[jira] [Commented] (DRILL-5210) External Sort BatchGroup leaks memory if an OOM occurs during read

["Paul Rogers (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/DRILL-5210?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15945719#comment-15945719 ] 

Paul Rogers commented on DRILL-5210:
------------------------------------

QA can verify using the fault-injection mechanism, but doing so is not a high priority as development unit tests already do so.

> External Sort BatchGroup leaks memory if an OOM occurs during read
> ------------------------------------------------------------------
>
>                 Key: DRILL-5210
>                 URL: https://issues.apache.org/jira/browse/DRILL-5210
>             Project: Apache Drill
>          Issue Type: Sub-task
>    Affects Versions: 1.9.0
>            Reporter: Paul Rogers
>            Assignee: Paul Rogers
>             Fix For: 1.10.0
>
>
> The External Sort operator (batch) can spill to disk when it runs out of memory. To do so, it uses a class called {{BatchGroup}}. Later, when the sort merges spilled runs, {{BatchGroup}} reads the run back into memory one batch at a time.
> If an OOM error occurs during the read operation, the partially-read batches leak: they are not released. The fragment executor then issues a memory leak error while shutting down the query.
> This error has probably not been caught until now because the {{BatchGroup}} code does not make use of the fault injector. Elsewhere in the external sort, we use the fault injector to insert a (simulated) OOM exception so we can determine if clean-up occurs properly. No such fault injection code exists in {{BatchGroup}}.



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