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https://issues.apache.org/jira/browse/HDFS-6982?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14126180#comment-14126180
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Maysam Yabandeh commented on HDFS-6982:
---------------------------------------

bq. Just to make sure I understand, does it mean that the rolling window 
resides in the separated process instead of in the NN?

Yeah, in the second architecture everything is outside nn: nntop tails the 
audit log files, parses them, aggregates them, and then publishes the top users 
via both a simple web UI and jmx. But just to clarify the attached patch was 
for the first architecture, where nntop is part of the namenode process, and 
directly receives the audit log events by registering as an audit logger.

> 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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