/*

* 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.File;

import java.io.FileInputStream;

import java.io.IOException;

import java.io.OutputStream;

import java.nio.channels.FileChannel;

import java.util.Optional;

import java.util.zip.Checksum;

import javax.annotation.Nullable;

import scala.None$;

import scala.Option;

import scala.Product2;

import scala.Tuple2;

import scala.collection.Iterator;

import com.google.common.io.Closeables;

import org.slf4j.Logger;

import org.slf4j.LoggerFactory;

import org.apache.spark.Partitioner;

import org.apache.spark.ShuffleDependency;

import org.apache.spark.SparkConf;

import org.apache.spark.SparkException;

import org.apache.spark.network.shuffle.checksum.ShuffleChecksumHelper;

import org.apache.spark.shuffle.api.ShuffleExecutorComponents;

import org.apache.spark.shuffle.api.ShuffleMapOutputWriter;

import org.apache.spark.shuffle.api.ShufflePartitionWriter;

import org.apache.spark.shuffle.api.WritableByteChannelWrapper;

import org.apache.spark.shuffle.checksum.ShuffleChecksumSupport;

import org.apache.spark.internal.config.package$;

import org.apache.spark.scheduler.MapStatus;

import org.apache.spark.scheduler.MapStatus$;

import org.apache.spark.serializer.Serializer;

import org.apache.spark.serializer.SerializerInstance;

import org.apache.spark.shuffle.ShuffleWriteMetricsReporter;

import org.apache.spark.shuffle.ShuffleWriter;

import org.apache.spark.storage.*;

import org.apache.spark.util.Utils;

/**

* This class implements sort-based shuffle's hash-style shuffle fallback path. This write path

* writes incoming records to separate files, one file per reduce partition, then concatenates these

* per-partition files to form a single output file, regions of which are served to reducers.

* Records are not buffered in memory. It writes output in a format

* that can be served / consumed via {@link org.apache.spark.shuffle.IndexShuffleBlockResolver}.

* <p>

* This write path is inefficient for shuffles with large numbers of reduce partitions because it

* simultaneously opens separate serializers and file streams for all partitions. As a result,

* {@link SortShuffleManager} only selects this write path when

* <ul>

* <li>no map-side combine is specified, and</li>

* <li>the number of partitions is less than or equal to

* <code>spark.shuffle.sort.bypassMergeThreshold</code>.</li>

* </ul>

*

* This code used to be part of {@link org.apache.spark.util.collection.ExternalSorter} but was

* refactored into its own class in order to reduce code complexity; see SPARK-7855 for details.

* <p>

* There have been proposals to completely remove this code path; see SPARK-6026 for details.

*/

final class BypassMergeSortShuffleWriter<K, V>

}