[jira] [Work started] (HADOOP-7878) Regression HADOOP-7777 switch changes too clever for the StaticMapping

["Steve Loughran (Work started) (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/HADOOP-7878?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Work on HADOOP-7878 started by Steve Loughran.

> Regression HADOOP-7777 switch changes too clever for the StaticMapping
> ----------------------------------------------------------------------
>
>                 Key: HADOOP-7878
>                 URL: https://issues.apache.org/jira/browse/HADOOP-7878
>             Project: Hadoop Common
>          Issue Type: Bug
>          Components: util
>    Affects Versions: 0.23.0, 0.24.0
>            Reporter: Steve Loughran
>            Assignee: Steve Loughran
>              Labels: regression
>   Original Estimate: 0.5h
>  Remaining Estimate: 0.5h
>
> This doesn't show up until you apply the HDFS-2492 patch, but the attempt to make the {{StaticMapping}} topology clever by deciding if it is single rack or multi rack based on its rack->node mapping breaks the HDFS {{TestBlocksWithNotEnoughRacks}} test. Why? Because the racks go in after the switch topology is cached by the {{BlockManager}}, which assumes the system is always single-switch.
> Fix: default to assuming multi-switch; remove the intelligence, add a setter for anyone who really wants to simulate single-switch racks. 
> Test: verify that a newly created simple mapping is multi switch

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