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Date: Thu, 3 Mar 2016 01:03:18 +0000 (UTC)
From: "Enis Soztutar (JIRA)" <jira@apache.org>
To: issues@hbase.apache.org
Message-ID: <JIRA.12946022.1456886194000.202296.1456966998442@Atlassian.JIRA>
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 <JIRA.12946022.1456886194540@arcas>
Subject: [jira] [Commented] (HBASE-15376) ScanNext metric is size-based
 while every other per-operation metric is time based
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    [ https://issues.apache.org/jira/browse/HBASE-15376?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15176876#comment-15176876 ] 

Enis Soztutar commented on HBASE-15376:
---------------------------------------

Can you also change the ScanNext histograms to be size-based by calling newSizeHistogram() 
{code}
    scanNextHisto = getMetricsRegistry().newTimeHistogram(SCAN_NEXT_KEY);
{code}

> ScanNext metric is size-based while every other per-operation metric is time based
> ----------------------------------------------------------------------------------
>
>                 Key: HBASE-15376
>                 URL: https://issues.apache.org/jira/browse/HBASE-15376
>             Project: HBase
>          Issue Type: Sub-task
>            Reporter: Enis Soztutar
>         Attachments: HBASE-15376.patch
>
>
> We have per-operation metrics for {{Get}}, {{Mutate}}, {{Delete}}, {{Increment}}, and {{ScanNext}}. 
> The metrics are emitted like: 
> {code}
>    "Get_num_ops" : 4837505,
>     "Get_min" : 0,
>     "Get_max" : 296,
>     "Get_mean" : 0.2934618155433431,
>     "Get_median" : 0.0,
>     "Get_75th_percentile" : 0.0,
>     "Get_95th_percentile" : 1.0,
>     "Get_99th_percentile" : 1.0,
> ...
>     "ScanNext_num_ops" : 194705,
>     "ScanNext_min" : 0,
>     "ScanNext_max" : 18441,
>     "ScanNext_mean" : 7468.274651395701,
>     "ScanNext_median" : 583.0,
>     "ScanNext_75th_percentile" : 583.0,
>     "ScanNext_95th_percentile" : 13481.0,
>     "ScanNext_99th_percentile" : 13481.0,
> {code}
> The problem is that all of Get,Mutate,Delete,Increment,Append,Replay are time based tracking how long the operation ran, while ScanNext is tracking returned response sizes (returned cell-sizes to be exact). Obviously, this is very confusing and you would only know this subtlety if you read the metrics collection code. 
> Not sure how useful is the ScanNext metric as it is today. We can deprecate it, and introduce a time based one to keep track of scan request latencies. 
> ps. Shamelessly using the parent jira (since these seem relavant). 


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