org.apache.spark.rdd.UnionRDD Scala Example

Source File: QueueInputDStream.scala From drizzle-spark with Apache License 2.0

5 votes

package org.apache.spark.streaming.dstream

import java.io.{NotSerializableException, ObjectInputStream, ObjectOutputStream}

import scala.collection.mutable.{ArrayBuffer, Queue}
import scala.reflect.ClassTag

import org.apache.spark.rdd.{RDD, UnionRDD}
import org.apache.spark.streaming.{StreamingContext, Time}

private[streaming]
class QueueInputDStream[T: ClassTag](
    ssc: StreamingContext,
    val queue: Queue[RDD[T]],
    oneAtATime: Boolean,
    defaultRDD: RDD[T]
  ) extends InputDStream[T](ssc) {

  override def start() { }

  override def stop() { }

  private def readObject(in: ObjectInputStream): Unit = {
    throw new NotSerializableException("queueStream doesn't support checkpointing. " +
      "Please don't use queueStream when checkpointing is enabled.")
  }

  private def writeObject(oos: ObjectOutputStream): Unit = {
    logWarning("queueStream doesn't support checkpointing")
  }

  override def compute(validTime: Time): Option[RDD[T]] = {
    val buffer = new ArrayBuffer[RDD[T]]()
    queue.synchronized {
      if (oneAtATime && queue.nonEmpty) {
        buffer += queue.dequeue()
      } else {
        buffer ++= queue
        queue.clear()
      }
    }
    if (buffer.nonEmpty) {
      if (oneAtATime) {
        Some(buffer.head)
      } else {
        Some(new UnionRDD(context.sc, buffer.toSeq))
      }
    } else if (defaultRDD != null) {
      Some(defaultRDD)
    } else {
      Some(ssc.sparkContext.emptyRDD)
    }
  }

}

Source File: TestableQueueInputDStream.scala From SparkUnitTestingExamples with Apache License 2.0

5 votes

package org.apache.spark.streaming

import java.io.{ObjectInputStream, ObjectOutputStream}

import org.apache.spark.rdd.{RDD, UnionRDD}
import org.apache.spark.streaming.dstream.InputDStream

import scala.collection.mutable.{ArrayBuffer, Queue}
import scala.reflect.ClassTag

class TestableQueueInputDStream[T: ClassTag](
                                              ssc: StreamingContext,
                                              val queue: Queue[RDD[T]],
                                              oneAtATime: Boolean,
                                              defaultRDD: RDD[T]
                                              ) extends InputDStream[T](ssc) {

  override def start() { }

  override def stop() { }

  private def readObject(in: ObjectInputStream): Unit = {
    logWarning("queueStream doesn't support checkpointing")
  }

  private def writeObject(oos: ObjectOutputStream): Unit = {
    logWarning("queueStream doesn't support checkpointing")
  }

  override def compute(validTime: Time): Option[RDD[T]] = {
    val buffer = new ArrayBuffer[RDD[T]]()
    queue.synchronized {
      if (oneAtATime && queue.nonEmpty) {
        buffer += queue.dequeue()
      } else {
        buffer ++= queue
        queue.clear()
      }
    }
    if (buffer.nonEmpty) {
      if (oneAtATime) {
        Some(buffer.head)
      } else {
        Some(new UnionRDD(context.sc, buffer.toSeq))
      }
    } else if (defaultRDD != null) {
      Some(defaultRDD)
    } else {
      Some(ssc.sparkContext.emptyRDD)
    }
  }

