如何在转换为DF时将Kafka中的时间戳添加到Spark Streaming

问题描述

我在做卡夫卡的火花直播。我想把我的RDD从卡夫卡转换成数据帧。我正在使用以下方法。Val SSC=new StreamingContext("local[*]"，"KafkaExample"，Second(4))

    val kafkaParams = Map[String, Object](
    "bootstrap.servers" -> "dofff2.dl.uk.feefr.com:8002",
    "security.protocol" -> "SASL_PLAINTEXT",
    "key.deserializer" -> classOf[StringDeserializer],
    "value.deserializer" -> classOf[StringDeserializer],
    "group.id" -> "1",
    "auto.offset.reset" -> "latest",
    "enable.auto.commit" -> (false: java.lang.Boolean)
    )

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

   val strmk = stream.map(record => (record.value))
  val rdd1 = strmk.map(line => line.split(',')).map(s => (s(0).toString, s(1).toString,s(2).toString,s(3).toString,s(4).toString, s(5).toString,s(6).toString,s(7).toString))

  rdd1.foreachRDD((rdd, time) => {
  val sqlContext = SQLContextSingleton.getInstance(rdd.sparkContext)
  import sqlContext.implicits._
  val requestsDataFrame = rdd.map(w => Record(w._1, w._2, w._3,w._4, w._5, w._6,w._7, w._8)).toDF()
  requestsDataFrame.createOrReplaceTempView("requests")
  val word_df =sqlContext.sql("select * from  requests ")
  println(s"========= $time =========")
  word_df.show()
  })

但在数据帧中，我还想包括来自卡夫卡的时间戳。有人能帮我怎么做吗？

推荐答案

卡夫卡记录有多种属性。

参见https://spark.apache.org/docs/2.2.0/structured-streaming-kafka-integration.html

请注意，对于Kafka，有一种流和批处理方法。

示例：

import java.sql.Timestamp

import org.apache.spark.sql.SparkSession
import org.apache.spark.sql.functions._
import org.apache.spark.sql.streaming.OutputMode

val sparkSession = SparkSession.builder
  .master("local")
  .appName("example")
  .getOrCreate()

import sparkSession.implicits._
sparkSession.sparkContext.setLogLevel("ERROR")
val socketStreamDs = sparkSession.readStream
  .format("kafka")
  .option("kafka.bootstrap.servers", "localhost:9092")
  .option("subscribe", "AAA")
  .option("startingOffsets", "earliest")
  .load()
  //.as[String]
  //
  //.selectExpr("CAST(key AS STRING)", "CAST(value AS STRING)", "CAST(timestamp AS STRING)")
  .selectExpr("CAST(key AS STRING)", "CAST(value AS STRING)", "timestamp")
  .writeStream
    .format("console")
    .option("truncate", "false")
    .outputMode(OutputMode.Append())
    .start().awaitTermination()

我的示例输出如下：

-------------------------------------------
Batch: 0
-------------------------------------------
+----+-----+-----------------------+
|key |value|timestamp              |
+----+-----+-----------------------+
|null|RRR  |2019-02-07 04:37:34.983|
|null|HHH  |2019-02-07 04:37:36.802|
|null|JJJ  |2019-02-07 04:37:39.1  |
+----+-----+-----------------------+

您只需展开上面的语句：

stream.map { record => (record.timestamp(), record.key(), record.value()) }

这篇关于如何在转换为DF时将Kafka中的时间戳添加到Spark Streaming的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！