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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