Question

Я пытаюсь читать темы Кафки через Apache Spark Streaming и не могу понять, как преобразовать данные в DStream в DataFrame и затем сохранить во временной таблице.Сообщения в Kafka представлены в формате Avro, которые были созданы Kafka JDBC Connect из базы данных.У меня есть код ниже, который работает нормально, пока он не выполнит spark.read.json для чтения JSON в dataframe.

package consumerTest


import io.confluent.kafka.serializers.KafkaAvroDeserializer
import org.apache.spark.sql.{SQLContext, SparkSession}
import org.apache.spark.{SparkConf, SparkContext}
import org.apache.spark.streaming._
import org.apache.spark.streaming.StreamingContext._
import org.apache.spark.streaming.kafka010.ConsumerStrategies.Subscribe
import org.apache.spark.streaming.kafka010.LocationStrategies.PreferConsistent
import org.apache.spark.streaming.kafka010._

import scala.util.parsing.json.{JSON, JSONObject}

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

    val spark = SparkSession.builder
      .master("local")
      .appName("my-spark-app")
      .config("spark.serializer", "org.apache.spark.serializer.KryoSerializer")
      .getOrCreate();

    import spark.implicits._


    val ssc = new StreamingContext(spark.sparkContext, Seconds(10))

    val kafkaParams = Map[String, Object](
      "bootstrap.servers" -> "<kafka-server>:9092",
      "key.deserializer" -> classOf[KafkaAvroDeserializer],
      "value.deserializer" -> classOf[KafkaAvroDeserializer],
      "group.id" -> "sakwq",
      "auto.offset.reset" -> "earliest",
      "enable.auto.commit" -> "false",
      "schema.registry.url" -> "http://<schema-registry>:8181"
    )

    val topics = Array("cdcemployee")

    val stream = KafkaUtils.createDirectStream[String, Object](
      ssc,
      PreferConsistent,
      Subscribe[String, Object](topics, kafkaParams)
    )


    val data = stream.map(record => {
      println(record.value.toString())
      record.value
      val df = spark.read.json(record.value.toString())

    })


    data.print();



    ssc.start()
    ssc.awaitTermination()
  }


}

Я получаю исключение нулевого указателя при выполнении строки val df = spark.read.json(record.value.toString())

