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https://issues.apache.org/jira/browse/HDFS-7501?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Harsh J updated HDFS-7501:
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Attachment: HDFS-7501-3.patch
I went ahead and modified the patch with the suggested change above, and also
added some indent cleanup + comments to the great test written there (aside of
the fix to the test as required for the new changes).
New test fails as expected without the fix, and passes all 3 criterion with the
fix.
Attaching and marking as Patch Available to run full module tests via jenkins.
> TransactionsSinceLastCheckpoint can be negative on SBNs
> -------------------------------------------------------
>
> Key: HDFS-7501
> URL: https://issues.apache.org/jira/browse/HDFS-7501
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: namenode
> Affects Versions: 2.5.0
> Reporter: Harsh J
> Assignee: Gautam Gopalakrishnan
> Priority: Trivial
> Attachments: HDFS-7501-2.patch, HDFS-7501-3.patch, HDFS-7501.patch
>
>
> The metric TransactionsSinceLastCheckpoint is derived as FSEditLog.txid minus
> NNStorage.mostRecentCheckpointTxId.
> In Standby mode, the former does not increment beyond the loaded or
> last-when-active value, but the latter does change due to checkpoints done
> regularly in this mode. Thereby, the SBN will eventually end up showing
> negative values for TransactionsSinceLastCheckpoint.
> This is not an issue as the metric only makes sense to be monitored on the
> Active NameNode, but we should perhaps just show the value 0 by detecting if
> the NN is in SBN form, as allowing a negative number is confusing to view
> within a chart that tracks it.
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