[jira] [Updated] (MAPREDUCE-5979) FairScheduler: zero weight can cause sort failures

["Karthik Kambatla (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/MAPREDUCE-5979?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Karthik Kambatla updated MAPREDUCE-5979:
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    Summary: FairScheduler: zero weight can cause sort failures  (was: MR1 FairScheduler zero weight can cause sort failures)

> FairScheduler: zero weight can cause sort failures
> --------------------------------------------------
>
>                 Key: MAPREDUCE-5979
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-5979
>             Project: Hadoop Map/Reduce
>          Issue Type: Bug
>          Components: scheduler
>    Affects Versions: 1.2.1
>            Reporter: Anubhav Dhoot
>            Assignee: Anubhav Dhoot
>         Attachments: MAPREDUCE-5979.001.patch, MAPREDUCE-5979.002.patch
>
>
> When the weight is set to zero (which is possible with a custom weight adjuster) we can get failures in comparing schedulables.
> This is because when calculating running tasks to weight ratio could result in a 0.0/0.0 which ends up as NaN. Comparisons with NaN are undefined such that (int)Math.signum(NaN - anyNumber) will be 0 causing different criteria to be used in comparison which may not be consistent. This will result in 
> {{IllegalArgumentException: Comparison method violates its general contract!}}
>  



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