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https://issues.apache.org/jira/browse/MAPREDUCE-6919?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Erik Krogen updated MAPREDUCE-6919:
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Attachment: mapred_ShuffleMetrics_ShuffleConnections.png
> ShuffleMetrics.ShuffleConnections Gauge Metric Rises Infinitely
> ---------------------------------------------------------------
>
> Key: MAPREDUCE-6919
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-6919
> Project: Hadoop Map/Reduce
> Issue Type: Bug
> Components: mrv2
> Reporter: Erik Krogen
> Attachments: mapred_ShuffleMetrics_ShuffleConnections.png
>
>
> We recently noticed that the mapred.ShuffleMetrics.ShuffleConnections metric
> rises indefinitely (see attached graph), despite supposedly being a gauge
> measuring the number of currently open connections:
> {code:title=ShuffleHandler.java}
> @Metric("# of current shuffle connections")
> MutableGaugeInt shuffleConnections;
> {code}
> It seems this is because the metric is incremented once for each map file
> sent, but decremented once for each request. Thus a request which fetches
> multiple map files permanently increments shuffleConnections by (mapsFetched
> - 1).
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