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From "Lohit Vijayarenu (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-6982) nntop: top­-like tool for name node users
Date Fri, 12 Sep 2014 23:18:35 GMT

    [ https://issues.apache.org/jira/browse/HDFS-6982?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14132282#comment-14132282
] 

Lohit Vijayarenu commented on HDFS-6982:
----------------------------------------

To add to what [~maysamyabandeh] already added, our initial though was that if we can aggregate
this kind of information within NameNode, then we could do throttling kind of feature on per
user/rpc basis. This would be a feedback tool for auto-tuning within NameNode. There was also
thoughts around having hot paths on similar lines which could be used by Replication manager
possibly. So, having this within NameNode makes lot of sense. 

> nntop: top­-like tool for name node users
> -----------------------------------------
>
>                 Key: HDFS-6982
>                 URL: https://issues.apache.org/jira/browse/HDFS-6982
>             Project: Hadoop HDFS
>          Issue Type: New Feature
>            Reporter: Maysam Yabandeh
>            Assignee: Maysam Yabandeh
>         Attachments: HDFS-6982.patch, HDFS-6982.v2.patch, nntop-design-v1.pdf
>
>
> In this jira we motivate the need for nntop, a tool that, similarly to what top does
in Linux, gives the list of top users of the HDFS name node and gives insight about which
users are sending majority of each traffic type to the name node. This information turns out
to be the most critical when the name node is under pressure and the HDFS admin needs to know
which user is hammering the name node and with what kind of requests. Here we present the
design of nntop which has been in production at Twitter in the past 10 months. nntop proved
to have low cpu overhead (< 2% in a cluster of 4K nodes), low memory footprint (less than
a few MB), and quite efficient for the write path (only two hash lookup for updating a metric).



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