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https://issues.apache.org/jira/browse/HDFS-4173?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13501379#comment-13501379
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Colin Patrick McCabe commented on HDFS-4173:
--------------------------------------------
bq. so this would cause the NN to initialize the shared edits dir on standby
startup, wouldn't it?
There's an "if" statement like this:
{code}
if (u.getScheme().equals(NNStorage.LOCAL_URI_SCHEME)) {
...
} else {
// format
}
{code}
Since the NFS shared edits directory has a LOCAL_URI_SCHEME (it's a path, after
all), it won't be affected by this change.
The question of whether the SNN and NN will both try to auto-format the same
(QJM-managed) {{JournalNode}} quorum when starting up for the first time is
more concerning. We could hook into {{FSEditLog#initJournalsForWrite}}. In HA
mode, that only gets called later, when a NN becomes active.
> If the NameNode has already been formatted, but a QuroumJournal has not,
> auto-format it on startup
> --------------------------------------------------------------------------------------------------
>
> Key: HDFS-4173
> URL: https://issues.apache.org/jira/browse/HDFS-4173
> Project: Hadoop HDFS
> Issue Type: Improvement
> Components: journal-node, name-node
> Affects Versions: 2.0.3-alpha
> Reporter: Colin Patrick McCabe
> Assignee: Colin Patrick McCabe
> Priority: Minor
> Attachments: HDFS-4173.001.patch
>
>
> If we have multiple edit log directories, and some of them are formatted, but
> others are not, we format the unformatted ones. However, when we implemented
> QuorumJournalManager, we did not extend this behavior to it. It makes sense
> to do this.
> One use case is if you want to add a QuorumJournalManager URI
> ({{journal://}}) to an existing {{NameNode}}, without reformatting
> everything. There is currently no easy way to do this, since {{namenode
> \-format}} will nuke everything, and there's no other way to format the
> {{JournalNodes}}.
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