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https://issues.apache.org/jira/browse/HDFS-5709?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13862066#comment-13862066
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Andrew Wang commented on HDFS-5709:
-----------------------------------
These are good points. I agree that we shouldn't do a silent rename, and a
mandatory pre-upgrade tool isn't a great option either. However, making the
user ls -R and rename everything is still a pretty big hassle. After the
rename, I think you'd also need to saveNamespace on both NNs to flush any
references to .snapshot in the edit log.
Maybe we could have a config option (by default unset) that will rename a
reserved path on upgrade to a user-provided one. Something like
{{dfs.namenode.upgrade.rename.reserved.snapshot=.user-snapshot}}. If we need
more complex behavior, we could even do something with path globbing.
This also might not be the last time we want to add a new reserved path, so it
seems worth having a better upgrade story for the future.
> Improve upgrade with existing files and directories named ".snapshot"
> ---------------------------------------------------------------------
>
> Key: HDFS-5709
> URL: https://issues.apache.org/jira/browse/HDFS-5709
> Project: Hadoop HDFS
> Issue Type: Improvement
> Components: namenode
> Affects Versions: 3.0.0, 2.2.0
> Reporter: Andrew Wang
> Labels: snapshots, upgrade
>
> Right now in trunk, upgrade fails messily if the old fsimage or edits refer
> to a directory named ".snapshot". We should at least print a better error
> message (which I believe was the original intention in HDFS-4666), and [~atm]
> proposed automatically renaming these files and directories.
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