如何从Spark Streaming开始从Kafka主题中读取记录？

Question

我正在尝试使用Spark Streaming从Kafka主题中读取记录.

这是我的代码:

object KafkaConsumer {

  import ApplicationContext._

  def main(args: Array[String]) = {

    val kafkaParams = Map[String, Object](
      "bootstrap.servers" -> "localhost:9092",
      "key.deserializer" -> classOf[StringDeserializer],
      "value.deserializer" -> classOf[StringDeserializer],
      "group.id" -> s"${UUID.randomUUID().toString}",
      "auto.offset.reset" -> "earliest",
      "enable.auto.commit" -> (false: java.lang.Boolean)
    )

    val topics = Array("pressure")
    val stream = KafkaUtils.createDirectStream[String, String](
      streamingContext,
      PreferConsistent,
      Subscribe[String, String](topics, kafkaParams)
    )
    stream.print()
    stream.map(record => (record.key, record.value)).count().print()
    streamingContext.start()
  }
}

我运行时没有显示任何内容.

要检查pressure主题中是否确实存在数据,我使用命令行方法,它会显示记录:

bin/kafka-console-consumer.sh \
  --bootstrap-server localhost:9092 \
  --topic pressure \
  --from-beginning

输出:

TimeStamp:07/13/16 15:20:45:226769,{'Pressure':'834'}
TimeStamp:07/13/16 15:20:45:266287,{'Pressure':'855'}
TimeStamp:07/13/16 15:20:45:305694,{'Pressure':'837'}

怎么了？

Answer 1

你错过了streamingContext.awaitTermination().