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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.scheduler
import java.io._
import java.nio.ByteBuffer
import scala.collection.mutable.ArrayBuffer
import org.apache.spark.SparkEnv
import org.apache.spark.storage.BlockId
import org.apache.spark.util.Utils
// Task result. Also contains updates to accumulator variables.
private[spark] sealed trait TaskResult[T]
/** A reference to a DirectTaskResult that has been stored in the worker's BlockManager. */
private[spark] case class IndirectTaskResult[T](blockId: BlockId, size: Int)
extends TaskResult[T] with Serializable
/** A TaskResult that contains the task's return value and accumulator updates. */
private[spark] class DirectTaskResult[T](
var valueBytes: ByteBuffer,
var accumUpdates: Seq[AccumulableInfo])
extends TaskResult[T] with Externalizable {
private var valueObjectDeserialized = false
private var valueObject: T = _
def this() = this(null.asInstanceOf[ByteBuffer], null)
override def writeExternal(out: ObjectOutput): Unit = Utils.tryOrIOException {
out.writeInt(valueBytes.remaining)
Utils.writeByteBuffer(valueBytes, out)
out.writeInt(accumUpdates.size)
accumUpdates.foreach(out.writeObject)
}
override def readExternal(in: ObjectInput): Unit = Utils.tryOrIOException {
val blen = in.readInt()
val byteVal = new Array[Byte](blen)
in.readFully(byteVal)
valueBytes = ByteBuffer.wrap(byteVal)
val numUpdates = in.readInt
if (numUpdates == 0) {
accumUpdates = null
} else {
val _accumUpdates = new ArrayBuffer[AccumulableInfo]
for (i <- 0 until numUpdates) {
_accumUpdates += in.readObject.asInstanceOf[AccumulableInfo]
}
accumUpdates = _accumUpdates
}
valueObjectDeserialized = false
}
/**
* When `value()` is called at the first time, it needs to deserialize `valueObject` from
* `valueBytes`. It may cost dozens of seconds for a large instance. So when calling `value` at
* the first time, the caller should avoid to block other threads.
*
* After the first time, `value()` is trivial and just returns the deserialized `valueObject`.
*/
def value(): T = {
if (valueObjectDeserialized) {
valueObject
} else {
// This should not run when holding a lock because it may cost dozens of seconds for a large
// value.
val resultSer = SparkEnv.get.serializer.newInstance()
valueObject = resultSer.deserialize(valueBytes)
valueObjectDeserialized = true
valueObject
}
}
}
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