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From "dhruba borthakur (JIRA)" <j...@apache.org>
Subject [jira] Created: (HADOOP-1377) Creation time and modification time for hadoop files and directories
Date Wed, 16 May 2007 16:50:16 GMT
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
            Reporter: dhruba borthakur
         Assigned To: dhruba borthakur

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

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