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https://issues.apache.org/jira/browse/HDFS-6382?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14010734#comment-14010734
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Hangjun Ye commented on HDFS-6382:
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Implementing it outside NN is definitely another option, and I agree with Colin
that it's not feasible to implement a complex clean up policy (like based on
storage space) inside NN.
TTL is a very simple (but general) policy and we might even consider it as an
attribute of file, like the number of replicas. Seems it wouldn't introduce
much complexity to handle it in the NN.
Another benefit to having it inside NN is we don't have to handle the
authentication/authorization problem in a separate system. For example we have
a shared HDFS cluster for many internal users, we don't want someone to set TTL
policy to other one's files. NN could handle it easily by its own
authentication/authorization mechanism.
So far a TTL-based clean up policy is good enough for our scenario (Zesheng and
I are from the same company and we are supporting our company's internal usage
for Hadoop) and it's would be nice to have a simple and workable solution in
HDFS.
> 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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