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From "Zesheng Wu (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-6382) HDFS File/Directory TTL
Date Fri, 16 May 2014 11:43:14 GMT

    [ https://issues.apache.org/jira/browse/HDFS-6382?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13999746#comment-13999746
] 

Zesheng Wu commented on HDFS-6382:
----------------------------------

Thanks [~cnauroth], I agree with your example MapReduce scenario and the risk,  but this risk
can't be avoided even if we use outside tools. For example, we use a nightly cron job just
like Andrew mentioned, imagine a MapReduce job gets submitted, we derive input splits from
a file, and then the file is deleted by the cron job after input split calculation but before
the map tasks start running and reading the blocks, the risk is the same. What I want to declare
is that the TTL is just a convenient way to finish tasks like I described in the proposal,
the users should learn how to use it and use it correctly, rather than use a complicated way
and there's no obvious advantage.

> HDFS File/Directory TTL
> -----------------------
>
>                 Key: HDFS-6382
>                 URL: https://issues.apache.org/jira/browse/HDFS-6382
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>          Components: hdfs-client, namenode
>    Affects Versions: 2.4.0
>            Reporter: Zesheng Wu
>
> In production environment, we always have scenario like this, we want to backup files
on hdfs for some time and then hope to delete these files automatically. For example, we keep
only 1 day's logs on local disk due to limited disk space, but we need to keep about 1 month's
logs in order to debug program bugs, so we keep all the logs on hdfs and delete logs which
are older than 1 month. This is a typical scenario of HDFS TTL. So here we propose that hdfs
can support TTL.
> Following are some details of this proposal:
> 1. HDFS can support TTL on a specified file or directory
> 2. If a TTL is set on a file, the file will be deleted automatically after the TTL is
expired
> 3. If a TTL is set on a directory, the child files and directories will be deleted automatically
after the TTL is expired
> 4. The child file/directory's TTL configuration should override its parent directory's
> 5. A global configuration is needed to configure that whether the deleted files/directories
should go to the trash or not
> 6. A global configuration is needed to configure that whether a directory with TTL should
be deleted when it is emptied by TTL mechanism or not.



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