Github user JoshRosen commented on a diff in the pull request: https://github.com/apache/spark/pull/1499#discussion_r15494109 --- Diff: core/src/main/scala/org/apache/spark/shuffle/sort/SortShuffleManager.scala --- @@ -0,0 +1,80 @@ +/* + * 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.sort + +import java.io.{DataInputStream, FileInputStream} + +import org.apache.spark.shuffle._ +import org.apache.spark.{TaskContext, ShuffleDependency} +import org.apache.spark.shuffle.hash.HashShuffleReader +import org.apache.spark.storage.{DiskBlockManager, FileSegment, ShuffleBlockId} + +private[spark] class SortShuffleManager extends ShuffleManager { + /** + * Register a shuffle with the manager and obtain a handle for it to pass to tasks. + */ + override def registerShuffle[K, V, C]( + shuffleId: Int, + numMaps: Int, + dependency: ShuffleDependency[K, V, C]): ShuffleHandle = { + new BaseShuffleHandle(shuffleId, numMaps, dependency) + } + + /** + * Get a reader for a range of reduce partitions (startPartition to endPartition-1, inclusive). + * Called on executors by reduce tasks. + */ + override def getReader[K, C]( + handle: ShuffleHandle, + startPartition: Int, + endPartition: Int, + context: TaskContext): ShuffleReader[K, C] = { + // We currently use the same block store shuffle fetcher as the hash-based shuffle. + new HashShuffleReader( + handle.asInstanceOf[BaseShuffleHandle[K, _, C]], startPartition, endPartition, context) + } + + /** Get a writer for a given partition. Called on executors by map tasks. */ + override def getWriter[K, V](handle: ShuffleHandle, mapId: Int, context: TaskContext) + : ShuffleWriter[K, V] = { + new SortShuffleWriter(handle.asInstanceOf[BaseShuffleHandle[K, V, _]], mapId, context) + } + + /** Remove a shuffle's metadata from the ShuffleManager. */ + override def unregisterShuffle(shuffleId: Int): Unit = {} + + /** Shut down this ShuffleManager. */ + override def stop(): Unit = {} + + /** Get the location of a block in a map output file. Uses the index file we create for it. */ + def getBlockLocation(blockId: ShuffleBlockId, diskManager: DiskBlockManager): FileSegment = { + // The block is actually going to be a range of a single map output file for this map, so + // figure out the ID of the consolidated file, then the offset within that from our index + val realId = ShuffleBlockId(blockId.shuffleId, blockId.mapId, 0) + val indexFile = diskManager.getFile(realId.name + ".index") + val in = new DataInputStream(new FileInputStream(indexFile)) --- End diff -- This index should be pretty small, so I suppose we could keep it in memory instead of writing it to a file. On the other hand, it might be likely to remain in the filesystem cache.
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