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https://issues.apache.org/jira/browse/MAPREDUCE-7029?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16320734#comment-16320734
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Hadoop QA commented on MAPREDUCE-7029:
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| (x) *{color:red}-1 overall{color}* |
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|| Vote || Subsystem || Runtime || Comment ||
| {color:blue}0{color} | {color:blue} reexec {color} | {color:blue} 0m
0s{color} | {color:blue} Docker mode activated. {color} |
| {color:red}-1{color} | {color:red} patch {color} | {color:red} 0m 6s{color}
| {color:red} MAPREDUCE-7029 does not apply to trunk. Rebase required? Wrong
Branch? See https://wiki.apache.org/hadoop/HowToContribute for help. {color} |
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|| Subsystem || Report/Notes ||
| JIRA Issue | MAPREDUCE-7029 |
| JIRA Patch URL |
https://issues.apache.org/jira/secure/attachment/12905510/MAPREDUCE-7029.003.patch
|
| Console output |
https://builds.apache.org/job/PreCommit-MAPREDUCE-Build/7282/console |
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This message was automatically generated.
> FileOutputCommitter#commitTask should delete task directory
> -----------------------------------------------------------
>
> Key: MAPREDUCE-7029
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-7029
> Project: Hadoop Map/Reduce
> Issue Type: Improvement
> Affects Versions: 2.8.2
> Environment: - Google Cloud Storage (with the GCS connector:
> https://github.com/GoogleCloudPlatform/bigdata-interop/tree/master/gcs) for
> HCFS compatibility.
> - FileOutputCommitter algorithm v2.
> - Running on Google Compute Engine with Java 8, Debian 8, Hadoop 2.8.2, Spark
> 2.2.0.
> Reporter: Karthik Palaniappan
> Priority: Minor
> Attachments: MAPREDUCE-7029.001.patch, MAPREDUCE-7029.002.patch,
> MAPREDUCE-7029.003.patch
>
>
> I ran a Spark job that outputs thousands of parquet files (aka there are
> thousands of reducers), and it hung for several minutes in the driver after
> all tasks were complete. Here is a very simple repro of the job (to be run in
> a spark-shell):
> {code:scala}
> spark.range(1L << 20).repartition(1 << 14).write.save("gs://some/path")
> {code}
> Spark actually calls into Mapreduce's FileOuputCommitter. Job committing
> (specifically cleanupJob()) recursively deletes the job temporary directory,
> which is something like "gs://some/path/_temporary". If I understand
> correctly, on HDFS, this would be O(1), but on GCS (and every HCFS I know),
> this requires a full file tree walk. Deleting tens of thousands of objects in
> GCS takes several minutes.
> I propose that commitTask() recursively deletes its the task attempt temp
> directory (something like "gs://some/path/_temporary/attempt1/task1"). On
> HDFS, this is O(1) per task, so this is very little overhead per task. On GCS
> (and other HCFSs), this adds parallelism for deleting the job temp directory.
> With the attached patch, the repro above went from taking ~10 minutes to
> taking ~5 minutes, and task time did not significantly change.
> Side note: I found this issue with Spark, but I assume it applies to a
> Mapreduce job with thousands of reducers as well.
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