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https://issues.apache.org/jira/browse/AMBARI-20712?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Jonathan Hurley updated AMBARI-20712:
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Attachment: AMBARI-20712.patch
> Parallel Requests With Intersecting Hosts Don't Block Correctly
> ---------------------------------------------------------------
>
> Key: AMBARI-20712
> URL: https://issues.apache.org/jira/browse/AMBARI-20712
> Project: Ambari
> Issue Type: Bug
> Affects Versions: 2.5.1
> Reporter: Jonathan Hurley
> Assignee: Jonathan Hurley
> Priority: Blocker
> Fix For: 2.5.1
>
> Attachments: AMBARI-20712.patch
>
>
> AMBARI-20646 introduced a regression which can be seen when deploying a
> cluster via blueprint with Kerberization. The problem is caused by the change
> which was made to only pull in the most recent stage in progress per request.
> There was logic which prevented concurrently executing request stages to be
> scheduled if a prior request had an un-executed stage with a conflicting
> host. For example:
> - Request 1
> -- Stage 1 (IN_PROGRESS)
> --- Host 1
> --- Host 2
> --- Host 3
> -- Stage 2 (PENDING)
> --- Host 4
> - Request 2
> -- Stage 1
> --- Host 4
> In the above scenario, the scheduler was tricked into thinking that Request 2
> can run even though Host-4 has a conflict. This is because it was only
> looking at the stage in progress.
> We can't simply look at all stages in progress since this would cause the
> performance bug to manifest again. So, the solution is to have the database
> tell us which hosts are blocking from prior requests. This SQL should be very
> fast and will only run in the specific cases where there are multiple
> concurrent requests (which is typically at blueprint time).
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