18/05/10 09:49:11 ERROR Executor: Exception in task 0.0 in stage 0.0 (TID 0)
java.lang.NullPointerException
    at org.apache.spark.sql.SparkSession.sessionState$lzycompute(SparkSession.scala:135)
    at org.apache.spark.sql.SparkSession.sessionState(SparkSession.scala:133)
    at org.apache.spark.sql.DataFrameReader.<init>(DataFrameReader.scala:689)
    at org.apache.spark.sql.SparkSession.read(SparkSession.scala:645)
    at consumerTest.Consumer$.$anonfun$main$1(Consumer.scala:63)
    at consumerTest.Consumer$.$anonfun$main$1$adapted(Consumer.scala:60)
    at scala.collection.Iterator$$anon$11.next(Iterator.scala:409)
    at scala.collection.Iterator$$anon$10.next(Iterator.scala:393)
    at scala.collection.Iterator$class.foreach(Iterator.scala:893)
    at scala.collection.AbstractIterator.foreach(Iterator.scala:1336)
    at scala.collection.generic.Growable$class.$plus$plus$eq(Growable.scala:59)
    at scala.collection.mutable.ArrayBuffer.$plus$plus$eq(ArrayBuffer.scala:104)
    at scala.collection.mutable.ArrayBuffer.$plus$plus$eq(ArrayBuffer.scala:48)
    at scala.collection.TraversableOnce$class.to(TraversableOnce.scala:310)
    at scala.collection.AbstractIterator.to(Iterator.scala:1336)
    at scala.collection.TraversableOnce$class.toBuffer(TraversableOnce.scala:302)
    at scala.collection.AbstractIterator.toBuffer(Iterator.scala:1336)
    at scala.collection.TraversableOnce$class.toArray(TraversableOnce.scala:289)
    at scala.collection.AbstractIterator.toArray(Iterator.scala:1336)
    at org.apache.spark.rdd.RDD$$anonfun$take$1$$anonfun$29.apply(RDD.scala:1354)
    at org.apache.spark.rdd.RDD$$anonfun$take$1$$anonfun$29.apply(RDD.scala:1354)
    at org.apache.spark.SparkContext$$anonfun$runJob$5.apply(SparkContext.scala:2069)
    at org.apache.spark.SparkContext$$anonfun$runJob$5.apply(SparkContext.scala:2069)
    at org.apache.spark.scheduler.ResultTask.runTask(ResultTask.scala:87)
    at org.apache.spark.scheduler.Task.run(Task.scala:108)
    at org.apache.spark.executor.Executor$TaskRunner.run(Executor.scala:338)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
    at java.lang.Thread.run(Thread.java:748)
18/05/10 09:49:11 WARN TaskSetManager: Lost task 0.0 in stage 0.0 (TID 0, localhost, executor driver): java.lang.NullPointerException
    at org.apache.spark.sql.SparkSession.sessionState$lzycompute(SparkSession.scala:135)
    at org.apache.spark.sql.SparkSession.sessionState(SparkSession.scala:133)
    at org.apache.spark.sql.DataFrameReader.<init>(DataFrameReader.scala:689)
    at org.apache.spark.sql.SparkSession.read(SparkSession.scala:645)
    at consumerTest.Consumer$.$anonfun$main$1(Consumer.scala:63)
    at consumerTest.Consumer$.$anonfun$main$1$adapted(Consumer.scala:60)
    at scala.collection.Iterator$$anon$11.next(Iterator.scala:409)
    at scala.collection.Iterator$$anon$10.next(Iterator.scala:393)
    at scala.collection.Iterator$class.foreach(Iterator.scala:893)
    at scala.collection.AbstractIterator.foreach(Iterator.scala:1336)
    at scala.collection.generic.Growable$class.$plus$plus$eq(Growable.scala:59)
    at scala.collection.mutable.ArrayBuffer.$plus$plus$eq(ArrayBuffer.scala:104)
    at scala.collection.mutable.ArrayBuffer.$plus$plus$eq(ArrayBuffer.scala:48)
    at scala.collection.TraversableOnce$class.to(TraversableOnce.scala:310)
    at scala.collection.AbstractIterator.to(Iterator.scala:1336)
    at scala.collection.TraversableOnce$class.toBuffer(TraversableOnce.scala:302)
    at scala.collection.AbstractIterator.toBuffer(Iterator.scala:1336)
    at scala.collection.TraversableOnce$class.toArray(TraversableOnce.scala:289)
    at scala.collection.AbstractIterator.toArray(Iterator.scala:1336)
    at org.apache.spark.rdd.RDD$$anonfun$take$1$$anonfun$29.apply(RDD.scala:1354)
    at org.apache.spark.rdd.RDD$$anonfun$take$1$$anonfun$29.apply(RDD.scala:1354)
    at org.apache.spark.SparkContext$$anonfun$runJob$5.apply(SparkContext.scala:2069)
    at org.apache.spark.SparkContext$$anonfun$runJob$5.apply(SparkContext.scala:2069)
    at org.apache.spark.scheduler.ResultTask.runTask(ResultTask.scala:87)
    at org.apache.spark.scheduler.Task.run(Task.scala:108)
    at org.apache.spark.executor.Executor$TaskRunner.run(Executor.scala:338)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
    at java.lang.Thread.run(Thread.java:748)

Кроме того, вот пример данных, которые печатаются при выполнении оператора println(record.value.toString()), еслиЯ удаляю оператор spark.read.json