}

Source File: VLBFGS1.scala From spark-vl-bfgs with Apache License 2.0

5 votes

package org.apache.spark.ml.optim

import java.util.Random

import scala.language.implicitConversions

import org.apache.hadoop.fs.{FileSystem, Path}

import org.apache.spark.{SparkConf, SparkContext}
import org.apache.spark.ml.optim.VectorFreeLBFGS.{Oracle, VectorSpace}
import org.apache.spark.ml.optim.VectorRDDFunctions._
import org.apache.spark.mllib.linalg.{BLAS, Vector, Vectors}
import org.apache.spark.mllib.random.RandomRDDs
import org.apache.spark.mllib.regression.LabeledPoint
import org.apache.spark.rdd.{RDD, UnionRDD}
import org.apache.spark.storage.StorageLevel


  private def gradient(data: RDD[Array[LabeledPoint]], dx: RDD[Vector]): RDD[Vector] = {
    data.cartesian(dx).map { case (points, x) =>
      val g = Vectors.zeros(x.size)
      points.foreach { case LabeledPoint(b, a) =>
        val err = BLAS.dot(a, x) - b
        BLAS.axpy(err, a, g)
      }
      g
    }.treeSum()
  }

  def main(args: Array[String]): Unit = {
    val conf = new SparkConf().setAppName("VLBFGS").setMaster("local[*]")
    val sc = new SparkContext(conf)
    sc.setCheckpointDir("/tmp/checkpoint")
    val n = 1000
    val p = 100
    val random = new Random(0L)
    val xExact = Vectors.dense(Array.fill(p)(random.nextDouble()))
    val data = RandomRDDs.normalVectorRDD(sc, n, p, 4, 11L).mapPartitionsWithIndex { (idx, part) =>
      val random = new Random(100 + idx)
      part.map { v =>
        val target = BLAS.dot(v, xExact) + 0.1 * random.nextGaussian()
        LabeledPoint(target, v)
      }
    }.glom()
    .cache()

    val x = solve(data).first()

    println(s"x_exact = $xExact")
    println(s"x_vlbfgs = $x")

    sc.stop()
  }
}

Source File: QueueInputDStream.scala From sparkoscope with Apache License 2.0

5 votes

package org.apache.spark.streaming.dstream

import java.io.{NotSerializableException, ObjectInputStream, ObjectOutputStream}

import scala.collection.mutable.{ArrayBuffer, Queue}
import scala.reflect.ClassTag

import org.apache.spark.rdd.{RDD, UnionRDD}
import org.apache.spark.streaming.{StreamingContext, Time}

private[streaming]
class QueueInputDStream[T: ClassTag](
    ssc: StreamingContext,
    val queue: Queue[RDD[T]],
    oneAtATime: Boolean,
    defaultRDD: RDD[T]
  ) extends InputDStream[T](ssc) {

  override def start() { }

  override def stop() { }

  private def readObject(in: ObjectInputStream): Unit = {
    throw new NotSerializableException("queueStream doesn't support checkpointing. " +
      "Please don't use queueStream when checkpointing is enabled.")
  }

  private def writeObject(oos: ObjectOutputStream): Unit = {
    logWarning("queueStream doesn't support checkpointing")
  }

  override def compute(validTime: Time): Option[RDD[T]] = {
    val buffer = new ArrayBuffer[RDD[T]]()
    queue.synchronized {
      if (oneAtATime && queue.nonEmpty) {
        buffer += queue.dequeue()
      } else {
        buffer ++= queue
        queue.clear()
      }
    }
    if (buffer.nonEmpty) {
      if (oneAtATime) {
        Some(buffer.head)
      } else {
        Some(new UnionRDD(context.sc, buffer.toSeq))
      }
    } else if (defaultRDD != null) {
      Some(defaultRDD)
    } else {
      Some(ssc.sparkContext.emptyRDD)
    }
  }

}

Source File: QueueInputDStream.scala From multi-tenancy-spark with Apache License 2.0

