[jira] [Commented] (TAJO-603) Move container allocation from SubQuery down to QueryUnitAttempt

["Jihoon Son (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/TAJO-603?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13902973#comment-13902973 ] 

Jihoon Son commented on TAJO-603:
---------------------------------

Hi, Min.
It is always good approach that makes the code simpler, but this case is quite complicated.
In Tajo, containers are not allocated for each QueryUnitAttempt. Actually, when the required number of tasks are greater than the total number of task slots, only one container is launched for each task slot. 
This complex procedure is due to the large overhead for launching containers. Since starting a container takes quite a long time, we launch only necessary number of containers.

Please correct me if I misunderstand your idea.
Thanks.

> Move container allocation from SubQuery down to QueryUnitAttempt
> ----------------------------------------------------------------
>
>                 Key: TAJO-603
>                 URL: https://issues.apache.org/jira/browse/TAJO-603
>             Project: Tajo
>          Issue Type: Sub-task
>            Reporter: Min Zhou
>             Fix For: 1.0-incubating
>
>         Attachments: schedule.png
>
>
> Tajo currently allocates all of the containers in SubQuery. That make things complicated.  Both SubQuery and DefaultTaskScheduler should hold a copy of allocated containers and running tasks.  And the event flow is difficult to understand. 



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