[jira] [Updated] (MAPREDUCE-6919) ShuffleMetrics.ShuffleConnections Gauge Metric Rises Infinitely

["Erik Krogen (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/MAPREDUCE-6919?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Erik Krogen updated MAPREDUCE-6919:
-----------------------------------
    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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