    {"CDCTRANSACTIONID": 182241, "CDCTIMESTAMP": "2018-03-26 18:04:44:776 - 04:00", "CDCCHANGESEQ": 14, "CDCCONTINUATIONPOSITION": 0, "CDCARRAYINDEX": 0, "CDCFRAGMENT": 0, "CDCOPERATION": 4, "EmpNum": 57, "LastName": null, "FirstName": null, "Address": null, "Address2": null, "City": "San Francisco", "State": null, "PostalCode": null, "DeptCode": "300", "Position": null, "HomePhone": null, "WorkPhone": null, "VacationDaysLeft": null, "SickDaysLeft": null, "StartDate": null, "Birthdate": null}
{"CDCTRANSACTIONID": 182241, "CDCTIMESTAMP": "2018-03-26 18:04:44:776 - 04:00", "CDCCHANGESEQ": 14, "CDCCONTINUATIONPOSITION": 0, "CDCARRAYINDEX": 0, "CDCFRAGMENT": 0, "CDCOPERATION": 3, "EmpNum": 57, "LastName": null, "FirstName": null, "Address": null, "Address2": null, "City": "Raleigh", "State": null, "PostalCode": null, "DeptCode": "", "Position": null, "HomePhone": null, "WorkPhone": null, "VacationDaysLeft": null, "SickDaysLeft": null, "StartDate": null, "Birthdate": null}
{"CDCTRANSACTIONID": 197086, "CDCTIMESTAMP": "2018-03-27 11:18:48:022 - 04:00", "CDCCHANGESEQ": 15, "CDCCONTINUATIONPOSITION": 0, "CDCARRAYINDEX": 0, "CDCFRAGMENT": 0, "CDCOPERATION": 4, "EmpNum": 57, "LastName": null, "FirstName": null, "Address": null, "Address2": null, "City": "New York", "State": null, "PostalCode": null, "DeptCode": null, "Position": null, "HomePhone": null, "WorkPhone": null, "VacationDaysLeft": null, "SickDaysLeft": null, "StartDate": null, "Birthdate": null}
{"CDCTRANSACTIONID": 197086, "CDCTIMESTAMP": "2018-03-27 11:18:48:022 - 04:00", "CDCCHANGESEQ": 15, "CDCCONTINUATIONPOSITION": 0, "CDCARRAYINDEX": 0, "CDCFRAGMENT": 0, "CDCOPERATION": 3, "EmpNum": 57, "LastName": null, "FirstName": null, "Address": null, "Address2": null, "City": "San Francisco", "State": null, "PostalCode": null, "DeptCode": null, "Position": null, "HomePhone": null, "WorkPhone": null, "VacationDaysLeft": null, "SickDaysLeft": null, "StartDate": null, "Birthdate": null}
{"CDCTRANSACTIONID": 363712, "CDCTIMESTAMP": "2018-04-04 15:30:46:551 - 04:00", "CDCCHANGESEQ": 16, "CDCCONTINUATIONPOSITION": 0, "CDCARRAYINDEX": 0, "CDCFRAGMENT": 0, "CDCOPERATION": 4, "EmpNum": 57, "LastName": null, "FirstName": null, "Address": null, "Address2": null, "City": "San Diego", "State": null, "PostalCode": null, "DeptCode": null, "Position": null, "HomePhone": null, "WorkPhone": null, "VacationDaysLeft": null, "SickDaysLeft": null, "StartDate": null, "Birthdate": null}
{"CDCTRANSACTIONID": 363712, "CDCTIMESTAMP": "2018-04-04 15:30:46:551 - 04:00", "CDCCHANGESEQ": 16, "CDCCONTINUATIONPOSITION": 0, "CDCARRAYINDEX": 0, "CDCFRAGMENT": 0, "CDCOPERATION": 3, "EmpNum": 57, "LastName": null, "FirstName": null, "Address": null, "Address2": null, "City": "New York", "State": null, "PostalCode": null, "DeptCode": null, "Position": null, "HomePhone": null, "WorkPhone": null, "VacationDaysLeft": null, "SickDaysLeft": null, "StartDate": null, "Birthdate": null}