5 votes

package org.apache.spark.streaming.dstream

import java.io.{NotSerializableException, ObjectInputStream, ObjectOutputStream}

import scala.collection.mutable.{ArrayBuffer, Queue}
import scala.reflect.ClassTag

import org.apache.spark.rdd.{RDD, UnionRDD}
import org.apache.spark.streaming.{StreamingContext, Time}

private[streaming]
class QueueInputDStream[T: ClassTag](
    ssc: StreamingContext,
    val queue: Queue[RDD[T]],
    oneAtATime: Boolean,
    defaultRDD: RDD[T]
  ) extends InputDStream[T](ssc) {

  override def start() { }

  override def stop() { }

  private def readObject(in: ObjectInputStream): Unit = {
    throw new NotSerializableException("queueStream doesn't support checkpointing. " +
      "Please don't use queueStream when checkpointing is enabled.")
  }

  private def writeObject(oos: ObjectOutputStream): Unit = {
    logWarning("queueStream doesn't support checkpointing")
  }

  override def compute(validTime: Time): Option[RDD[T]] = {
    val buffer = new ArrayBuffer[RDD[T]]()
    queue.synchronized {
      if (oneAtATime && queue.nonEmpty) {
        buffer += queue.dequeue()
      } else {
        buffer ++= queue
        queue.clear()
      }
    }
    if (buffer.nonEmpty) {
      if (oneAtATime) {
        Some(buffer.head)
      } else {
        Some(new UnionRDD(context.sc, buffer.toSeq))
      }
    } else if (defaultRDD != null) {
      Some(defaultRDD)
    } else {
      Some(ssc.sparkContext.emptyRDD)
    }
  }

}

Source File: UnionDStream.scala From iolap with Apache License 2.0

5 votes

package org.apache.spark.streaming.dstream

import org.apache.spark.streaming.{Duration, Time}
import org.apache.spark.rdd.RDD
import org.apache.spark.rdd.UnionRDD

import scala.collection.mutable.ArrayBuffer
import scala.reflect.ClassTag

private[streaming]
class UnionDStream[T: ClassTag](parents: Array[DStream[T]])
  extends DStream[T](parents.head.ssc) {

  require(parents.length > 0, "List of DStreams to union is empty")
  require(parents.map(_.ssc).distinct.size == 1, "Some of the DStreams have different contexts")
  require(parents.map(_.slideDuration).distinct.size == 1,
    "Some of the DStreams have different slide durations")

  override def dependencies: List[DStream[_]] = parents.toList

  override def slideDuration: Duration = parents.head.slideDuration

  override def compute(validTime: Time): Option[RDD[T]] = {
    val rdds = new ArrayBuffer[RDD[T]]()
    parents.map(_.getOrCompute(validTime)).foreach {
      case Some(rdd) => rdds += rdd
      case None => throw new Exception("Could not generate RDD from a parent for unifying at time "
        + validTime)
    }
    if (rdds.size > 0) {
      Some(new UnionRDD(ssc.sc, rdds))
    } else {
      None
    }
  }
}

Source File: QueueInputDStream.scala From iolap with Apache License 2.0

5 votes

package org.apache.spark.streaming.dstream

import java.io.{NotSerializableException, ObjectInputStream, ObjectOutputStream}

import scala.collection.mutable.{ArrayBuffer, Queue}
import scala.reflect.ClassTag

import org.apache.spark.rdd.{RDD, UnionRDD}
import org.apache.spark.streaming.{Time, StreamingContext}

private[streaming]
class QueueInputDStream[T: ClassTag](
    @transient ssc: StreamingContext,
    val queue: Queue[RDD[T]],
    oneAtATime: Boolean,
    defaultRDD: RDD[T]
  ) extends InputDStream[T](ssc) {

  override def start() { }

  override def stop() { }

  private def readObject(in: ObjectInputStream): Unit = {
    throw new NotSerializableException("queueStream doesn't support checkpointing. " +
      "Please don't use queueStream when checkpointing is enabled.")
  }

  private def writeObject(oos: ObjectOutputStream): Unit = {
    logWarning("queueStream doesn't support checkpointing")
  }

  override def compute(validTime: Time): Option[RDD[T]] = {
    val buffer = new ArrayBuffer[RDD[T]]()
    if (oneAtATime && queue.size > 0) {
      buffer += queue.dequeue()
    } else {
      buffer ++= queue.dequeueAll(_ => true)
    }
    if (buffer.size > 0) {
      if (oneAtATime) {
        Some(buffer.head)
      } else {
        Some(new UnionRDD(ssc.sc, buffer.toSeq))
      }
    } else if (defaultRDD != null) {
      Some(defaultRDD)
    } else {
      None
    }
  }

