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From "Steve Loughran (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HADOOP-15209) DistCp to eliminate needless deletion of files under already-deleted directories
Date Thu, 08 Mar 2018 16:40:00 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-15209?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16391493#comment-16391493

Steve Loughran commented on HADOOP-15209:

FWIW, managed to fail distcp if you run it against an S3 store w/ simulated inconsistency
turned on (no s3guard); operation saw duplicate entries in the directory listing at the destination.
2018-03-08 16:33:17,517 [Thread-131] WARN  mapred.LocalJobRunner (LocalJobRunner.java:run(590))
- job_local148600535_0001
org.apache.hadoop.tools.CopyListing$DuplicateFileException: File s3a://hwdev-steve-frankfurt-new/SLOW/hadoop-auth/src
and s3a://hwdev-steve-frankfurt-new/SLOW/hadoop-auth/src would cause duplicates. Aborting
	at org.apache.hadoop.tools.CopyListing.validateFinalListing(CopyListing.java:175)
	at org.apache.hadoop.tools.CopyListing.buildListing(CopyListing.java:93)
	at org.apache.hadoop.tools.GlobbedCopyListing.doBuildListing(GlobbedCopyListing.java:89)
	at org.apache.hadoop.tools.CopyListing.buildListing(CopyListing.java:86)
	at org.apache.hadoop.tools.mapred.CopyCommitter.listTargetFiles(CopyCommitter.java:575)
	at org.apache.hadoop.tools.mapred.CopyCommitter.deleteMissing(CopyCommitter.java:402)
	at org.apache.hadoop.tools.mapred.CopyCommitter.commitJob(CopyCommitter.java:117)
	at org.apache.hadoop.mapred.LocalJobRunner$Job.run(LocalJobRunner.java:567)
2018-03-08 16:33:18,469 [main] INFO  mapreduce.Job (Job.java:monitorAndPrintJob(1660)) - Job
job_local148600535_0001 failed with state FAILED due to: NA
2018-03-08 16:33:18,478 [main] INFO  mapreduce.Job (Job.java:monitorAndPrintJob(1665)) - Counters:
	File System Counters
		FILE: Number of bytes read=1621092
		FILE: Number of bytes written=1632776
		FILE: Number of read operations=0
		FILE: Number of large read operations=0
		FILE: Number of write operations=0
		S3A: Number of bytes read=0
		S3A: Number of bytes written=895927
		S3A: Number of read operations=1673
		S3A: Number of large read operations=0
		S3A: Number of write operations=904
	Map-Reduce Framework
		Map input records=96

I'm not going to fix that here

> DistCp to eliminate needless deletion of files under already-deleted directories
> --------------------------------------------------------------------------------
>                 Key: HADOOP-15209
>                 URL: https://issues.apache.org/jira/browse/HADOOP-15209
>             Project: Hadoop Common
>          Issue Type: Improvement
>          Components: tools/distcp
>    Affects Versions: 2.9.0
>            Reporter: Steve Loughran
>            Assignee: Steve Loughran
>            Priority: Major
>         Attachments: HADOOP-15209-001.patch, HADOOP-15209-002.patch, HADOOP-15209-003.patch,
HADOOP-15209-004.patch, HADOOP-15209-005.patch, HADOOP-15209-006.patch
> DistCP issues a delete(file) request even if is underneath an already deleted directory.
This generates needless load on filesystems/object stores, and, if the store throttles delete,
can dramatically slow down the delete operation.
> If the distcp delete operation can build a history of deleted directories, then it will
know when it does not need to issue those deletes.
> Care is needed here to make sure that whatever structure is created does not overload
the heap of the process.

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