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https://issues.apache.org/jira/browse/HDFS-4739?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Aaron T. Myers updated HDFS-4739:
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Attachment: HDFS-4739.patch
Attached patch fixes the issue by:
# Discounting truly required segments from the calculation of which segments to
purge.
# Fixing an OBO error which made the original test case appear to work properly.
> NN can miscalculate the number of extra edit log segments to retain
> -------------------------------------------------------------------
>
> Key: HDFS-4739
> URL: https://issues.apache.org/jira/browse/HDFS-4739
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: namenode
> Affects Versions: 2.0.4-alpha
> Reporter: Aaron T. Myers
> Assignee: Aaron T. Myers
> Attachments: HDFS-4739.patch
>
>
> The code in NNStorageRetentionManager#purgeOldStorage is intended to place a
> cap on the number of _extra_ edit log segments retained beyond what is
> strictly required to replay the FS history since the last fsimage. In fact
> this code currently places a limit on the _total_ number of extra edit log
> segments. If the number of required segments is greater than the configured
> cap, there will be no data loss, but an ugly error will be thrown and the NN
> will fail to start.
> The fix is simple, and in the meantime a work-around is just to raise the
> value of dfs.namenode.max.extra.edits.segments.retained and start the NN.
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