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https://issues.apache.org/jira/browse/HADOOP-12837?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15163409#comment-15163409
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Chris Nauroth commented on HADOOP-12837:
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Hello [~jagdishk].
Is this referring to a directory or a file? If it's a directory, then s3n
always returns 0 for mtime. This is also true of s3a. I don't believe there
are currently any plans in progress to change this behavior.
The expected atomicity semantics of implementing directory mtime are more
challenging to implement against a blob store compared to a traditional file
system or HDFS. If a new file or sub-directory gets created under a directory,
then users have an expectation that the corresponding update to mtime at the
parent folder is atomic with respect to the file/directory creation operation.
On HDFS, we can take a central lock at the NameNode to do all of the metadata
manipulations as a transaction. For a blob store, this is multiple HTTP
operations on different blob keys, and those multiple operations do not execute
as an atomic transaction.
The Azure file system does provide mtime on directories, but it does not
provide atomicity of the mtime updates. (I just mention this to demonstrate
that the behavior is not always consistent across different file system
implementations.)
> FileStatus.getModificationTime not working on S3
> ------------------------------------------------
>
> Key: HADOOP-12837
> URL: https://issues.apache.org/jira/browse/HADOOP-12837
> Project: Hadoop Common
> Issue Type: Bug
> Components: fs/s3
> Reporter: Jagdish Kewat
>
> Hi Team,
> We have observed an issue with the FileStatus.getModificationTime() API on S3
> filesystem. The method always returns 0.
> I googled for this however couldn't find any solution as such which would fit
> in my scheme of things. S3FileStatus seems to be an option however I would be
> using this API on HDFS as well as S3 both so can't go for it.
> I tried to run the job on:
> * Release label:emr-4.2.0
> * Hadoop distribution:Amazon 2.6.0
> * Hadoop Common jar: hadoop-common-2.6.0.jar
> Please advise if any patch or fix available for this.
> Thanks,
> Jagdish
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