Spark REST API: calculate time per job name

SparkAppStats.scala

import java.text.SimpleDateFormat
import java.util.Date
import org.json4s._
import org.json4s.jackson.JsonMethods.parse
import scala.io.Source.fromURL

object SparkAppStats {

  val url = "http://<host>:4040/api/v1/applications/<app-name>/jobs"

  /**
   * (partial) representation of a Spark Stage object 
   */
  case class SparkJob(jobId: Int, name: String, submissionTime: Date, completionTime: Option[Date], stageIds: List[Int]) {
    def getDurationMillis: Option[Long] = completionTime.map(_.getTime - submissionTime.getTime)
  }
  
  implicit val formats = new DefaultFormats {
    override def dateFormatter = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss.SSSZ")
  }

  /**
   * Prints total millis and avg millis per job name, e.g. 
   * TIME: 182570	AVG: 16597	NAME: count at MyAggregator.scala:132
   * TIME: 230973	AVG: 1297	  NAME: parquet at MyRepository.scala:99
   * TIME: 120393	AVG: 2188	  NAME: collect at MyCollector.scala:30
   */
  def main (args: Array[String]) {
    val json = fromURL(url + "/jobs").mkString
    val completedJobs: List[SparkJob] = parse(json)
      .extract[List[SparkJob]]
      .filter(j => j.getDurationMillis.isDefined)

    completedJobs
      .groupBy(_.name)
      .mapValues(list => (list.map(_.getDurationMillis.get).sum, list.size))
      .foreach { case (name, (time, count)) => println(s"TIME: $time\tAVG: ${time / count}\tNAME: $name") }
  }
}