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https://issues.apache.org/jira/browse/HDFS-6382?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14018506#comment-14018506
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Hangjun Ye commented on HDFS-6382:
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Thanks Colin. We would start to draft a design doc and ask you guys' help to
review.
Yes, the xattrs has saved the big burden for saving the policy, the major
question left is where to run the logic.
Besides these 3 options, another related stuff might be the "trash". Currently
trash is implemented as a client-side capability, the trash cleanup logic
(trash emptier) depends on FileSystem to operate namespace and basically is a
client-side function. But the trash emptier runs *inside* NN as a daemon
thread, instead of a separate daemon process. I guess it interacts with NN via
RPC even it runs inside NN.
We could observe some similarities of trash, balancer, and the proposed TTL:
mainly need data from NN; could be implemented as client-side capability (via
RPC); need to be run periodically. So if possible we unify all these stuff in
one framework/daemon? It also echos Haohui's points earlier. And if it's
implemented clearly enough, the user could optionally run it inside NN as a
daemon thread to have less jobs to maintain, as long as the user would like to
take the risk of running additional logic inside NN (w/o changing NN's logic
for this, as it still interacts with NN like a client).
That's just a premature idea, we might still want to have the TTL as a separate
daemon firstly as it's most straight forward. Let's discuss more after we have
the design doc.
> 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
>
> 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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