}

Source File: WindowedDStream.scala From iolap with Apache License 2.0

5 votes

package org.apache.spark.streaming.dstream

import org.apache.spark.rdd.{PartitionerAwareUnionRDD, RDD, UnionRDD}
import org.apache.spark.storage.StorageLevel
import org.apache.spark.streaming._
import org.apache.spark.streaming.Duration

import scala.reflect.ClassTag

private[streaming]
class WindowedDStream[T: ClassTag](
    parent: DStream[T],
    _windowDuration: Duration,
    _slideDuration: Duration)
  extends DStream[T](parent.ssc) {

  if (!_windowDuration.isMultipleOf(parent.slideDuration)) {
    throw new Exception("The window duration of windowed DStream (" + _windowDuration + ") " +
    "must be a multiple of the slide duration of parent DStream (" + parent.slideDuration + ")")
  }

  if (!_slideDuration.isMultipleOf(parent.slideDuration)) {
    throw new Exception("The slide duration of windowed DStream (" + _slideDuration + ") " +
    "must be a multiple of the slide duration of parent DStream (" + parent.slideDuration + ")")
  }

  // Persist parent level by default, as those RDDs are going to be obviously reused.
  parent.persist(StorageLevel.MEMORY_ONLY_SER)

  def windowDuration: Duration = _windowDuration

  override def dependencies: List[DStream[_]] = List(parent)

  override def slideDuration: Duration = _slideDuration

  override def parentRememberDuration: Duration = rememberDuration + windowDuration

  override def persist(level: StorageLevel): DStream[T] = {
    // Do not let this windowed DStream be persisted as windowed (union-ed) RDDs share underlying
    // RDDs and persisting the windowed RDDs would store numerous copies of the underlying data.
    // Instead control the persistence of the parent DStream.
    parent.persist(level)
    this
  }

  override def compute(validTime: Time): Option[RDD[T]] = {
    val currentWindow = new Interval(validTime - windowDuration + parent.slideDuration, validTime)
    val rddsInWindow = parent.slice(currentWindow)
    val windowRDD = if (rddsInWindow.flatMap(_.partitioner).distinct.length == 1) {
      logDebug("Using partition aware union for windowing at " + validTime)
      new PartitionerAwareUnionRDD(ssc.sc, rddsInWindow)
    } else {
      logDebug("Using normal union for windowing at " + validTime)
      new UnionRDD(ssc.sc, rddsInWindow)
    }
    Some(windowRDD)
  }
}

Source File: UnionDStream.scala From spark1.52 with Apache License 2.0

5 votes

package org.apache.spark.streaming.dstream

import org.apache.spark.streaming.{Duration, Time}
import org.apache.spark.rdd.RDD
import org.apache.spark.rdd.UnionRDD

import scala.collection.mutable.ArrayBuffer
import scala.reflect.ClassTag

private[streaming]
class UnionDStream[T: ClassTag](parents: Array[DStream[T]])
  extends DStream[T](parents.head.ssc) {

  require(parents.length > 0, "List of DStreams to union is empty")
  require(parents.map(_.ssc).distinct.size == 1, "Some of the DStreams have different contexts")
  require(parents.map(_.slideDuration).distinct.size == 1,
    "Some of the DStreams have different slide durations")

  override def dependencies: List[DStream[_]] = parents.toList

  override def slideDuration: Duration = parents.head.slideDuration

  override def compute(validTime: Time): Option[RDD[T]] = {
    val rdds = new ArrayBuffer[RDD[T]]()
    parents.map(_.getOrCompute(validTime)).foreach {
      case Some(rdd) => rdds += rdd
      case None => throw new Exception("Could not generate RDD from a parent for unifying at time "
        + validTime)
    }
    if (rdds.size > 0) {
      Some(new UnionRDD(ssc.sc, rdds))
    } else {
      None
    }
  }
}

