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From "dhruba borthakur (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-1377) Creation time and modification time for hadoop files and directories
Date Fri, 22 Jun 2007 21:59:26 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-1377?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12507527

dhruba borthakur commented on HADOOP-1377:

Ok, I agree. let's submit this patch with Modification Time only (no Creation Time). And it
saves us 8 bytes per file on the NameNode!


> Creation time and modification time for hadoop files and directories
> --------------------------------------------------------------------
>                 Key: HADOOP-1377
>                 URL: https://issues.apache.org/jira/browse/HADOOP-1377
>             Project: Hadoop
>          Issue Type: New Feature
>          Components: dfs
>            Reporter: dhruba borthakur
>            Assignee: dhruba borthakur
>             Fix For: 0.14.0
>         Attachments: 1377-noctime.patch, 1377.patch, CreationModificationTime.html, CreationTime8.patch
> This issue will document the requirements, design and implementation of creation times
and modification times of hadoop files and directories.
> My proposal is to have support two additional attributes for each file and directory
in HDFS. The "creation time" is the time when the file/directory was created. It is a 8 byte
integer stored in each FSDirectory.INode. The "modification time" is the time when the last
modification occured to the file/directory. It is an 8 byte integer stored in the FSDirectory.INode.
These two fields are stored in in the FSEdits and FSImage as part of the transaction that
created the file/directory.
> My current proposal is to not support "access time" for a file/directory. It is costly
to implement and current applications might not need it.
> In the current implementation, the "modification time" for a file will be same as its
creation time because HDFS files are currently unmodifiable. Setting file attributes (e.g.
setting the replication factor) of a file does not modify the "modification time" of that
file. The "modification time" for a directory is either its creation time or the time when
the most recent file-delete or file-create occured in that directory.
> A new command named "hadoop dfs -lsl" will display the creation time and modification
time of the files/directories that it lists. The output of the existing command "hadoop dfs
-ls" will not be affected.
> The ClientProtocol will change because DFSFileInfo will have two additional fields: the
creation time and modification time of the file that it represents. This information can be
retrieved by clients thorugh the ClientProtocol.getListings() method. The FileSystem public
API will have two additional methods: getCreationTime and getModificationTime().
> The datanodes are completely transparent to this design and implementation and requires
no change.

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