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https://issues.apache.org/jira/browse/MAPREDUCE-7465?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17802259#comment-17802259
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Steve Loughran commented on MAPREDUCE-7465:
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[~arnaud.nauwynck]:
https://spark.apache.org/docs/latest/cloud-integration.html#committing-work-into-cloud-storage-safely-and-fast
> performance problem in FileOutputCommiter for big list processed by single
> thread
> ----------------------------------------------------------------------------------
>
> Key: MAPREDUCE-7465
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-7465
> Project: Hadoop Map/Reduce
> Issue Type: Improvement
> Components: performance
> Affects Versions: 3.2.3, 3.3.2, 3.2.4, 3.3.5, 3.3.3, 3.3.4, 3.3.6
> Reporter: Arnaud Nauwynck
> Priority: Minor
> Labels: pull-request-available
>
> when commiting a big hadoop job (for example via Spark) having many
> partitions,
> the class FileOutputCommiter process thousands of dirs/files to rename with a
> single Thread. This is performance issue, caused by lot of waits on
> FileStystem storage operations.
> I propose that above a configurable threshold (default=3, configurable via
> property 'mapreduce.fileoutputcommitter.parallel.threshold'), the class
> FileOutputCommiter process the list of files to rename using parallel
> threads, using the default jvm ExecutorService (ForkJoinPool.commonPool())
> See Pull-Request:
> [https://github.com/apache/hadoop/pull/6378|https://github.com/apache/hadoop/pull/6378]
> Notice that sub-class instances of FileOutputCommiter are supposed to be
> created at runtime dependending of a configurable property
> ([https://github.com/apache/hadoop/blob/trunk/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core/src/main/java/org/apache/hadoop/mapreduce/lib/output/PathOutputCommitterFactory.java|PathOutputCommitterFactory.java]).
> But for example in Parquet + Spark, this is buggy and can not be changed at
> runtime.
> There is an ongoing Jira and PR to fix it in Parquet + Spark:
> [https://issues.apache.org/jira/browse/PARQUET-2416|https://issues.apache.org/jira/browse/PARQUET-2416]
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