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https://issues.apache.org/jira/browse/SPARK-2277?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14050951#comment-14050951
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Rui Li commented on SPARK-2277:
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Suppose task1 prefers node1 but node1 is not available at the moment. However,
we know node1 is on rack1, which makes task1 prefers rack1 for RACK_LOCAL
locality. The problem is, we don't know if there's alive host on rack1, so we
cannot check the availability of this preference.
Please let me know if I misunderstand anything :)
> Make TaskScheduler track whether there's host on a rack
> -------------------------------------------------------
>
> Key: SPARK-2277
> URL: https://issues.apache.org/jira/browse/SPARK-2277
> Project: Spark
> Issue Type: Improvement
> Components: Spark Core
> Affects Versions: 1.0.0
> Reporter: Rui Li
>
> When TaskSetManager adds a pending task, it checks whether the tasks's
> preferred location is available. Regarding RACK_LOCAL task, we consider the
> preferred rack available if such a rack is defined for the preferred host.
> This is incorrect as there may be no alive hosts on that rack at all.
> Therefore, TaskScheduler should track the hosts on each rack, and provides an
> API for TaskSetManager to check if there's host alive on a specific rack.
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