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From "Hudson (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-7501) TransactionsSinceLastCheckpoint can be negative on SBNs
Date Sun, 29 Mar 2015 13:20:53 GMT

    [ https://issues.apache.org/jira/browse/HDFS-7501?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14385762#comment-14385762
] 

Hudson commented on HDFS-7501:
------------------------------

FAILURE: Integrated in Hadoop-Mapreduce-trunk-Java8 #147 (See [https://builds.apache.org/job/Hadoop-Mapreduce-trunk-Java8/147/])
HDFS-7501. TransactionsSinceLastCheckpoint can be negative on SBNs. Contributed by Gautam
Gopalakrishnan. (harsh: rev 3d9132d434c39e9b6e142e5cf9fd7a8afa4190a6)
* hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSNamesystem.java
* hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt
* hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/metrics/TestNameNodeMetrics.java


> 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
>             Fix For: 2.8.0
>
>         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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