.String().getClass)
    p
  }

  val builder = new StreamsBuilderS()

  private def wordSplit(intopic: String, outTopic: String) = {
    val produced = Produced.`with`(Serdes.String(), Serdes.String())
    val textLines: KStreamS[String, String] = builder.stream(intopic)
    val data: KStreamS[String, String] = textLines.flatMapValues(value => value.toLowerCase.split("\\W+").toIterable)
    data.to(outTopic, produced)
  }

  private def readAndWriteJson(intopic: String, outTopic: String) = {
    val produced = Produced.`with`(Serdes.String(), Serdes.String())
    val textLines: KStreamS[String, String] = builder.stream(intopic)
    val data: KStreamS[String, String] = textLines.mapValues(value => {
      val person = Try(parse(value).extract[Person]).toOption
      println("1::", person)
      val personNameAndEmail = person.map(a => PersonNameAndEmail(a.name, a.email))
      println("2::", personNameAndEmail)
      write(personNameAndEmail)
    })
    data.to(outTopic, produced)
  }


  wordSplit("lines", "wordCount")
  readAndWriteJson("person", "personName")
  val streams: KafkaStreams = new KafkaStreams(builder.build(), config)
  streams.start()
  streams

  Runtime.getRuntime.addShutdownHook(new Thread(() => {
    streams.close(10, TimeUnit.SECONDS)
  }))
}

case class Person(name: String, age: Int, email: String)
case class PersonNameAndEmail(name: String, email: String)

为什么一个Kafka流阻止另一个Kafka流入门？

1 个答案: