org.apache.spark.rdd.BlockRDD.scala Maven / Gradle / Ivy
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* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.spark.rdd
import scala.reflect.ClassTag
import org.apache.spark._
import org.apache.spark.storage.{BlockId, BlockManager}
private[spark] class BlockRDDPartition(val blockId: BlockId, idx: Int) extends Partition {
val index = idx
}
private[spark]
class BlockRDD[T: ClassTag](sc: SparkContext, @transient val blockIds: Array[BlockId])
extends RDD[T](sc, Nil) {
@transient lazy val _locations = BlockManager.blockIdsToLocations(blockIds, SparkEnv.get)
@volatile private var _isValid = true
override def getPartitions: Array[Partition] = {
assertValid()
(0 until blockIds.length).map { i =>
new BlockRDDPartition(blockIds(i), i).asInstanceOf[Partition]
}.toArray
}
override def compute(split: Partition, context: TaskContext): Iterator[T] = {
assertValid()
val blockManager = SparkEnv.get.blockManager
val blockId = split.asInstanceOf[BlockRDDPartition].blockId
blockManager.get[T](blockId) match {
case Some(block) => block.data.asInstanceOf[Iterator[T]]
case None =>
throw new Exception(s"Could not compute split, block $blockId of RDD $id not found")
}
}
override def getPreferredLocations(split: Partition): Seq[String] = {
assertValid()
_locations(split.asInstanceOf[BlockRDDPartition].blockId)
}
/**
* Remove the data blocks that this BlockRDD is made from. NOTE: This is an
* irreversible operation, as the data in the blocks cannot be recovered back
* once removed. Use it with caution.
*/
private[spark] def removeBlocks() {
blockIds.foreach { blockId =>
sparkContext.env.blockManager.master.removeBlock(blockId)
}
_isValid = false
}
/**
* Whether this BlockRDD is actually usable. This will be false if the data blocks have been
* removed using `this.removeBlocks`.
*/
private[spark] def isValid: Boolean = {
_isValid
}
/** Check if this BlockRDD is valid. If not valid, exception is thrown. */
private[spark] def assertValid() {
if (!isValid) {
throw new SparkException(
"Attempted to use %s after its blocks have been removed!".format(toString))
}
}
protected def getBlockIdLocations(): Map[BlockId, Seq[String]] = {
_locations
}
}