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From "Andrew Wang (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-6688) Hadoop JMX stats are not refreshed
Date Tue, 15 Jul 2014 23:45:11 GMT

    [ https://issues.apache.org/jira/browse/HDFS-6688?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14062875#comment-14062875

Andrew Wang commented on HDFS-6688:

I admit we don't have the greatest (any?) documentation for metrics. Typically I have to dig
around in the code. The stale node feature I don't think has much in the way of docs either,
so if you see a good place to add a mention, we'd happily take a docs patch.

The 10.5 mins is also somewhat configurable. It's calculated from this in DatanodeManager:

    this.heartbeatExpireInterval = 2 * heartbeatRecheckInterval
        + 10 * 1000 * heartbeatIntervalSeconds;

So if you adjust "dfs.namenode.heartbeat.recheck-interval" and "dfs.heartbeat.interval" you
have some control.

> Hadoop JMX stats are not refreshed
> ----------------------------------
>                 Key: HDFS-6688
>                 URL: https://issues.apache.org/jira/browse/HDFS-6688
>             Project: Hadoop HDFS
>          Issue Type: Bug
>         Environment: Ubuntu
>            Reporter: Biju Nair
> Even when the HDFS datanode process is stopped the JMX attribute Hadoop.NameNode.FSNamesystemState.NumLiveDataNodes/NumDeadDataNodes
attribute values doesn't change. Also Hadoop.NameNode.NameNodeInfo.Attributes.LiveNodes shows
the stopped datanode details. If these attributes reflect the actual changes in the datanode,
they can be used to monitor the health of the HDFS cluster which currently can't be used.

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