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Date: Mon, 10 Feb 2014 13:06:19 +0000 (UTC)
From: "Chris Burroughs (JIRA)" <jira@apache.org>
To: commits@cassandra.apache.org
Message-ID: <JIRA.12694216.1392019881636.16714.1392037579533@arcas>
In-Reply-To: <JIRA.12694216.1392019881636@arcas>
References: <JIRA.12694216.1392019881636@arcas>
Subject: [jira] [Commented] (CASSANDRA-6683) BADNESS_THRESHOLD does not
 working correctly with DynamicEndpointSnitch
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    [ https://issues.apache.org/jira/browse/CASSANDRA-6683?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13896462#comment-13896462 ] 

Chris Burroughs commented on CASSANDRA-6683:
--------------------------------------------

Earlier DES problems reported in CASSANDRA-6465

> BADNESS_THRESHOLD does not working correctly with DynamicEndpointSnitch
> -----------------------------------------------------------------------
>
>                 Key: CASSANDRA-6683
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-6683
>             Project: Cassandra
>          Issue Type: Bug
>          Components: Core
>         Environment: Linux 3.8.0-33-generic
>            Reporter: Kirill Bogdanov
>              Labels: snitch
>             Fix For: 2.0.5
>
>
> There is a problem in *DynamicEndpointSnitch.java* in sortByProximityWithBadness()
> Before calling sortByProximityWithScore we comparing each nodes score ratios to the badness threshold.
> {code}
> if ((first - next) / first >  BADNESS_THRESHOLD)
>             {
>                 sortByProximityWithScore(address, addresses);
>                 return;
>             }
> {code}
> This is not always the correct comparison because *first* score can be less than *next*  score and in that case we will compare a negative number with positive.
> The solution is to compute absolute value of the ratio:
> {code}
> if (Math.abs((first - next) / first) > BADNESS_THRESHOLD)
> {code}
> This issue causing an incorrect sorting of DCs based on their performance and affects performance of the snitch.
> Thanks.
>  


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