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From Amit Joshi <mailtojoshia...@gmail.com>
Subject [Spark-Kafka-Streaming] Verifying the approach for multiple queries
Date Sun, 09 Aug 2020 18:36:53 GMT
Hi,

I have a scenario where a kafka topic is being written with different types
of json records.
I have to regroup the records based on the type and then fetch the schema
and parse and write as parquet.
I have tried structured programming. But dynamic schema is a constraint.
So I have used DStreams and though I know the approach I have taken may not
be good.
If anyone can pls let me know if the approach will scale and possible pros
and cons.
I am collecting the grouped records and then again forming the dataframe
for each grouped record.
createKeyValue -> This is creating the key value pair with schema
information.

stream.foreachRDD { (rdd, time) =>
  val offsetRanges = rdd.asInstanceOf[HasOffsetRanges].offsetRanges
  val result = rdd.map(createKeyValue).reduceByKey((x,y) => x ++ y).collect()
  result.foreach(x=> println(x._1))
  result.map(x=> {
    val spark =
SparkSession.builder().config(rdd.sparkContext.getConf).getOrCreate()
    import spark.implicits._
    import org.apache.spark.sql.functions._
    val df = x._2 toDF("value")
    df.select(from_json($"value", x._1._2, Map.empty[String,String]).as("data"))
      .select($"data.*")
      //.withColumn("entity", lit("invoice"))
      .withColumn("year",year($"TimeUpdated"))
      .withColumn("month",month($"TimeUpdated"))
      .withColumn("day",dayofmonth($"TimeUpdated"))
      .write.partitionBy("name","year","month","day").mode("append").parquet(path)
  })
  stream.asInstanceOf[CanCommitOffsets].commitAsync(offsetRanges)
}

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