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https://issues.apache.org/jira/browse/HDFS-6982?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14196664#comment-14196664
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Maysam Yabandeh commented on HDFS-6982:
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Let me take an example.
Time period: 60 seconds
Bucket duration: 20 seconds
Bucket/window = 3
Event1: time 00:10:55
Current time: 00:11:03
Current sum for the past window (1 min) = 1
Event2: time 00:11:54
Current time: 00:12:07
Current sum for the past window (1 min) = 1
Now for this behavior to be implemented correctly we need to zero the content
of the bucket number 3 because both Event1 and Event2 map to the same bucket
but Event1 is irrelevant at time 00:12:07 since it happened before the last 60
seconds.
Makes 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, HDFS-6982.v3.patch,
> HDFS-6982.v4.patch, HDFS-6982.v5.patch, HDFS-6982.v6.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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