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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.shuffle
import org.apache.spark._
import org.apache.spark.internal.{config, Logging}
import org.apache.spark.serializer.SerializerManager
import org.apache.spark.storage.{BlockManager, ShuffleBlockFetcherIterator}
import org.apache.spark.util.CompletionIterator
import org.apache.spark.util.collection.ExternalSorter
/**
* Fetches and reads the partitions in range [startPartition, endPartition) from a shuffle by
* requesting them from other nodes' block stores.
*/
private[spark] class BlockStoreShuffleReader[K, C](
handle: BaseShuffleHandle[K, _, C],
startPartition: Int,
endPartition: Int,
context: TaskContext,
serializerManager: SerializerManager = SparkEnv.get.serializerManager,
blockManager: BlockManager = SparkEnv.get.blockManager,
mapOutputTracker: MapOutputTracker = SparkEnv.get.mapOutputTracker)
extends ShuffleReader[K, C] with Logging {
private val dep = handle.dependency
/** Read the combined key-values for this reduce task */
override def read(): Iterator[Product2[K, C]] = {
val wrappedStreams = new ShuffleBlockFetcherIterator(
context,
blockManager.shuffleClient,
blockManager,
mapOutputTracker.getMapSizesByExecutorId(handle.shuffleId, startPartition, endPartition),
serializerManager.wrapStream,
// Note: we use getSizeAsMb when no suffix is provided for backwards compatibility
SparkEnv.get.conf.getSizeAsMb("spark.reducer.maxSizeInFlight", "48m") * 1024 * 1024,
SparkEnv.get.conf.getInt("spark.reducer.maxReqsInFlight", Int.MaxValue),
SparkEnv.get.conf.get(config.REDUCER_MAX_BLOCKS_IN_FLIGHT_PER_ADDRESS),
SparkEnv.get.conf.get(config.MAX_REMOTE_BLOCK_SIZE_FETCH_TO_MEM),
SparkEnv.get.conf.getBoolean("spark.shuffle.detectCorrupt", true))
val serializerInstance = dep.serializer.newInstance()
// Create a key/value iterator for each stream
val recordIter = wrappedStreams.flatMap { case (blockId, wrappedStream) =>
// Note: the asKeyValueIterator below wraps a key/value iterator inside of a
// NextIterator. The NextIterator makes sure that close() is called on the
// underlying InputStream when all records have been read.
serializerInstance.deserializeStream(wrappedStream).asKeyValueIterator
}
// Update the context task metrics for each record read.
val readMetrics = context.taskMetrics.createTempShuffleReadMetrics()
val metricIter = CompletionIterator[(Any, Any), Iterator[(Any, Any)]](
recordIter.map { record =>
readMetrics.incRecordsRead(1)
record
},
context.taskMetrics().mergeShuffleReadMetrics())
// An interruptible iterator must be used here in order to support task cancellation
val interruptibleIter = new InterruptibleIterator[(Any, Any)](context, metricIter)
val aggregatedIter: Iterator[Product2[K, C]] = if (dep.aggregator.isDefined) {
if (dep.mapSideCombine) {
// We are reading values that are already combined
val combinedKeyValuesIterator = interruptibleIter.asInstanceOf[Iterator[(K, C)]]
dep.aggregator.get.combineCombinersByKey(combinedKeyValuesIterator, context)
} else {
// We don't know the value type, but also don't care -- the dependency *should*
// have made sure its compatible w/ this aggregator, which will convert the value
// type to the combined type C
val keyValuesIterator = interruptibleIter.asInstanceOf[Iterator[(K, Nothing)]]
dep.aggregator.get.combineValuesByKey(keyValuesIterator, context)
}
} else {
interruptibleIter.asInstanceOf[Iterator[Product2[K, C]]]
}
// Sort the output if there is a sort ordering defined.
val resultIter = dep.keyOrdering match {
case Some(keyOrd: Ordering[K]) =>
// Create an ExternalSorter to sort the data.
val sorter =
new ExternalSorter[K, C, C](context, ordering = Some(keyOrd), serializer = dep.serializer)
sorter.insertAll(aggregatedIter)
context.taskMetrics().incMemoryBytesSpilled(sorter.memoryBytesSpilled)
context.taskMetrics().incDiskBytesSpilled(sorter.diskBytesSpilled)
context.taskMetrics().incPeakExecutionMemory(sorter.peakMemoryUsedBytes)
// Use completion callback to stop sorter if task was finished/cancelled.
context.addTaskCompletionListener[Unit](_ => {
sorter.stop()
})
CompletionIterator[Product2[K, C], Iterator[Product2[K, C]]](sorter.iterator, sorter.stop())
case None =>
aggregatedIter
}
resultIter match {
case _: InterruptibleIterator[Product2[K, C]] => resultIter
case _ =>
// Use another interruptible iterator here to support task cancellation as aggregator
// or(and) sorter may have consumed previous interruptible iterator.
new InterruptibleIterator[Product2[K, C]](context, resultIter)
}
}
}
