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https://issues.apache.org/jira/browse/HDFS-12626?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16199303#comment-16199303
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Chen Liang commented on HDFS-12626:
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There are definitely different ways to handle this, but the simpler solution
I'm thinking is that, simply having a thread that periodically checks all the
open key entries, if they have been there for a very long time, say, more than
X hours, we treat them as dead entries and remove them. The tricky thing is
what this X should be. Because if X is too small, then the client might still
be writing after X hours. Basically, X should be longer than the time any
single key write would take. Here I'm thinking of something like X = 24 hours.
Because I don't see a use case where a single key write would take this long
(maybe I'm wrong). Also, since I assume client crash is relatively rare so the
number of dead entries shouldn't be too large, so it should be okay to reclaim
them only once every day.
Any thoughts? [~xyao] [~anu]
> Ozone : delete open key entries that will no longer be closed
> -------------------------------------------------------------
>
> Key: HDFS-12626
> URL: https://issues.apache.org/jira/browse/HDFS-12626
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Reporter: Chen Liang
> Assignee: Chen Liang
>
> HDFS-12543 introduced the notion of "open key" where when a key is opened, an
> open key entry gets persisted, only after client calls a close will this
> entry be made visible. One issue is that if the client does not call close
> (e.g. failed), then that open key entry will never be deleted from meta data.
> This JIRA tracks this issue.
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