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Date: Fri, 6 Jul 2012 22:22:35 +0000 (UTC)
From: "Hadoop QA (JIRA)" <jira@apache.org>
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Subject: [jira] [Commented] (HADOOP-8541) Better high-percentile latency
 metrics
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    [ https://issues.apache.org/jira/browse/HADOOP-8541?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13408399#comment-13408399 ] 

Hadoop QA commented on HADOOP-8541:
-----------------------------------

+1 overall.  Here are the results of testing the latest attachment 
  http://issues.apache.org/jira/secure/attachment/12535408/hadoop-8541-3.patch
  against trunk revision .

    +1 @author.  The patch does not contain any @author tags.

    +1 tests included.  The patch appears to include 2 new or modified test files.

    +1 javac.  The applied patch does not increase the total number of javac compiler warnings.

    +1 javadoc.  The javadoc tool did not generate any warning messages.

    +1 eclipse:eclipse.  The patch built with eclipse:eclipse.

    +1 findbugs.  The patch does not introduce any new Findbugs (version 1.3.9) warnings.

    +1 release audit.  The applied patch does not increase the total number of release audit warnings.

    +1 core tests.  The patch passed unit tests in hadoop-common-project/hadoop-common.

    +1 contrib tests.  The patch passed contrib unit tests.

Test results: https://builds.apache.org/job/PreCommit-HADOOP-Build/1177//testReport/
Console output: https://builds.apache.org/job/PreCommit-HADOOP-Build/1177//console

This message is automatically generated.
                
> Better high-percentile latency metrics
> --------------------------------------
>
>                 Key: HADOOP-8541
>                 URL: https://issues.apache.org/jira/browse/HADOOP-8541
>             Project: Hadoop Common
>          Issue Type: Improvement
>          Components: metrics
>    Affects Versions: 2.0.0-alpha
>            Reporter: Andrew Wang
>            Assignee: Andrew Wang
>         Attachments: hadoop-8541-1.patch, hadoop-8541-2.patch, hadoop-8541-3.patch
>
>
> Based on discussion in HBASE-6261 and with some HDFS devs, I'd like to make better high-percentile latency metrics a part of hadoop-common.
> I've already got a working implementation of [1], an efficient algorithm for estimating quantiles on a stream of values. It allows you to specify arbitrary quantiles to track (e.g. 50th, 75th, 90th, 95th, 99th), along with tight error bounds. This estimator can be snapshotted and reset periodically to get a feel for how these percentiles are changing over time.
> I propose creating a new MutableQuantiles class that does this. [1] isn't completely without overhead (~1MB memory for reasonably sized windows), which is why I hesitate to add it to the existing MutableStat class.
> [1] Cormode, Korn, Muthukrishnan, and Srivastava. "Effective Computation of Biased Quantiles over Data Streams" in ICDE 2005.

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