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https://issues.apache.org/jira/browse/HADOOP-17531?focusedWorklogId=559843&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-559843
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ASF GitHub Bot logged work on HADOOP-17531:
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Author: ASF GitHub Bot
Created on: 02/Mar/21 07:38
Start Date: 02/Mar/21 07:38
Worklog Time Spent: 10m
Work Description: jojochuang commented on a change in pull request #2732:
URL: https://github.com/apache/hadoop/pull/2732#discussion_r585324372
##########
File path: hadoop-tools/hadoop-distcp/src/site/markdown/DistCp.md.vm
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@@ -362,6 +362,7 @@ Command Line Options
| `-copybuffersize <copybuffersize>` | Size of the copy buffer to use. By
default, `<copybuffersize>` is set to 8192B | |
| `-xtrack <path>` | Save information about missing source files to the
specified path. | This option is only valid with `-update` option. This is an
experimental property and it cannot be used with `-atomic` option. |
| `-direct` | Write directly to destination paths | Useful for avoiding
potentially very expensive temporary file rename operations when the
destination is an object store |
+| `-useIterator` | Uses single threaded listStatusIterator to build listing |
Useful for saving memory at the client side. |
Review comment:
Does it implicitly void -numListstatusThreads? sounds like a bad new for
running distcp on cloud storage where latency is big.
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Issue Time Tracking
-------------------
Worklog Id: (was: 559843)
Time Spent: 0.5h (was: 20m)
> DistCp: Reduce memory usage on copying huge directories
> -------------------------------------------------------
>
> Key: HADOOP-17531
> URL: https://issues.apache.org/jira/browse/HADOOP-17531
> Project: Hadoop Common
> Issue Type: Improvement
> Reporter: Ayush Saxena
> Priority: Critical
> Labels: pull-request-available
> Attachments: MoveToStackIterator.patch, gc-NewD-512M-3.8ML.log
>
> Time Spent: 0.5h
> Remaining Estimate: 0h
>
> Presently distCp, uses the producer-consumer kind of setup while building the
> listing, the input queue and output queue are both unbounded, thus the
> listStatus grows quite huge.
> Rel Code Part :
> https://github.com/apache/hadoop/blob/trunk/hadoop-tools/hadoop-distcp/src/main/java/org/apache/hadoop/tools/SimpleCopyListing.java#L635
> This goes on bredth-first traversal kind of stuff(uses queue instead of
> earlier stack), so if you have files at lower depth, it will like open up the
> entire tree and the start processing....
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