{"CDCTRANSACTIONID": 363785, "CDCTIMESTAMP": "2018-04-04 15:35:11:492 - 04:00", "CDCCHANGESEQ": 17, "CDCCONTINUATIONPOSITION": 0, "CDCARRAYINDEX": 0, "CDCFRAGMENT": 0, "CDCOPERATION": 2, "EmpNum": 57, "LastName": "bobba2s", "FirstName": "Saikrishna Teja", "Address": "9220 Bothwell St", "Address2": "", "City": "San Diego", "State": "NC", "PostalCode": "27617", "DeptCode": "300", "Position": "", "HomePhone": "919 931-5737", "WorkPhone": "919 931-5737", "VacationDaysLeft": 10, "SickDaysLeft": 5, "StartDate": 16979, "Birthdate": 7270}
{"CDCTRANSACTIONID": 364688, "CDCTIMESTAMP": "2018-04-04 16:39:05:602 - 04:00", "CDCCHANGESEQ": 18, "CDCCONTINUATIONPOSITION": 0, "CDCARRAYINDEX": 0, "CDCFRAGMENT": 0, "CDCOPERATION": 1, "EmpNum": 59, "LastName": "Bobba", "FirstName": "Saikrishna Teja", "Address": "9220 Bothwell St", "Address2": "", "City": "Raleigh", "State": "NC", "PostalCode": "27617", "DeptCode": "300", "Position": "", "HomePhone": "919 931-5737", "WorkPhone": "919 931-5737", "VacationDaysLeft": 10, "SickDaysLeft": 5, "StartDate": 16979, "Birthdate": 7270}
{"CDCTRANSACTIONID": 384368, "CDCTIMESTAMP": "2018-04-05 15:43:15:478 - 04:00", "CDCCHANGESEQ": 19, "CDCCONTINUATIONPOSITION": 0, "CDCARRAYINDEX": 0, "CDCFRAGMENT": 0, "CDCOPERATION": 4, "EmpNum": 59, "LastName": null, "FirstName": null, "Address": null, "Address2": null, "City": "San Francisco", "State": "CA", "PostalCode": null, "DeptCode": null, "Position": null, "HomePhone": null, "WorkPhone": null, "VacationDaysLeft": null, "SickDaysLeft": null, "StartDate": null, "Birthdate": null}
{"CDCTRANSACTIONID": 384368, "CDCTIMESTAMP": "2018-04-05 15:43:15:478 - 04:00", "CDCCHANGESEQ": 19, "CDCCONTINUATIONPOSITION": 0, "CDCARRAYINDEX": 0, "CDCFRAGMENT": 0, "CDCOPERATION": 3, "EmpNum": 59, "LastName": null, "FirstName": null, "Address": null, "Address2": null, "City": "Raleigh", "State": "NC", "PostalCode": null, "DeptCode": null, "Position": null, "HomePhone": null, "WorkPhone": null, "VacationDaysLeft": null, "SickDaysLeft": null, "StartDate": null, "Birthdate": null}
{"CDCTRANSACTIONID": 650254, "CDCTIMESTAMP": "2018-04-18 16:19:35:669 - 04:00", "CDCCHANGESEQ": 20, "CDCCONTINUATIONPOSITION": 0, "CDCARRAYINDEX": 0, "CDCFRAGMENT": 0, "CDCOPERATION": 4, "EmpNum": 59, "LastName": null, "FirstName": null, "Address": null, "Address2": null, "City": "San Diego", "State": null, "PostalCode": null, "DeptCode": null, "Position": null, "HomePhone": null, "WorkPhone": null, "VacationDaysLeft": null, "SickDaysLeft": null, "StartDate": null, "Birthdate": null}

Может кто-нибудь помочь мне с тем, как преобразовать это в фрейм данных и временно сохранить его в таблице?

edit:

Shankar Koirala · Answer 1 · 10 мая 2018

stream содержит СДР для каждого interval времени, поэтому для каждого interval времени вы можете преобразовать rdd в datafarme как

stream.foreachRDD(rddRaw => {
  val rdd = rddRaw.map(_.value.toString) // or rddRaw.map(_._2)
  val df = spark.read.json(rdd)
})

Это должно дать вам кадр данных, как и ожидалось.

Надеюсь, это поможет!

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Spark Streaming - потоковые сообщения в формате json в DataFrame

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