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From "Tyler Hobbs (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (CASSANDRA-6683) BADNESS_THRESHOLD does not working correctly with DynamicEndpointSnitch
Date Thu, 20 Feb 2014 22:45:20 GMT

     [ https://issues.apache.org/jira/browse/CASSANDRA-6683?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Tyler Hobbs updated CASSANDRA-6683:
-----------------------------------

    Attachment: 6683.patch

6683.patch (and [branch|https://github.com/thobbs/cassandra/tree/CASSANDRA-6683]) sorts the
scores and compares each of them against the scores in the subsnitch ordering.

> 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
>            Assignee: Tyler Hobbs
>              Labels: snitch
>             Fix For: 2.0.6
>
>         Attachments: 6683.patch
>
>
> 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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