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https://issues.apache.org/jira/browse/HADOOP-17531?focusedWorklogId=559854&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-559854
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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 08:41
Start Date: 02/Mar/21 08:41
Worklog Time Spent: 10m
Work Description: ayushtkn commented on a change in pull request #2732:
URL: https://github.com/apache/hadoop/pull/2732#discussion_r585357165
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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:
Thanx @jojochuang for having a look.
Yes, It indeed isn't meant for object stores, I am trying a multi threaded
approach for object stores too as part of HADOOP-17558, that won't be too much
memory efficient, but still find a balance between speed and memory. I have a
WIP patch for that as well, will share that on the jira
This is basically for HDFS or FS where listing is not slow, but there are
memory constraints, my scenario is basically for DR, where it is in general
HDFS->HDFS or HDFS->S3
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Issue Time Tracking
-------------------
Worklog Id: (was: 559854)
Time Spent: 40m (was: 0.5h)
> 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: 40m
> 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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