Source File: QueueInputDStream.scala From spark1.52 with Apache License 2.0

5 votes

package org.apache.spark.streaming.dstream

import java.io.{NotSerializableException, ObjectInputStream, ObjectOutputStream}

import scala.collection.mutable.{ArrayBuffer, Queue}
import scala.reflect.ClassTag

import org.apache.spark.rdd.{RDD, UnionRDD}
import org.apache.spark.streaming.{Time, StreamingContext}

private[streaming]
class QueueInputDStream[T: ClassTag](
    @transient ssc: StreamingContext,
    val queue: Queue[RDD[T]],
    oneAtATime: Boolean,
    defaultRDD: RDD[T]
  ) extends InputDStream[T](ssc) {

  override def start() { }

  override def stop() { }

  private def readObject(in: ObjectInputStream): Unit = {
    throw new NotSerializableException("queueStream doesn't support checkpointing. " +
      "Please don't use queueStream when checkpointing is enabled.")
  }

  private def writeObject(oos: ObjectOutputStream): Unit = {
    logWarning("queueStream doesn't support checkpointing")
  }

  override def compute(validTime: Time): Option[RDD[T]] = {
    val buffer = new ArrayBuffer[RDD[T]]()
    if (oneAtATime && queue.size > 0) {
      buffer += queue.dequeue()
    } else {
      buffer ++= queue.dequeueAll(_ => true)
    }
    if (buffer.size > 0) {
      if (oneAtATime) {
        Some(buffer.head)
      } else {
        Some(new UnionRDD(ssc.sc, buffer.toSeq))
      }
    } else if (defaultRDD != null) {
      Some(defaultRDD)
    } else {
      None
    }
  }

}

Source File: WindowedDStream.scala From spark1.52 with Apache License 2.0

5 votes

package org.apache.spark.streaming.dstream

import org.apache.spark.rdd.{PartitionerAwareUnionRDD, RDD, UnionRDD}
import org.apache.spark.storage.StorageLevel
import org.apache.spark.streaming._
import org.apache.spark.streaming.Duration

import scala.reflect.ClassTag

private[streaming]
class WindowedDStream[T: ClassTag](
    parent: DStream[T],
    _windowDuration: Duration,
    _slideDuration: Duration)
  extends DStream[T](parent.ssc) {

  if (!_windowDuration.isMultipleOf(parent.slideDuration)) {
    throw new Exception("The window duration of windowed DStream (" + _windowDuration + ") " +
    "must be a multiple of the slide duration of parent DStream (" + parent.slideDuration + ")")
  }

  if (!_slideDuration.isMultipleOf(parent.slideDuration)) {
    throw new Exception("The slide duration of windowed DStream (" + _slideDuration + ") " +
    "must be a multiple of the slide duration of parent DStream (" + parent.slideDuration + ")")
  }

  // Persist parent level by default, as those RDDs are going to be obviously reused.
  //默认持久化级别,那些将要明显重用RDDS
  parent.persist(StorageLevel.MEMORY_ONLY_SER)

  def windowDuration: Duration = _windowDuration

  override def dependencies: List[DStream[_]] = List(parent)

  override def slideDuration: Duration = _slideDuration

  override def parentRememberDuration: Duration = rememberDuration + windowDuration

  override def persist(level: StorageLevel): DStream[T] = {
    // Do not let this windowed DStream be persisted as windowed (union-ed) RDDs share underlying
    // RDDs and persisting the windowed RDDs would store numerous copies of the underlying data.
    // Instead control the persistence of the parent DStream.
    parent.persist(level)
    this
  }

  override def compute(validTime: Time): Option[RDD[T]] = {
    val currentWindow = new Interval(validTime - windowDuration + parent.slideDuration, validTime)
    val rddsInWindow = parent.slice(currentWindow)
    val windowRDD = if (rddsInWindow.flatMap(_.partitioner).distinct.length == 1) {
      logDebug("Using partition aware union for windowing at " + validTime)
      new PartitionerAwareUnionRDD(ssc.sc, rddsInWindow)
    } else {
      logDebug("Using normal union for windowing at " + validTime)
      new UnionRDD(ssc.sc, rddsInWindow)
    }
    Some(windowRDD)
  }
}

