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From "Doug Cutting (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-6382) HDFS File/Directory TTL
Date Fri, 18 Jul 2014 16:48:07 GMT

    [ https://issues.apache.org/jira/browse/HDFS-6382?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14066507#comment-14066507
] 

Doug Cutting commented on HDFS-6382:
------------------------------------

bq. But the trash emptier runs inside NN as a daemon thread, instead of a separate daemon
process.

The trash emptier was embedded in the NN mostly just to avoid making folks have to manage
another daemon process.  However, embedding the emptier has many of the hazards that Chris
and Colin described above for embedding TTL.  So, if we add a separate daemon process for
TTL, then we might also have that process empty the trash and remove the embedded emptier.

> 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
>            Assignee: Zesheng Wu
>         Attachments: HDFS-TTL-Design -2.pdf, HDFS-TTL-Design-3.pdf, HDFS-TTL-Design.pdf
>
>
> 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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