[jira] [Commented] (IMPALA-9318) Guard rail for mt_dop value

["ASF subversion and git services (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/IMPALA-9318?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17129536#comment-17129536 ] 

ASF subversion and git services commented on IMPALA-9318:
---------------------------------------------------------

Commit 9125de7ae3d2ba0eca59097fd9732a6fbb609107 in impala's branch refs/heads/master from Joe McDonnell
[ https://gitbox.apache.org/repos/asf?p=impala.git;h=9125de7 ]

IMPALA-9318: Add admission control setting to cap MT_DOP

This introduces the max-mt-dop setting for admission
control. If a statement runs with an MT_DOP setting that
exceeds the max-mt-dop, then the MT_DOP setting is
downgraded to the max-mt-dop value. If max-mt-dop is set
to a negative value, no limit is applied. max-mt-dop is
set via the llama-site.xml and can be set at the daemon
level or at the resource pool level. When there is no
max-mt-dop setting, it defaults to -1, so no limit is
applied. The max-mt-dop is evaluated once prior to query
planning. The MT_DOP settings for queries past planning
are not reevaluated if the policy changes.

If a statement is downgraded, it's runtime profile contains
a message explaining the downgrade:
MT_DOP limited by admission control: Requested MT_DOP=9 reduced to MT_DOP=4.

Testing:
 - Added custom cluster test with various max-mt-dop settings
 - Ran core tests

Change-Id: I3affb127a5dca517591323f2b1c880aa4b38badd
Reviewed-on: http://gerrit.cloudera.org:8080/16020
Reviewed-by: Impala Public Jenkins <im...@cloudera.com>
Tested-by: Impala Public Jenkins <im...@cloudera.com>


> Guard rail for mt_dop value
> ---------------------------
>
>                 Key: IMPALA-9318
>                 URL: https://issues.apache.org/jira/browse/IMPALA-9318
>             Project: IMPALA
>          Issue Type: Improvement
>            Reporter: Tim Armstrong
>            Assignee: Joe McDonnell
>            Priority: Major
>              Labels: multithreading
>
> We may want to consider adding a guard-rail that limits the dop that can be set (globally or by a particular resource pool). This would be to prevent scenarios where a user could set a high mt_dop value and use all the resources.



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