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From "Hadoop QA (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-1869) access times of HDFS files
Date Fri, 05 Sep 2008 05:43:44 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-1869?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12628554#action_12628554
] 

Hadoop QA commented on HADOOP-1869:
-----------------------------------

-1 overall.  Here are the results of testing the latest attachment 
  http://issues.apache.org/jira/secure/attachment/12389459/accessTime6.patch
  against trunk revision 692287.

    +1 @author.  The patch does not contain any @author tags.

    +1 tests included.  The patch appears to include 4 new or modified tests.

    +1 javadoc.  The javadoc tool did not generate any warning messages.

    +1 javac.  The applied patch does not increase the total number of javac compiler warnings.

    -1 findbugs.  The patch appears to introduce 10 new Findbugs warnings.

    -1 core tests.  The patch failed core unit tests.

    +1 contrib tests.  The patch passed contrib unit tests.

Test results: http://hudson.zones.apache.org/hudson/job/Hadoop-Patch/3181/testReport/
Findbugs warnings: http://hudson.zones.apache.org/hudson/job/Hadoop-Patch/3181/artifact/trunk/build/test/findbugs/newPatchFindbugsWarnings.html
Checkstyle results: http://hudson.zones.apache.org/hudson/job/Hadoop-Patch/3181/artifact/trunk/build/test/checkstyle-errors.html
Console output: http://hudson.zones.apache.org/hudson/job/Hadoop-Patch/3181/console

This message is automatically generated.

> 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, accessTime6.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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