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Harsh J commented on HDFS-7501: ------------------------------- [~daryn] - Just wanted to check if exposing out and using the lastLoadedTxnId from the EditLogTailer instead in StandbyNN mode would be OK to do instead? > 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.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. -- This message was sent by Atlassian JIRA (v6.3.4#6332)