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https://issues.apache.org/jira/browse/HADOOP-17306?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17228567#comment-17228567
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Vinayakumar B commented on HADOOP-17306:
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Hi [~Jim_Brennan], Thanks for pointing to test failures.
AFAIK, test failures are due to setting timestamp of {{LocalResource}} with
value returned by {{File.lastModified()}} all in test code explicitly for the
scriptfile used for tests. As mentioned in this Jira title,
{{File.lastModified()}} is broken and looses accuracy. I tried replacing
{{File.lastModified()}} calls with
{{Files.getLastModifiedTime(file.toPath()).toMillis()}}, all tests passed.
AM's sets the timestamp using the value returned by
{{FileStatus#getModifiedTime()}} in which case, it will be consistent. So I
dont think any problem with the production code as long as
{{FileStatus#getModificationTime()}} is used.
As Steve mentioned, relying on modificationTime and length may not be a good
idea to detect changes. There could be possibilities of corruption
> RawLocalFileSystem's lastModifiedTime() looses milli seconds in JDK < 10.b09
> ----------------------------------------------------------------------------
>
> Key: HADOOP-17306
> URL: https://issues.apache.org/jira/browse/HADOOP-17306
> Project: Hadoop Common
> Issue Type: Bug
> Components: fs
> Reporter: Vinayakumar B
> Assignee: Vinayakumar B
> Priority: Major
> Labels: pull-request-available
> Time Spent: 1h 40m
> Remaining Estimate: 0h
>
> RawLocalFileSystem's FileStatus uses {{File.lastModified()}} api from JDK.
> This api looses milliseconds due to JDK bug.
> [https://bugs.java.com/bugdatabase/view_bug.do?bug_id=8177809]
> This bug fixed in JDK 10 b09 onwards and still exists in JDK 8 which is still
> being used in many productions.
> Apparently, {{Files.getLastModifiedTime()}} from java's nio package returns
> correct time.
> Use {{Files.getLastModifiedTime()}} instead of {{File.lastModified}} as
> workaround.
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