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From "Alexis Daboville (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HADOOP-16248) Fix MutableQuantiles memory leak
Date Mon, 13 May 2019 11:00:00 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-16248?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16838465#comment-16838465

Alexis Daboville commented on HADOOP-16248:

[~prongs]: thanks for the link (and the more comprehensive patch).

[~stevel@apache.org]: it looks like CI failed because it tried to apply the attached screenshot
rather than the actual patch (not too sure how fix?):
HADOOP-16248 patch is being downloaded at Wed May  8 13:11:08 UTC 2019 from
  https://issues.apache.org/jira/secure/attachment/12965566/mutable-quantiles-leak.png ->

> Fix MutableQuantiles memory leak
> --------------------------------
>                 Key: HADOOP-16248
>                 URL: https://issues.apache.org/jira/browse/HADOOP-16248
>             Project: Hadoop Common
>          Issue Type: Bug
>    Affects Versions: 2.9.2
>            Reporter: Alexis Daboville
>            Priority: Major
>         Attachments: mutable-quantiles-leak.png, mutable-quantiles.patch
> In some circumstances (high GC, high CPU usage, creating lots of
>  S3AFileSystem) it is possible for MutableQuantiles::scheduler [1] to fall
>  behind processing tasks that are submitted to it; because tasks are
>  submitted on a regular schedule, the unbounded queue backing the
>  {{ExecutorService}} might grow to several gigs [2]. By using
>  {{scheduleWithFixedDelay}} instead, we ensure that under pressure this leak won't
>  happen. In order to mitigate the growth, a simple fix [3] is proposed, simply replacing
{{scheduler.scheduleAtFixedRate}} by {{scheduler.scheduleWithFixedDelay}}.
> [1] it is single threaded and shared across all instances of {{MutableQuantiles}}: [https://github.com/apache/hadoop/blob/trunk/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/metrics2/lib/MutableQuantiles.java#L66-L68]
> [2] see attached mutable-quantiles-leak.png.
> [3] mutable-quantiles.patch

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