Source File: QueueInputDStream.scala From Spark-2.3.1 with Apache License 2.0

5 votes

package org.apache.spark.streaming.dstream

import java.io.{NotSerializableException, ObjectInputStream, ObjectOutputStream}

import scala.collection.mutable.{ArrayBuffer, Queue}
import scala.reflect.ClassTag

import org.apache.spark.rdd.{RDD, UnionRDD}
import org.apache.spark.streaming.{StreamingContext, Time}

private[streaming]
class QueueInputDStream[T: ClassTag](
    ssc: StreamingContext,
    val queue: Queue[RDD[T]],
    oneAtATime: Boolean,
    defaultRDD: RDD[T]
  ) extends InputDStream[T](ssc) {

  override def start() { }

  override def stop() { }

  private def readObject(in: ObjectInputStream): Unit = {
    throw new NotSerializableException("queueStream doesn't support checkpointing. " +
      "Please don't use queueStream when checkpointing is enabled.")
  }

  private def writeObject(oos: ObjectOutputStream): Unit = {
    logWarning("queueStream doesn't support checkpointing")
  }

  override def compute(validTime: Time): Option[RDD[T]] = {
    val buffer = new ArrayBuffer[RDD[T]]()
    queue.synchronized {
      if (oneAtATime && queue.nonEmpty) {
        buffer += queue.dequeue()
      } else {
        buffer ++= queue
        queue.clear()
      }
    }
    if (buffer.nonEmpty) {
      if (oneAtATime) {
        Some(buffer.head)
      } else {
        Some(new UnionRDD(context.sc, buffer.toSeq))
      }
    } else if (defaultRDD != null) {
      Some(defaultRDD)
    } else {
      Some(ssc.sparkContext.emptyRDD)
    }
  }

}

Source File: UnionDStream.scala From BigDatalog with Apache License 2.0

5 votes

package org.apache.spark.streaming.dstream

import scala.collection.mutable.ArrayBuffer
import scala.reflect.ClassTag

import org.apache.spark.SparkException
import org.apache.spark.streaming.{Duration, Time}
import org.apache.spark.rdd.RDD
import org.apache.spark.rdd.UnionRDD

private[streaming]
class UnionDStream[T: ClassTag](parents: Array[DStream[T]])
  extends DStream[T](parents.head.ssc) {

  require(parents.length > 0, "List of DStreams to union is empty")
  require(parents.map(_.ssc).distinct.size == 1, "Some of the DStreams have different contexts")
  require(parents.map(_.slideDuration).distinct.size == 1,
    "Some of the DStreams have different slide durations")

  override def dependencies: List[DStream[_]] = parents.toList

  override def slideDuration: Duration = parents.head.slideDuration

  override def compute(validTime: Time): Option[RDD[T]] = {
    val rdds = new ArrayBuffer[RDD[T]]()
    parents.map(_.getOrCompute(validTime)).foreach {
      case Some(rdd) => rdds += rdd
      case None => throw new SparkException("Could not generate RDD from a parent for unifying at" +
        s" time $validTime")
    }
    if (rdds.size > 0) {
      Some(new UnionRDD(ssc.sc, rdds))
    } else {
      None
    }
  }
}

