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https://issues.apache.org/jira/browse/HDFS-3743?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14588342#comment-14588342
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Jian Fang commented on HDFS-3743:
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Any progress on this Jira? The JN auto format is critical to run hadoop as a
service in a cloud environment because there is no system admin to work on the
replacement node and everything is automated. If the patch is not available
now, what would be the workaround for this issue in an automatic fashion?
> QJM: improve formatting behavior for JNs
> ----------------------------------------
>
> Key: HDFS-3743
> URL: https://issues.apache.org/jira/browse/HDFS-3743
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Affects Versions: QuorumJournalManager (HDFS-3077)
> Reporter: Todd Lipcon
> Assignee: Todd Lipcon
>
> Currently, the JournalNodes automatically format themselves when a new writer
> takes over, if they don't have any data for that namespace. However, this has
> a few problems:
> 1) if the administrator accidentally points a new NN at the wrong quorum (eg
> corresponding to another cluster), it will auto-format a directory on those
> nodes. This doesn't cause any data loss, but would be better to bail out with
> an error indicating that they need to be formatted.
> 2) if a journal node crashes and needs to be reformatted, it should be able
> to re-join the cluster and start storing new segments without having to fail
> over to a new NN.
> 3) if 2/3 JNs get accidentally reformatted (eg the mount point becomes
> undone), and the user starts the NN, it should fail to start, because it may
> end up missing edits. If it auto-formats in this case, the user might have
> silent "rollback" of the most recent edits.
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