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https://issues.apache.org/jira/browse/HADOOP-1869?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12626806#action_12626806
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dhruba borthakur commented on HADOOP-1869:
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Ok, from Raghu's and Konstantin's comments, I guess nobody is stuck on how the
API looks like. Whether it is setAccessTime() or utimes(), everybody is ok with
it. It appears that both Raghu and Konstantin are +1 on this one. Please let me
know if this is not the case.
The point that is being discussed is whether utimes/setAccessTime allows
setting the time to any user-specified value or whether it sets it to current
time on namenode. I still vote for allowing an user to set any access time...
this is what POSIX does and it allows restore utilities to use a standard API.
From Raghu's comments, it appears to me that he is +1 on it too.
>So to me it makes more sense to introduce a new create method with FileStatus
>of the existing file as a parameter or a
> copy method with an option to replicate FileStatus fields.
I do not like the idea of having a custom API as described above.
> access times of HDFS files
> --------------------------
>
> Key: HADOOP-1869
> URL: https://issues.apache.org/jira/browse/HADOOP-1869
> Project: Hadoop Core
> Issue Type: New Feature
> Components: dfs
> Reporter: dhruba borthakur
> Assignee: dhruba borthakur
> Fix For: 0.19.0
>
> Attachments: accessTime1.patch, accessTime4.patch, accessTime5.patch
>
>
> HDFS should support some type of statistics that allows an administrator to
> determine when a file was last accessed.
> Since HDFS does not have quotas yet, it is likely that users keep on
> accumulating files in their home directories without much regard to the
> amount of space they are occupying. This causes memory-related problems with
> the namenode.
> Access times are costly to maintain. AFS does not maintain access times. I
> thind DCE-DFS does maintain access times with a coarse granularity.
> One proposal for HDFS would be to implement something like an "access bit".
> 1. This access-bit is set when a file is accessed. If the access bit is
> already set, then this call does not result in a transaction.
> 2. A FileSystem.clearAccessBits() indicates that the access bits of all files
> need to be cleared.
> An administrator can effectively use the above mechanism (maybe a daily cron
> job) to determine files that are recently used.
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