Source File: QueueInputDStream.scala From BigDatalog with Apache License 2.0

5 votes

package org.apache.spark.streaming.dstream

import java.io.{NotSerializableException, ObjectInputStream, ObjectOutputStream}

import scala.collection.mutable.{ArrayBuffer, Queue}
import scala.reflect.ClassTag

import org.apache.spark.rdd.{RDD, UnionRDD}
import org.apache.spark.streaming.{Time, StreamingContext}

private[streaming]
class QueueInputDStream[T: ClassTag](
    ssc: StreamingContext,
    val queue: Queue[RDD[T]],
    oneAtATime: Boolean,
    defaultRDD: RDD[T]
  ) extends InputDStream[T](ssc) {

  override def start() { }

  override def stop() { }

  private def readObject(in: ObjectInputStream): Unit = {
    throw new NotSerializableException("queueStream doesn't support checkpointing. " +
      "Please don't use queueStream when checkpointing is enabled.")
  }

  private def writeObject(oos: ObjectOutputStream): Unit = {
    logWarning("queueStream doesn't support checkpointing")
  }

  override def compute(validTime: Time): Option[RDD[T]] = {
    val buffer = new ArrayBuffer[RDD[T]]()
    if (oneAtATime && queue.size > 0) {
      buffer += queue.dequeue()
    } else {
      buffer ++= queue.dequeueAll(_ => true)
    }
    if (buffer.size > 0) {
      if (oneAtATime) {
        Some(buffer.head)
      } else {
        Some(new UnionRDD(context.sc, buffer.toSeq))
      }
    } else if (defaultRDD != null) {
      Some(defaultRDD)
    } else {
      Some(ssc.sparkContext.emptyRDD)
    }
  }

}

Source File: WindowedDStream.scala From BigDatalog with Apache License 2.0

5 votes

package org.apache.spark.streaming.dstream

import org.apache.spark.rdd.{PartitionerAwareUnionRDD, RDD, UnionRDD}
import org.apache.spark.storage.StorageLevel
import org.apache.spark.streaming._
import org.apache.spark.streaming.Duration

import scala.reflect.ClassTag

private[streaming]
class WindowedDStream[T: ClassTag](
    parent: DStream[T],
    _windowDuration: Duration,
    _slideDuration: Duration)
  extends DStream[T](parent.ssc) {

  if (!_windowDuration.isMultipleOf(parent.slideDuration)) {
    throw new Exception("The window duration of windowed DStream (" + _windowDuration + ") " +
    "must be a multiple of the slide duration of parent DStream (" + parent.slideDuration + ")")
  }

  if (!_slideDuration.isMultipleOf(parent.slideDuration)) {
    throw new Exception("The slide duration of windowed DStream (" + _slideDuration + ") " +
    "must be a multiple of the slide duration of parent DStream (" + parent.slideDuration + ")")
  }

  // Persist parent level by default, as those RDDs are going to be obviously reused.
  parent.persist(StorageLevel.MEMORY_ONLY_SER)

  def windowDuration: Duration = _windowDuration

  override def dependencies: List[DStream[_]] = List(parent)

  override def slideDuration: Duration = _slideDuration

  override def parentRememberDuration: Duration = rememberDuration + windowDuration

  override def persist(level: StorageLevel): DStream[T] = {
    // Do not let this windowed DStream be persisted as windowed (union-ed) RDDs share underlying
    // RDDs and persisting the windowed RDDs would store numerous copies of the underlying data.
    // Instead control the persistence of the parent DStream.
    parent.persist(level)
    this
  }

  override def compute(validTime: Time): Option[RDD[T]] = {
    val currentWindow = new Interval(validTime - windowDuration + parent.slideDuration, validTime)
    val rddsInWindow = parent.slice(currentWindow)
    val windowRDD = if (rddsInWindow.flatMap(_.partitioner).distinct.length == 1) {
      logDebug("Using partition aware union for windowing at " + validTime)
      new PartitionerAwareUnionRDD(ssc.sc, rddsInWindow)
    } else {
      logDebug("Using normal union for windowing at " + validTime)
      new UnionRDD(ssc.sc, rddsInWindow)
    }
    Some(windowRDD)
  }
}

org.apache.spark.rdd.UnionRDD Scala Examples