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From "Kihwal Lee (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HADOOP-13742) Expose "NumOpenConnectionsPerUser" as a metric
Date Thu, 10 Nov 2016 22:52:58 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-13742?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15655437#comment-15655437
] 

Kihwal Lee commented on HADOOP-13742:
-------------------------------------

First of all, the use of "Vs" is probably not the best choice. "Vs" is for two comparable
things.

I am wondering whether introducing a separate metrics class is better. (Something similar
to {{RpcDetailedMetrics}})  For typical metrics, a counter is simply incremented and the diff
shows the rate. If users are only interested in instantaneous counts and do not care at all
about cumulative counts, the approach in the patch might be okay.  But I am thinking cumulative
values are useful too.  

If we are to proceed with the proposed approach, I suggest simply synchronize on the lock
object inside {{incrUserConnections()}} and {{decrUserConnections()}} and lose the private
methods. Then no need to have {{AtomicInteger}}.  The ideal way will be range-locking the
map, but I don't know whether there is any known good implementation of it. In any case, the
number of rpc reader threads is typically small, so this level of synchronization/monitor
lock should be okay.

> Expose "NumOpenConnectionsPerUser" as a metric
> ----------------------------------------------
>
>                 Key: HADOOP-13742
>                 URL: https://issues.apache.org/jira/browse/HADOOP-13742
>             Project: Hadoop Common
>          Issue Type: Improvement
>            Reporter: Brahma Reddy Battula
>            Assignee: Brahma Reddy Battula
>         Attachments: HADOOP-13742-002.patch, HADOOP-13742-003.patch, HADOOP-13742-004.patch,
HADOOP-13742.patch
>
>
> To track user level connections( How many connections for each user) in busy cluster
where so many connections to server.



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