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https://issues.apache.org/jira/browse/HADOOP-13704?focusedWorklogId=724563&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-724563
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ASF GitHub Bot logged work on HADOOP-13704:
-------------------------------------------
Author: ASF GitHub Bot
Created on: 10/Feb/22 15:21
Start Date: 10/Feb/22 15:21
Worklog Time Spent: 10m
Work Description: ahmarsuhail opened a new pull request #3978:
URL: https://github.com/apache/hadoop/pull/3978
### Description of PR
JIRA: https://issues.apache.org/jira/browse/HADOOP-13704
This PR implements an optimised version of getContentSummary which uses the
result from the listFiles iterator.
Explanation of new `buildDirectorySet` method added:
Since the listFiles operation can return the directory `a/b/c` as a single
object, we need to recurse over the path `a/b/c` to ensure we have counted all
directories. We do this by keeping two sets, dirSet (Set of all directories
under the base path) and pathTraversed (Set of paths we have recursed over so
far).
Iterating over directory structure `basePath/a/b/c`, `basePath/a/b/d`, we
will first find all the directories in `basePath/a/b/c`. Once this is
completed, the pathTraversed set will have `{basePath/a/b}` and dirSet will
have `{basePath/a, basePath/a/b, basePath/a/b/c}`.
Then for `basePath/a/b/d`, just add `basePath/a/b/d` to the dirSet and don't
do any additional work as path `basePath/a/b` has already been traversed.
The Jira ticket mentions that we should add in some instrumentation to
measure usage. T's already code that does this
[here](https://github.com/apache/hadoop/blob/trunk/hadoop-tools/hadoop-aws/src/main/java/org/apache/hadoop/fs/s3a/S3AFileSystem.java#L3256)and
usage is tested in an integration test
[here](https://github.com/apache/hadoop/blob/trunk/hadoop-tools/hadoop-aws/src/test/java/org/apache/hadoop/fs/s3a/performance/ITestS3AMiscOperationCost.java#L144)
.
### How was this patch tested?
Tested in eu-west-1 by running
`mvn -Dparallel-tests -DtestsThreadCount=16 clean verify`
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Issue Time Tracking
-------------------
Worklog Id: (was: 724563)
Remaining Estimate: 0h
Time Spent: 10m
> S3A getContentSummary() to move to listFiles(recursive) to count children;
> instrument use
> -----------------------------------------------------------------------------------------
>
> Key: HADOOP-13704
> URL: https://issues.apache.org/jira/browse/HADOOP-13704
> Project: Hadoop Common
> Issue Type: Sub-task
> Components: fs/s3
> Affects Versions: 2.8.0
> Reporter: Steve Loughran
> Priority: Minor
> Time Spent: 10m
> Remaining Estimate: 0h
>
> Hive and a bit of Spark use {{getContentSummary()}} to get some summary stats
> of a filesystem. This is very expensive on S3A (and any other object store),
> especially as the base implementation does the recursive tree walk.
> Because of HADOOP-13208, we have a full enumeration of files under a path
> without directory costs...S3A can/should switch to this to speed up those
> places where the operation is called.
> Also
> * API call needs FS spec and contract tests
> * S3A could instrument invocation, so as to enable real-world popularity to
> be measured
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