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https://issues.apache.org/jira/browse/HDFS-8929?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14734747#comment-14734747
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Vinayakumar B commented on HDFS-8929:
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Changes looks great.
Just one more improvement in Test.
Timestamp update can be verified after sending every edits in
TestJournalNode#testJournal().
+1 once addressed.
> Add a metric to expose the timestamp of the last journal
> --------------------------------------------------------
>
> Key: HDFS-8929
> URL: https://issues.apache.org/jira/browse/HDFS-8929
> Project: Hadoop HDFS
> Issue Type: New Feature
> Components: journal-node
> Reporter: Akira AJISAKA
> Assignee: Surendra Singh Lilhore
> Attachments: HDFS-8929-001.patch, HDFS-8929-002.patch,
> HDFS-8929-003.patch
>
>
> If there are three JNs and only one JN is failing to journal, we can detect
> it by monitoring the difference of the last written transaction id among JNs
> from NN WebUI or JN metrics. However, it's difficult to define the threshold
> to alert because the increase rate of the number of transaction depends on
> how busy the cluster is. Therefore I'd like to propose a metric to expose the
> timestamp of the last journal. That way we can easily alert if a JN is
> failing to journal for some fixed period.
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