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https://issues.apache.org/jira/browse/HIVE-23443?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17107565#comment-17107565
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Prasanth Jayachandran commented on HIVE-23443:
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I was able to repro the issue with unit test. Included that in .2 patch.
[~pgaref] The guaranteed updates is hairy piece to touch for now, so not doing
it in this ticket.
.2 patch is same as .1 with added junit tests. Could you please take a look?
> LLAP speculative task pre-emption seems to be not working
> ---------------------------------------------------------
>
> Key: HIVE-23443
> URL: https://issues.apache.org/jira/browse/HIVE-23443
> Project: Hive
> Issue Type: Bug
> Reporter: Prasanth Jayachandran
> Assignee: Prasanth Jayachandran
> Priority: Major
> Attachments: HIVE-23443.1.patch, HIVE-23443.2.patch
>
>
> I think after HIVE-23210 we are getting a stable sort order and it is causing
> pre-emption to not work in certain cases.
> {code:java}
> "attempt_1589167813851_0000_119_01_000008_0
> (hive_20200511055921_89598f09-19f1-4969-ab7a-82e2dd796273-119/Map 1, started
> at 2020-05-11 05:59:22, in preemption queue, can finish)",
> "attempt_1589167813851_0008_84_01_000008_1
> (hive_20200511055928_7ae29ca3-e67d-4d1f-b193-05651023b503-84/Map 1, started
> at 2020-05-11 06:00:23, in preemption queue, can finish)" {code}
> Scheduler only peek's at the pre-emption queue and looks at whether it is
> non-finishable.
> [https://github.com/apache/hive/blob/master/llap-server/src/java/org/apache/hadoop/hive/llap/daemon/impl/TaskExecutorService.java#L420]
> In the above case, all tasks are speculative but state change is not
> triggering pre-emption queue re-ordering so peek() always returns canFinish
> task even though non-finishable tasks are in the queue.
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